Dear Readers,
I like to use the LPC2148 for a project but have some questions.
--Question 1--
In the datasheets there is a note for ADC-input regarding voltages above
VDD (just in case the pins are used as 5V tolerant input)
For instance if P0.5/ADC0.7 and P0.4/ADC0.6 are used as ADC input then a
voltage greater than 3.3V on ADC0.7 will disturb a measurement of ADC0.6.
Now the question: If P0.5/ADC0.7 is not setup as ADC input, can it be
used as a 5V tolerant input without disturbing the P0.4/ADC0.6 input?
The User Manual writes:
'An inside circuit disconnects ADC hardware from the associated
pin whenever a digital function is selected on that pin.'
So I think it is Ok but I would like to hear a confirmation before
designing the pcb.
--Question 2--
A low on P0.14 while the LPC2148 resets will force the bootloader to
become active. P0.14 also supports the SDA function of the I2C1
controller. Now suppose that there is a I2C communication in process,
SDA is pulled 'low' by a I2C-device on the I2C bus and suddenly a
reset
occurs. (caused by a dip in the powersupply or something)
Does this result in a system stop because it starts the bootloader
instead of restarting the application?
Thanks in advance,
Aalt
--
=============================Aalt Lokhorst
Schut Geometrische Meettechniek bv
Duinkerkenstraat 21
9723 BN Groningen
P.O. Box 5225
9700 GE Groningen
The Netherlands
Tel: +31-50-5877877
Fax: +31-50-5877899
E-mail: L...@Schut.com
=============================
LPC2148 ADC input and bootloader questions
Started by ●December 7, 2006
Reply by ●December 7, 20062006-12-07
--- In l..., "Aalt Lokhorst" wrote:
> --Question 1--
> In the datasheets there is a note for ADC-input regarding voltages
above
> VDD (just in case the pins are used as 5V tolerant input)
> For instance if P0.5/ADC0.7 and P0.4/ADC0.6 are used as ADC input
then a
> voltage greater than 3.3V on ADC0.7 will disturb a measurement of
ADC0.6.
>
> Now the question: If P0.5/ADC0.7 is not setup as ADC input, can it
be
> used as a 5V tolerant input without disturbing the P0.4/ADC0.6
input?
>
> The User Manual writes:
> 'An inside circuit disconnects ADC hardware from the associated
> pin whenever a digital function is selected on that pin.'
>
> So I think it is Ok but I would like to hear a confirmation before
> designing the pcb.
>
I'm not 100% sure about the LPC2148, but on some of the devices this
is NOT a safe assumption: having voltages higher than 3V3 on pins
that have an ADC function causes invalid results on other ADC pins,
even if the pin with the higher voltage is not configured for ADC.
You should really get this question asnwered definitively by NXP for
the particular device before proceeding (not every piece of info
posted here is correct).
>
> --Question 2--
> A low on P0.14 while the LPC2148 resets will force the bootloader
to
> become active. P0.14 also supports the SDA function of the I2C1
> controller. Now suppose that there is a I2C communication in
process,
> SDA is pulled 'low' by a I2C-device on the I2C bus and suddenly a
reset
> occurs. (caused by a dip in the powersupply or something)
> Does this result in a system stop because it starts the bootloader
> instead of restarting the application?
>
> Thanks in advance,
> Aalt
>
> --
Just shows what a bad idea sharing the bootloader request pin in with
other functions actually is.....
I'd avoid if at all possible using this pin for anything other than a
bootloader request.
Brendan
> --Question 1--
> In the datasheets there is a note for ADC-input regarding voltages
above
> VDD (just in case the pins are used as 5V tolerant input)
> For instance if P0.5/ADC0.7 and P0.4/ADC0.6 are used as ADC input
then a
> voltage greater than 3.3V on ADC0.7 will disturb a measurement of
ADC0.6.
>
> Now the question: If P0.5/ADC0.7 is not setup as ADC input, can it
be
> used as a 5V tolerant input without disturbing the P0.4/ADC0.6
input?
>
> The User Manual writes:
> 'An inside circuit disconnects ADC hardware from the associated
> pin whenever a digital function is selected on that pin.'
