Is this uC damaged?1 ADC ch reflects its value on other 2

Diego Colombo · ‎2018-02-23

Posted on February 23, 2018 at 14:05

Hi ,i'm talking about STM32F410RBT

I'm using 12 ADC channels in DMA mode.I did any sort of manipulation around the hardware built on a prototype board,and it is not unlikely that something went wrong,despite only 3.3V are used.

The analog signals are very slow,i sample it at 1KHz

The acquired values are sent to an UART,at the pretty high speed of 460800 bps,and then a serial to USB converter send it to a PC where i wrote a primitive 12 channel minimal 'oscilloscope viewer'.

I tested each channel with an arbitrary function generator,then with some analog sensor and everything worked fine

Now what i see is that an ADC channel,say CH9,reflects its value on CH10 e CH11,that strangely does not move when a signal is applied to them.

I checked serial,USB and PC simply forcing known levels in the ADC out buffer.

I was in doubt that something was changed wrongly in my DMA acquisition,and that the fact that the affected channels were the last to be sampled was the reason.

So i exchanged them with CH0,CH1,CH2,but the problem still looks related to the 'physical' ADC channels CH9,CH10,CH11.

I'm always prone to blame my code rather than a good uC,so i ask to you,in the community,if this behaviour is symptom of fault or wrong code,if you experimented it.

Many thanks for your attention

Diego,

Milan

Italy

Diego Colombo · ‎2018-02-26

Posted on February 26, 2018 at 09:35

You re right

i did it by myself because i did not want to to charge PCB cost to my chief,that never expressed the intention to spend money for PCB to do preliminary tests ,end even less i wanted to spend my money for it.

I should have done this anyway,even at my expenses,because it would have been worth it considering the days I later lost.

I didn't know pcbway.com,thanks.

Normally i use EuroCircuits,not so cheap but it has very good communication channels,end it is in the UE.

Aboute chinese PCB producers,i'm shure that their quality is more than enough for my prototypes,but the question mark to me is mainly one:can i be shure that the PCB will be delivered in time or it could be left floating in italian custom,with the risk of being sent back for several reasons?

The other way that i should have considered is to use a PCB for the custom analog part +evaluation board ,despite it is less compact of a custom circuit, about SMD mounting lot of problem never exist.

waclawek.jan · ‎2018-02-26

Posted on February 26, 2018 at 10:40

The lesson for me is that my home made SMD PCB [...]

I've been bitten by this on pro PCBs too, after extensive debugging sessions involving the soldering iron.

The lesson for me was to watch a suspicious pin's GPIO_IDR bit in the debugger, while wiggling the voltage on the track (or vice versa, setting the pin to output and wiggling the pin's state while watching the voltage on the track), depending on what's on that track, while not touching the pin physically.

JW