Does anyone know of a good resource (tutorial, document, etc.) on how
to use the ADC in MSP430? (specifically MSP430F1612). This is my first
time. Also regarding circuit layout do's and don'ts.... Thanks
ADC toutorial for MSP?
Started by ●January 26, 2009
Reply by ●January 26, 20092009-01-26
I learned how to use the ADC by reviewing all of the TI code examples.
Worked out well.
Standard good PCB practices prevail. Keep analog and digital grounds
separate. Connect at one spot only. Short signal leads. Input RC filter
if your timing can stand it.
Edd
> Does anyone know of a good resource (tutorial, document, etc.) on how
> to use the ADC in MSP430? (specifically MSP430F1612). This is my first
> time. Also regarding circuit layout do's and don'ts.... Thanks
>
Worked out well.
Standard good PCB practices prevail. Keep analog and digital grounds
separate. Connect at one spot only. Short signal leads. Input RC filter
if your timing can stand it.
Edd
> Does anyone know of a good resource (tutorial, document, etc.) on how
> to use the ADC in MSP430? (specifically MSP430F1612). This is my first
> time. Also regarding circuit layout do's and don'ts.... Thanks
>
Reply by ●January 26, 20092009-01-26
> Does anyone know of a good resource (tutorial,
document, etc.) on how
> to use the ADC in MSP430? (specifically MSP430F1612). This is my first
> time. Also regarding circuit layout do's and don'ts.... Thanks
>
Hi merapcb,
That is a great question. For the ADC12 software, TI has a lot of
great code samples on their website that are fine in a vacuum. The
ADC12 chapter of the F1xx family user's guide is a great reference,
too. I would love to plug our state machine book and its ADC chapter,
but since it is for the F22x4/F22x2 it wouldn't help with the ADC12.
Pity.
As far as the hardware layout goes, others on here will give you good
advice on that. I have a different perspective about the on-chip ADCs.
First, for a chip vendor to say they include "an ADC" on a
microcontroller has about the same meaning as saying they can sell
you "a microcontroller." Just as lots of parameters define a specific
microcontroller, lots of parameters define the capability of a
particular ADC. Whether or not the on-chip ADC, of any
microcontroller, will do you any good depends on whether the silicon
dart toss happens to land on your particular requirements, such as
bandwidth, power consumption, etc.
My assumption about ADCs on any MSP430 is that they are optimized for
power consumption. Just a crazy guess, I know. So that means that for
anything other than simple measurements, such as checking a battery, I
would prefer to start with an external ADC, and put it near my signal
of interest. Of course, depending on which ADC one chose, that would
jack up the power budget and the system cost, but physics does require
expenditures somewhere, and not just faith in clever marketing.
If you find that these expenditures of current and cost for a necessary
high-quality external ADC seems painful, then you might not be in an
MSP430 application.
Another issue that arises sometimes with MSP430 ADCs is the nature of
the power supply. If you are part of the minority that truly has an
legitimate MSP430 application, then the chances are that your power
supply, for example a coin cell or a science fair energy harvester of
some sort, is optimized for the tens of microamps and not the low
milliamps. So, when the ADC is working the power supply might be near
the end of its rope, instead of the normal idle cruising at orders of
magnitude lower power. As such, the best layout in the world is only
going to mitigate the stress on the power supply, not eliminate it. If
that signal is really that important, then you might need a beefier
power supply, which in turn might knock you out of the MSP430.
In the early days of the MSP430 demos that we built for TI, we ran into
this conflict often, which is why the fruit-powered demos tend to use a
static LCD, and not a blinky (dim) LED, or even a muxed LCD. In your
application, replace that dim LED with the ADC and you will see my
point.
Tom
> to use the ADC in MSP430? (specifically MSP430F1612). This is my first
> time. Also regarding circuit layout do's and don'ts.... Thanks
>
Hi merapcb,
That is a great question. For the ADC12 software, TI has a lot of
great code samples on their website that are fine in a vacuum. The
ADC12 chapter of the F1xx family user's guide is a great reference,
too. I would love to plug our state machine book and its ADC chapter,
but since it is for the F22x4/F22x2 it wouldn't help with the ADC12.
Pity.
As far as the hardware layout goes, others on here will give you good
advice on that. I have a different perspective about the on-chip ADCs.
First, for a chip vendor to say they include "an ADC" on a
microcontroller has about the same meaning as saying they can sell
you "a microcontroller." Just as lots of parameters define a specific
microcontroller, lots of parameters define the capability of a
particular ADC. Whether or not the on-chip ADC, of any
microcontroller, will do you any good depends on whether the silicon
dart toss happens to land on your particular requirements, such as
bandwidth, power consumption, etc.
My assumption about ADCs on any MSP430 is that they are optimized for
power consumption. Just a crazy guess, I know. So that means that for
anything other than simple measurements, such as checking a battery, I
would prefer to start with an external ADC, and put it near my signal
of interest. Of course, depending on which ADC one chose, that would
jack up the power budget and the system cost, but physics does require
expenditures somewhere, and not just faith in clever marketing.
If you find that these expenditures of current and cost for a necessary
high-quality external ADC seems painful, then you might not be in an
MSP430 application.
Another issue that arises sometimes with MSP430 ADCs is the nature of
the power supply. If you are part of the minority that truly has an
legitimate MSP430 application, then the chances are that your power
supply, for example a coin cell or a science fair energy harvester of
some sort, is optimized for the tens of microamps and not the low
milliamps. So, when the ADC is working the power supply might be near
the end of its rope, instead of the normal idle cruising at orders of
magnitude lower power. As such, the best layout in the world is only
going to mitigate the stress on the power supply, not eliminate it. If
that signal is really that important, then you might need a beefier
power supply, which in turn might knock you out of the MSP430.
In the early days of the MSP430 demos that we built for TI, we ran into
this conflict often, which is why the fruit-powered demos tend to use a
static LCD, and not a blinky (dim) LED, or even a muxed LCD. In your
application, replace that dim LED with the ADC and you will see my
point.
Tom
Reply by ●January 26, 20092009-01-26
Hi Tom,
You raise some interesting points....
Firstly, and not related to ADC, the issue of having a "legitimate"
MSP application - LOL. I guess you are right, and I can say in my case
that what started out as truly legitimate, is now legacy and I just
can't move over to another processor at the moment (no offense to the
MSP!).
Now regarding the ADC, again I presume you are right, in the sense
that it "depends" on many things. I was/am in fact not going to use an
ADC at the moment but wanted to provision one on my board as I know I
will be using one in the future. But actually I don't know if that is
such a wise thing to do, because I guess to properly spec it out and
get it to work requires more time than I have at the moment. So maybe
perhaps, I should just forget about it at the moment and do a proper
job when I have the time and can design it in properly.
