Offset error or conversion error?

[orn]

Posted on October 10, 2012 at 22:00The original post was too long to process during our migration. Please click on the attachment to read the original post.

[Tesla DeLorean]

Posted on October 10, 2012 at 22:31

Is the STM32F4 running at 3.3V?

Doesn't the STM32F4-Discovery run at 3V, and wouldn't that impact the constant used in the conversion? You should check the supply voltage rather than rely on the example being correct, other boards will likely use different voltages, I'm using ones running at 2.8V

[orn]

Posted on October 10, 2012 at 22:57

The STM32F4 is working with a power supply via USB, it could be the problem? is better to use an external power supply?

[Tesla DeLorean]

Posted on October 10, 2012 at 23:08

The STM32F4 is working with a power supply via USB, it could be the problem? is better to use an external power supply?

No, the problem would appear to be the use of the 3300 constant, when the reference voltage is in fact 3V, where the constant would need to be 3000. I have suggested you measure the supply voltage to the device, because it's not 5V from the USB, but comes via a regulator and a diode. This way you'd be sure/clear about what the ADC is using as a reference, and consequently limited by.

[orn]

Posted on October 10, 2012 at 23:15

ok, I understand, thanks Clive