TLIN1027-Q1: TLIN1027-Q1

Hi Jayashree,

I can't look at your schematic waveform because the image is very blurry. You can actually copy and paste images into the E2E reply. Can you post the schematic again?

Looking at the waveforms they don't look very good. What speed is your system running at? How are you sending data to the TX pin?

Best,

Chris

Hi Chris,

Thanks for the response.

The system is running at 10.4kps speed and we trying KWP 2000 fast init . Through i.MX6ULL host processor I am sending the data to the TX pin using linux system call.

I am attaching the schematics snap shot for your reference.

With regards,

Jayashree.

Hi Jayashree,

If this is a Leader (formerly master) node, then the device requires a 1K pullup and a diode between Vsup and the LIN bus:

If this a follower (formerly slave) node, then the device does not need a pull up to Vsup, it has an internal pull up.

Can you disconnect the UART_TX from the TLIN device and send me a scope shot of just that. The rise times seem really slow. Also do you know if the UART_TX pin is open drain? If that is the case you will want to populate your pull up resistor on TX. That would help drastically with the rise times and is required if the pin is open drain.

Best,

Chris

Hi Chris,

I had tried using diode with pull up resistor approach also, in that case I am getting bus init error. When I tried with only pull up as mentioned in schematics then I am not getting bus init response.

As per the K-line protocol the K-line bus will be default high and once we initiate the process then the K-line bus goes low for 25ms and again it becomes high for 25ms. Is this scenario is required for this transceiver also? I had attached standard K-line response with an interpreter in other design for your reference. I have captured waveform in large scale in order to cover complete response format.

But in our case when I am probing I didnt observed the above mentioned steps. Initially when we are trying to initialize it self some data is coming continuously. I am attaching the waveform for your reference.

Is there any sample wave forms for this transceiver initial response? Just to verify mine.

Can you disconnect the UART_TX from the TLIN device and send me a scope shot of just that.

Ans: Ok, I will share you this once I probe it.

do you know if the UART_TX pin is open drain? If that is the case you will want to populate your pull up resistor on TX. That would help drastically with the rise times and is required if the pin is open drain.

Ans : As per the datasheet it says for UART_RX, the 1st pin only we need to connect the pull up. But this scenario also I had tried.

With regards,

Jayashree.

Jayashree,

I will see if I can find some waveforms of this device. The UART_TX has to do with the  i.MX6ULL host processor that you are using. You should check if the TX pin on that device is open drain.

This scope shot  also doesn't seem to have the best resolution. Are you zooming into this part of the waveform or are you retaking the scope shot at this time scale. Zooming in could cause the waveform to look triangular.

In general the waveform should be very rectangular especially at these slow speeds. If the waveform actually is this triangle shape it is going to make it very hard for your device to sample the signal.

Best,

Chris

Hi Chris,

Please share me the wave forms if you get it.

Actually I am zooming the waveform. I will retake and share you proper one.

Is there any other transceiver that supports K-line protocol rather than TLIN1027-Q1?

Jayashree,

The SN65HVDA195 would also be a candidate for K-line, but note that like the TLIN1027-Q1, it is only compatible with K-line, not complain to the specification.

Regards,

Eric Hackett 

Jayashree,

I am still waiting to hear back about waveforms.

As Eric said the SN65HVDA195 would also work for K-Line, however I want to make sure we figure out the issue with the input signals first. The input signal on the TXD pin would not be ideal for either device.

Best,

Chris

Hi Chris,

I had removed the UART_TX connection between the processor and transceiver and probed at the processor side. The observed way form is attached for your reference. It is almost similar to the waveform observed earlier.

With regards,

Jayashree.

Jayashree,

I forgot to respond to something you said earlier, but you are correct that you do not need the external pull up resistor and diode at all. In fact, the K-Line protocol calls for a 100k pull up resistor and we have an internal 45K pull up resistor so nothing can be done to change that. The best thing to do is to remove the external pull up completely from the device and just use the internal 45K pull up.

As I expected it looks like the processor is not driving a proper signal. I think the reason the rise times are so slow can be due to the fact that the pin is open drain and if there are no pull up resistors it is just using the internal resistance to charge and discharge the pin. What is the part number of the processor you are using and the pin for TX? I'll look through and see if it requires any external components in order to drive a stronger signal.

Best,

Chris