Just some thoughts.... thanks for sharing your views.
Mera
--- In m..., "Tom Baugh" wrote:
>
> > Does anyone know of a good resource (tutorial, document, etc.) on how
> > to use the ADC in MSP430? (specifically MSP430F1612). This is my first
> > time. Also regarding circuit layout do's and don'ts.... Thanks
> >
> Hi merapcb,
>
> That is a great question. For the ADC12 software, TI has a lot of
> great code samples on their website that are fine in a vacuum. The
> ADC12 chapter of the F1xx family user's guide is a great reference,
> too. I would love to plug our state machine book and its ADC chapter,
> but since it is for the F22x4/F22x2 it wouldn't help with the ADC12.
> Pity.
>
> As far as the hardware layout goes, others on here will give you good
> advice on that. I have a different perspective about the on-chip ADCs.
>
> First, for a chip vendor to say they include "an ADC" on a
> microcontroller has about the same meaning as saying they can sell
> you "a microcontroller." Just as lots of parameters define a specific
> microcontroller, lots of parameters define the capability of a
> particular ADC. Whether or not the on-chip ADC, of any
> microcontroller, will do you any good depends on whether the silicon
> dart toss happens to land on your particular requirements, such as
> bandwidth, power consumption, etc.
>
> My assumption about ADCs on any MSP430 is that they are optimized for
> power consumption. Just a crazy guess, I know. So that means that for
> anything other than simple measurements, such as checking a battery, I
> would prefer to start with an external ADC, and put it near my signal
> of interest. Of course, depending on which ADC one chose, that would
> jack up the power budget and the system cost, but physics does require
> expenditures somewhere, and not just faith in clever marketing.
>
> If you find that these expenditures of current and cost for a necessary
> high-quality external ADC seems painful, then you might not be in an
> MSP430 application.
>
> Another issue that arises sometimes with MSP430 ADCs is the nature of
> the power supply. If you are part of the minority that truly has an
> legitimate MSP430 application, then the chances are that your power
> supply, for example a coin cell or a science fair energy harvester of
> some sort, is optimized for the tens of microamps and not the low
> milliamps. So, when the ADC is working the power supply might be near
> the end of its rope, instead of the normal idle cruising at orders of
> magnitude lower power. As such, the best layout in the world is only
> going to mitigate the stress on the power supply, not eliminate it. If
> that signal is really that important, then you might need a beefier
> power supply, which in turn might knock you out of the MSP430.
>
> In the early days of the MSP430 demos that we built for TI, we ran into
> this conflict often, which is why the fruit-powered demos tend to use a
> static LCD, and not a blinky (dim) LED, or even a muxed LCD. In your
> application, replace that dim LED with the ADC and you will see my
> point.
>
> Tom
>
You raise some interesting points....
Firstly, and not related to ADC, the issue of having a "legitimate"
MSP application - LOL. I guess you are right, and I can say in my case
that what started out as truly legitimate, is now legacy and I just
can't move over to another processor at the moment (no offense to the
MSP!).
Now regarding the ADC, again I presume you are right, in the sense
that it "depends" on many things. I was/am in fact not going to use an
ADC at the moment but wanted to provision one on my board as I know I
will be using one in the future. But actually I don't know if that is
such a wise thing to do, because I guess to properly spec it out and
get it to work requires more time than I have at the moment. So maybe
perhaps, I should just forget about it at the moment and do a proper
job when I have the time and can design it in properly.
Just some thoughts.... thanks for sharing your views.
Mera
--- In m..., "Tom Baugh" wrote:
>
> > Does anyone know of a good resource (tutorial, document, etc.) on how
> > to use the ADC in MSP430? (specifically MSP430F1612). This is my first
> > time. Also regarding circuit layout do's and don'ts.... Thanks
> >
> Hi merapcb,
>
> That is a great question. For the ADC12 software, TI has a lot of
> great code samples on their website that are fine in a vacuum. The
> ADC12 chapter of the F1xx family user's guide is a great reference,
> too. I would love to plug our state machine book and its ADC chapter,
> but since it is for the F22x4/F22x2 it wouldn't help with the ADC12.
> Pity.
>
> As far as the hardware layout goes, others on here will give you good
> advice on that. I have a different perspective about the on-chip ADCs.
>
> First, for a chip vendor to say they include "an ADC" on a
> microcontroller has about the same meaning as saying they can sell
> you "a microcontroller." Just as lots of parameters define a specific
> microcontroller, lots of parameters define the capability of a
> particular ADC. Whether or not the on-chip ADC, of any
> microcontroller, will do you any good depends on whether the silicon
> dart toss happens to land on your particular requirements, such as
> bandwidth, power consumption, etc.
>
> My assumption about ADCs on any MSP430 is that they are optimized for
> power consumption. Just a crazy guess, I know. So that means that for
> anything other than simple measurements, such as checking a battery, I
> would prefer to start with an external ADC, and put it near my signal
> of interest. Of course, depending on which ADC one chose, that would
> jack up the power budget and the system cost, but physics does require
> expenditures somewhere, and not just faith in clever marketing.
>
> If you find that these expenditures of current and cost for a necessary
> high-quality external ADC seems painful, then you might not be in an
> MSP430 application.
>
> Another issue that arises sometimes with MSP430 ADCs is the nature of
> the power supply. If you are part of the minority that truly has an
> legitimate MSP430 application, then the chances are that your power
> supply, for example a coin cell or a science fair energy harvester of
> some sort, is optimized for the tens of microamps and not the low
> milliamps. So, when the ADC is working the power supply might be near
> the end of its rope, instead of the normal idle cruising at orders of
> magnitude lower power. As such, the best layout in the world is only
> going to mitigate the stress on the power supply, not eliminate it. If
> that signal is really that important, then you might need a beefier
> power supply, which in turn might knock you out of the MSP430.
>
> In the early days of the MSP430 demos that we built for TI, we ran into
> this conflict often, which is why the fruit-powered demos tend to use a
> static LCD, and not a blinky (dim) LED, or even a muxed LCD. In your
> application, replace that dim LED with the ADC and you will see my
> point.
>
> Tom
>
Reply by ●January 26, 20092009-01-26
Tom,
I still wonder why are you keeping your fingers busy in this list. It seems you have neither knowledge or real interest on this MCU, so why bother to stay here and write dumb things?
MSP430's ADC12 is a pretty good machine. I can get 1/2LSB from it in low power designs as well as with lots of LEDs and other power demanding circuits around. It is all matter of doing the design correctly. The most important part is the ADC12 that works really fine inside a MCU.
The voltage reference is also good enough, so there is no point to claim an external ADC should be better.
Merapcb,
As already writen in another post you can get lots of documentation and examples around in the web. The User's Guide tells all about and the specific device data sheet gives you some technical details.
Common application would just start the Vref, configure the scan mode, clock source, number of channels and start the scan. Then you can use interrupt to get the values or poll the values reading the memory positions for each channel.
The below example sets the ADC12 of the MSP430F149/F1611 to do an auto-scan with 2.5V ref:
Setup_AD dint
mov.w #044F0h,&ADC12CTL0 ; VREF ON = 2.5V, ADCON (ENC off)
mov.w #0BBF0h,&ADC12CTL0 ; VREF ON = 2.5V, ADCON (now can chenge the bits), setup=768clk
mov.w #00297h,&ADC12CTL1 ; repetitive, multiple channel, start chn 0, ADC12CLK/4, MCLK
mov.b #010h,&ADC12MCTL0 ; enable read channel 0
mov.b #011h,&ADC12MCTL1 ; same 1
mov.b #012h,&ADC12MCTL2 ; 2
mov.b #013h,&ADC12MCTL3 ; 3
mov.b #014h,&ADC12MCTL4 ; 4
mov.b #015h,&ADC12MCTL5 ; 5
mov.b #016h,&ADC12MCTL6 ; 6
mov.b #017h,&ADC12MCTL7 ; 7
mov.b #018h,&ADC12MCTL8 ; 8
mov.b #019h,&ADC12MCTL9 ; 9
mov.b #09ah,&ADC12MCTL10 ; 10 last channel
mov.w #0400h,&ADC12IE ; enable int after ch10 conversion
mov.w #044F3h,&ADC12CTL0 ; VREF ON, ADC ON, START
Regarding PCB you can also find lots of information on web. You can use the same recomendations for almost any kind of ADC. According to the resolution you need (you may not need the whole 12bits and then can be more relaxed on layout design) there are few important rules: use a GND layer (in a multilayer PCB) with no interruptions to avoid uneven current flow; you can use a single GND connection (no separate GNDs for analog and digital) because for this 12bit resolution it makes no difference since the GNDs are connected inseide the MSP chip die, use tantalum capacitors for Vref and VCC, use a ferrite bead (or small inductor) between digital VCC and analog VCC (of course, feed your MSP in the digital VCC - the inductor will help reducing noise in the analog VCC), put the decoupling caps near to the MSP's pins. Then use a software filter to reduce conversion errors due to random noise. Keep in mind the input impedance of the ADC inputs and use a buffer if your analog source has a high output impedance (above few hundred ohm).
Oversampling can give you even more resolution but you have to study the subject a bit more.
All above recomendations are just an overview. You can find better ones here in the list or searching the web. One very important thing is understand the effective resolution and the size of the noise you have in your application.
best regards,
Augusto
De:m...
Para:m...
Cia:
Data:Mon, 26 Jan 2009 16:30:40 -0000
Assunto:[msp430] Re: ADC toutorial for MSP?
> Does anyone know of a good resource (tutorial, document, etc.) on how
> to use the ADC in MSP430? (specifically MSP430F1612). This is my first
> time. Also regarding circuit layout do's and don'ts.... Thanks
>
Hi merapcb,
That is a great question. For the ADC12 software, TI has a lot of
great code samples on their website that are fine in a vacuum. The
ADC12 chapter of the F1xx family user's guide is a great reference,
too. I would love to plug our state machine book and its ADC chapter,
but since it is for the F22x4/F22x2 it wouldn't help with the ADC12.
Pity.
As far as the hardware layout goes, others on here will give you good
advice on that. I have a different perspective about the on-chip ADCs.
First, for a chip vendor to say they include "an ADC" on a
microcontroller has about the same meaning as saying they can sell
you "a microcontroller." Just as lots of parameters define a specific
microcontroller, lots of parameters define the capability of a
particular ADC. Whether or not the on-chip ADC, of any
microcontroller, will do you any good depends on whether the silicon
dart toss happens to land on your particular requirements, such as
bandwidth, power consumption, etc.
My assumption about ADCs on any MSP430 is that they are optimized for
power consumption. Just a crazy guess, I know. So that means that for
anything other than simple measurements, such as checking a battery, I
would prefer to start with an external ADC, and put it near my signal
of interest. Of course, depending on which ADC one chose, that would
jack up the power budget and the system cost, but physics does require
expenditures somewhere, and not just faith in clever marketing.
If you find that these expenditures of current and cost for a necessary
high-quality external ADC seems painful, then you might not be in an
MSP430 application.
Another issue that arises sometimes with MSP430 ADCs is the nature of
the power supply. If you are part of the minority that truly has an
legitimate MSP430 application, then the chances are that your power
supply, for example a coin cell or a science fair energy harvester of
some sort, is optimized for the tens of microamps and not the low
milliamps. So, when the ADC is working the power supply might be near
the end of its rope, instead of the normal idle cruising at orders of
magnitude lower power. As such, the best layout in the world is only
going to mitigate the stress on the power supply, not eliminate it. If
that signal is really that important, then you might need a beefier
power supply, which in turn might knock you out of the MSP430.
In the early days of the MSP430 demos that we built for TI, we ran into
this conflict often, which is why the fruit-powered demos tend to use a
static LCD, and not a blinky (dim) LED, or even a muxed LCD. In your
application, replace that dim LED with the ADC and you will see my
point.
Tom
I still wonder why are you keeping your fingers busy in this list. It seems you have neither knowledge or real interest on this MCU, so why bother to stay here and write dumb things?
MSP430's ADC12 is a pretty good machine. I can get 1/2LSB from it in low power designs as well as with lots of LEDs and other power demanding circuits around. It is all matter of doing the design correctly. The most important part is the ADC12 that works really fine inside a MCU.
The voltage reference is also good enough, so there is no point to claim an external ADC should be better.
Merapcb,
As already writen in another post you can get lots of documentation and examples around in the web. The User's Guide tells all about and the specific device data sheet gives you some technical details.
Common application would just start the Vref, configure the scan mode, clock source, number of channels and start the scan. Then you can use interrupt to get the values or poll the values reading the memory positions for each channel.
