I've connected a Rasperry Pi to a MSP430 uC using a 3 wire 8bit SPI interface. The SPI communication seems to work (I've checked on both ends and the data is correct).
On the PI I communicate using a user-land spidev client (no persistent state machine). On the MSP430 the SPI state machine is only initialized at startup.
If I touch the SPI clock wire with one of the multi-meter's connectors (+ or -, doesn't make a difference) the SPI connection goes out-of-sync (I see garbage data on both ends) until I reset the MSP.
Is this normal behavior or am I facing a connectivity/grounding problem?