ADC shows wrong output

[sarang]

Posted on September 03, 2009 at 22:37

ADC shows wrong output

[sarang]

Posted on May 17, 2011 at 13:22

The ADC2 issue is common to all our boards. What is over-voltage damage on ADC?

[jj]

Posted on May 17, 2011 at 13:22

In an earlier post you mentioned that you had ''not'' properly tied your ADC input signal to common (board) ground. In this process - you may have damaged (over-stressed) the ADC inputs (spec has a max ADC value). However - since you likely fed that signal to ''all'' of your ADC inputs (perhaps in sequence) I suspect that multiple ADC inputs would have been damaged - not just ADC2.

Perhaps ADC2 requires a different set-up than the others. Don't believe you state ''which'' STM32 device you're using - be sure that the ADC feature is available on your device - and is properly and sequentially enabled.

[sarang]

Posted on May 17, 2011 at 13:22

Well, the reference manual states that the only difference between ADC2 and the others is that it doesnot have DMA. I am using single conversions (no DMA). The setup and code i use for ADC1 was tweaked for ADC2 and ADC3. ADC3 worked with the tweak. One observation i made was the ADC input pins have voltages on them without any input.

[jj]

Posted on May 17, 2011 at 13:22

There are a variety of STM32s. Different package sizes, different performance grades - my guess is that your particular device (we don't know which one you are using)may be treating ADC2 in a different manner.

Be sure you're reading/following the most current spec for ''your particular device!'' (has caught me/cohorts) If you allow ADC inputs to float the voltages you measure are without real meaning - this is not good practice. If your device has a valid ADC2 - and you've not damaged that pin - again I bet that you have typo in ADC2 set-up. Get someone else to stare at your code - same guy can miss simple mistake repeatedly...