>
> So I think it is Ok but I would like to hear a confirmation before
> designing the pcb.
>
I'm not 100% sure about the LPC2148, but on some of the devices this
is NOT a safe assumption: having voltages higher than 3V3 on pins
that have an ADC function causes invalid results on other ADC pins,
even if the pin with the higher voltage is not configured for ADC.
You should really get this question asnwered definitively by NXP for
the particular device before proceeding (not every piece of info
posted here is correct).
>
> --Question 2--
> A low on P0.14 while the LPC2148 resets will force the bootloader
to
> become active. P0.14 also supports the SDA function of the I2C1
> controller. Now suppose that there is a I2C communication in
process,
> SDA is pulled 'low' by a I2C-device on the I2C bus and suddenly a
reset
> occurs. (caused by a dip in the powersupply or something)
> Does this result in a system stop because it starts the bootloader
> instead of restarting the application?
>
> Thanks in advance,
> Aalt
>
> --
Just shows what a bad idea sharing the bootloader request pin in with
other functions actually is.....
I'd avoid if at all possible using this pin for anything other than a
bootloader request.
Brendan
Reply by ●December 7, 20062006-12-07
1) as far as I understand it as well yes,
2) it's up to you to ensure that you pull P0.14 up during any form of board
reset or it will as you suggest simply sit in the bootloader.
(assuming you have a common power supply for your I2C device and that you're
using some form of conditioning chip to monitor the power levels and hence
control the RST line, can you not simply apply this RST to your I2C device
as well to ensure it's not playing havoc with the bus during a chip reset?
Just a thought.
Andy
-----Original Message-----
From: l... [mailto:l...]On Behalf Of
Aalt Lokhorst
Sent: 07 December 2006 13:49
To: l...
Subject: [lpc2000] LPC2148 ADC input and bootloader questions
Dear Readers,
I like to use the LPC2148 for a project but have some questions.
--Question 1--
In the datasheets there is a note for ADC-input regarding voltages above
VDD (just in case the pins are used as 5V tolerant input)
For instance if P0.5/ADC0.7 and P0.4/ADC0.6 are used as ADC input then a
voltage greater than 3.3V on ADC0.7 will disturb a measurement of ADC0.6.
Now the question: If P0.5/ADC0.7 is not setup as ADC input, can it be
used as a 5V tolerant input without disturbing the P0.4/ADC0.6 input?
The User Manual writes:
'An inside circuit disconnects ADC hardware from the associated
pin whenever a digital function is selected on that pin.'
So I think it is Ok but I would like to hear a confirmation before
designing the pcb.
--Question 2--
A low on P0.14 while the LPC2148 resets will force the bootloader to
become active. P0.14 also supports the SDA function of the I2C1
controller. Now suppose that there is a I2C communication in process,
SDA is pulled 'low' by a I2C-device on the I2C bus and suddenly a reset
occurs. (caused by a dip in the powersupply or something)
Does this result in a system stop because it starts the bootloader
instead of restarting the application?
Thanks in advance,
Aalt
--
============================= Aalt Lokhorst
Schut Geometrische Meettechniek bv
Duinkerkenstraat 21
9723 BN Groningen
P.O. Box 5225
9700 GE Groningen
The Netherlands
Tel: +31-50-5877877
Fax: +31-50-5877899
E-mail: L...@Schut.com
=============================
2) it's up to you to ensure that you pull P0.14 up during any form of board
reset or it will as you suggest simply sit in the bootloader.
(assuming you have a common power supply for your I2C device and that you're
using some form of conditioning chip to monitor the power levels and hence
control the RST line, can you not simply apply this RST to your I2C device
as well to ensure it's not playing havoc with the bus during a chip reset?
Just a thought.
Andy
-----Original Message-----
From: l... [mailto:l...]On Behalf Of
Aalt Lokhorst
Sent: 07 December 2006 13:49
To: l...
Subject: [lpc2000] LPC2148 ADC input and bootloader questions
Dear Readers,
I like to use the LPC2148 for a project but have some questions.
