Software based test for ADC

Hello to all,

I m working on the wireless product which is having the DSP, ADC, WLAN
chipset, LCD, ect. Now as a part of this project, i m working on the
Power ON Self diagnostic test for all the major components.
In our project the ADC is not yet finalised but it is 16 bit SAR type.
Is there any standard procedure to test the functionality of ADC, like
memory testing. Could any one please refer some information in
regards.

Thanks in advance.

Nutty

"Nutty" <nutty.sawant@gmail.com> wrote in message 
news:1179910053.928348.106850@m36g2000hse.googlegroups.com...
> Hello to all,
>
> I m working on the wireless product which is having the DSP, ADC, WLAN
> chipset, LCD, ect. Now as a part of this project, i m working on the
> Power ON Self diagnostic test for all the major components.
> In our project the ADC is not yet finalised but it is 16 bit SAR type.
> Is there any standard procedure to test the functionality of ADC, like
> memory testing. Could any one please refer some information in
> regards.
>
> Thanks in advance.
>
> Nutty

You could read a known voltage. 

Nutty wrote:
> Hello to all,
> 
> I m working on the wireless product which is having the DSP, ADC, WLAN
> chipset, LCD, ect. Now as a part of this project, i m working on the
> Power ON Self diagnostic test for all the major components.
> In our project the ADC is not yet finalised but it is 16 bit SAR type.
> Is there any standard procedure to test the functionality of ADC, like
> memory testing. Could any one please refer some information in
> regards.

Normally, you arrange a known voltage(s) onto the ADC IPs.
If you have any PWM channels, they can be good for this, as
they give very precise Vcc ratio test levels thru a LPF.
For a less precise test, but quicker test, a slowish ramp into the ADC, 
coupled with timed-samples, could be used.

-jg

Nutty <nutty.sawant@gmail.com> posted:

"[..] Now as a part of this project, i m working on the
Power ON Self diagnostic test for all the major components.
In our project the ADC is not yet finalised but it is 16 bit SAR type.
Is there any standard procedure to test the functionality of ADC, like
memory testing. Could any one please refer some information in
regards."

Hello,

In general this can not be accomplished, especially in the case of a
self diagnostic test in a deployed product which you do not have
access to. For example, how can the software control (and therefore
know the true value of) whatever physical quantity which the ADC is
trying to measure? If the true value is not known, the value reported
by the ADC can not in general be validated.

After you have finalized which ADC you will use, your software may be
able to perform some checks without human intervention, for example if the
manufacturer has documented that the ADC will take at most a
predetermined amount of time after being powered on to function
correctly, and if the manufacturer has documented that some reply
(unfortunately not actually the analog to digital conversion readings)
pins will behave in a particular way in response to particular
commands from the computer (for example command it to change some parameters
and afterwards read its configuration to check whether those
parameters are reported back), you could try something but testing
whether analog to digital conversions actually work would not be
possible.

Manually test your product's ADC (e.g. by providing it with input
which you vary with a potentiometer or if your product's ADC will be
connected to for example a speedometer, move it at known speeds)
before releasing the product to the customer.

Regards,
Colin Paul Gloster

In article <1179910053.928348.106850@m36g2000hse.googlegroups.com>, 
nutty.sawant@gmail.com says...
> Hello to all,
> 
> I m working on the wireless product which is having the DSP, ADC, WLAN
> chipset, LCD, ect. Now as a part of this project, i m working on the
> Power ON Self diagnostic test for all the major components.
> In our project the ADC is not yet finalised but it is 16 bit SAR type.
> Is there any standard procedure to test the functionality of ADC, like
> memory testing. Could any one please refer some information in
> regards.
> 
> Thanks in advance.


In some data logging applications,  I have been able to get a startup
confidence check on the ADC by connecting one of the multi-channel
ADC inputs to a resistor-divider connected to an IO pin on the MPU.
You  set the I/O pin high and measure the signal with the ADC.
Then set the pin low and measure the signal again.  If the two values
are within your confidence limits, you can assume that the ADC is
working.

If you have just a single-channel ADC, you would have to add a 
multiplexer on the input to use this technique, and that has
other implications for the stability and accuracy of the ADC data.

Mark Borgerson

Nutty wrote:

> Hello to all,
> 
> I m working on the wireless product which is having the DSP, ADC, WLAN
> chipset, LCD, ect. Now as a part of this project, i m working on the
> Power ON Self diagnostic test for all the major components.
> In our project the ADC is not yet finalised but it is 16 bit SAR type.
> Is there any standard procedure to test the functionality of ADC, like
> memory testing. Could any one please refer some information in
> regards.

While the decisions about the product design are still in the melting pot it
would be worth working through what sort of tests you would be satisfied
with and ensuring that the hardware support for those tests were designed
in. 

I would suggest having perhaps a zero and span check where you switch in the
appropriate levels while doing the data read check. You might have to fight
for a know mid value check. This is not an exhaustive check and, with a
multiplying DAC you could even self calibrate the input.

-- 
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Forth based HIDECS Consultancy .....<http://www.amleth.demon.co.uk/>
Mob: +44 (0)7811-639972
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