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ADS4226EVM: SPI Issues when accessing through a FPGA

Part Number: ADS4226EVM

For the 4226 EVM, I have interfaced that to a FPGA.

Therefore, I have swapped the zero-ohm links from the USB SPI with the  FPGA SPI.

The signals, SCLK, SS_N, and SDATA, into the ADC are working (As SDOUT is replying). However if I read back the configuration from the ADC via the SPI, the following occurs:

* Write Address: x00, Data: x01

* Read Addresses: x01 to xF2 inclusive

* When reading back the first non-zero register,  SDOUT  correctly outputs the value e.g. Read Address: x25, Read data: x05

* But, SDOUT goes high-impedance for the rest of the reads.    

I'm sure I'm missed something?

Thanks

  • Tim,

    It appears you are doing everything properly. Did you do a reset, either hard or soft, before doing any writes and or reads? After this reset, are you keeping the RESET pin low? Are you doing any writes in between reads? Can you read address 0x25 twice in a row and get a valid read back?

    Regards,

    Jim

  • Jim,

    This has resolved itself - when we soldered some flying leads to the SMT Buffer chip (1.8V SDOUT => 3.3V SDOUT), it started working. Thanks!

    Tim