--Question 1--
In the datasheets there is a note for ADC-input regarding voltages above
VDD (just in case the pins are used as 5V tolerant input)
For instance if P0.5/ADC0.7 and P0.4/ADC0.6 are used as ADC input then a
voltage greater than 3.3V on ADC0.7 will disturb a measurement of ADC0.6.
Now the question: If P0.5/ADC0.7 is not setup as ADC input, can it be
used as a 5V tolerant input without disturbing the P0.4/ADC0.6 input?
The User Manual writes:
'An inside circuit disconnects ADC hardware from the associated
pin whenever a digital function is selected on that pin.'
So I think it is Ok but I would like to hear a confirmation before
designing the pcb.
--Question 2--
A low on P0.14 while the LPC2148 resets will force the bootloader to
become active. P0.14 also supports the SDA function of the I2C1
controller. Now suppose that there is a I2C communication in process,
SDA is pulled 'low' by a I2C-device on the I2C bus and suddenly a reset
occurs. (caused by a dip in the powersupply or something)
Does this result in a system stop because it starts the bootloader
instead of restarting the application?
Thanks in advance,
Aalt
--
============================= Aalt Lokhorst
Schut Geometrische Meettechniek bv
Duinkerkenstraat 21
9723 BN Groningen
P.O. Box 5225
9700 GE Groningen
The Netherlands
Tel: +31-50-5877877
Fax: +31-50-5877899
E-mail: L...@Schut.com
=============================
Reply by ●December 7, 20062006-12-07
Look what is written on the errata sheet for 2129:
"AINx.1 Corruption of an ADC conversion if any of the ADC input pins
has a voltage higher than V3A.
Problem: The result of an ADC conversion will be corrupted if any of
the GPIO pins which have an analog input as an alternate function is
connected to a voltage higher than V 3A."
The important point is:
"----any of the GPIO pins which have an analog input as an alternate
function---"
Look at the errata sheet for your device, 2148.
And good lucky.
;)
--- In l..., "Brendan Murphy"
wrote:
>
> --- In l..., "Aalt Lokhorst" wrote:
> > --Question 1--
> > In the datasheets there is a note for ADC-input regarding
voltages
> above
> > VDD (just in case the pins are used as 5V tolerant input)
> > For instance if P0.5/ADC0.7 and P0.4/ADC0.6 are used as ADC input
> then a
> > voltage greater than 3.3V on ADC0.7 will disturb a measurement of
> ADC0.6.
> >
> > Now the question: If P0.5/ADC0.7 is not setup as ADC input, can
it
> be
> > used as a 5V tolerant input without disturbing the P0.4/ADC0.6
> input?
> >
> > The User Manual writes:
> > 'An inside circuit disconnects ADC hardware from the associated
> > pin whenever a digital function is selected on that pin.'
> >
> > So I think it is Ok but I would like to hear a confirmation
before
> > designing the pcb.
> > I'm not 100% sure about the LPC2148, but on some of the devices
this
> is NOT a safe assumption: having voltages higher than 3V3 on pins
> that have an ADC function causes invalid results on other ADC pins,
> even if the pin with the higher voltage is not configured for ADC.
>
> You should really get this question asnwered definitively by NXP
for
> the particular device before proceeding (not every piece of info
> posted here is correct).
>
> >
> > --Question 2--
> > A low on P0.14 while the LPC2148 resets will force the bootloader
> to
> > become active. P0.14 also supports the SDA function of the I2C1
> > controller. Now suppose that there is a I2C communication in
> process,
> > SDA is pulled 'low' by a I2C-device on the I2C bus and suddenly a
> reset
> > occurs. (caused by a dip in the powersupply or something)
> > Does this result in a system stop because it starts the
bootloader
> > instead of restarting the application?
> >
> > Thanks in advance,
> > Aalt
> >
> > --
>
> Just shows what a bad idea sharing the bootloader request pin in
with
> other functions actually is.....
>
> I'd avoid if at all possible using this pin for anything other than
a
> bootloader request.
>
> Brendan
>
"AINx.1 Corruption of an ADC conversion if any of the ADC input pins
has a voltage higher than V3A.
