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DSP can not communicate with ADAR7251 via SPI

Question asked by hitbuyi on Feb 7, 2015
Latest reply on Oct 20, 2016 by soyoo

The ADAR7251's  spi timing required is as following figure, the first 3 bytes a command sent by TMS320F28335, after AD receive the command, it send  2 bytes data to TI 28335,


  I set SPIA FIFO level  to  5  bytes(the first 3 bytes are command, the last  2 bytes are dummy write)


  firstly , I sent 5 byte to  disable CRC


  0x00  0xFD,0x00, 0x00,0x01, 0x33,0x06


  cuz when POR,  ADAR7251's CRS is enabled, the 0x33, 0x06 is CRC comand, ADDR15 is set to 0 voltage



  I  check the sent 5-bytes from TI 28335 on the oscilloscope(view line SPI MOSI), it is right. but  no bits appears on the line SOMI,  would someone help me?   it puzzled me a few days