Problem with single ended ADC example project CY8CKIT-030

Don't worry about the placing of your question, we'll find it as long as you use a PSoC 3 entry, forum software is not capable of editing or re-positioning a post (to be true, forum software isn't capable of many things at all)..

There are some knowledge-base entries concerning your issue: Since ADC cannot be made totally error-free they always show some mismatching, but this can be calculated-off with some simple math.

Errors you find are

- Noise

- Offset Error

- Gain error

- Temerature error

and probably some more I've forgotten. Each of these errors initially built into the chip can be minimized,

have a look aththis knowledge-base articles (I found them by typing "ADC error" into the field "Keyword search" at top of this page) http://www.cypress.com/?id=4&rID=43218

Happy coding!

Bob

You are using the wrong GetResult, GetResult16, should be GetResult32,

see notes below for API (dont forget to decalre output as 32 bit) -

You also need to be careful with the input configuration. It decides how close to the rails your input signal can get.

When you config the DelSig the range is shown pictorialy

If you are looking for real R-R performance you have to bypass the buffer. If you are

not concerned or need the gain the buffer provides. Look at your current config,

R-R with G = 1, buffer enabled., if you look at the graphic its not R-R, its < R-R

performance. Does not allow you to get to ground or to Vdd with input to buffer.

I am getting a Keil error, "Build error: L251: RESTRICTED MODULE IN LIBRARY NOT SUPPORTED "

So I cannot run your code.

Regards, Dana.

I could open it and compile free of any warning with Creator 3.0

Bob

Looks like my desktop Creator has to be reinstalled, compile on laptop fine.

I debugged, and changed/addeed code with this -

#include <stdio.h>

unsigned char buff[ 20 ];     // Buffer holding character conversion of ADC results in mV

unsigned char i = 0;

LCD_Position(1u,10u);

sprintf( buff, "%6d", ADC_DelSig_1_CountsTo_mVolts ( i32Output ) );

for ( i = 0; i < 6; LCD_Position( 1u, 10u + i ), LCD_PutChar( buff[ i ] ), i++ );

//LCD_PrintNumber( ADC_DelSig_1_CountsTo_mVolts (i32Output) );

And I get basically results you are looking for.

Note I do see values > 0xFFFF and have not measured to see if

input went outside CM range.

Regards, Dana.

I believe that basic operation, with buffer bypassed, gives you

a range of Vss to Vdd and correct readings. Its when you go outside

CM range, in this case Vss - 100 mV > Vx > Vdd + 100 mV that your

readings go outside 0 - 0xFFFF.

So just saturate your readings, eg

Vx = ( Vx > 0xFFFF ) ? 0xFFFF : Vx;        // Test for radings exceeding Vdd

Vx = ( Vx < 0 ) ? 0 : Vx;                              // Test for readings < 0

You can add the 100 mV into above tests is so desired, although that would

generate result < 0 or > 0xFFFF.

Regards, Dana.