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PGA460: Question about temperature measurement

Jaatje
Prodigy 185 points
Part Number: PGA460

Hi!

In the datasheet (p.38, SLASEC8B), the command to measure the temperature is ''0x55, 0x04, 0x00, 0xFB" (sync, time/noise command, temperature, checksum) and the command to request the results is "0x55, 0x06, 0xF9" (sync, temp result, checksum). However, I only get 255 (unsigned char) or 127 after the correcton calculation (T = (Temp_measured - 64)/1.5).

Other commands work flawlessly, am I missing something? Would be really cool (haha) to measure the temperature! Any pointers are greatly appreciated.

  • 0
    TI__Mastermind 27950 points

    Jaatje,

    Your process is correct for the master transmitted commands:

    • 1) Command 4 - Temperature and Noise Level Measurement: 0x{55 04 00 FB}
    • 2) Wait 100us
    • 3) Command 6 - Temperature and Noise Level Result: 0x{55 06 F9}

    I checked this on the GUI's Interface terminal, and the results update correctly. Are you waiting at least 100us between commands 4 and 6? According the datasheet:

    "The temperature measurement's sample and conversion time requires at least 100 us after the temperature measurement command is issued. Do not send other commands during this time to allow the temperature value to properly update."

  • 0 in reply to Akeem Whitehead
    Prodigy 185 points

    Hi Akeem,

    Between the commands there's a 2ms delay. Increasing it to whatever amount does not change the output. I also made sure that the command is fully sent to the PGA460 and that the Serial port is being monitored for incoming data. From this I can conclude that after sending the commands, I just do not get a response.

    Are there any settings or certain bits in the register that have to be 1/0 to make this command execute? I used the memory map after calibration in the EVM with time decouple at 64ms (as in the tutorial), might that be a reason?

    Edit: Tried it with only the temperature command, but still it returns nothing back. All other commands work fine....

  • 0 in reply to Jaatje
    TI__Mastermind 27950 points

    Hi Jaatje,

    Do all of the other device commands work and provide responses in the case they are response-commands?

    When you checked that the command is being sent, did you do so physically with an oscilloscope or digital logic analyzer?

    Even if the temperature sensor were damaged, command 6 should still return data as part of the digital state machine; very strange.