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ADS1606 no DRDY

Giannis Roussos
Expert 2290 points
Other Parts Discussed in Thread: ADS1606

Hello,

I am trying to interface the ADS1606 A/D converter with the Stellaris LM3S9D96 MCU. I am using the ADS1606-EVM evaluation module and the DK-LM3S9D96 Development Board.

I have set up the EPI of the Stellaris in HB16 mode and I am able to read single measurement, without using the FIFO of the ADS.

However, when I set the ADC to use the FIFO very often the ADC stops giving DRDYn interrupts and the signal is always high. After a reset interrupts start again for a while.

I haven't been able to understand what this behaviour means. Does the ADS1606 stop operating if the host doesn't retreive the measurements?

  • 0
    TI__Guru**** 172706 points

    Hi Giannis,

    Is it possible for you to post a screen capture of your FIFO reads along with DRDY of the ADS1606?  I suspect you may be on the edge of getting all data out of the device between DRDY pulses which could impact the synchronization of the serial interface.  What is the FIFO level set for now?  Have you tried reducing it to see if this issue goes away?

  • 0 in reply to Tom Hendrick
    Expert 2290 points

    Hi Tom,

    I will do what you suggest on Monday and get back to you.From memory I can tell you that with the EPI clock and ADC clock equal (8Khz for now), the 14 RDn pulses take up 80-90% of the time between DRDYn pulses. I will also check the CSn signal and provide a capture.

    So far I have managed to narrow down the problem to external interference: If I don't apply any external analog signal to the ADS1606EVM the problem doesn't occur, at least in the 30minutes that I left it running. However, if I use a signal generator to analog signal, or switch on/off a fluorescent bulb near by the ADC stops.

    I have tried also without the FIFO, reading one value per DRDYn pulse. In this case the ADC never stops creating DRDYn pulses, but I can make it output garbage values by applying specific frequencies in the analog signal input.

    The whole system now is a mess with a lot of jumper cables, so it's very susceptible to EMI. We are designing our own board with a Stellaris and an SRAM chip to stack on top of the ADS1606EVM and get rid of all the cables. Hopefully this will solve the problem.