The below example sets the ADC12 of the MSP430F149/F1611 to do an auto-scan with 2.5V ref:
Setup_AD dint
mov.w #044F0h,&ADC12CTL0 ; VREF ON = 2.5V, ADCON (ENC off)
mov.w #0BBF0h,&ADC12CTL0 ; VREF ON = 2.5V, ADCON (now can chenge the bits), setup=768clk
mov.w #00297h,&ADC12CTL1 ; repetitive, multiple channel, start chn 0, ADC12CLK/4, MCLK
mov.b #010h,&ADC12MCTL0 ; enable read channel 0
mov.b #011h,&ADC12MCTL1 ; same 1
mov.b #012h,&ADC12MCTL2 ; 2
mov.b #013h,&ADC12MCTL3 ; 3
mov.b #014h,&ADC12MCTL4 ; 4
mov.b #015h,&ADC12MCTL5 ; 5
mov.b #016h,&ADC12MCTL6 ; 6
mov.b #017h,&ADC12MCTL7 ; 7
mov.b #018h,&ADC12MCTL8 ; 8
mov.b #019h,&ADC12MCTL9 ; 9
mov.b #09ah,&ADC12MCTL10 ; 10 last channel
mov.w #0400h,&ADC12IE ; enable int after ch10 conversion
mov.w #044F3h,&ADC12CTL0 ; VREF ON, ADC ON, START
Regarding PCB you can also find lots of information on web. You can use the same recomendations for almost any kind of ADC. According to the resolution you need (you may not need the whole 12bits and then can be more relaxed on layout design) there are few important rules: use a GND layer (in a multilayer PCB) with no interruptions to avoid uneven current flow; you can use a single GND connection (no separate GNDs for analog and digital) because for this 12bit resolution it makes no difference since the GNDs are connected inseide the MSP chip die, use tantalum capacitors for Vref and VCC, use a ferrite bead (or small inductor) between digital VCC and analog VCC (of course, feed your MSP in the digital VCC - the inductor will help reducing noise in the analog VCC), put the decoupling caps near to the MSP's pins. Then use a software filter to reduce conversion errors due to random noise. Keep in mind the input impedance of the ADC inputs and use a buffer if your analog source has a high output impedance (above few hundred ohm).
Oversampling can give you even more resolution but you have to study the subject a bit more.
All above recomendations are just an overview. You can find better ones here in the list or searching the web. One very important thing is understand the effective resolution and the size of the noise you have in your application.
best regards,
Augusto
De:m...
Para:m...
Cia:
Data:Mon, 26 Jan 2009 16:30:40 -0000
Assunto:[msp430] Re: ADC toutorial for MSP?
> Does anyone know of a good resource (tutorial, document, etc.) on how
> to use the ADC in MSP430? (specifically MSP430F1612). This is my first
> time. Also regarding circuit layout do's and don'ts.... Thanks
>
Hi merapcb,
That is a great question. For the ADC12 software, TI has a lot of
great code samples on their website that are fine in a vacuum. The
ADC12 chapter of the F1xx family user's guide is a great reference,
too. I would love to plug our state machine book and its ADC chapter,
but since it is for the F22x4/F22x2 it wouldn't help with the ADC12.
Pity.
As far as the hardware layout goes, others on here will give you good
advice on that. I have a different perspective about the on-chip ADCs.
First, for a chip vendor to say they include "an ADC" on a
microcontroller has about the same meaning as saying they can sell
you "a microcontroller." Just as lots of parameters define a specific
microcontroller, lots of parameters define the capability of a
particular ADC. Whether or not the on-chip ADC, of any
microcontroller, will do you any good depends on whether the silicon
dart toss happens to land on your particular requirements, such as
bandwidth, power consumption, etc.
My assumption about ADCs on any MSP430 is that they are optimized for
power consumption. Just a crazy guess, I know. So that means that for
anything other than simple measurements, such as checking a battery, I
would prefer to start with an external ADC, and put it near my signal
of interest. Of course, depending on which ADC one chose, that would
jack up the power budget and the system cost, but physics does require
expenditures somewhere, and not just faith in clever marketing.
If you find that these expenditures of current and cost for a necessary
high-quality external ADC seems painful, then you might not be in an
MSP430 application.
Another issue that arises sometimes with MSP430 ADCs is the nature of
the power supply. If you are part of the minority that truly has an
legitimate MSP430 application, then the chances are that your power
supply, for example a coin cell or a science fair energy harvester of
some sort, is optimized for the tens of microamps and not the low
milliamps. So, when the ADC is working the power supply might be near
the end of its rope, instead of the normal idle cruising at orders of
magnitude lower power. As such, the best layout in the world is only
going to mitigate the stress on the power supply, not eliminate it. If
that signal is really that important, then you might need a beefier
power supply, which in turn might knock you out of the MSP430.
In the early days of the MSP430 demos that we built for TI, we ran into
this conflict often, which is why the fruit-powered demos tend to use a
static LCD, and not a blinky (dim) LED, or even a muxed LCD. In your
application, replace that dim LED with the ADC and you will see my
point.
Tom
Reply by ●March 18, 20092009-03-18
Hi all,
May be a basic question on MSP430 ADC,
I would like to know that is it possible to directly connect the
AVcc(Vcc) pin to VREF+ and use it as an external reference,
in this case please let me know what are the necessary things to be taken care.
Thankyou
Paddu..
--- In m..., "Augusto Einsfeldt" wrote:
>
> Tom,
> I still wonder why are you keeping your fingers busy in this list. It seems you have neither knowledge or real interest on this MCU, so why bother to stay here and write dumb things?
> MSP430's ADC12 is a pretty good machine. I can get 1/2LSB from it in low power designs as well as with lots of LEDs and other power demanding circuits around. It is all matter of doing the design correctly. The most important part is the ADC12 that works really fine inside a MCU.
> The voltage reference is also good enough, so there is no point to claim an external ADC should be better.
>
> Merapcb,
> As already writen in another post you can get lots of documentation and examples around in the web. The User's Guide tells all about and the specific device data sheet gives you some technical details.
> Common application would just start the Vref, configure the scan mode, clock source, number of channels and start the scan. Then you can use interrupt to get the values or poll the values reading the memory positions for each channel.
