TJA1028 LIN Communication Block?

[I0nizer]

Hello,

I'm trying to narrow down an issue between either the dev board I am using, or the TJA1028 LIN transceiver I am using. I am using a LAUNCHXL2-570LC43 dev board to try and send a LIN message through two of these transceivers to another LAUNCHXL2-570LC43 board to receive it. However, I am unable to transmit a whole message through the transceiver. For some reason, only the header can make it through the TX line to the LIN line. I measured at the TX line on the board and saw that for some reason it is only sending the header to the transceiver. It's not that the messages are not making it through the transceiver, it's that only the headers are being sent at all. As if the code that deals with sending LIN messages after the header was just erased. 

However, whenever I have the exact same code running on the board, but connect the TX and RX lines together, I can clearly see the whole message. In addition, whenever I am communicating with two NUCLEO-H753ZI boards, the entire message is transferred, not just the header. So the transceiver itself is definitely working, and the dev board is working on its own, but the combination of the transceiver with the dev board is causing some issue.

In addition to this, I can send a full message from the NUCLEO board and even see it on the LIN bus, but then it never reaches the LAUNCHXL2 RX line. Even when the setup remains otherwise the same.

I have looked through the datasheet, but have not found anything that relates to this inconsistency. I wanted to ask if there was possibly something that I missed with regards to the data sheet. Could there be some timing issue that prevents a connected micro-controller from even sending or receiving any communications?

[TomasVaverka]

Hello,

Are not there any changes on the EN and RSTN pins while sending the message?

Does the current consumption of the TJA1028 remain the same?

BR, Tomas

[I0nizer]

Hello,

I have measured both the transceivers and both EN & RSTN never drop low enough to be considered switched off. Any change in their voltage level is minimal and most likely due to noise.

There is also no change in the current consumption of either TJA1028.

Thanks & Regards

[TomasVaverka · Accepted solution]

Hello,

I do not see any reason for the data fields to not pass through the TJA1028 in Normal mode. It sounds to me like a SW issue related to the LAUNCHXL2-570LC43 dev board I am not familiar with. It might be helpful to post this question on the TI forum as well. 

BR, Tomas

[I0nizer]

Hello,

Yes, I had measured the voltage level of the RX line and saw that the voltage was not dropping low enough to measure any change. However, it was still dropping slightly lower than the normal level in such a pattern that the LIN message was recognizable. This issue did not occur on a board that had not yet been programmed which means it must be a software issue. Thank you for your patience and help.

Thanks & Regards