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use other gpio pins as i2c

时间:2016-07-12 11:41:40      阅读:151      评论:0      收藏:0      [点我收藏+]

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As of June 2016 Raspbian already has the necessary modifications. You only need to enable the overlay in config.txt (step 6 onwards).

I finally got this working as follows:

  1. Rebuild the kernel with i2c_gpio module. You must edit the bcm2708_defconfig or bcmrpi_defconfig and add the line CONFIG_I2C_GPIO=m before running the make defconfig.
  2. Install kernel and modules using mkknlimg for device tree support as described in the kernel building docs.
  3. Convert the example i2c_gpio config to a device tree fragment as follows:

    // Overlay for i2c_gpio bitbanging host bus.
    /dts-v1/;
    /plugin/;
    
    / {
            compatible = "brcm,bcm2708";
    
            fragment@0 {
                    target-path = "/";
                    __overlay__ {
                            i2c_gpio: i2c@0 {
                                    compatible = "i2c-gpio";
                                    gpios = <&gpio 23 0 /* sda */
                                             &gpio 24 0 /* scl */
                                            >;
                                    i2c-gpio,delay-us = <2>; /* ~100 kHz */
                                    #address-cells = <1>;
                                    #size-cells = <0>;
                            };
                    };
            };
            __overrides__ {
                    i2c_gpio_sda = <&i2c_gpio>,"gpios:4";
                    i2c_gpio_scl = <&i2c_gpio>,"gpios:16";
                    i2c_gpio_delay_us = <&i2c_gpio>,"i2c-gpio,delay-us:0";
            };
    };
    
    • This will default to using gpio 23 and 24 for software i2c.
    • delay-us should be 2 for 100kHz operation.
    • The following lines should be removed because they will prevent the driver from working on Raspberry Pi: i2c-gpio,sda-open-drain; i2c-gpio,scl-open-drain;
  4. Build the device tree blob with dtc -@ -I dts -O dtb -o i2c-gpio.dtb i2c-gpio.dts

  5. Copy the blob to /boot/overlays/

  6. Add a line in /boot/config.txt dtoverlay=i2c-gpio

    If you want to use different pins, put dtoverlay=i2c-gpio,i2c_gpio_sda=<pin>,i2c_gpio_scl=<pin> instead. You can also change the rate with i2c_gpio_delay_us=<usecs>.

  7. Reboot.
  8. modprobe i2c-dev and you now should have /dev/i2c-3 in addition to any others you previously configured.

use other gpio pins as i2c

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原文地址:http://www.cnblogs.com/raffeale/p/5662744.html

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