>
> The below example sets the ADC12 of the MSP430F149/F1611 to do an auto-scan with 2.5V ref:
>
> Setup_AD dint
> mov.w #044F0h,&ADC12CTL0 ; VREF ON = 2.5V, ADCON (ENC off)
> mov.w #0BBF0h,&ADC12CTL0 ; VREF ON = 2.5V, ADCON (now can chenge the bits), setup=768clk
> mov.w #00297h,&ADC12CTL1 ; repetitive, multiple channel, start chn 0, ADC12CLK/4, MCLK
> mov.b #010h,&ADC12MCTL0 ; enable read channel 0
> mov.b #011h,&ADC12MCTL1 ; same 1
> mov.b #012h,&ADC12MCTL2 ; 2
> mov.b #013h,&ADC12MCTL3 ; 3
> mov.b #014h,&ADC12MCTL4 ; 4
> mov.b #015h,&ADC12MCTL5 ; 5
> mov.b #016h,&ADC12MCTL6 ; 6
> mov.b #017h,&ADC12MCTL7 ; 7
> mov.b #018h,&ADC12MCTL8 ; 8
> mov.b #019h,&ADC12MCTL9 ; 9
> mov.b #09ah,&ADC12MCTL10 ; 10 last channel
> mov.w #0400h,&ADC12IE ; enable int after ch10 conversion
> mov.w #044F3h,&ADC12CTL0 ; VREF ON, ADC ON, START
>
> Regarding PCB you can also find lots of information on web. You can use the same recomendations for almost any kind of ADC. According to the resolution you need (you may not need the whole 12bits and then can be more relaxed on layout design) there are few important rules: use a GND layer (in a multilayer PCB) with no interruptions to avoid uneven current flow; you can use a single GND connection (no separate GNDs for analog and digital) because for this 12bit resolution it makes no difference since the GNDs are connected inseide the MSP chip die, use tantalum capacitors for Vref and VCC, use a ferrite bead (or small inductor) between digital VCC and analog VCC (of course, feed your MSP in the digital VCC - the inductor will help reducing noise in the analog VCC), put the decoupling caps near to the MSP's pins. Then use a software filter to reduce conversion errors due to random noise. Keep in mind the input impedance of the ADC inputs and use a buffer if your analog source has a high output impedance (above few hundred ohm).
> Oversampling can give you even more resolution but you have to study the subject a bit more.
> All above recomendations are just an overview. You can find better ones here in the list or searching the web. One very important thing is understand the effective resolution and the size of the noise you have in your application.
> best regards,
> Augusto
>
>
> De:m...
>
> Para:m...
>
> Cia:
>
> Data:Mon, 26 Jan 2009 16:30:40 -0000
>
> Assunto:[msp430] Re: ADC toutorial for MSP?
>
> > Does anyone know of a good resource (tutorial, document, etc.) on how
> > to use the ADC in MSP430? (specifically MSP430F1612). This is my first
> > time. Also regarding circuit layout do's and don'ts.... Thanks
> >
> Hi merapcb,
>
> That is a great question. For the ADC12 software, TI has a lot of
> great code samples on their website that are fine in a vacuum. The
> ADC12 chapter of the F1xx family user's guide is a great reference,
> too. I would love to plug our state machine book and its ADC chapter,
> but since it is for the F22x4/F22x2 it wouldn't help with the ADC12.
> Pity.
>
> As far as the hardware layout goes, others on here will give you good
> advice on that. I have a different perspective about the on-chip ADCs.
>
> First, for a chip vendor to say they include "an ADC" on a
> microcontroller has about the same meaning as saying they can sell
> you "a microcontroller." Just as lots of parameters define a specific
> microcontroller, lots of parameters define the capability of a
> particular ADC. Whether or not the on-chip ADC, of any
> microcontroller, will do you any good depends on whether the silicon
> dart toss happens to land on your particular requirements, such as
> bandwidth, power consumption, etc.
>
> My assumption about ADCs on any MSP430 is that they are optimized for
> power consumption. Just a crazy guess, I know. So that means that for
> anything other than simple measurements, such as checking a battery, I
> would prefer to start with an external ADC, and put it near my signal
> of interest. Of course, depending on which ADC one chose, that would
> jack up the power budget and the system cost, but physics does require
> expenditures somewhere, and not just faith in clever marketing.
>
> If you find that these expenditures of current and cost for a necessary
> high-quality external ADC seems painful, then you might not be in an
> MSP430 application.
>
> Another issue that arises sometimes with MSP430 ADCs is the nature of
> the power supply. If you are part of the minority that truly has an
> legitimate MSP430 application, then the chances are that your power
> supply, for example a coin cell or a science fair energy harvester of
> some sort, is optimized for the tens of microamps and not the low
> milliamps. So, when the ADC is working the power supply might be near
> the end of its rope, instead of the normal idle cruising at orders of
> magnitude lower power. As such, the best layout in the world is only
> going to mitigate the stress on the power supply, not eliminate it. If
> that signal is really that important, then you might need a beefier
> power supply, which in turn might knock you out of the MSP430.
>
> In the early days of the MSP430 demos that we built for TI, we ran into
> this conflict often, which is why the fruit-powered demos tend to use a
> static LCD, and not a blinky (dim) LED, or even a muxed LCD. In your
> application, replace that dim LED with the ADC and you will see my
> point.
>
> Tom
>
>
>
>
>
>
>
May be a basic question on MSP430 ADC,
I would like to know that is it possible to directly connect the
AVcc(Vcc) pin to VREF+ and use it as an external reference,
in this case please let me know what are the necessary things to be taken care.
Thankyou
Paddu..
--- In m..., "Augusto Einsfeldt" wrote:
>
> Tom,
> I still wonder why are you keeping your fingers busy in this list. It seems you have neither knowledge or real interest on this MCU, so why bother to stay here and write dumb things?
> MSP430's ADC12 is a pretty good machine. I can get 1/2LSB from it in low power designs as well as with lots of LEDs and other power demanding circuits around. It is all matter of doing the design correctly. The most important part is the ADC12 that works really fine inside a MCU.
> The voltage reference is also good enough, so there is no point to claim an external ADC should be better.
>
> Merapcb,
> As already writen in another post you can get lots of documentation and examples around in the web. The User's Guide tells all about and the specific device data sheet gives you some technical details.
> Common application would just start the Vref, configure the scan mode, clock source, number of channels and start the scan. Then you can use interrupt to get the values or poll the values reading the memory positions for each channel.
>
> The below example sets the ADC12 of the MSP430F149/F1611 to do an auto-scan with 2.5V ref:
>
> Setup_AD dint
> mov.w #044F0h,&ADC12CTL0 ; VREF ON = 2.5V, ADCON (ENC off)
> mov.w #0BBF0h,&ADC12CTL0 ; VREF ON = 2.5V, ADCON (now can chenge the bits), setup=768clk
> mov.w #00297h,&ADC12CTL1 ; repetitive, multiple channel, start chn 0, ADC12CLK/4, MCLK
> mov.b #010h,&ADC12MCTL0 ; enable read channel 0
> mov.b #011h,&ADC12MCTL1 ; same 1
> mov.b #012h,&ADC12MCTL2 ; 2
> mov.b #013h,&ADC12MCTL3 ; 3
> mov.b #014h,&ADC12MCTL4 ; 4
> mov.b #015h,&ADC12MCTL5 ; 5
> mov.b #016h,&ADC12MCTL6 ; 6
> mov.b #017h,&ADC12MCTL7 ; 7
> mov.b #018h,&ADC12MCTL8 ; 8
> mov.b #019h,&ADC12MCTL9 ; 9
> mov.b #09ah,&ADC12MCTL10 ; 10 last channel
> mov.w #0400h,&ADC12IE ; enable int after ch10 conversion
> mov.w #044F3h,&ADC12CTL0 ; VREF ON, ADC ON, START
>
> Regarding PCB you can also find lots of information on web. You can use the same recomendations for almost any kind of ADC. According to the resolution you need (you may not need the whole 12bits and then can be more relaxed on layout design) there are few important rules: use a GND layer (in a multilayer PCB) with no interruptions to avoid uneven current flow; you can use a single GND connection (no separate GNDs for analog and digital) because for this 12bit resolution it makes no difference since the GNDs are connected inseide the MSP chip die, use tantalum capacitors for Vref and VCC, use a ferrite bead (or small inductor) between digital VCC and analog VCC (of course, feed your MSP in the digital VCC - the inductor will help reducing noise in the analog VCC), put the decoupling caps near to the MSP's pins. Then use a software filter to reduce conversion errors due to random noise. Keep in mind the input impedance of the ADC inputs and use a buffer if your analog source has a high output impedance (above few hundred ohm).