Problem: The result of an ADC conversion will be corrupted if any of
the GPIO pins which have an analog input as an alternate function is
connected to a voltage higher than V 3A."
The important point is:
"----any of the GPIO pins which have an analog input as an alternate
function---"
Look at the errata sheet for your device, 2148.
And good lucky.
;)
--- In l..., "Brendan Murphy"
wrote:
>
> --- In l..., "Aalt Lokhorst" wrote:
> > --Question 1--
> > In the datasheets there is a note for ADC-input regarding
voltages
> above
> > VDD (just in case the pins are used as 5V tolerant input)
> > For instance if P0.5/ADC0.7 and P0.4/ADC0.6 are used as ADC input
> then a
> > voltage greater than 3.3V on ADC0.7 will disturb a measurement of
> ADC0.6.
> >
> > Now the question: If P0.5/ADC0.7 is not setup as ADC input, can
it
> be
> > used as a 5V tolerant input without disturbing the P0.4/ADC0.6
> input?
> >
> > The User Manual writes:
> > 'An inside circuit disconnects ADC hardware from the associated
> > pin whenever a digital function is selected on that pin.'
> >
> > So I think it is Ok but I would like to hear a confirmation
before
> > designing the pcb.
> > I'm not 100% sure about the LPC2148, but on some of the devices
this
> is NOT a safe assumption: having voltages higher than 3V3 on pins
> that have an ADC function causes invalid results on other ADC pins,
> even if the pin with the higher voltage is not configured for ADC.
>
> You should really get this question asnwered definitively by NXP
for
> the particular device before proceeding (not every piece of info
> posted here is correct).
>
> >
> > --Question 2--
> > A low on P0.14 while the LPC2148 resets will force the bootloader
> to
> > become active. P0.14 also supports the SDA function of the I2C1
> > controller. Now suppose that there is a I2C communication in
> process,
> > SDA is pulled 'low' by a I2C-device on the I2C bus and suddenly a
> reset
> > occurs. (caused by a dip in the powersupply or something)
> > Does this result in a system stop because it starts the
bootloader
> > instead of restarting the application?
> >
> > Thanks in advance,
> > Aalt
> >
> > --
>
> Just shows what a bad idea sharing the bootloader request pin in
with
> other functions actually is.....
>
> I'd avoid if at all possible using this pin for anything other than
a
> bootloader request.
>
> Brendan
>
Reply by ●December 8, 20062006-12-08
Thanks Brendan, Andy and others,
I will forget about using the P0.14 pin for I2C communication.
I hope that I can reach someone at NXP for the ADC-input related
question. I know about the problems in the LPC2129 (I have used that
device also) The LPC2129 has only 4 ADC-inputs, so reserving these pins
was not a real problem. For the LPC2148 the story is different. I need
only a few ADC-inputs and it would be nice to use the other pins for 5V
tolerant GPIO without disturbing the ADC.
Thanks again,
Aalt
--
=============================Aalt Lokhorst
Schut Geometrische Meettechniek bv
Duinkerkenstraat 21
9723 BN Groningen
P.O. Box 5225
9700 GE Groningen
The Netherlands
Tel: +31-50-5877877
Fax: +31-50-5877899
E-mail: L...@Schut.com
=======================
I will forget about using the P0.14 pin for I2C communication.
I hope that I can reach someone at NXP for the ADC-input related
question. I know about the problems in the LPC2129 (I have used that
device also) The LPC2129 has only 4 ADC-inputs, so reserving these pins
was not a real problem. For the LPC2148 the story is different. I need
only a few ADC-inputs and it would be nice to use the other pins for 5V
tolerant GPIO without disturbing the ADC.
Thanks again,
Aalt
--
=============================Aalt Lokhorst
Schut Geometrische Meettechniek bv
Duinkerkenstraat 21
9723 BN Groningen
P.O. Box 5225
9700 GE Groningen
The Netherlands
Tel: +31-50-5877877
Fax: +31-50-5877899
E-mail: L...@Schut.com
=======================
Reply by ●December 8, 20062006-12-08
I took a look on
http://www.standardics.nxp.com/support/documents/microcontrollers/pdf/errata.lpc2148.pdf
Theres no recommendation for not to use these pins as 5V tolerant, even if
they have ADC funcionallity.
