如何使用 Linux 获取触摸屏原始数据的坐标 [英] How to get Coordinates of Touchscreen Rawdata using Linux

查看：20 发布时间：2022/1/4 22:15:09 linux linux-kernel driver touchscreen raw-input

本文介绍了如何使用 Linux 获取触摸屏原始数据的坐标的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我们有一个 3m 的微触摸显示屏.它通过 USB 连接到我的 Debian 系统并被识别为人机界面(隐藏).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) 的位置并将其通过 netcat 管道传输到另一台主机.

We have a 3m microtouch display. It's connected to my Debian system via USB and recognized as human interface (hid). I am trying to access and push realtime information... if its getting touched I want to know where (x,y) and pipe it through netcat to another host.

不幸的是，我只能使用以下方法获取原始数据:

Unfortunately I am only able to get raw data using:

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......

You get hexcode that seem nowhere documented...

有人知道如何获取这些信息吗?必须有一种方法可以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.我找不到任何记录在案的来源...

Does anybody have a clue how to get that information? There must be a way to extract it from the hexcode. Unfortunately I have no idea how to interpret the hexcode. I couldn't find any source where its documented...

内核是否可以实时为我提供所需的信息?

Is there a way the Kernel could provide me those desired information in realtime?

作为一种解决方法，是否有 X-Server 可以告诉我的解决方案?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，如果有人在触摸，它不会告诉我...

As a workaround, is there, maybe, a solution where the X-Server could tell me? The touchscreen behaves like a mouse in X. I actually already tried to get x,y-position of the mouse via xlib. But it was too slow and wouldn't tell me if somebody is touching or not...

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

基于控制台的解决方案

您可以使用 evtest 工具获取解析后的坐标.

Console-based solution

You can obtain parsed coordinates using evtest tool.

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

如果您需要多点触控坐标:

If you need multi-touch coordinates:

ABS_MT_SLOT 代表手指数
ABS_MT_POSITION_X 和 ABS_MT_POSITION_Y -- 坐标

ABS_MT_SLOT represents number of finger
ABS_MT_POSITION_X and ABS_MT_POSITION_Y -- coordinates

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

手指 #1:

 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，如果您需要通过网络发送单点触摸坐标，您可以使用这样的脚本:

For example, if you need to send single-touch coordinates via network, you can use script like this:

#!/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，请参阅内核文档中的第 5 节.您可以使用 select() 系统调用等待下一个数据部分.

Program-based solution

You can write C application that will read your event file. Obtained binary data can be easily interpreted, see section 5 in kernel documentation. You can wait for next data portion using select() syscall.

#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...
");
        return EXIT_SUCCESS;
    }

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

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

Coordinates units

First of all you need to know next things:

坐标原点在哪里(即[x=0;y=0])
您的设备用于表示坐标的单位

此信息通常可以在您设备的驱动程序代码中找到.

This information usually can be found in driver code for your device.

这个是您的驱动程序设备.

因此，您似乎需要将 evtest 中的轴值除以 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，你需要这样做:

So it seems like you need to divide your axis value from evtest by 65535 and multiply it by width or height of device (in pixels). For example, if you get X=30000, and width of your LCD panel is 1080 pixels, you need to do:

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

这篇关于如何使用 Linux 获取触摸屏原始数据的坐标的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！

查看全文

如何使用 Linux 获取触摸屏原始数据的坐标 [英] How to get Coordinates of Touchscreen Rawdata using Linux

问题描述

推荐答案

基于控制台的解决方案

Console-based solution

基于程序的解决方案

Program-based solution

坐标单位

Coordinates units

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如何使用 Linux 获取触摸屏原始数据的坐标 [英] How to get Coordinates of Touchscreen Rawdata using Linux

问题描述

推荐答案

基于控制台的解决方案

Console-based solution

基于程序的解决方案

Program-based solution

坐标单位

Coordinates units

相关文章

服务器开发最新文章

热门教程

热门工具

登录 关闭

登录关闭