Beaglebone GPIO输入无法正常工作 [英] Beaglebone gpio input not working

问题描述

我正在使用beaglebone通过sysfs接口从特定的引脚访问数字输入.而且我可以更改输出状态，但不能更改输入:(.我要做的是，我有两个引脚pinA和pinB.pinA我使其成为输出，pinB我作为输入.将pinA连接到pinB.通过发送，将pinA配置为输出引脚通过传入传入sysfs和pinB中的direction属性作为输入.然后我将PinA的值更改为1，并给出1作为输出(我使用LED进行了测试).但是，当我读取PinB的值时，它给出的只是0，甚至我将0传递给pinA的值.可能是什么原因?

I am using beaglebone to access digital input from specific pin using sysfs interface. And I can change the output states but not the input :(. What I did is, I have two pins pinA and pinB. pinA I made it output and pinB I made input. Connected pinA to pinB. Configured pinA as output pin by sending out to direction attribute in sysfs and pinB as input by passing in. And I changed value of PinA to 1 and it is giving 1 as output (I tested using LED). But when I read the value of PinB it is giving 0 only, even I pass 0 to value of pinA. what may be the reason ?

谢谢:)

推荐答案

据我了解，您执行的步骤是:

As I understood, the steps you followed:

echo 7 > /sys/kernel/debug/omap_mux/gpmc_ad6
echo 38 > /sys/class/gpio/export
echo in > /sys/class/gpio/gpio38/direction
cat /sys/class/gpio/gpio38/value

我也犯了同样的错误，花了我几个小时，但答案很简单:问题是从"echo 7"开始的第一行.看一下混合位:

I also did the same mistake and it took me hours, but the answer was simple: The first line starting with "echo 7" is the problem. Look at the muxing bits:

Bit 5: 1 - Input, 0 - Output

Bit 4: 1 - Pull up, 0 - Pull down

Bit 3: 1 - Pull disabled, 0 - Pull enabled

Bit 2 \

Bit 1 |- Mode

Bit 0 /

您输入的是回声7，即-> 0 0 0111，它表示:位0,1和2为1，因此已设置模式.没问题.但是，您只是忘记设置它是输入还是输出.它应该是这样的:

You were entering echo 7 which is --> 0 0 0111 and it means: bit 0,1 and 2 is 1, so the mode is set. No problem. However you just forgot to set whether it's an input or output. And it should be like this:

echo 0x27 > /sys/kernel/debug/omap_mux/gpmc_ad6

您的位现在是:1 0 0111二进制，即0x27(十六进制).

your bits are now: 1 0 0111 binary which is 0x27 (hex).

当您输入内容时输入"cat/sys/class/gpio/gpio38/value"时，您会看到一个奇妙的1 :)我相信您会和我一样开心:)

When you write "cat /sys/class/gpio/gpio38/value" while giving input, you can see a wonderful 1 :) I’m sure you will be very happy as much as I was :)

还有一件事，您适合使用约1.8V的模拟输入，但GPIO使用3.3v进行操作.

Also, one more thing, you are right for Analog input about 1.8V, but GPIO operates with 3.3v.

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