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TS3A227E Used for UART Interface for debug

David Mckinney
Expert 6410 points
Other Parts Discussed in Thread: TS3A227E, TS3A227E-EVM

Can the TS3A227E interface be used to implement UART communications, over the head set jack audio path to allow debugging?

Will it detect the 3.3 V on the SLEEVE contact vs. the 600 Ω ~ 4 kΩ impedance it's looking for?

 

We would like the switch matrix in the TS3A227E to pass the 3.3 V through to the MICP pin, where it can be detected to actuate a mux scheme to switch the Left / Right  lines to be UART TXD and RXD.

 

Please advise if applying 3.3 V to the TS3A227E SLEEVE contact will achieve the desired result.

  • 0
    TI__Mastermind 45340 points

    David,

    I will try and summarize what I think you are asking.   Are you trying to put 3.3 V on the TS3A227E sleeve pin and have it pass through to the MICP pin of the TS3A227E? 

    Placing 3.3 V on the sleeve pin does not violate the datasheet recommendation with VDD >=3.3V  

    I will need to know what is on ring2 in your use case to help determine how the TS3A227E automatic detection will behave.  Note you may always use the I2C control to mannually configure the switch to connect SLEEVE and MICP. 

    If the TS3A227E device configures itself for a three pole configuration it will ground the sleeve pin and not pass 3.3 V

    If the device configures it self as a 4 pole OMTP device it will ground the sleeve pin and not pass the 3.3 V signal.

    In order to pass 3.3 V through the sleeve pin to MICP you need the device configured for a standard 4 pole device so it does not ground the sleeve pin.  You may always manually configure this device through the devices I2C communication pins.   

    I'm still looking into how the device will automatically configure it self when it sees 3.3 V on the sleeve pin.  In your use case what is present on Ring 2.  As you can see from this post below the audio jack detection configuration is based on a comparison from what is connected on sleeve and ring2.

    Thank you,

    Adam

  • 0 in reply to Adam Torma
    TI__Expert 6410 points

    SLEEVE will be 3.3 V and RING2 will be ground.  The question is whether the TS3A227E can detect this voltage and configure itself to the switch state shown in Figure 31 without software intervention.

  • 0 in reply to David Mckinney
    TI__Mastermind 45340 points
    David,

    I think we will need to simulate how the algorithm will behave when it sees 3.3 V on SLEEVE and GND on RING2. This can take some time with the design team. I think the fastest approach is to get a TS3A227E-EVM and just try it and see how the device configures it self. I have placed an order for the EVM and should have it in my office in a couple of days.

    Thank you,
    Adam
  • 0 in reply to Adam Torma
    TI__Expert 6410 points

    HI Adam;

    Can you give me an update on testing this on an EVM board?

  • 0 in reply to David Mckinney
    TI__Expert 6410 points

    Hi Adam;

    I received the TS3A227EVM board and tested it with the following results:  I setup the EVM in standalone mode and used an Aardvark to read the I2C.  The Motorola headset appears to detect correctly, and the debug appears to detect the same as the Motorola headset.