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ADS1241 clock frequency

Alice Pavanini
Prodigy 80 points
Other Parts Discussed in Thread: ADS1248, ADS1241

Hello,

I'm using ADS1241and I experienced the following problem:

when I use it with a crystal like 4.9152MHz it works correctly.

But when I use the internal oscillator of my MCU (for example, 4 MHz or sub-multiplies) or even a 4 MHz crystal, it starts shifting out data on DOUT without waiting for my command (RDATA). Most significant byte of DOR is shifted out while I am sending the command, and the other to bytes are shifted out during the first 16 SCLK cycles of the 24 that I send to read out DOR. It behaves like it received a RDATAC instead of RDATA. But I checked every rising/falling edges of my signals and they look ok.

In my hardware I changed nothing but the crystal.

I also use ADS1248 and it works fine with every frequency in its range.

If you have any suggestion, I thank you.

  • 0
    TI__Guru** 113765 points

    Alice,

    There could be an issue when the clock is applied in relation to device power up.  I would suggest resetting the ADS1241 after the clock is applied from the MCU.  Then I would set the configuration of the device in the manner in which you want to operate it and run the calibration routines like SELFCAL.

    If you suspect the ADS1241 to be in RDATAC mode, monitor the DRDY pin.  If it is in RDATAC mode, you will see this pin toggle between high and low.  If it is in RDATAC mode, you can always stop continuous readings with the STOPC command.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 80 points

    I solved, I was operating the device in SPI mode (0,0) instead of mode (0,1). So it was as if the ADC read 0x03 (RDATAC) instead of 0x01 (RDATA) and didn't listen to any other command (i.e. STOPC). I didn't realize this issue before since the same MCU also drives an ADS1248, which works correctly on both SPI modes.

    Thanks again and regards