ADC calibration

[mrx23dot]

I have a theory that ADC calibration value is not auto applied.

based on ch32v307 implementation
https://github.com/Ivansquark/ch32/blob/7529e796615f2c7dd53d1fc4d1ddf597556f1f2c/ch32v307/freertos_socket_server/C/src/adc.c#L35C5-L35C21

[cnlohr]

I believe you may be correct. I don't think anyone's ever vetted it. Perhaps we should just remove the cal from the ch32v003fun demo? I don't know a good way to apply the cal. And, I haven't seen an issue with any ADC readings so far. What does it look like for them to be out of cal?

[mrx23dot]

simplest would be into a separate example:

static u32 adcOffset;

adc_init():
adcOffset = RDATAR; /* offset >= 0 */

adc_read():
u32 val = RDATAR;
return (val <= adcOffset) ? 0 : (val - adcOffset);

some application might need calibration.