LIN Communication Problems

喜鹊王子

LIN Communication Problems [Copy link]

 When debugging LIN communication, I found that the value of the transmit data register (LINTDy) is the same as the value of the receive data register (LINRDy). Is this normal? In addition, when using polling to send data, the receive interrupt will also be triggered. Has anyone encountered this problem?

chunyang

If there is no independent transmit and receive control, and only one chip is enabled, then when the chip is enabled, because LIN is a single-wire bus, the transmit and receive are connected together internally, so it will definitely transmit and receive automatically. As long as there is a logic 0 on the bus, of course the receive interrupt will be triggered.

ienglgge

When polling is used to send data, the receiving interrupt will also be triggered. Is there anything connected to the pin? Check the program configuration to see if there is any setting such as automatic initialization.

喜鹊王子

ienglgge posted on 2018-11-8 14:44 When polling is used to send data, the receive interrupt will also be triggered. Is there anything else connected to the pin? Check the program configuration to see if there is a self-initial...

A single transmission will not generate a receive interrupt. If the receive-send-receive-... cycle is repeated, the first transmission will not trigger a receive interrupt, but starting from the second transmission, each transmission will trigger a receive interrupt. I have read the chip manual and have not seen this mechanism. LIN itself should not be this mechanism, right?

喜鹊王子

chunyang posted on 2018-11-6 21:13 If there is no independent transmit and receive control, and only one chip is enabled, then when the chip is enabled, because LIN is a single-wire bus, the transmit and receive are connected together internally, ...

A single transmission will not generate a receive interrupt, and if the receive-transmit-receive-... cycle is repeated, the first transmission will not trigger a receive interrupt, but from the second transmission onwards, each transmission will trigger a receive interrupt. I looked at the chip manual and didn't see this mechanism. LIN itself should not have this mechanism, right?

chunyang

Posted by Magpie Prince on 2018-11-9 08:26 A single transmission will not generate a receive interrupt. If you cycle through receive-send-receive-..., the first transmission will not generate a receive interrupt, but the second transmission will...

You should check your program carefully. The serial port interrupt is a mechanism of the MCU, not generated by the LIN interface chip itself. As long as you enable the receive interrupt in your program, the data output given by LIN will naturally cause the MCU to generate a receive interrupt. Don't enable the receive when you are sending, but enable it when you need to receive. If you enable the receive first, you need to clear the receive flag in the serial port receive register before enabling the receive interrupt. This is the minimum process flow of serial port programming.