ALFAT SD Board electrical issue using SPI

Hello everyone,

I’m using a Stellaris LM4F120 LaunchPad Evaluation Board (EK-LM4F120XL) to communicate with the ALFAT SD Board.

I have some issue using the SPI communication.
In fact, i’m using a bread board interfacing my launchpad and the ALFAT SD Board, everything seems to be OK and all connections are done by wires for debug.
But when i try to send something throught the SPI, the electrical level is around 100 mV on the SPI_MOSI from my launchpad and MISO from the ALFAT SD. When i disconnect this pin, (out of charge) the electrical level is back to 3.3V.
Moreover, the clock pin and the CS pin are OK.

I think it’s an impedance issue but not sure where is the problem.

Maybe you have some advice ?

Thank you :slight_smile: