MC33662 LIN Transceiver Not Working

[andrew_meessema]

I am using the MC33662 LIN Transceiver. I have used it on a couple different PCBs (all with KEA64) with different traces and different components. I have not gotten any of them to work and have finally narrowed it down to the transceiver, however, have not been able to figure out what is wrong with the transceiver.

After supplying power to the transceiver, Vsup 12V, the transceiver is then enabled (no delay enacted) with 3.3V. The wake pin is grounded as our application does not require the wake-up function. We just use enable to wake the device after it has been powered off for an indefinite amount of time after supplying Vsup. 

The problem that I am facing is that the RxD (pin 1) and TxD (pin 4) do not function at all as RxD does not report the LIN bus voltage and TxD does not output to the bus. I've tested by directly sending data on pin 6, LIN bus, and monitoring RxD with no result as well as sending data over TxD and monitoring the LIN bus to no avail.

Is the device being woken properly? Not too sure what is going on and looking for any suggestions as to why the chip isn't working. I've looked through the RF multiple times and been through a few forums for different LIN transceivers and haven't found anything. I can provide more information about the setup if necessary but that's all I could think of for what the chip needs to function properly.

[kerryzhou]

Hi Andrew Meesseman,

    If the TX pin have signals, just the LIN bus don't have the signals when you power on the MC33662 LIN transceiver, I think your MC33662 circuit may have problems.

   Please refer to the MC33662 EVB board to check your circuit again:

KIT33662LEFEVBE | Evaluation Kit | MC33662L, LIN2.1/SAEJ2602-2, LIN Phy | NXP 

   The user guider and the schematic is:

 https://www.nxp.com/docs/en/user-guide/KT33662UG.pdf 

   Please double check your MC33662 circuit.

   When you test it, send the data in the TX, then check the LIN bus directly, not the RX pin.

Wish it helps you!

If you still have question about it, please kindly let me know.

Kerry

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[andrew_meessema]

Thank you for the feedback.

However, that's how I've been testing to see if the circuit is working. I will send something on TxD and monitor the LIN bus directly. But even if I were to monitor RxD, I should still be able to see the signal from TxD because RxD just reports the voltage of the LIN bus. I haven't tried testing this way because it is redundant and monitoring the LIN bus should just show the output from TxD. I thought that it was a circuit problem at first so I put a new MC33662 on in place of the one I was originally testing on and the second circuit didn't work either.

I have the TRK-KEA64 dev board and am  going to write something to test on this to see if the problem persists.

[kerryzhou]

Hi Andrew,

  So, now, when you send the data in the TXD, you can't find some in the LIN bus?

   You also can check this post:

LPC54608 LIN master basic usage sharing 

  I also use the MC33662 to send the LIN data, you can find some wave in the TX and LIN bus.

  Wish it helps you!

  If you still have question about it, please kindly let me know.

Kerry

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[andrew_meessema]

Hi Kerry, 

Thank you for your help. I believe the transceiver has been working all along.

When I was testing code and debugging, I was sending messages over the LIN bus via a UART to USB cable (3.3V), however, the minimum LIN bus voltage is 8V so Rx was reporting that the bus voltage was always held low. And on the other hand, when I was sending data over LIN Tx, I was monitoring the LIN bus with an oscilloscope being triggered at 3.3V as I was testing with UART Tx beforehand. I noticed this and set the trigger threshold to be 11/12V and I am now receiving the waveform on the LIN bus. So the chip has been working all along!