RS485 on linux-4.9.88-fsimx6-B2019.08

  • Dear support team,

    can you say if iMX6 RS485 is working on the new 4.9.88 kernel?

    On the previous 4.1.15 release RS485 was not working out of the box. So I made some changes to drivers/tty/serial/imx.c to get it working (but without DMA). You can find it in this forum some threads below (RS485 while booting from March 2018). It seems you have made some changes to the original serial driver from kernel 4.9.88. In mainline kernel the RS485 seems not to be working well even in later kernel versions (4.20 and maybe even later). In your driver I'm missing the test for "linux,rs485-enabled-at-boot-time" what can be set in the device tree. That's important because otherwise the RS485 may be "disturbed" by the armstone while booting because it's blocking the write enable line until the driver will be setup for RS485 in the application. So what is the reliable state of RS485 in the new driver? Is DMA working now also when sending more than 8 bytes?

    Thanks in advance.

    Kind regards.

  • Dear Mr. Schubert,

    RS485 works on kernel 4.9.88. You can open the device in rootfs and set the necessary RS485 flags.

    The changes to enable rs485 while booting are not implemented yet. We have noticed that and we will add this in the future to the uart driver.

    We made some changes in the driver to support RS485 9 bit mode.

    Your F&S Support Team

    F&S Elektronik Systeme GmbH
    As this is an international forum, please try to post in English.
    Da dies ein internationales Forum ist, bitten wir darum, Beiträge möglichst in Englisch zu verfassen.