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Original question:

ADS7953: Clarification on SDO and SDI timing

ADS7953: Channel data error in auto-2 mode

Di Wang
Expert 1740 points

Part Number: ADS7953

Hi there,

I'm using ADS7953 CH0-CH13 to measure the temperatures in auto-2 mode. I found CH9-CH13 data is equal to CH0-CH4, which looks like CH9-CH13 is just repeating the data of CH0-CH4. Here is my codes. I would like to know which part I should check for this issue. I also attach the SCH here.

Thanks.

send(0x9340)  //select CH13 as the last channel

send(0x3C40)

send(0x3840)

for i in range(14)

    val[i] = send(0x3840)

  • 0
    TI__Mastermind 25070 points

    Hello,

    For what I can see it looks as if you are using the correct commands.

    I suggest taking an oscilloscope connected to the digital lines, CS, SCLK, SDI, SDO

    This will confirm that what you are expecting from your code is in fact what is happening

    This will also help confirm what channels are being converted. the first four bits of the SDO frame will display what channel the conversion data is for. This will be a very quick and direct way to confirm if the last four channels are being repeated or not. 

    Other way is: change the input voltage to channel 9 (or any of the suspected repeated channels) to a known DC value, and check if the SDO data follows the DC input, or shows the suspected repeated channel value. 

    On a side note, you do not need to reprogram the register in Auto mode 2 to sequence through the channels. The purpose of this mode is for the device to do it automatically with each frame. Meaning, after you select the last channel, and send the first frame to restart at ch0 and set the Vref range, 

    You only need to send repeated 0x0000h codes and the device will automatically loop through the channels. it will also restart at Ch0 when the loop is done. 

    Regards

    Cynthia