Reply by glgo...@hotmail.com●September 12, 20082008-09-12
Just started working on ADC10 using ez430-RF2500. I tried to get values directly
from the output of an amplified signal however it looks so different from the
value displayed on the oscilloscope. I was supposed to get an ECG signal.
Do i need to connect the ground reference to the ground used for the ecg signal?
And also, is ez430-RF2500 unable to convert negative values to positive
values?
You should see nothing but junk without common grounds.
Your input needs to be between Vref and Gnd.
--- In m..., glgoh@... wrote: >
> Just started working on ADC10 using ez430-RF2500. I tried to get values directly from the output of an amplified signal however it
looks so different from the value displayed on the oscilloscope. I
was supposed to get an ECG signal. >
> Do i need to connect the ground reference to the ground used for the ecg signal? And also, is ez430-RF2500 unable to convert negative
values to positive values? >
> This is the code i used to sample my signal.
>
> void main(void)
> {
> WDTCTL = WDTPW + WDTHOLD; // Stop WDT weili luv darek > ADC10CTL1 = CONSEQ_2 + INCH_3; // Repeat
single channel
> ADC10CTL0 = SREF_1 + ADC10SHT_1 + MSC + REFON + REF2_5V + ADC10ON + ADC10IE; > TACCR0 = 1000; //
Delay to allow Ref to settle > TACCTL0 |= CCIE; //
Compare-mode interrupt > TACTL = TASSEL_2 + MC_1; // TACLK
= SMCLK, Up mode > __bis_SR_register(CPUOFF + GIE); // LPM0,
TA0_ISR will force exit > TACCTL0 &= ~CCIE; //
Disable timer Interrupt > ADC10DTC1 = 0x08; // 8
conversions
> ADC10AE0 |= 0x08; // P2.0 ADC option select >
> for (;;)
> {
> ADC10CTL0 &= ~ENC;
> while (ADC10CTL1 & BUSY); // Wait if ADC10 core is active > ADC10SA = 0x200; // Data
buffer start
> ADC10CTL0 |= ENC + ADC10SC; // Sampling and conversion start > __bis_SR_register(CPUOFF + GIE); // LPM0,
ADC10_ISR will force exit > printf("%d\n" , ADC10MEM);
> }
> }
>
Reply by glgo...@hotmail.com●September 12, 20082008-09-12
What do you mean needs to be between Vref and Gnd?
>You should see nothing but junk without common
grounds.
>Your input needs to be between Vref and Gnd.
Reply by "e.tury"●September 12, 20082008-09-12
If Vref = 2.5volts and GND = 0 volts, the signal you want to convert
must be between these voltages. A voltage less than 0 may damage the
device. A voltage greater than 2.5 volts will always read 0x3FF, and if
goes above VCC may damage the device.
--- In m..., glgoh@... wrote: >
> What do you mean needs to be between Vref and Gnd?
>
> >You should see nothing but junk without common grounds.
> >Your input needs to be between Vref and Gnd.
>
Reply by aschuh●September 12, 20082008-09-12
You need to connect both grounds. Signalground and Vref ground on your
MSP430. The absolut maximum inputvoltage of the ADC10 is 3.6V.
So your inputsignal needs to be between 0V and 3.6V, no negative
Voltage allowed!
--- In m..., glgoh@... wrote: >
> What do you mean needs to be between Vref and Gnd?
>
> >You should see nothing but junk without common grounds.
> >Your input needs to be between Vref and Gnd.
>
Reply by glgo...@hotmail.com●September 12, 20082008-09-12
But my signal has negative. so what should i do den?
Reply by Dan Muzzey●September 12, 20082008-09-12
Are your trying to measure a negative signal with an A/D converter that
only goes between Vref and zero? Take a step back and ask yourself if
that should work.
________________________________
From: m... [mailto:m...] On Behalf
Of g...@hotmail.com
Sent: Friday, September 12, 2008 10:57 AM
To: m...
Subject: [msp430] Re: ADC10 unknown results?
But my signal has negative. so what should i do den?
Reply by f0rep1ay●September 12, 20082008-09-12
So u mean that if i set my Veref and V-eref to 2.5 V and -2.5 V
respectively. I would be able to get the values. And just a check, my
timer sampling rate isit at 1 KHz? Cos i set it to TACCR0 = 1000
--- In m..., "Dan Muzzey" wrote: >
> Are your trying to measure a negative signal with an A/D converter that > only goes between Vref and zero? Take a step back
and ask yourself if > that should work.
>
> ________________________________
>
> From: m... [mailto:m...] On Behalf > Of glgoh@...
> Sent: Friday, September 12, 2008 10:57 AM
> To: m...
> Subject: [msp430] Re: ADC10 unknown results?
>
> But my signal has negative. so what should i do den?
>
>
>
Reply by Dan Muzzey●September 12, 20082008-09-12
No.
That is unless you want to destroy the chip.
Follow these steps:
1. Get the data sheet.
2. Look up input ranges.
3. Realize that -1V is less than 0V
4. Design a circuit that will do what you need to do.
________________________________
From: m... [mailto:m...] On Behalf
Of f0rep1ay
Sent: Friday, September 12, 2008 11:14 AM
To: m...
Subject: [msp430] Re: ADC10 unknown results?
So u mean that if i set my Veref and V-eref to 2.5 V and -2.5 V
respectively. I would be able to get the values. And just a check, my
timer sampling rate isit at 1 KHz? Cos i set it to TACCR0 = 1000
--- In m... , "Dan
Muzzey" wrote: >
> Are your trying to measure a negative signal with an A/D converter that > only goes between Vref and zero? Take a step back and
ask yourself if > that should work.
>
> ________________________________
>
> From: m... [mailto:m... ] On
Behalf > Of glgoh@...
> Sent: Friday, September 12, 2008 10:57 AM
> To: m...
> Subject: [msp430] Re: ADC10 unknown results?
>
> But my signal has negative. so what should i do den?
>
>
>
Reply by f0rep1ay●September 12, 20082008-09-12
Sorry about acting noob. But here i am, just getting started on the
chip. I was told to use this chip and i hardly have any knowledge on
embedding system. Thought negative was possible due to 2's complement.
--- In m..., Onestone wrote: >
> You need to go away and study for about two years before coming here and > asking such stupid questions. Normally I try to think
that there isn't
> such a thing as a stupid question, but occasionally some people come
> along who should never have been allowed near an engineering class, and
> here I'll make an exception. These questions are so basic, and the
> answers should be so obvious even to a first term electronics student,
> that it sounds very troll like to me. Read the manual, read the data
> sheet, learn a few very basic principles of electronics and then try to
> attempt to actually design something. At the moment you haven't a
> snowballs chance in hell of even understanding the simplest answers that > you have already been given.
>
> Al
>
> f0rep1ay wrote:
>
> >So u mean that if i set my Veref and V-eref to 2.5 V and -2.5 V
> >respectively. I would be able to get the values. And just a check, my
> >timer sampling rate isit at 1 KHz? Cos i set it to TACCR0 = 1000
> >
> >--- In m..., "Dan Muzzey" wrote:
> >
> >
> >>Are your trying to measure a negative signal with an A/D converter
> >>
> >>
> >that
> >
> >
> >>only goes between Vref and zero? Take a step back and ask yourself
> >>
> >>
> >if
> >
> >
> >>that should work.
> >>
> >>________________________________
> >>
> >>From: m... [mailto:m...] On
> >>
> >>
> >Behalf
> >
> >
> >>Of glgoh@
> >>Sent: Friday, September 12, 2008 10:57 AM
> >>To: m...
> >>Subject: [msp430] Re: ADC10 unknown results?
> >>
> >>But my signal has negative. so what should i do den?
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >
> >
> >
> >
> >
> >
> >
> >