RS-485 not working with revpi-connect-4 (new device)

[wickywaka]

We added support for revpi-connect-4 here #1078

During further testing, I see that we don't have a device node/file in /dev for rs-485. So may be there is something missing in the device trees. Any idea what can it be?

Here the relevant post on revolution pi forums: https://revolutionpi.com/forum/viewtopic.php?t=4196

[ddtdanilo]

any news on this?

[ludovic-cook-e]

Hi, I'm not a Balena OS user, but I also had to create an image for the RevPi Connect 4 using Yocto.

I had the RS485 working in my image by adding this udev file (https://gitlab.com/revolutionpi/revpi-base-files/-/blob/v0.2.0/udev/50-revpi.rules) into ${D}${sysconfdir}/udev/rules.d/ with the following patch

--- a/50-revpi.rules
+++ b/50-revpi.rules
@@ -2,7 +2,7 @@
 # 
 # SPDX-License-Identifier: GPL-2.0-or-later
 
-PROGRAM="/bin/grep -Fz -m 1 'kunbus,revpi-' /sys/firmware/devicetree/base/compatible"
+PROGRAM="/bin/grep -F -m 1 'kunbus,revpi-' /sys/firmware/devicetree/base/compatible"
 RESULT=="kunbus,revpi-core", GOTO="revpi_core"
 RESULT=="kunbus,revpi-core-2022", GOTO="revpi_core"
 RESULT=="kunbus,revpi-core-s-2022", GOTO="revpi_core"

Doing so seems to create /dev/ttyRS485, which is a working RS485 interface.

Btw, I don't have /dev/node/file in my image, so there might be more work to be done to link the RS485 to this interface.

I hope this helps :)