> Oversampling can give you even more resolution but you have to study the subject a bit more.
> All above recomendations are just an overview. You can find better ones here in the list or searching the web. One very important thing is understand the effective resolution and the size of the noise you have in your application.
> best regards,
> Augusto
>
>
> De:m...
>
> Para:m...
>
> Cia:
>
> Data:Mon, 26 Jan 2009 16:30:40 -0000
>
> Assunto:[msp430] Re: ADC toutorial for MSP?
>
> > Does anyone know of a good resource (tutorial, document, etc.) on how
> > to use the ADC in MSP430? (specifically MSP430F1612). This is my first
> > time. Also regarding circuit layout do's and don'ts.... Thanks
> >
> Hi merapcb,
>
> That is a great question. For the ADC12 software, TI has a lot of
> great code samples on their website that are fine in a vacuum. The
> ADC12 chapter of the F1xx family user's guide is a great reference,
> too. I would love to plug our state machine book and its ADC chapter,
> but since it is for the F22x4/F22x2 it wouldn't help with the ADC12.
> Pity.
>
> As far as the hardware layout goes, others on here will give you good
> advice on that. I have a different perspective about the on-chip ADCs.
>
> First, for a chip vendor to say they include "an ADC" on a
> microcontroller has about the same meaning as saying they can sell
> you "a microcontroller." Just as lots of parameters define a specific
> microcontroller, lots of parameters define the capability of a
> particular ADC. Whether or not the on-chip ADC, of any
> microcontroller, will do you any good depends on whether the silicon
> dart toss happens to land on your particular requirements, such as
> bandwidth, power consumption, etc.
>
> My assumption about ADCs on any MSP430 is that they are optimized for
> power consumption. Just a crazy guess, I know. So that means that for
> anything other than simple measurements, such as checking a battery, I
> would prefer to start with an external ADC, and put it near my signal
> of interest. Of course, depending on which ADC one chose, that would
> jack up the power budget and the system cost, but physics does require
> expenditures somewhere, and not just faith in clever marketing.
>
> If you find that these expenditures of current and cost for a necessary
> high-quality external ADC seems painful, then you might not be in an
> MSP430 application.
>
> Another issue that arises sometimes with MSP430 ADCs is the nature of
> the power supply. If you are part of the minority that truly has an
> legitimate MSP430 application, then the chances are that your power
> supply, for example a coin cell or a science fair energy harvester of
> some sort, is optimized for the tens of microamps and not the low
> milliamps. So, when the ADC is working the power supply might be near
> the end of its rope, instead of the normal idle cruising at orders of
> magnitude lower power. As such, the best layout in the world is only
> going to mitigate the stress on the power supply, not eliminate it. If
> that signal is really that important, then you might need a beefier
> power supply, which in turn might knock you out of the MSP430.
>
> In the early days of the MSP430 demos that we built for TI, we ran into
> this conflict often, which is why the fruit-powered demos tend to use a
> static LCD, and not a blinky (dim) LED, or even a muxed LCD. In your
> application, replace that dim LED with the ADC and you will see my
> point.
>
> Tom
>
>
>
>
>
>
>
Reply by ●March 18, 20092009-03-18
Yes.
>
> Hi all,
>
> May be a basic question on MSP430 ADC,
> I would like to know that is it possible to directly connect the
> AVcc(Vcc) pin to VREF+ and use it as an external reference,
> in this case please let me know what are the necessary things to be taken care.
>
>
> Thankyou
>
> Paddu..
>
> --- In m..., "Augusto Einsfeldt" wrote:
> >
> > Tom,
> > I still wonder why are you keeping your fingers busy in this list. It seems you have neither knowledge or real interest on this MCU, so why bother to stay here and write dumb things?
> > MSP430's ADC12 is a pretty good machine. I can get 1/2LSB from it in low power designs as well as with lots of LEDs and other power demanding circuits around. It is all matter of doing the design correctly. The most important part is the ADC12 that works really fine inside a MCU.
> > The voltage reference is also good enough, so there is no point to claim an external ADC should be better.
> >
> > Merapcb,
> > As already writen in another post you can get lots of documentation and examples around in the web. The User's Guide tells all about and the specific device data sheet gives you some technical details.
> > Common application would just start the Vref, configure the scan mode, clock source, number of channels and start the scan. Then you can use interrupt to get the values or poll the values reading the memory positions for each channel.
> >
> > The below example sets the ADC12 of the MSP430F149/F1611 to do an auto-scan with 2.5V ref:
> >
> > Setup_AD dint
> > mov.w #044F0h,&ADC12CTL0 ; VREF ON = 2.5V, ADCON (ENC off)
> > mov.w #0BBF0h,&ADC12CTL0 ; VREF ON = 2.5V, ADCON (now can chenge the bits), setup=768clk
> > mov.w #00297h,&ADC12CTL1 ; repetitive, multiple channel, start chn 0, ADC12CLK/4, MCLK
> > mov.b #010h,&ADC12MCTL0 ; enable read channel 0
> > mov.b #011h,&ADC12MCTL1 ; same 1
> > mov.b #012h,&ADC12MCTL2 ; 2
> > mov.b #013h,&ADC12MCTL3 ; 3
> > mov.b #014h,&ADC12MCTL4 ; 4
> > mov.b #015h,&ADC12MCTL5 ; 5
> > mov.b #016h,&ADC12MCTL6 ; 6
> > mov.b #017h,&ADC12MCTL7 ; 7
> > mov.b #018h,&ADC12MCTL8 ; 8
> > mov.b #019h,&ADC12MCTL9 ; 9
> > mov.b #09ah,&ADC12MCTL10 ; 10 last channel
> > mov.w #0400h,&ADC12IE ; enable int after ch10 conversion
> > mov.w #044F3h,&ADC12CTL0 ; VREF ON, ADC ON, START
> >
> > Regarding PCB you can also find lots of information on web. You can use the same recomendations for almost any kind of ADC. According to the resolution you need (you may not need the whole 12bits and then can be more relaxed on layout design) there are few important rules: use a GND layer (in a multilayer PCB) with no interruptions to avoid uneven current flow; you can use a single GND connection (no separate GNDs for analog and digital) because for this 12bit resolution it makes no difference since the GNDs are connected inseide the MSP chip die, use tantalum capacitors for Vref and VCC, use a ferrite bead (or small inductor) between digital VCC and analog VCC (of course, feed your MSP in the digital VCC - the inductor will help reducing noise in the analog VCC), put the decoupling caps near to the MSP's pins. Then use a software filter to reduce conversion errors due to random noise. Keep in mind the input impedance of the ADC inputs and use a buffer if your analog source has a high output impedance (above few hundred ohm).
