LIN transmission on 5748 EVB fails sometimes

[xinweichang]

I am now working on 5748G EVB using the Freescale examples (AN4830) to transmit LIN frames. However, I found the EVB fails to send out a LIN frame sometimes using the same code. I have checked the LIN transceiver power and it was OK. When the error occurs, the in LINESR the stuck at zero bit (SZF) and bit error flag(BEF) is set, and the there is no frame send out. I am sure the code once worked, is there something else I could have omitted?

[PetrS]

Hi,

The LIN transceiver is not powered from the EVB, thus the transmission will not work, because of bit error (RX pin does not see the same signal that is on TX pin).

So connect 12V to the LIN 1 connector (P11.3) to power the transceiver. This enables the LIN transceiver to loop TX back to RX so entire transmit frames can be issued successfully.

Or you can do either external or internal loopback for the test. For the external loopback disconnect TX/RX signals from the transceiver and connect both together; remove J12 jumpers and place just single to J12 1-3.

Internal loopback is done if LINCR1[LBKM] bit is set in module initialization mode. Then the RX pin is ignored and you can see signal on TX pin if it is configured in SIUL still.

BR, Petr

[xinweichang]

By the way, is the Loop Back Mode working without a LIN transceiver? Maybe I can use it to check if it's related to LIN transceiver.