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ADS1263: ADS1263 - Issue in Reading data from 10 channels

nivetha arun
Prodigy 200 points

Part Number: ADS1263
Other Parts Discussed in Thread: ADS1299, ADS1261

Hi,

I'm using ADS1263 IC. I can able to read data from One channel (AIN0). when i configured AIN0 as positive input multiplexer and AINCOM as Negative input multiplexer. I verified it in logic analyzer.

Question:

I need to know, How to read data continuously with 400 SPS when I configured AIN0 to AIN9 as positive input multiplexerand AINCOM as Negative input multiplexer?  

Configuration and Hardware setup:

AVDD = +2.5V and AVSS = -2.5V, 32 bit Resolution, 400SPS, Gain = 1, AINCOM = Negative Input Multiplexer, AIN0 to AIN9 = Positive Input Multiplexer.

Trial Error: 

  1. Code algorithm:
    1. Monitoring DRDY pin 
    2. In a loop of Total channels (10), 
      1. WriteReg(0x06, channelxEnable)
      2. Send RDATA1 Command
      3. Sending 0xFF for 5 times, One for reading Status byte, other 4 Bytes for reading 32 bit data.

        2. Error:

         I'm giving input to the channel AIN0, but the same output is replicating on all channels. Checked in Logic analyzer. 

And for each channel Im reading status byte, but Only for the first channel its 0X45(i.e ADC1 data new since the last ADC1 read option ) for the other channels its 0x05(i.e ADC1 data not new since the last ADC1 read operation ). 

What is the right flow to read data from all channels.

 

Thanks in Advance.

  • 0
    TI__Guru 58961 points

    Hi nivetha arun,

    Are you sending the WREG to change the multiplexer so you can sample from each channel? I'd expect your software flow to be something like:

    • initialization (set mux to AINP = AIN0 and AINN = AINCOM)
    • start conversions (command or START pin)
    • Wait for DRDY to transition high to low
    • read data
    • change multiplexer to AINP = AIN1 and AINN = AINCOM
    • start conversions (command or START pin)
    • Wait for DRDY to transition high to low
    • read data
    • change multiplexer to AINP = AIN2 and AINN = AINCOM
    • etc.

    Is this what you are doing?

    -Bryan

  • 0 in reply to Bryan Lizon86
    Prodigy 200 points

    Thank you the response,

    I tried the flow which you recommended. I can able to read data from all channels, by monitoring DRDY for each time to read read each channel. So that I couldn't attain my sampling rate of 400 for all channels. Because, CH1 data to CH2 data read itself is taking 2.5ms. 

    But, I need to monitor DRDY one time and read data from all channels. I need to read all 10 channel data in 2.5ms itself. Since I'm using 400SPS I'm mentioning 2.5ms. I have used ADS1299 IC of yours, there I used this method to read data.

    If you see the above image, here In one data ready I'm reading all channels output. This is how I'm expecting the output. Could you please tell me Is this possible here? 

  • 0 in reply to nivetha arun
    TI__Guru 58961 points

    Hi nivetha arun,

    The ADS1299 is a simultaneous sampling ADC. That means the ADS1299 has 8 independent ADCs inside a single chip, and all ADCs are sampling at the same time i.e. the ADC reads each channel in parallel

    The ADS1261 is a multiplexed ADC. That means the ADS1261 has a single ADC inside with an 11-channel mux before the ADC, so the device must cycle the mux every time you want to read a new channel i.e. the ADC reads each channel in series

    You must use the method I described to get data from the ADS1263. You will also need to increase the ADC sample rate because of the multiplexing behavior. You can refer to Table 9-13 in the ADS1263 datasheet for first conversion latency times. This table tells you how much time it will take to get the first data for any channel. If you multiply that value by 8x (or however many channels you want to measure), that tells you how long it will take to get one data from all channels

    Refer to this app note for more information: https://www.ti.com/lit/an/sbaa535a/sbaa535a.pdf?ts=1772461536067&ref_url=https%253A%252F%252Fwww.google.com%252F

    -Bryan