https://github.com/Xilinx/embeddedsw/blob/45a18907084e77bb3a450a035d280130d7ff6e26/XilinxProcessorIPLib/drivers/sdps/src/xsdps_host.c#L1752 Should it be R4 instead of RESP_R1B? See https://yannik520.github.io/sdio.html "The normal response to CMD5 is R4 in either SD or SPI format."