我们有一个 3m 微触摸显示屏。它通过 USB 连接到我的 Debian 系统，并被识别为人机界面 (hid)。我正在尝试访问和推送实时信息...如果它被触及，我想知道 (x,y) 的位置并通过 netcat 将其通过管道传输到另一台主机。

不幸的是，我只能使用以下方法获取原始数据:

cat /dev/input/event2 | hexdump

或

evtest

你得到的十六进制代码似乎没有任何记录......

有人知道如何获取该信息吗？必须有办法从十六进制代码中提取它。不幸的是我不知道如何解释十六进制代码。我找不到任何记录它的来源...

有没有办法让内核实时向我提供这些所需的信息？

作为解决方法，X-Server 是否可以告诉我一个解决方案？触摸屏的行为就像 X 中的鼠标。实际上我已经尝试通过 xlib 获取鼠标的 x、y 位置。但是它太慢了，不会告诉我是否有人在触摸......

evtest 示例输出:

Event: time 1425319271.595631, type 3 (EV_ABS), code 57 (ABS_MT_TRACKING_ID), value 51
Event: time 1425319271.595631, type 3 (EV_ABS), code 53 (ABS_MT_POSITION_X), value 10304
Event: time 1425319271.595631, type 3 (EV_ABS), code 54 (ABS_MT_POSITION_Y), value 30629
Event: time 1425319271.595631, type 3 (EV_ABS), code 48 (ABS_MT_TOUCH_MAJOR), value 893
Event: time 1425319271.595631, type 3 (EV_ABS), code 49 (ABS_MT_TOUCH_MINOR), value 414
Event: time 1425319271.595631, type 1 (EV_KEY), code 330 (BTN_TOUCH), value 1
Event: time 1425319271.595631, type 3 (EV_ABS), code 0 (ABS_X), value 10304
Event: time 1425319271.595631, type 3 (EV_ABS), code 1 (ABS_Y), value 30629
Event: time 1425319271.595631, -------------- SYN_REPORT ------------
Event: time 1425319271.601632, type 3 (EV_ABS), code 53 (ABS_MT_POSITION_X), value 10306
Event: time 1425319271.601632, type 3 (EV_ABS), code 54 (ABS_MT_POSITION_Y), value 30625
Event: time 1425319271.601632, type 3 (EV_ABS), code 48 (ABS_MT_TOUCH_MAJOR), value 962
Event: time 1425319271.601632, type 3 (EV_ABS), code 49 (ABS_MT_TOUCH_MINOR), value 421
Event: time 1425319271.601632, type 3 (EV_ABS), code 47 (ABS_MT_SLOT), value 1
Event: time 1425319271.601632, type 3 (EV_ABS), code 57 (ABS_MT_TRACKING_ID), value 52
Event: time 1425319271.601632, type 3 (EV_ABS), code 53 (ABS_MT_POSITION_X), value 15416
Event: time 1425319271.601632, type 3 (EV_ABS), code 54 (ABS_MT_POSITION_Y), value 24159
Event: time 1425319271.601632, type 3 (EV_ABS), code 48 (ABS_MT_TOUCH_MAJOR), value 649
Event: time 1425319271.601632, type 3 (EV_ABS), code 49 (ABS_MT_TOUCH_MINOR), value 354
Event: time 1425319271.601632, type 3 (EV_ABS), code 0 (ABS_X), value 10306
Event: time 1425319271.601632, type 3 (EV_ABS), code 1 (ABS_Y), value 30625
Event: time 1425319271.601632, -------------- SYN_REPORT ------------
Event: time 1425319271.606626, type 3 (EV_ABS), code 47 (ABS_MT_SLOT), value 0
Event: time 1425319271.606626, type 3 (EV_ABS), code 53 (ABS_MT_POSITION_X), value 10318
Event: time 1425319271.606626, type 3 (EV_ABS), code 54 (ABS_MT_POSITION_Y), value 30609
Event: time 1425319271.606626, type 3 (EV_ABS), code 48 (ABS_MT_TOUCH_MAJOR), value 1014
Event: time 1425319271.606626, type 3 (EV_ABS), code 49 (ABS_MT_TOUCH_MINOR), value 426
Event: time 1425319271.606626, type 3 (EV_ABS), code 47 (ABS_MT_SLOT), value 1
Event: time 1425319271.606626, type 3 (EV_ABS), code 54 (ABS_MT_POSITION_Y), value 24161
Event: time 1425319271.606626, type 3 (EV_ABS), code 48 (ABS_MT_TOUCH_MAJOR), value 681
Event: time 1425319271.606626, type 3 (EV_ABS), code 49 (ABS_MT_TOUCH_MINOR), value 376
Event: time 1425319271.606626, type 3 (EV_ABS), code 0 (ABS_X), value 10318
Event: time 1425319271.606626, type 3 (EV_ABS), code 1 (ABS_Y), value 30609
Event: time 1425319271.606626, -------------- SYN_REPORT ------------
Event: time 1425319271.611629, type 3 (EV_ABS), code 47 (ABS_MT_SLOT), value 0
Event: time 1425319271.611629, type 3 (EV_ABS), code 53 (ABS_MT_POSITION_X), value 10320
Event: time 1425319271.611629, type 3 (EV_ABS), code 54 (ABS_MT_POSITION_Y), value 30605
Event: time 1425319271.611629, type 3 (EV_ABS), code 48 (ABS_MT_TOUCH_MAJOR), value 1053
Event: time 1425319271.611629, type 3 (EV_ABS), code 49 (ABS_MT_TOUCH_MINOR), value 430
Event: time 1425319271.611629, type 3 (EV_ABS), code 47 (ABS_MT_SLOT), value 1
Event: time 1425319271.611629, type 3 (EV_ABS), code 48 (ABS_MT_TOUCH_MAJOR), value 705
Event: time 1425319271.611629, type 3 (EV_ABS), code 49 (ABS_MT_TOUCH_MINOR), value 392
Event: time 1425319271.611629, type 3 (EV_ABS), code 0 (ABS_X), value 10320
Event: time 1425319271.611629, type 3 (EV_ABS), code 1 (ABS_Y), value 30605