:)
Good Lucky and I recommend you test it first.
;)
On 08/12/06, Aalt Lokhorst wrote:
>
> Thanks Brendan, Andy and others,
>
> I will forget about using the P0.14 pin for I2C communication.
>
> I hope that I can reach someone at NXP for the ADC-input related
> question. I know about the problems in the LPC2129 (I have used that
> device also) The LPC2129 has only 4 ADC-inputs, so reserving these pins
> was not a real problem. For the LPC2148 the story is different. I need
> only a few ADC-inputs and it would be nice to use the other pins for 5V
> tolerant GPIO without disturbing the ADC.
>
> Thanks again,
> Aalt
>
> --
> =============================> Aalt Lokhorst
> Schut Geometrische Meettechniek bv
> Duinkerkenstraat 21
> 9723 BN Groningen
> P.O. Box 5225
> 9700 GE Groningen
> The Netherlands
> Tel: +31-50-5877877
> Fax: +31-50-5877899
> E-mail: L...@Schut.com
> =======================>
--
Thiago Pinheiro Felix da Silva e Lima
Engenheiro
http://www.standardics.nxp.com/support/documents/microcontrollers/pdf/errata.lpc2148.pdf
Theres no recommendation for not to use these pins as 5V tolerant, even if
they have ADC funcionallity.
:)
Good Lucky and I recommend you test it first.
;)
On 08/12/06, Aalt Lokhorst wrote:
>
> Thanks Brendan, Andy and others,
>
> I will forget about using the P0.14 pin for I2C communication.
>
> I hope that I can reach someone at NXP for the ADC-input related
> question. I know about the problems in the LPC2129 (I have used that
> device also) The LPC2129 has only 4 ADC-inputs, so reserving these pins
> was not a real problem. For the LPC2148 the story is different. I need
> only a few ADC-inputs and it would be nice to use the other pins for 5V
> tolerant GPIO without disturbing the ADC.
>
> Thanks again,
> Aalt
>
> --
> =============================> Aalt Lokhorst
> Schut Geometrische Meettechniek bv
> Duinkerkenstraat 21
> 9723 BN Groningen
> P.O. Box 5225
> 9700 GE Groningen
> The Netherlands
> Tel: +31-50-5877877
> Fax: +31-50-5877899
> E-mail: L...@Schut.com
> =======================>
--
Thiago Pinheiro Felix da Silva e Lima
Engenheiro
Reply by ●December 8, 20062006-12-08
Actually given you're having to do this anyway can you let us all know -
obviously if you do run into this and find that it is still actually a
problem it's quite important that we let Philips know... I'd hope that it
isn't an issue that affects this variant but without empirical evidence it's
one of those worrying things at the back of your mind... either way it'd be
useful for us to hear what you find out, so keep us all informed :) and good
luck...
Andy
-----Original Message-----
From: l... [mailto:l...]On Behalf Of
Thiago Pinheiro Felix da Silva e Lima
Sent: 08 December 2006 13:06
To: l...
Subject: Re: [lpc2000] LPC2148 ADC input and bootloader questions
I took a look on
http://www.standardics.nxp.com/support/documents/microcontrollers/pdf/erra
ta.lpc2148.pdf
Theres no recommendation for not to use these pins as 5V tolerant, even
if
they have ADC funcionallity.
:)
Good Lucky and I recommend you test it first.
;)
On 08/12/06, Aalt Lokhorst wrote:
>
> Thanks Brendan, Andy and others,
>
> I will forget about using the P0.14 pin for I2C communication.
>
> I hope that I can reach someone at NXP for the ADC-input related
> question. I know about the problems in the LPC2129 (I have used that
> device also) The LPC2129 has only 4 ADC-inputs, so reserving these pins
> was not a real problem. For the LPC2148 the story is different. I need
> only a few ADC-inputs and it would be nice to use the other pins for 5V
> tolerant GPIO without disturbing the ADC.