> > Oversampling can give you even more resolution but you have to study the subject a bit more.
> > All above recomendations are just an overview. You can find better ones here in the list or searching the web. One very important thing is understand the effective resolution and the size of the noise you have in your application.
> > best regards,
> > Augusto
> >
> >
> > De:m...
> >
> > Para:m...
> >
> > Cia:
> >
> > Data:Mon, 26 Jan 2009 16:30:40 -0000
> >
> > Assunto:[msp430] Re: ADC toutorial for MSP?
> >
> > > Does anyone know of a good resource (tutorial, document, etc.) on how
> > > to use the ADC in MSP430? (specifically MSP430F1612). This is my first
> > > time. Also regarding circuit layout do's and don'ts.... Thanks
> > >
> > Hi merapcb,
> >
> > That is a great question. For the ADC12 software, TI has a lot of
> > great code samples on their website that are fine in a vacuum. The
> > ADC12 chapter of the F1xx family user's guide is a great reference,
> > too. I would love to plug our state machine book and its ADC chapter,
> > but since it is for the F22x4/F22x2 it wouldn't help with the ADC12.
> > Pity.
> >
> > As far as the hardware layout goes, others on here will give you good
> > advice on that. I have a different perspective about the on-chip ADCs.
> >
> > First, for a chip vendor to say they include "an ADC" on a
> > microcontroller has about the same meaning as saying they can sell
> > you "a microcontroller." Just as lots of parameters define a specific
> > microcontroller, lots of parameters define the capability of a
> > particular ADC. Whether or not the on-chip ADC, of any
> > microcontroller, will do you any good depends on whether the silicon
> > dart toss happens to land on your particular requirements, such as
> > bandwidth, power consumption, etc.
> >
> > My assumption about ADCs on any MSP430 is that they are optimized for
> > power consumption. Just a crazy guess, I know. So that means that for
> > anything other than simple measurements, such as checking a battery, I
> > would prefer to start with an external ADC, and put it near my signal
> > of interest. Of course, depending on which ADC one chose, that would
> > jack up the power budget and the system cost, but physics does require
> > expenditures somewhere, and not just faith in clever marketing.
> >
> > If you find that these expenditures of current and cost for a necessary
> > high-quality external ADC seems painful, then you might not be in an
> > MSP430 application.
> >
> > Another issue that arises sometimes with MSP430 ADCs is the nature of
> > the power supply. If you are part of the minority that truly has an
> > legitimate MSP430 application, then the chances are that your power
> > supply, for example a coin cell or a science fair energy harvester of
> > some sort, is optimized for the tens of microamps and not the low
> > milliamps. So, when the ADC is working the power supply might be near
> > the end of its rope, instead of the normal idle cruising at orders of
> > magnitude lower power. As such, the best layout in the world is only
> > going to mitigate the stress on the power supply, not eliminate it. If
> > that signal is really that important, then you might need a beefier
> > power supply, which in turn might knock you out of the MSP430.
> >
> > In the early days of the MSP430 demos that we built for TI, we ran into
> > this conflict often, which is why the fruit-powered demos tend to use a
> > static LCD, and not a blinky (dim) LED, or even a muxed LCD. In your
> > application, replace that dim LED with the ADC and you will see my
> > point.
> >
> > Tom
> >
> >
> >
> >
> >
> >
>
>
> Hi all,
>
> May be a basic question on MSP430 ADC,
> I would like to know that is it possible to directly connect the
> AVcc(Vcc) pin to VREF+ and use it as an external reference,
> in this case please let me know what are the necessary things to be taken care.
>
>
> Thankyou
>
> Paddu..
>
> --- In m..., "Augusto Einsfeldt" wrote:
> >
> > Tom,
> > I still wonder why are you keeping your fingers busy in this list. It seems you have neither knowledge or real interest on this MCU, so why bother to stay here and write dumb things?
> > MSP430's ADC12 is a pretty good machine. I can get 1/2LSB from it in low power designs as well as with lots of LEDs and other power demanding circuits around. It is all matter of doing the design correctly. The most important part is the ADC12 that works really fine inside a MCU.
> > The voltage reference is also good enough, so there is no point to claim an external ADC should be better.
> >
> > Merapcb,
> > As already writen in another post you can get lots of documentation and examples around in the web. The User's Guide tells all about and the specific device data sheet gives you some technical details.
> > Common application would just start the Vref, configure the scan mode, clock source, number of channels and start the scan. Then you can use interrupt to get the values or poll the values reading the memory positions for each channel.
