I2C 不适用于树莓派 4（但有时）

Question

我的问题是有时 i2c 在我的树莓派 4 上不工作。我有这个错误：unable to access '/dev/i2*': No such file or folder 和 Error: Could not open file /dev/i2c-1 或 /dev/i2c/1': No such file or directory 执行 i2cdetect -y 1 时。

我想我正确地遵循了安装说明：

• 我在/boot/config.txt文件中添加了这一行：dtparam=i2c1=on、dtparam=i2c_arm=on、dtoverlay=i2c-bcm2835、dtoverlay=i2c-dev
• 我已将 i2c-dev 和 i2c-bcm2835 添加到 /etc/modules 文件

我发现当这个错误附加时，我的 gpio 引脚看起来像这样 (gpio readall)：

 +-----+-----+---------+------+---+---Pi 4B--+---+------+---------+-----+-----+
 | BCM | wPi |   Name  | Mode | V | Physical | V | Mode | Name    | wPi | BCM |
 +-----+-----+---------+------+---+----++----+---+------+---------+-----+-----+
 |     |     |    3.3v |      |   |  1 || 2  |   |      | 5v      |     |     |
 |   2 |   8 |   SDA.1 |   IN | 1 |  3 || 4  |   |      | 5v      |     |     |
 |   3 |   9 |   SCL.1 |   IN | 1 |  5 || 6  |   |      | 0v      |     |     |
 |   4 |   7 | GPIO. 7 |   IN | 1 |  7 || 8  | 1 | ALT5 | TxD     | 15  | 14  |
 |     |     |      0v |      |   |  9 || 10 | 1 | ALT5 | RxD     | 16  | 15  |
 |  17 |   0 | GPIO. 0 |  OUT | 1 | 11 || 12 | 0 | IN   | GPIO. 1 | 1   | 18  |
 |  27 |   2 | GPIO. 2 |   IN | 0 | 13 || 14 |   |      | 0v      |     |     |
 |  22 |   3 | GPIO. 3 |   IN | 0 | 15 || 16 | 0 | IN   | GPIO. 4 | 4   | 23  |
 |     |     |    3.3v |      |   | 17 || 18 | 1 | IN   | GPIO. 5 | 5   | 24  |
 |  10 |  12 |    MOSI |   IN | 0 | 19 || 20 |   |      | 0v      |     |     |
 |   9 |  13 |    MISO |   IN | 0 | 21 || 22 | 0 | IN   | GPIO. 6 | 6   | 25  |
 |  11 |  14 |    SCLK |   IN | 0 | 23 || 24 | 1 | IN   | CE0     | 10  | 8   |
 |     |     |      0v |      |   | 25 || 26 | 1 | IN   | CE1     | 11  | 7   |
 |   0 |  30 |   SDA.0 |   IN | 1 | 27 || 28 | 1 | IN   | SCL.0   | 31  | 1   |
 |   5 |  21 | GPIO.21 |  OUT | 1 | 29 || 30 |   |      | 0v      |     |     |
 |   6 |  22 | GPIO.22 |   IN | 0 | 31 || 32 | 1 | OUT  | GPIO.26 | 26  | 12  |
 |  13 |  23 | GPIO.23 | ALT4 | 1 | 33 || 34 |   |      | 0v      |     |     |
 |  19 |  24 | GPIO.24 |   IN | 0 | 35 || 36 | 0 | IN   | GPIO.27 | 27  | 16  |
 |  26 |  25 | GPIO.25 |   IN | 0 | 37 || 38 | 0 | IN   | GPIO.28 | 28  | 20  |
 |     |     |      0v |      |   | 39 || 40 | 0 | IN   | GPIO.29 | 29  | 21  |
 +-----+-----+---------+------+---+----++----+---+------+---------+-----+-----+
 | BCM | wPi |   Name  | Mode | V | Physical | V | Mode | Name    | wPi | BCM |
 +-----+-----+---------+------+---+---Pi 4B--+---+------+---------+-----+-----+

