STM32 - discovery : ADC reference Voltage ?

[thomas23]

Posted on May 20, 2014 at 16:46

Hello,

I am trying to get the reference voltage value with ADC (Channel 18).On the VCT6 datasheet, it is said that reference calibration values (for VREF) are stored in memory at the address 0x1FFFF7BA. (Value for VREF at VDDA = 3.3V)When I read the memory, I obtain this value : 0x614 (1556 dec).How can I deduce the real value of VREF on my board ?Conversion with ADC at channel 18 gives me this value : 0x6B0 (1712 dec).Does this mean that my ''real'' VREF is (3.3 * 0x6AB / 0x614) = 3.6V ?Thank you !

[Tesla DeLorean]

Posted on May 20, 2014 at 16:53

I think a meter or scope would tell you it's 3.0V

Does this mean that my ''real'' VREF is (3.3 * 0x6AB / 0x614) = 3.6V ? More like (3.3 * 0x614) / 0x6AB = 2.999V

[thomas23]

Posted on May 20, 2014 at 17:03

Ok, the scope is not very precise because of noise, but the value was around 2.8~3.0. So indeed, 2.999 sounds right, I just didnt find this logical to do the division like this.

Thank you for your help !