UART, I2C access on the M.2 E-Key slot

ROCK 3 Series
1

I have a Rock 3A and wanted to access a custom M.2 module (E-Key) through UART and I2C.

  1. how do I enable the UART on the M.2 E-Key interface (pin22: UART1_RX_M0 and pin 32: UART1_TX_M0)
    and
  2. how do I enable the I2C on the M.2 E-Key interface (pin60: I2C4_SCL_M1 and pin 58: I2C4_SDA_M1 )

I am running Debian(rock-3a_debian_bullseye_xfce_b25.img.xz) and UART1_M0 and I2C4_M1 do not show up in the rsetup configuration.

/dev/ shows I2C-0,I2C-5,I2C-6 but non of those show my device when I do a i2cdetect -y BUSNR
/dev/ shows about 66 tty’s, but so far I have not found the one answering on my card.
BTW, my card is documented here:

2

have you already tried rsetup and dto? https://docs.radxa.com/en/rock3/rock3a/os-config/rsetup
or older wiki about dtb: https://wiki.radxa.com/Rock3/Ubuntu/device-tree-overlays

3

As I said,

dtb:
Which of the following maps to the 2 interfaces in question?

RK3566/RK3568 Available Overlay (ROCK 3A, ROCK 3B, Radxa CM3)

rk3568-can1-m0 rk3568-can1-m1
rk3568-i2c2-m0 rk3568-i2c3-m0
rk3568-pwm1-m0 rk3568-pwm1-m1 rk3568-pwm2-m0 rk3568-pwm2-m1 rk3568-pwm8-m0-fan rk3568-pwm9-m0 rk3568-pwm12-m0 rk3568-pwm12-m1 rk3568-pwm13-m0 rk3568-pwm13-m1 rk3568-pwm14-m0 rk3568-pwm14-m1 k3568-pwm15-m0 rk3568-pwm15-m1
rk3568-spi3-m1-cs0-spidev
rk3568-uart0 rk3568-uart3-m0 rk3568-uart3-m1 rk3568-uart5-m1 rk3568-uart7-m1 rk3568-uart8-m1 rk3568-uart9-m1
rk3568-w1-gpio

Also, if I open the /boot/uEnv.txt file, I see:
uEnv.txt has been retired.
Please use:
rsetup command to confiure device overlays;
sudo nano /etc/kernel/cmdline && sudo u-boot-update to update kernel arguments.

4

The WiFi settings were preventing the UART from appearing.
I used the dtb to remove the WiFi settings that were bothering me.

Hoko

5

Hello hoko,
Where do I remove the WiFi settings? Every time I see anything dtb related it points me to the rsetup tool. Could you please share some more details.
Thanks.

6

Follow the steps below. If you fail to do so, the program may not boot.

root# cd /tmp
root# cp /lib/linux-image-6.6.23/rockchip/rk3568-rock-3a.dtb .
root# dtc -I dtb -O dts -o rk3568-rock-3a_org.dts rk3568-rock-3a.dtb

Change [1] in rk3568-rock-3a.dts to [2].

root# dtc -O dtb -I dts -o rk3568-rock-3a.dtb rk3568-rock-3a.dts
root# mv rk3568-rock-3a.dtb /lib/linux-image-6.6.23/rockchip/rk3568-rock-3a.dtb

[1]

        serial@fe650000 {
            compatible = "rockchip,rk3568-uart\0snps,dw-apb-uart";
            reg = <0x00 0xfe650000 0x00 0x100>;
            interrupts = <0x00 0x75 0x04>;
            clocks = <0x0e 0x11f 0x0e 0x11c>;
            clock-names = "baudclk\0apb_pclk";
            dmas = <0x26 0x02 0x26 0x03>;
            pinctrl-0 = <0x95 0x96 0x97>;
            pinctrl-names = "default";
            reg-io-width = <0x04>;
            reg-shift = <0x02>;
            status = "okay";
            uart-has-rtscts;

            bluetooth {
                    compatible = "brcm,bcm43438-bt";
                    clocks = <0x98 0x01>;
                    clock-names = "lpo";
                    device-wakeup-gpios = <0x99 0x0d 0x00>;
                    host-wakeup-gpios = <0x99 0x0c 0x00>;
                    shutdown-gpios = <0x99 0x0a 0x00>;
                    pinctrl-names = "default";
                    pinctrl-0 = <0x9a 0x9b 0x9c>;
                    vbat-supply = <0x25>;
                    vddio-supply = <0x1a>;
            };
    };

[2]

        serial@fe650000 {
            compatible = "rockchip,rk3568-uart\0snps,dw-apb-uart";
            reg = <0x00 0xfe650000 0x00 0x100>;
            interrupts = <0x00 0x75 0x04>;
            clocks = <0x0e 0x11f 0x0e 0x11c>;
            clock-names = "baudclk\0apb_pclk";
            dmas = <0x26 0x02 0x26 0x03>;
            pinctrl-0 = <0x95 0x96 0x97>;
            pinctrl-names = "default";
            reg-io-width = <0x04>;
            reg-shift = <0x02>;
            status = "okay";
            uart-has-rtscts;
    };
7

The AI ​​just told me. It seems you can also override the steps below. Let me know if you succeed.

    /dts-v1/;
   /plugin/;

   / {
    compatible = "rockchip,rk3568";

    fragment@0 {
    target = <&serial2>; // serial@fe650000 が UART2 の場合
    __overlay__ {
        bluetooth: bluetooth@0 {
            status = "disabled";
            };
        };
    };
};
8

Thanks for sending the commands. Executing them mostly worked, and the computer is still booting.
I had to change the last commands to:

dtc -O dtb -I dts -o rk3568-rock-3a.dtb rk3568-rock-3a_org.dts
sudo mv rk3568-rock-3a.dtb /lib/linux-image-5.10.160-12-rk356x/rockchip/rk3568-rock-3a.dtb`

Also the 2nd dtc command printed a ton of warnings. One was related to the UART:

rk3568-rock-3a_org.dts:3882.3-32: Warning (dmas_property): /serial@fe650000:dmas: cell 0 is not a phandle reference
rk3568-rock-3a_org.dts:3876.18-3889.4: Warning (dmas_property): /serial@fe650000: Missing property '#dma-cells' in node /phy@fe830000 or bad phandle (referred from dmas[0])

And this procedure did not change anything. I still don’t know which /dev/ttyXX is mapped to the hardware UART1_M0. I tried all UARTs that I could enable in the rsetup and all ttyX.
I also see a mapping for I2C4_M1 in the dts file, but i2cdetect does not show my device.
Maybe you have some more advise.
I’ll keep searching. Thanks.

9

And I don’t understand anything, that the AI told you. :frowning: