This board does not have any traditional GPIO OUT with the exception of the two user-accesible on-board LEDs. Instead, there is an LSD system that is used to control relays and such. The LSD circuit utilizes a MCZ33996EK chip. Apparently SPI is used to command this chip. Thus, the challenges in controlling DOUT is 1) getting the SPI configuration settings correct, and 2) sending messages that the MCZ33996EK understands. Is there an example (or can one be created) that demonstrates control of DOUT on X-RDVCU5775EVB with MBDT?
