Hi Duncan, We have verified a very stable readback using the EVM and GUI. Here is my sequence 1. With SPI_DIG_EN=1, write 0x0[1] REGISTER_READOUT_ENABLE=0 2. With SPI_DIG_EN=1, write any register, such as reg 0x05 as 0xAAAA 3. With SPI_DIG_EN=1, write 0x0[1] REGISTER_READOUT_ENABLE=1 4. With SPI_DIG_EN=1, write any register, such as reg 0x05 as any data. 5. See Readback data consistently on the oscilloscope while probing SDOUT at TP12, as well as P14 (SPI signals). Make sure to use the board GND and not DGND of P13, which is USB GND Then, 1. With SPI_DIG_EN=0, write 0x0[1] REGISTER_READOUT_ENABLE=0 2. With SPI_DIG_EN=0, write any register, such as reg 0xC5 as 0xAAAA 3. With SPI_DIG_EN=0, write 0x0[1] REGISTER_READOUT_ENABLE=1 4. With SPI_DIG_EN=0, write any register, such as reg 0xC5 as any data. 5. See Readback data consistently on the oscilloscope while probing SDOUT at TP12, as well as P14 (SPI signals). Make sure to use the board GND and not DGND of P13, which is USB GND Q1: Which header are you using to provide the SPI signals? P14 should be ok. Then remove FB17 to disable the digital isolators. Q2: Which DEMOD register are you testing this with? Q3: Are you writing the SPI with an FPGA? Q4: Can you test with the EVM GUI first to verify that the device will readback correctly?
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