最佳答案

基于控制台的解决方案

您可以使用evtest 工具获取解析坐标。

1. 如果您只需要单点触摸坐标:查找 ABS_X 和 ABS_Y 字段:

    type 3 (EV_ABS), code 0 (ABS_X), value 10306
    type 3 (EV_ABS), code 1 (ABS_Y), value 30625
   

2. 如果需要多点触控坐标:

   • ABS_MT_SLOT代表手指数
   • ABS_MT_POSITION_X 和 ABS_MT_POSITION_Y -- 坐标

   手指#0:

    type 3 (EV_ABS), code 47 (ABS_MT_SLOT), value 0
    type 3 (EV_ABS), code 53 (ABS_MT_POSITION_X), value 10318
    type 3 (EV_ABS), code 54 (ABS_MT_POSITION_Y), value 30609
   

   1 号手指:

    type 3 (EV_ABS), code 47 (ABS_MT_SLOT), value 1
    type 3 (EV_ABS), code 53 (ABS_MT_POSITION_X), value 20301
    type 3 (EV_ABS), code 54 (ABS_MT_POSITION_Y), value 24161
   

例如，如果需要通过网络发送单点触摸坐标，可以使用如下脚本:

#!/bin/sh

# ---- Global variables ----

input=/dev/input/event0
code_prefix="ABS"
code="${code_prefix}_[XY]"
val_regex=".*(${code_prefix}_\(.\)), value \([-]\?[0-9]\+\)"
val_subst="\1=\2"

# ---- Functions ----

send_axis() {
    # 1. Convert axis value ($1) from device specific units
    # 2. Send this axis value via UDP packet
    echo $1
}

process_line() {  
    while read line; do
        axis=$(echo $line | grep "^Event:" | grep $code | \
               sed "s/$val_regex/$val_subst/")

        if [ -n "$axis" ]; then
            send_axis $axis
        fi
    done
}

# ---- Entry point ----

if [ $(id -u) -ne 0 ]; then
    echo "This script must be run from root" >&2
    exit 1
fi

evtest $input | process_line

基于程序的解决方案

您可以编写 C 应用程序来读取您的事件文件。获得的二进制数据可以很容易地解释，参见 kernel documentation 中的第 5 节. 您可以使用 select() 系统调用等待下一个数据部分。

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <linux/input.h>

#define EVENT_DEVICE    "/dev/input/event2"
#define EVENT_TYPE      EV_ABS
#define EVENT_CODE_X    ABS_X
#define EVENT_CODE_Y    ABS_Y

/* TODO: Close fd on SIGINT (Ctrl-C), if it's open */
   
int main(int argc, char *argv[])
{
    struct input_event ev;
    int fd;
    char name[256] = "Unknown";

    if ((getuid()) != 0) {
        fprintf(stderr, "You are not root! This may not work...\n");
        return EXIT_SUCCESS;
    }

    /* Open Device */
    fd = open(EVENT_DEVICE, O_RDONLY);
    if (fd == -1) {
        fprintf(stderr, "%s is not a vaild device\n", EVENT_DEVICE);
        return EXIT_FAILURE;
    }

    /* Print Device Name */
    ioctl(fd, EVIOCGNAME(sizeof(name)), name);
    printf("Reading from:\n");
    printf("device file = %s\n", EVENT_DEVICE);
    printf("device name = %s\n", name);

    for (;;) {
        const size_t ev_size = sizeof(struct input_event);
        ssize_t size;

        /* TODO: use select() */

        size = read(fd, &ev, ev_size);
        if (size < ev_size) {
            fprintf(stderr, "Error size when reading\n");
            goto err;
        }

        if (ev.type == EVENT_TYPE && (ev.code == EVENT_CODE_X
                      || ev.code == EVENT_CODE_Y)) {
            /* TODO: convert value to pixels */
            printf("%s = %d\n", ev.code == EVENT_CODE_X ? "X" : "Y",
                    ev.value);
        }
    }

    return EXIT_SUCCESS;

err:
    close(fd);
    return EXIT_FAILURE;
}

坐标单位

首先你需要知道接下来的事情:

• 坐标原点在哪里(即[x=0;y=0])
• 您的设备使用哪些单位来表示坐标

此信息通常可以在您设备的驱动程序代码中找到。

This是您设备的驱动程序。

因此，您似乎需要将 evtest 的轴值除以 65535，然后乘以设备的宽度或高度(以像素为单位)。例如，如果你得到 X=30000，你的 LCD 面板的宽度是 1080 像素，你需要做:

X = round((30000 / 65535) * 1080) = 494 pixels

关于linux - 如何使用 Linux 获取触摸屏原始数据的坐标，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/28841139/