>
> Thanks again,
> Aalt
>
> --
> ============================= > Aalt Lokhorst
> Schut Geometrische Meettechniek bv
> Duinkerkenstraat 21
> 9723 BN Groningen
> P.O. Box 5225
> 9700 GE Groningen
> The Netherlands
> Tel: +31-50-5877877
> Fax: +31-50-5877899
> E-mail: L...@Schut.com
> ======================= >
>
>
--
Thiago Pinheiro Felix da Silva e Lima
Engenheiro
obviously if you do run into this and find that it is still actually a
problem it's quite important that we let Philips know... I'd hope that it
isn't an issue that affects this variant but without empirical evidence it's
one of those worrying things at the back of your mind... either way it'd be
useful for us to hear what you find out, so keep us all informed :) and good
luck...
Andy
-----Original Message-----
From: l... [mailto:l...]On Behalf Of
Thiago Pinheiro Felix da Silva e Lima
Sent: 08 December 2006 13:06
To: l...
Subject: Re: [lpc2000] LPC2148 ADC input and bootloader questions
I took a look on
http://www.standardics.nxp.com/support/documents/microcontrollers/pdf/erra
ta.lpc2148.pdf
Theres no recommendation for not to use these pins as 5V tolerant, even
if
they have ADC funcionallity.
:)
Good Lucky and I recommend you test it first.
;)
On 08/12/06, Aalt Lokhorst wrote:
>
> Thanks Brendan, Andy and others,
>
> I will forget about using the P0.14 pin for I2C communication.
>
> I hope that I can reach someone at NXP for the ADC-input related
> question. I know about the problems in the LPC2129 (I have used that
> device also) The LPC2129 has only 4 ADC-inputs, so reserving these pins
> was not a real problem. For the LPC2148 the story is different. I need
> only a few ADC-inputs and it would be nice to use the other pins for 5V
> tolerant GPIO without disturbing the ADC.
>
> Thanks again,
> Aalt
>
> --
> ============================= > Aalt Lokhorst
> Schut Geometrische Meettechniek bv
> Duinkerkenstraat 21
> 9723 BN Groningen
> P.O. Box 5225
> 9700 GE Groningen
> The Netherlands
> Tel: +31-50-5877877
> Fax: +31-50-5877899
> E-mail: L...@Schut.com
> ======================= >
>
>
--
Thiago Pinheiro Felix da Silva e Lima
Engenheiro
Reply by ●December 8, 20062006-12-08
Thiago wrote
> I took a look on
> http://www.standardics.nxp.com/support/documents/microcontrollers/pdf/errata.lpc2148.pdf
> There4s no recommendation for not to use these pins as 5V tolerant, even if
> they have ADC funcionallity.
>
> :)
>
> Good Lucky and I recommend you test it first.
>
> ;)
I also have the impression that it should be Ok. But I will sleep better
if it is confirmed. I have called the product specialist of our
distributor and he will investigate it.
Next week I might have a better answer,
Have a nice weekend,
Aalt
--
=============================Aalt Lokhorst
Schut Geometrische Meettechniek bv
Duinkerkenstraat 21
9723 BN Groningen
P.O. Box 5225
9700 GE Groningen
The Netherlands
Tel: +31-50-5877877
Fax: +31-50-5877899
E-mail: L...@Schut.com
=============================
> I took a look on
> http://www.standardics.nxp.com/support/documents/microcontrollers/pdf/errata.lpc2148.pdf
> There4s no recommendation for not to use these pins as 5V tolerant, even if
> they have ADC funcionallity.
>
> :)
>
> Good Lucky and I recommend you test it first.
>
> ;)
I also have the impression that it should be Ok. But I will sleep better
if it is confirmed. I have called the product specialist of our
distributor and he will investigate it.
Next week I might have a better answer,
Have a nice weekend,
Aalt
--
=============================Aalt Lokhorst
Schut Geometrische Meettechniek bv
Duinkerkenstraat 21
9723 BN Groningen
P.O. Box 5225
9700 GE Groningen
The Netherlands
Tel: +31-50-5877877
Fax: +31-50-5877899
E-mail: L...@Schut.com
=============================
Reply by ●December 8, 20062006-12-08
I think you're taking the sensible approach (of getting it confirmed
from NXP). There's enough ambiguity in the following statement in the
User Manual to at least raise the question:
Note: if the ADC is used, signal levels on analog input pins must not
be above the level of V3A at any time. Otherwise, A/D converter
readings will be invalid.