> >
> > The below example sets the ADC12 of the MSP430F149/F1611 to do an auto-scan with 2.5V ref:
> >
> > Setup_AD dint
> > mov.w #044F0h,&ADC12CTL0 ; VREF ON = 2.5V, ADCON (ENC off)
> > mov.w #0BBF0h,&ADC12CTL0 ; VREF ON = 2.5V, ADCON (now can chenge the bits), setup=768clk
> > mov.w #00297h,&ADC12CTL1 ; repetitive, multiple channel, start chn 0, ADC12CLK/4, MCLK
> > mov.b #010h,&ADC12MCTL0 ; enable read channel 0
> > mov.b #011h,&ADC12MCTL1 ; same 1
> > mov.b #012h,&ADC12MCTL2 ; 2
> > mov.b #013h,&ADC12MCTL3 ; 3
> > mov.b #014h,&ADC12MCTL4 ; 4
> > mov.b #015h,&ADC12MCTL5 ; 5
> > mov.b #016h,&ADC12MCTL6 ; 6
> > mov.b #017h,&ADC12MCTL7 ; 7
> > mov.b #018h,&ADC12MCTL8 ; 8
> > mov.b #019h,&ADC12MCTL9 ; 9
> > mov.b #09ah,&ADC12MCTL10 ; 10 last channel
> > mov.w #0400h,&ADC12IE ; enable int after ch10 conversion
> > mov.w #044F3h,&ADC12CTL0 ; VREF ON, ADC ON, START
> >
> > Regarding PCB you can also find lots of information on web. You can use the same recomendations for almost any kind of ADC. According to the resolution you need (you may not need the whole 12bits and then can be more relaxed on layout design) there are few important rules: use a GND layer (in a multilayer PCB) with no interruptions to avoid uneven current flow; you can use a single GND connection (no separate GNDs for analog and digital) because for this 12bit resolution it makes no difference since the GNDs are connected inseide the MSP chip die, use tantalum capacitors for Vref and VCC, use a ferrite bead (or small inductor) between digital VCC and analog VCC (of course, feed your MSP in the digital VCC - the inductor will help reducing noise in the analog VCC), put the decoupling caps near to the MSP's pins. Then use a software filter to reduce conversion errors due to random noise. Keep in mind the input impedance of the ADC inputs and use a buffer if your analog source has a high output impedance (above few hundred ohm).
> > Oversampling can give you even more resolution but you have to study the subject a bit more.
> > All above recomendations are just an overview. You can find better ones here in the list or searching the web. One very important thing is understand the effective resolution and the size of the noise you have in your application.
> > best regards,
> > Augusto
> >
> >
> > De:m...
> >
> > Para:m...
> >
> > Cia:
> >
> > Data:Mon, 26 Jan 2009 16:30:40 -0000
> >
> > Assunto:[msp430] Re: ADC toutorial for MSP?
> >
> > > Does anyone know of a good resource (tutorial, document, etc.) on how
> > > to use the ADC in MSP430? (specifically MSP430F1612). This is my first
> > > time. Also regarding circuit layout do's and don'ts.... Thanks
> > >
> > Hi merapcb,
> >
> > That is a great question. For the ADC12 software, TI has a lot of
> > great code samples on their website that are fine in a vacuum. The
> > ADC12 chapter of the F1xx family user's guide is a great reference,
> > too. I would love to plug our state machine book and its ADC chapter,
> > but since it is for the F22x4/F22x2 it wouldn't help with the ADC12.
> > Pity.
> >
> > As far as the hardware layout goes, others on here will give you good
> > advice on that. I have a different perspective about the on-chip ADCs.
> >
> > First, for a chip vendor to say they include "an ADC" on a
> > microcontroller has about the same meaning as saying they can sell
> > you "a microcontroller." Just as lots of parameters define a specific
> > microcontroller, lots of parameters define the capability of a
> > particular ADC. Whether or not the on-chip ADC, of any
> > microcontroller, will do you any good depends on whether the silicon
> > dart toss happens to land on your particular requirements, such as
> > bandwidth, power consumption, etc.
> >
> > My assumption about ADCs on any MSP430 is that they are optimized for
> > power consumption. Just a crazy guess, I know. So that means that for
> > anything other than simple measurements, such as checking a battery, I
> > would prefer to start with an external ADC, and put it near my signal
> > of interest. Of course, depending on which ADC one chose, that would
> > jack up the power budget and the system cost, but physics does require
> > expenditures somewhere, and not just faith in clever marketing.
> >
> > If you find that these expenditures of current and cost for a necessary
> > high-quality external ADC seems painful, then you might not be in an
> > MSP430 application.
> >
> > Another issue that arises sometimes with MSP430 ADCs is the nature of
> > the power supply. If you are part of the minority that truly has an
> > legitimate MSP430 application, then the chances are that your power
> > supply, for example a coin cell or a science fair energy harvester of
> > some sort, is optimized for the tens of microamps and not the low
> > milliamps. So, when the ADC is working the power supply might be near
> > the end of its rope, instead of the normal idle cruising at orders of
> > magnitude lower power. As such, the best layout in the world is only
> > going to mitigate the stress on the power supply, not eliminate it. If
> > that signal is really that important, then you might need a beefier
> > power supply, which in turn might knock you out of the MSP430.
> >
> > In the early days of the MSP430 demos that we built for TI, we ran into
> > this conflict often, which is why the fruit-powered demos tend to use a
> > static LCD, and not a blinky (dim) LED, or even a muxed LCD. In your
> > application, replace that dim LED with the ADC and you will see my
> > point.
> >
> > Tom
> >
> >
> >
> >
> >
> >
>
Reply by ●March 18, 20092009-03-18
Yes, you can. But keep in mind your reference voltage must be stable and
accurate, since your ADC accurancy depends on this reference voltage. Do not
trust on conventional regulator's output stability. Noise comming from
external sources or from the MSP and surrounding circuitry can be easily coupled
and this would reduce your resolution in great deal. If you have 0.01Vpp (10mV)
noise in the AVCC (used as Vref for ADC) it does mean your effective resolution
will drop to 8 bits only.
Temperature and thermal noise can also introduce errors.
If you want to do this to increase the voltage range to 3V (instead of 2.5V) I would recomend keeping the internal Vref and use an attenuator (voltage divider) in the ADC inputs to keep the signal in the 2.5V range. A voltage divider has also the advantage to introduce a protection series resistor in the input to prevent excess of coupled noise to damage the MSP. Of course this will change the system's ADC input impedance and must be taken in account in your design.
-Augusto
De:m...
Para:m...
Cia:
Data:Wed, 18 Mar 2009 10:39:29 -0000
Assunto:Re:[msp430] Re: ADC toutorial for MSP?
Hi all,
May be a basic question on MSP430 ADC,
I would like to know that is it possible to directly connect the
AVcc(Vcc) pin to VREF+ and use it as an external reference,
in this case please let me know what are the necessary things to be taken care.
Thankyou
Paddu..
Temperature and thermal noise can also introduce errors.
If you want to do this to increase the voltage range to 3V (instead of 2.5V) I would recomend keeping the internal Vref and use an attenuator (voltage divider) in the ADC inputs to keep the signal in the 2.5V range. A voltage divider has also the advantage to introduce a protection series resistor in the input to prevent excess of coupled noise to damage the MSP. Of course this will change the system's ADC input impedance and must be taken in account in your design.
-Augusto
De:m...
Para:m...
Cia:
Data:Wed, 18 Mar 2009 10:39:29 -0000
Assunto:Re:[msp430] Re: ADC toutorial for MSP?
Hi all,
May be a basic question on MSP430 ADC,
I would like to know that is it possible to directly connect the
AVcc(Vcc) pin to VREF+ and use it as an external reference,
in this case please let me know what are the necessary things to be taken care.
Thankyou
Paddu..
