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TDC7200: Unable to set Trigger when start measurement bit is set

Bryan Lavin
Prodigy 10 points
Part Number: TDC7200
Other Parts Discussed in Thread: TDC1000

Hi,

I am unable to set the Trigger on the TDC7200 through SPI.

I wrote a short C++ code on the raspberry pi to debug the registers. The code reads the CONFIG register (0x00), then writes the value 0x03 to this register which should start a measurement and set the trigger. The code then reads back the registers to ensure that CONFIG1 has been set.

The output of executing this code is as follows:

Reading registers before start_meas

Reg [0x00] = 0x02

Send Trigger

Reading register after start_meas

Reg [0x00] = 0x03.

I have probed the trigger pin on the TDC7200 but when the start measurement is set the pin never changes state.

I have ensured that the Enable is set high.

Vreg is at 1.6v.

I have also probed the SPI bus on the TDC1000-TDC7200EVM and it has the same waveforms as the TDC1000 and RPI set up.

I would appreciate any help as I have looked at similar questions to this in the forums but I cannot find a solution.

Regards,

Bryan,

  • 0
    TI__Mastermind 31655 points
    Hi Bryan,

    Can you read the INT_STATUS register both before and immediately after setting the START_MEAS bit? I would also check the TIME and CLOCK registers right after setting the START_MEAS bit (this isn't recommended for normal operation, but is fine for debugging). All of those registers should be cleared as soon as you set the START_MEAS bit, and could give you a hint if something isn't getting set properly.

    It's unlikely, but there is also a possibility that the SPI activity right after setting the START_MEAS bit could be causing problems. Obviously it goes against the first suggestion, but what happens if you don't do any reads after setting the START_MEAS bit? Will it sit there indefinitely without sending a trigger signal?

    Finally, I would suggest monitoring the INTB pin while you perform these experiments. Please let me know what you see.

    Regards,
  • 0 in reply to Scott Cummins
    TI__Mastermind 31655 points
    Hi Brian,

    There hasn't been any activity here in a while, so I am closing the thread. If your problem hasn't been resolved, please just post again and it will reopen.