I have a board that has a MSP1612, a device on SPI and also a 5v rails for a sensor card.

When the sensor card is not connected all works fine.

When the sensor card is connected (and board powered on), SPI device fails. However when the board is powered on without the sensor card and then the sensor is plugged in (while board is on), SPI continues to work. If board is then powered off and on again the SPI works (even though sensor is present). But if SPI device is removed and replaced and then the board is powered on, the SPI device fails.

What I have observed is that on one of the MSP interrupt pins which goes to the SPI device, one can see the nice high-low pulses. But when the board is left powered on and working for some time and then the SPI link fails, it is seen that the high-low interrupt triggers are not coming but rather actually the voltage seems to rise momentarily upwards (say from 3.3v to 3.6v or so).

I suspect this has to do with some capacitance issue (based on the issue intermittently appearing based on modules being plugged/removed, or issue appearing over time). But what is strange is that an identical board is working fine.

So sorry for the long story, but I am hoping for some pointers as to how to probe in to this further or maybe the situation sounds familiar.

Thanks!
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