BPI-R3, OpenWRT, w1, GPIO, DTO

Banana Pi Router design BPI-R3/R3 Mini(MT7986)
1

Hi, I would like to connect w1 device (DS18B20 etc) to GPIO of BPI-R3 and got a big headache. OpenWRT v25.12.0

  1. Select a free pin of GPIO by command: “cat /sys/kernel/debug/gpio”. Chose 18pin (GPIO44, UART1_CTS)

  2. Created partition with FS FAT on a free space of eMMC - mmcblk0p6 (I found 20M free eMMC space.)

  3. Wrote compiled w1-gpio.dts file to the mmcblk0p6 partition. ( dtc -@ -I dts -O dtb -o w1-gpio.dtbo w1-gpio.dts )

/dts-v1/;
/plugin/;

/ {
   compatible = "bananapi,bpi-r3", "mediatek,mt7986a";

   fragment@0 {
       target = <&pio>;
       __overlay__ {
           w1_pins: w1-gpio-pins {
               pins = "GPIO44";
               function = "gpio";
           };
       };
   };

   fragment@1 {
       target = <&uart1>;
       __overlay__ {
          status = "disabled"; 
       };
   };

   fragment@2 {
       target-path = "/";
       __overlay__ {
           onewire {
               compatible = "w1-gpio";
               gpios = <&pio 44 0>;   /* GPIO44, pin 18 */
               pinctrl-names = "default";
               pinctrl-0 = <&w1_pins>;
               status = "okay";
           };
       };
   };
};
  1. I tried loading changes to U-Boot bootloader by fw_setenv command.
fw_setenv load_w1 ‘fatload mmc 0:6 $loadaddr w1-gpio.dtbo && fdt addr $loadaddr && fdt resize 8192 && fdt apply $loadaddr’

fw_setenv boot_production ‘run boot_update_conf ; led $bootled_pwr on ; run load_w1 ; run emmc_read_production && bootm $loadaddr#$bootconf ; led $bootled_pwr off’

As a result of reboot, nothing good happened. Folder /sys/bus/w1/devices is empty.

Please, help. Has anyone connected the w1 bus to GPIO?

2

I’m nearly sure that your overlay is not loaded…afaik for openwrt you have to modify bootconf in uboot. You can check with cat in /sys/firmware/devicetree/base/… If your nodes are changed (uart1 disable and pinctl node visible via ls)

3

I agree with you. I don’t see my changes in /sys/firmware/devicetree/base/ My problem is loading the dtbo file into U-Boot. I don’t know how to do this without compiling the kernel (by changing the configuration).

4

Additionally openwrt should use fit inage on R3 too,so you have to add the overlay to this fit too.

This definition is in target/linux/mediatek/image/filogic.mk

You have to copy your dtsi to the dts folder and add a patch for dts makefile in kernel.

Maybe look at our R4Pro changes to be done. There should be a patch in packages/boot/uboot-mediatek which adds R3 environment where you can then point to your overlay.