Having been bitten by this particular issue (before it was documented
anywhere) on the LPC2134, I'd get it confirmed before proceeding.
Brendan.
--- In l..., "Aalt Lokhorst" wrote:
>
> Thiago wrote
> > I took a look on
> >
http://www.standardics.nxp.com/support/documents/microcontrollers/pdf/
errata.lpc2148.pdf
> > There4s no recommendation for not to use these pins as 5V
tolerant, even if
> > they have ADC funcionallity.
> >
> > :)
> >
> > Good Lucky and I recommend you test it first.
> >
> > ;)
>
> I also have the impression that it should be Ok. But I will sleep
better
> if it is confirmed. I have called the product specialist of our
> distributor and he will investigate it.
>
> Next week I might have a better answer,
>
> Have a nice weekend,
> Aalt
>
> --
> =============================> Aalt Lokhorst
> Schut Geometrische Meettechniek bv
> Duinkerkenstraat 21
> 9723 BN Groningen
> P.O. Box 5225
> 9700 GE Groningen
> The Netherlands
> Tel: +31-50-5877877
> Fax: +31-50-5877899
> E-mail: Lokhorst@...
> =============================>
from NXP). There's enough ambiguity in the following statement in the
User Manual to at least raise the question:
Note: if the ADC is used, signal levels on analog input pins must not
be above the level of V3A at any time. Otherwise, A/D converter
readings will be invalid.
Having been bitten by this particular issue (before it was documented
anywhere) on the LPC2134, I'd get it confirmed before proceeding.
Brendan.
--- In l..., "Aalt Lokhorst" wrote:
>
> Thiago wrote
> > I took a look on
> >
http://www.standardics.nxp.com/support/documents/microcontrollers/pdf/
errata.lpc2148.pdf
> > There4s no recommendation for not to use these pins as 5V
tolerant, even if
> > they have ADC funcionallity.
> >
> > :)
> >
> > Good Lucky and I recommend you test it first.
> >
> > ;)
>
> I also have the impression that it should be Ok. But I will sleep
better
> if it is confirmed. I have called the product specialist of our
> distributor and he will investigate it.
>
> Next week I might have a better answer,
>
> Have a nice weekend,
> Aalt
>
> --
> =============================> Aalt Lokhorst
> Schut Geometrische Meettechniek bv
> Duinkerkenstraat 21
> 9723 BN Groningen
> P.O. Box 5225
> 9700 GE Groningen
> The Netherlands
> Tel: +31-50-5877877
> Fax: +31-50-5877899
> E-mail: Lokhorst@...
> =============================>
Reply by ●December 8, 20062006-12-08
RE: Bootloader questions
The simple fact is that the bootloader always runs after an external
(hardware) reset. It is the bootloader that starts ISP mode if 0.14 is low.
Internal hardware maps the bootloader interrupt vectors into address 0.
If there is a hardware reset, and P0.14 is low for upto 3ms or there is no
valid code checksum in user flash then the bootloader will run ISP mode.
P0.14 must remain high for at least 3ms after a hardware reset to prevent a
forced boot loader isp mode entry.
The bootloader is not mapped into address 0 if an internal watchdog reset
occurs or the program counter is reset to zero by software.
I suggest adding a FET that disconnects your SDA signal if reset is active
low and keeps it that way for at least 3ms after. SDA has to be pulled up
anyway, so just put the pullup on the CPU side of the FET.
You can achieve this using your reset circuit or, using just discrete
transistors and capacitors.
If you wish to use the ISP then add another FET to pull p0.14 low as and
when required.
j.
-----Original Message-----
From: l... [mailto:l...]On Behalf Of
Aalt Lokhorst
Sent: 07 December 2006 13:49
To: l...
Subject: [lpc2000] LPC2148 ADC input and bootloader questions
Dear Readers,
I like to use the LPC2148 for a project but have some questions.
