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AFE4490 diagnostic feature confusion

Maulik Vaghela
Expert 2500 points
Other Parts Discussed in Thread: AFE4490

Hi,

I am trying to use diagnostic feature of AFE4490. 

My sequence is :

1. I am waking up sensor by writing 1 at PWDN pin.

2. Soft reset the sensor.

3. Initialize afe4490. (Intialize Uart and register for interrupt).

4. Enable diagnostic mode by writing 0x000004 to control register 1.

5. after around 100ms , I am reading value from DIAG_DATA. (0x30).

now for normal case , I am getting output = 0  which is correct, but when I am shorting one LED (RED) by shorting both end of it, it's not giving any flag as 1. output is still 0. 

IS there any mistake for diagnostic sequence?

In datasheet it's mentioned that we need to enable modules before starting diagnostic.Is that necessary?  How do I do that?

  • 0
    TI__Mastermind 49986 points

    Hello Maulik,

    Based on your sequence, you must enable SPI read (bit0 of CONTROL0 register must be set to '1') 100ms after enabling diagnostics to read the status of the diagnostic register.

    I have listed a possible initialization sequence in a previous E2E post. (refer to link below)

    http://e2e.ti.com/support/applications/high_reliability/f/30/p/290393/1013308.aspx#1013308

     

    Regards

    Praveen.

  • 0 in reply to Praveen Aroul
    Expert 2500 points

    Hi Praveen, 

    Thank you for quick reply.

    Sorry I forgot to mention that but I am enabling the SPI read bit while reading from register. 

    and Yes, I am following sequence as you have mentioned, but somehow I am not able to get proper result.

    I have also tested by connecting LED's TXp to ground , still same output. 

  • 0 in reply to Maulik Vaghela
    TI__Mastermind 49986 points

    Maulik,

    Can you check for the following:

    1. If other register read (non-diagnostic reg) accesses are okay.

    2. disconnect the sensors (LED and PD) from the AFE and then test the diagnostic feature. Check if you are getting 0x1E20 when you read the diagnostic register. If you are still getting zeroes, it could only mean the sequence is incorrect.

    3. Can you forward your register settings and your initialization sequence (possibly your code) for review?

     

    Regards

    Praveen.

  • 0 in reply to Praveen Aroul
    Expert 2500 points

    Hi Praveen,

    Thank you very much for quick replies.

    I have checked things as you have mentioned:

    1. Yes, other register access are okay.

    2. Output comes as 0x001E20 which is expected after removing LED and PD.

    3. I think, my sequence is correct since we got output 0x1E20 in 2nd case. Still do you need register sequence?

    One question I have is , When I am testing with LED and PD connected to AFE,  I am getting output as 0x00 and 0x1030 alternatively without any shorting or fault. 

    Is there any problem that may cause this?

    Let us know if you need any other information. 

  • 0 in reply to Maulik Vaghela
    TI__Mastermind 49986 points

    Maulik, 

    Based on the diagnostic fault flags 0x1030, it seems like the photodiode is reversed.

    Can you check if the photodiode anode is connected to DET_N (INN) and photodiode cathode is connected to DET_P (INP)?

     

    Regards

    Praveen.