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ADS62P49 Serial Readout

rish patel
Prodigy 10 points
Other Parts Discussed in Thread: ADS62P29, ADS62P49

Hello,

I am having issue reading from ADS62P49 registers in SPI mode. I can write to the regs ok. I am following the TI ADS62P49/ADS62P29 Datatsheet page 18. To read from the regs, I set the bit DO in reg 0x00 (write 0x01 to addr 0x00) then initiate the read by specifying the addr for regs I need to read and monitor the SDOUT pin for data. I dont see the data on SDOUT pin.

I know my SPI write works as I can put the device in digital ramp test pattern mode by writing 0x04 to reg addr 0x75. I have probed the SPI pins and they look ok.

Please let me know if you have any suggestion.

Thank you.

 

  • 0
    TI__Mastermind 29220 points

    Hi,

    Are you continuing to toggle SCLK for the data bits that you wish to see read out?  Make sure you are not just clocking in the 8 data bits with SCLK and then stopping SCLK and SEN.  The SCLK must continue for the next 8 data bits after the address, and SEN must be active for the whole access cycle and not just for the 8 address bits.  (as per figure 10 of page 19 of the datasheet.)

    Also, address 0 would not be accessable for a read, I believe.  Writing '1' to bit 0 of register 0 disables writes to registers until you make bit 0 of register 0 be a '0' again.  This implies that while the device is set up for read back register 0 must still be available for writing.  Writing is disabled for the *rest* of the registers after register 0.  So if you are setting up for read back by writing to register 0 and then you try to read back from *all* registers starting with register 0 - then that first attempted readback from register 0 will actually be clearing it back to write mode if the SDATA pin is low during your readback.  And you may then be losing your readback mode before you even get to the 2nd register.

    Regards,

    Richard P.