当一切正常时，它看起来像这样：

 +-----+-----+---------+------+---+---Pi 4B--+---+------+---------+-----+-----+
 | BCM | wPi |   Name  | Mode | V | Physical | V | Mode | Name    | wPi | BCM |
 +-----+-----+---------+------+---+----++----+---+------+---------+-----+-----+
 |     |     |    3.3v |      |   |  1 || 2  |   |      | 5v      |     |     |
 |   2 |   8 |   SDA.1 | ALT0 | 1 |  3 || 4  |   |      | 5v      |     |     |
 |   3 |   9 |   SCL.1 | ALT0 | 1 |  5 || 6  |   |      | 0v      |     |     |
 |   4 |   7 | GPIO. 7 |   IN | 1 |  7 || 8  | 1 | ALT5 | TxD     | 15  | 14  |
 |     |     |      0v |      |   |  9 || 10 | 1 | ALT5 | RxD     | 16  | 15  |
 |  17 |   0 | GPIO. 0 |  OUT | 1 | 11 || 12 | 0 | IN   | GPIO. 1 | 1   | 18  |
 |  27 |   2 | GPIO. 2 |   IN | 0 | 13 || 14 |   |      | 0v      |     |     |
 |  22 |   3 | GPIO. 3 |   IN | 0 | 15 || 16 | 0 | IN   | GPIO. 4 | 4   | 23  |
 |     |     |    3.3v |      |   | 17 || 18 | 1 | IN   | GPIO. 5 | 5   | 24  |
 |  10 |  12 |    MOSI |   IN | 0 | 19 || 20 |   |      | 0v      |     |     |
 |   9 |  13 |    MISO |   IN | 0 | 21 || 22 | 0 | IN   | GPIO. 6 | 6   | 25  |
 |  11 |  14 |    SCLK |   IN | 0 | 23 || 24 | 1 | IN   | CE0     | 10  | 8   |
 |     |     |      0v |      |   | 25 || 26 | 1 | IN   | CE1     | 11  | 7   |
 |   0 |  30 |   SDA.0 |   IN | 1 | 27 || 28 | 1 | IN   | SCL.0   | 31  | 1   |
 |   5 |  21 | GPIO.21 |  OUT | 1 | 29 || 30 |   |      | 0v      |     |     |
 |   6 |  22 | GPIO.22 |   IN | 0 | 31 || 32 | 1 | OUT  | GPIO.26 | 26  | 12  |
 |  13 |  23 | GPIO.23 | ALT4 | 1 | 33 || 34 |   |      | 0v      |     |     |
 |  19 |  24 | GPIO.24 |   IN | 0 | 35 || 36 | 0 | IN   | GPIO.27 | 27  | 16  |
 |  26 |  25 | GPIO.25 |   IN | 0 | 37 || 38 | 0 | IN   | GPIO.28 | 28  | 20  |
 |     |     |      0v |      |   | 39 || 40 | 0 | IN   | GPIO.29 | 29  | 21  |
 +-----+-----+---------+------+---+----++----+---+------+---------+-----+-----+
 | BCM | wPi |   Name  | Mode | V | Physical | V | Mode | Name    | wPi | BCM |
 +-----+-----+---------+------+---+---Pi 4B--+---+------+---------+-----+-----+

你可以看到引脚之间的区别2 和 3i2c 何时工作，何时不工作。我忘了提到引脚 2 和 3 是我的 i2c 连接的地方。

是否需要等待以确保 i2c 已激活并在启动时正常工作？

Answer 1

我不知道你遵循了哪些指示，但你在那里做了很多事情。现在您启用了一组冲突的驱动程序模块。您所需要的只是

dtparam=i2c_arm=on

删除您添加到该文件的所有其他内容。

默认情况下，模块应该存在，因此无需手动复制任何内容。或者，下次只需使用raspi-config 启用默认的 I2C 总线，它也会执行相同的操作。

Answer 2

这个pinout guide 可能会帮助你整理东西。你表中的Mode列是explained here，但它似乎与你的第二张表不一致（即“当一切都好”).很难确切地说出发生了什么，但我不得不猜测你的情不自禁/boot/config.txt 中的作业是您问题的根源 - as suggested by PMF。

如果您还没有这样做，您还应该仔细阅读文件 /boot/overlays/README，因为它包含有关 i2c_arm、i2c_vc 和许多其他内容的有用信息。不要错过这个部分：

    N.B. It is recommended to only enable those interfaces that are needed.
    Leaving all interfaces enabled can lead to unwanted behaviour (i2c_vc
    interfering with Pi Camera, I2S and SPI hogging GPIO pins, etc.)
    Note also that i2c, i2c_arm and i2c_vc are aliases for the physical
    interfaces i2c0 and i2c1. Use of the numeric variants is still possible
    but deprecated because the ARM/VC assignments differ between board
    revisions. The same board-specific mapping applies to i2c_baudrate,
    and the other i2c baudrate parameters.   

您可以使用 /boot/config.txt 或 sudo raspi-config 启用其中一个或两个 i2c 总线。但是如果你想使用只要i2c1作为你的问题暗示，/boot/config.txt 中的一行简单代码通常可以完成这项工作：

dtparam=i2c_arm=on

在继续之前，您应该确保系统上安装了 i2c-tools 包，因为它对于故障排除非常方便：

$ sudo apt update
...
$ sudo apt install i2c-tools

将更改更改为 /boot/config.txt 并重新启动系统。引导完成后，您可以使用以下命令验证您的 i2c 总线是否已启用：

$ i2cdetect -l

输出应反映出 i2c1（默认i2c 总线已启用。如果您的 i2c 设备已连接，您可以运行此命令来验证它是否已正确连接到 i2c1：

$ i2cdetect -y 1

我会在这里停下来，因为你的问题没有解决选择适当的 dt 覆盖（也在/boot/config.txt 中设置）。如果您需要这方面的帮助，请告诉我们。