Eval -CN0326-PMD2 multiple communication is not working.

Question

Good day,
I have an Eval -CN0326-PMD2 board, that I am using on my SPI and it is working perfectly fine but the moment I connect another Eval -CN0326-PMD2 with a different CS the processor freezes and everything on the main board stops working.
Anyone that can help to set these boards on one SPI?

MarkThoren · Accepted Answer

Hi Frank22, 
 I may have spotted the problem - I'm nearly 100% certain that the ADuM5401 outputs are always driven, as in, DOUT (U4 pin 6) does NOT go high-impedance when CS_N (U4 pin 3) is driven high. 
 One quick test would be to insert a 1k resistor in series with both boards' DOUT pins. Note that if you've got a long trace or long cable, this will affect signal integrity, so place these resistors close to the processor, minimizing capacitance at the processor's pin. 
 Also note that the ADUM5401 symbol in the CN0326 is very confusing, the VOD/VID are arranged such that the input / output direction matches the other pins, NOT the ground domains. 
 -Mark)

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Eval -CN0326-PMD2 multiple communication is not working.