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Reading the wrong channel

Category: Datasheet/Specs
Product Number: LTC1867

Hello,

I am working on the LTC1867.

I can communicate correctly with it but I have a shift of one channel compared to the values ​​I expect.

For example, I want to read a voltage (1.25V) on channel 2, this voltage appears on channel 3. However, the commands I send seem to correspond for a reading of channel 21 I send the command 0x94 (I am in Unipolar mode). The code sequence I made is as follows: We put the CS/CONV pin high for 1 ms to launch a conversion then after I lower the pin and I use the HAL_SPI_TransmitReceive function (I am working on an stm32) to send my command 0x94 and receive my data.

When I do this my value of 1.25V arrives on channel 3 while I physically apply it to channel 2. Could you tell me where my error is?

Thank you in advance,

cordially.

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  • Hi,  .

    Based on my understanding, you are reading the correct conversion, but it is from Channel 3, right? Here are some insights:

    1.) Can you share a scope shot of your timing diagram? Since you are using LTC1867, I am expecting 16 serial clock pulses.
    2.) How did you conclude that the result of 1.25 V came from Channel 3? Did you try reading Channel 3 after Channel 2? It might seem that it came from Channel 3; rather, what I think that might happened is that the next conversion is clocking out the acquired data from Channel 2. 
    3.) Can you include how did you configure the SDI? Since you have mentioned using a Unipolar conversion and using Channels 2 and 3.


    Regards,
    Jo

Reply
  • Hi,  .

    Based on my understanding, you are reading the correct conversion, but it is from Channel 3, right? Here are some insights:

    1.) Can you share a scope shot of your timing diagram? Since you are using LTC1867, I am expecting 16 serial clock pulses.
    2.) How did you conclude that the result of 1.25 V came from Channel 3? Did you try reading Channel 3 after Channel 2? It might seem that it came from Channel 3; rather, what I think that might happened is that the next conversion is clocking out the acquired data from Channel 2. 
    3.) Can you include how did you configure the SDI? Since you have mentioned using a Unipolar conversion and using Channels 2 and 3.


    Regards,
    Jo

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