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ADS5402: Test pattern output

Igor Zafievsky
Prodigy 120 points
Part Number: ADS5402

Hello!

   Trying to turn on test pattern output on ADS5402 ADC. According to datasheet, I only need to disable HP mode (by writing 0x8200 to register 0x01) and then set pattern through writing to registers 3C, 3D and 3E. But when I do is as mentioned, I get all zeros on ADC output. Can someone explain, how I should correctly enable and disable test pattern generation in ADS5402?

Thanks in advance

Igor

  • 0
    TI__Genius 12780 points

    Hi Igor,

    By default, the HP mode is disabled (0x01 0x00), so have you tried writing to the pattern registers (3C,3D,3E) after power up?

    Best Regards,

    Dan

  • 0 in reply to dBrock
    Prodigy 120 points

    Yes, I've tried both cases: writing 3C, 3D, 3E registers after ADC reset (just write 0x8200 to 0x01) and write 0x8202 after reset, then write 0x8200 to 0x01 and fill 3C, 3D, 3E - same results, all zeroes on output. SPI has been checked with logic analyzers and readbacks - SPI looks like working fine.

    Regards

    Igor

  • 0 in reply to Igor Zafievsky
    TI__Genius 12780 points

    Hi Igor,

    Can you explain what you mean when you say 0x8200 to 0x01? Is this data then address?

    Please ensure that the power up sequence has been followed according to the datasheet, and that R/W bit is set to "0" when writing to the device.

    After HP mode is disabled (address data; 0x01 0x00), then you must write to all three test pattern registers. For all 1's, you would write to the three registers as follows (address data):

    0x3C 0xBFFC

    0x3D 0x3FFC

    0x3E 0x3FFC

    Best Regards,

    Dan

  • 0 in reply to dBrock
    Prodigy 120 points

    Hi!

    About values: You're right, writing value 0x8200 to the register 0x01 to disable HP mode, then 0x9554 to 0x3C, 0x2AA8 to 0x3D, 0x1554 to 0x3E - and still have zeros on output. Any ideas?

    Thanks in advance

    Igor

  • 0 in reply to Igor Zafievsky
    TI__Genius 12780 points

    Hi Igor,

    Ensure the ADC has been reset. Data coming out should be all zeros unless the common mode voltage is present (intended functionality). In this case, you should see the mid scale voltage (around 4096/2 ~= 2048 codes. I see about 2024 on the ADS5402EVM).

    I have validated that the following writes will enable the test pattern.

    0x01 0x0002 #enable HP1 mode

    0x01 0x0000 #Disable HP1 mode

    0x3C 0x8000 #enable Custom Pattern

    Now, you can write to 0x3C, 0x3D and 0x3E to start your required pattern. Here I will enable all ones.

    0x3C 0xBFFC

    0x3D 0x3FFC

    0x3E 0x3FFC

    In my firmware, I see all ones except for the MSB, so I need to switch to offset binary data output to correct this.

    0x01 0x0008

    Best Regards,

    Dan

  • 0 in reply to dBrock
    Prodigy 120 points

    Thanks, Dan, for a trick.

    Regards

    Igor