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DebugHAT AT24C02

DebugHAT AT24C02 EEPROM使用方法

参考文档

Kernel Compile Steps

  • arch/arm/boot/dts/overlays/rpi-at24c02-overlay.dts 
    // rpi-sense HAT
/dts-v1/;
/plugin/;

/ {
        compatible = "brcm,bcm2835";

        fragment@0 {
                target = <&i2c1>;
                __overlay__ {
                        #address-cells = <1>;
                        #size-cells = <0>;
                        status = "okay";

                        DebugHAT@50 {
                                compatible = "atmel,24c02";
                                reg = <0x50>;
                                status = "okay";
                        };
                };
        };
};
  • KERNEL=kernel7l
  • make bcm2711_defconfig
  • make -j4 dtbs
  • sudo cp arch/arm/boot/dts/overlays/rpi-at24c02.dtbo /boot/overlays/
  • /boot/config.txt 
    [...省略]
dtoverlay=rpi-at24c02
  • reboot

device tree

  • before 
    root@raspberrypi:/proc/device-tree/soc/i2c@7e804000# ls
'#address-cells'   compatible   phandle         reg
 clock-frequency   interrupts   pinctrl-0      '#size-cells'
 clocks            name         pinctrl-names   status
  • after 
    root@raspberrypi:/proc/device-tree/soc/i2c@7e804000# ls
'#address-cells'   compatible    name        pinctrl-names   status
 clock-frequency   DebugHAT@50   phandle     reg
 clocks            interrupts    pinctrl-0  '#size-cells'

Kernel module

模块驱动会自动加载，想知道原理，请查看

root@raspberrypi:/proc/device-tree/soc/i2c@7e804000# lsmod | grep at24
at24                   20480  0

以文件的形式访问EEPROM

root@raspberrypi:/sys/devices/platform/soc/fe804000.i2c/i2c-1/1-0050# xxd eeprom
00000000: 0eff ffff ffff ffff ffff ffff ffff ffff  ................
00000010: ffff ffff ffff ffff ffff ffff ffff ffff  ................
00000020: ffff ffff ffff ffff ffff ffff ffff ffff  ................
00000030: ffff ffff ffff ffff ffff ffff ffff ffff  ................
00000040: ffff ffff ffff ffff ffff ffff ffff ffff  ................
00000050: ffff ffff ffff ffff ffff ffff ffff ffff  ................
00000060: ffff ffff ffff ffff ffff ffff ffff ffff  ................
00000070: ffff ffff ffff ffff ffff ffff ffff ffff  ................
00000080: ffff ffff ffff ffff ffff ffff ffff ffff  ................
00000090: ffff ffff ffff ffff ffff ffff ffff ffff  ................
000000a0: ffff ffff ffff ffff ffff ffff ffff ffff  ................
000000b0: ffff ffff ffff ffff ffff ffff ffff ffff  ................
000000c0: ffff ffff ffff ffff ffff ffff ffff ffff  ................
000000d0: ffff ffff ffff ffff ffff ffff ffff ffff  ................
000000e0: ffff ffff ffff ffff ffff ffff ffff ffff  ................
000000f0: ffff ffff ffff ffff ffff ffff ffff ffff  ................

Overlay Compile Directly

  • rpi-at24c64-overlay.dts 
    // rpi-sense HAT
/dts-v1/;
/plugin/;

/ {
        compatible = "brcm,bcm2835";

        fragment@0 {
                target = <&i2c1>;
                __overlay__ {
                        #address-cells = <1>;
                        #size-cells = <0>;
                        status = "okay";

                        DebugHAT@51 {
                                compatible = "atmel,24c64";
                                reg = <0x51>;
                                status = "okay";
                        };
                };
        };
};
  • dtc -O dtb -o rpi-at24c64.dtbo rpi-at24c64-overlay.dts
  • sudo cp rpi-at24c64.dtbo /boot/overlays/
  • /boot/config.txt 
    [...省略]
dtoverlay=rpi-at24c64
  • reboot