NPi i.MX6ULL RS485 (RTS/CTS)

adamsugar · August 15, 2023, 2:01pm

Hello, I have a Seeed NPi - i.MX6ULL eMMC module in my possession.

I have installed Debian using the instructions provided here.

A.Boot from SD card

Step 1. Select the latest https://files.seeedstudio.com/linux/NPi+i.MX6ULL/imx6ull-debian-buster-console-armhf-latest-2gb.img.xz
Step 2. Connect an SD card to a PC or MAC with an SD card reader, an SD card with more than 4G memory is required.
Step 3. Click here to download Etcher, then use the Etcher to write the *.img.xz file directly to the SD card. Or extract the *.img.xz file into a *.img file, and then burn it to an SD card using another mirror write tool.

B. Boot from eMMC(NAND) card

Step 1. the process is the same as A. Boot from SD card if you first start up the NPi i.MX6ULL Dev Board.
Step 2. Select P22 in fire-config to enable flash boot then reboot.

I activated 485r1 afterwards. However, the CTS and RTS pins are not functioning. I’ve tried various methods, but they didn’t solve the issue. Can you assist me with this matter?

sudo cat /proc/tty/driver/IMX-uart

The output is as follows.

debian@npi:~$ sudo cat /proc/tty/driver/IMX-uart
serinfo:1.0 driver revision:
0: uart:IMX mmio:0x02020000 irq:19 tx:7574 rx:29 RTS|DTR|DSR|CD
1: uart:IMX mmio:0x021E8000 irq:64 tx:0 rx:0 DSR|CD
debian@npi:~$

Seeed_Jostar · August 16, 2023, 1:37am

Hi, according to the PinMap you can check that 19 and 21 should be RST and CTS, not 12 and 13, you need to reconfigure

adamsugar · August 16, 2023, 8:40am

First of all, thank you for responding to me. However, what you see there are not P12 and P13 GPIO pin selections. They are the order of the fire-config options located at positions 12 and 13 in order to activate the UARTs in RS485 mode. When I select and activate those options, I uncomment or comment out the necessary lines in the /boot/uEnv.txt file.

dtoverlay=/lib/firmware/imx-fire-485r1-overlay.dtbo
#dtoverlay=/lib/firmware/imx-fire-485r2-overlay.dtbo

I believe that changing the .dtbo file is necessary to fix the issue on my developer board, but I’m not entirely certain. I’m looking forward to your suggestions for a solution regarding this matter. Have a great day.