--Question 1--
In the datasheets there is a note for ADC-input regarding voltages above
VDD (just in case the pins are used as 5V tolerant input)
For instance if P0.5/ADC0.7 and P0.4/ADC0.6 are used as ADC input then a
voltage greater than 3.3V on ADC0.7 will disturb a measurement of ADC0.6.
Now the question: If P0.5/ADC0.7 is not setup as ADC input, can it be
used as a 5V tolerant input without disturbing the P0.4/ADC0.6 input?
The User Manual writes:
'An inside circuit disconnects ADC hardware from the associated
pin whenever a digital function is selected on that pin.'
So I think it is Ok but I would like to hear a confirmation before
designing the pcb.
--Question 2--
A low on P0.14 while the LPC2148 resets will force the bootloader to
become active. P0.14 also supports the SDA function of the I2C1
controller. Now suppose that there is a I2C communication in process,
SDA is pulled 'low' by a I2C-device on the I2C bus and suddenly a reset
occurs. (caused by a dip in the powersupply or something)
Does this result in a system stop because it starts the bootloader
instead of restarting the application?
Thanks in advance,
Aalt
--
============================= Aalt Lokhorst
Schut Geometrische Meettechniek bv
Duinkerkenstraat 21
9723 BN Groningen
P.O. Box 5225
9700 GE Groningen
The Netherlands
Tel: +31-50-5877877
Fax: +31-50-5877899
E-mail: L...@Schut.com
=============================
The simple fact is that the bootloader always runs after an external
(hardware) reset. It is the bootloader that starts ISP mode if 0.14 is low.
Internal hardware maps the bootloader interrupt vectors into address 0.
If there is a hardware reset, and P0.14 is low for upto 3ms or there is no
valid code checksum in user flash then the bootloader will run ISP mode.
P0.14 must remain high for at least 3ms after a hardware reset to prevent a
forced boot loader isp mode entry.
The bootloader is not mapped into address 0 if an internal watchdog reset
occurs or the program counter is reset to zero by software.
I suggest adding a FET that disconnects your SDA signal if reset is active
low and keeps it that way for at least 3ms after. SDA has to be pulled up
anyway, so just put the pullup on the CPU side of the FET.
You can achieve this using your reset circuit or, using just discrete
transistors and capacitors.
If you wish to use the ISP then add another FET to pull p0.14 low as and
when required.
j.
-----Original Message-----
From: l... [mailto:l...]On Behalf Of
Aalt Lokhorst
Sent: 07 December 2006 13:49
To: l...
Subject: [lpc2000] LPC2148 ADC input and bootloader questions
Dear Readers,
I like to use the LPC2148 for a project but have some questions.
--Question 1--
In the datasheets there is a note for ADC-input regarding voltages above
VDD (just in case the pins are used as 5V tolerant input)
For instance if P0.5/ADC0.7 and P0.4/ADC0.6 are used as ADC input then a
voltage greater than 3.3V on ADC0.7 will disturb a measurement of ADC0.6.
Now the question: If P0.5/ADC0.7 is not setup as ADC input, can it be
used as a 5V tolerant input without disturbing the P0.4/ADC0.6 input?
The User Manual writes:
'An inside circuit disconnects ADC hardware from the associated
pin whenever a digital function is selected on that pin.'
So I think it is Ok but I would like to hear a confirmation before
designing the pcb.
--Question 2--
A low on P0.14 while the LPC2148 resets will force the bootloader to
become active. P0.14 also supports the SDA function of the I2C1
controller. Now suppose that there is a I2C communication in process,
SDA is pulled 'low' by a I2C-device on the I2C bus and suddenly a reset
occurs. (caused by a dip in the powersupply or something)
Does this result in a system stop because it starts the bootloader
instead of restarting the application?
Thanks in advance,
Aalt
--
============================= Aalt Lokhorst
Schut Geometrische Meettechniek bv
Duinkerkenstraat 21
9723 BN Groningen
P.O. Box 5225
9700 GE Groningen
The Netherlands
Tel: +31-50-5877877
Fax: +31-50-5877899
E-mail: L...@Schut.com
=============================
