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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.
Is there some set up that could potentially prevent the LIN bus on the TMS570LC4357 from sending its message based on the hardware of its setup?
Thanks & Regards,
Ian
Hi Ian,
I hope you removed the "linEnableLoopback" function as shown above and following all other steps properly.
I mean
1. Calling Initialization function
Hi Jagadish,
Yes, I made sure to remove the linEnableLoopback function, and I did follow those necessary steps. I even measured the signal with a logic analyzer while having the LIN RX and TX lines of the board directly connected to one another to make sure I could see the signal, and I did. However, this behavior does not happen when connected to the transceiver instead of itself. In addition to this, the LAUNCHXL2 board is also stopping other devices from communicating with it. Two NUCLEO boards may communicate via a LIN bus made of two transceivers, but when one of those NUCLEO boards is replaced with a LAUNCHXL2 board then the signals from the NUCLEO board may still be seen on the bus, they cannot be seen on the LAUNCHXL2 RX line.
I also made sure to follow all of the steps in the example except for adding in the
P.S. I did a little more digging around and am absolutely sure that the issue is with the code rather than with the hardware. I say this because I set up two LAUNCHXL2 boards to communicate with one another and found that when the sending board is spamming the LIN bus with messages, but the receiving board is not yet programmed with code, I can see the header on the receiving board's RX line just fine. However, when I program the receiving board, suddenly the RX line of that board can never drop low enough to register any messages.
P.P.S. I have looked into the setup for the code generator, and I made sure to leave RX and TX for LIN floating. I did not enable pull-up or pull-down resistors for either one. Even still, I have not been able to intentionally bring down the voltage of the RX line. However, I did manage to do this by accident. I am working on a setup where I change the target configuration of the project and program the appropriate code onto the appropriate board. However, I accidentally put the code for sending the LIN message onto both of the boards so they both end up sending headers. When the headers collide with each other, then the RX line is able to drop to a low enough voltage to have activity recognized. I don't know why this is the case, but maybe this could be a clue to the issue with the setup?
Hi Ian,
I understood the root cause for the issue.
The issue is causing by the "TM4C129ENCPDT" IC which is using for XDS110 debug probe.
As you can see the LIN1RX line of the TMS570LC4357 controller is parallelly connected with the U0TX pin of the TM4C129ENCPDT IC.
If we verify the datasheet of the TM4C129ENCPDT controller the default state of this pin is logic High with TTL buffer.
So, due to this event though LIN transceiver trying to transmit the logic low to the TMS570 controller due to TTL Logic High from TM4C129ENCPDT the resultant value is becoming logic high only.
I found this root cause after i tested without connecting the RX line of the launchpad to the LIN.
In this case i observed LIN transceiver was transmitting signal perfectly but once it was connected with Launchpad LIN RX line then it is becoming corrupted.
So, now i changed my application to the LIN2 and tested again because LIN2 RX and TX lines are not connected to any other IC's, so now i got the proper waveform.
Here is my LIN2 application for your reference:
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Thanks & regards,
Jagadish.
Hi Jagadish,
Is there any way to disable the pull-up resistor on that U0TX pin? To change it to that it's default state is not high? Our company cannot switch over to LIN2 at this stage and I would like to know if there is a workaround for it.
Is this situation also remedied in part by the settings you set for the LIN port in Halcogen? Our project does not use the XDS110 debug probe. We are simply using a dev board that uses the XDS110 to practice setting up LIN communication. Our project uses J-Link. So, we should not be seeing that issue because that IC is not present in our setup. However, we do still see the issue and would it be remedied by having the LIN1 port set up like how you show in your files?
Thanks & Regards,
Ian
Is this situation also remedied in part by the settings you set for the LIN port in Halcogen? Our project does not use the XDS110 debug probe. We are simply using a dev board that uses the XDS110 to practice setting up LIN communication. Our project uses J-Link. So, we should not be seeing that issue because that IC is not present in our setup. However, we do still see the issue and would it be remedied by having the LIN1 port set up like how you show in your files?
Sorry I am not getting this.
Is your hardware have XDS110 (TM4C129ENCPDT) IC or not?
If your project doesn't have TM4C129ENCPDT this IC and doesn't connect this IC UART lines with the controller, then there should not be any issues. LIN should work properly in this case.
If your project has this IC and controller LIN lines connected with this IC like as shown above then one workaround i am thinking is to change the firmware of the XDS110 (TM4C129ENCPDT) debug IC, In its firmware if we change the corresponding UARTTX Line into the some GIO input functionality then issue should be resolve. But i don't know whether we could change that firmware and i don't know how to get its source code.
First i would like to know your hardware connectivity for these LIN1 pins. If possible, draw the hardware connectivity for these lines in some picture and share it to me.
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Thanks & regards,
Jagadish.
