at91sam9x5 linux 4.1.0下使能蜂鸣器驱动

测试环境：  CPU: AT91SAM9X35      Linux: Atmel提供的linux-at91-linux4sam_5.3 (Linux-4.1.0)

转载请注明： 凌云物网智科嵌入式实验室： http://iot-yun.com/     郭文学<[email protected]>

最新的atmel代码使用了Device Tree替换了以前的platform虚拟总线架构，该文章介绍了最新的Linux内核如何添加使能PWM控制蜂鸣器的全过程。目录结构：

1, DTS修改

2, Make menuconfig选项

3, 应用程序

4，测试

1, DTS修改

Linux内核里关于pwm-beeper驱动的DTS说明文档：

[[email protected] linux-at91-linux4sam_5.3]$ cat Documentation/devicetree/bindings/input/pwm-beeper.txt
* PWM beeper device tree bindings

Registers a PWM device as beeper.

Required properties:
- compatible: should be "pwm-beeper"
- pwms: phandle to the physical PWM device

在Linux内核的dts文件中，只有mini6410的dts文件中使用了pwm-beeper驱动，所以我们需要参考他来修改：

[[email protected] linux-at91-linux4sam_5.3]$ vim  arch/arm/boot/dts/s3c6410-mini6410.dts
    buzzer {
        compatible = "pwm-beeper";
        pwms = <&pwm 0 1000000 0>;
        pinctrl-names = "default";
        pinctrl-0 = <&pwm0_out>;
    };

修改at91sam9x35ek的DTS文件，添加pwm-beeper设备

[[email protected] linux-at91-linux4sam_5.3]$ vim  arch/arm/boot/dts/at91sam9x35ek.dts 

    ahb {
        apb {
            macb0: [email protected] {
                phy-mode = "rmii";
                status = "okay";
            };

            pwm0: [email protected] {
                pinctrl-names = "default";
                pinctrl-0 = <&pinctrl_pwm0_pwm2_0>;
                status = "okay";
            };

    ...............

    buzzer {
        compatible = "pwm-beeper";
        pwms = <&pwm0 2 1000000 0>;
        pinctrl-names = "default";
        pinctrl-0 = <&pinctrl_pwm0_pwm2_0>;
        status = "okay";
    };
   ...............

2， 内核make menuconfig

Linux内核自带PWM的beeper驱动drivers/input/misc/pwm-beeper.c，我们需要在make menuconfig中选中并使能它。

Device Drivers  --->
     Input device support  --->
           [*]   Miscellaneous devices  --->
                <*>   PWM beeper support
                 

内核编译启动后，我们可以看到新的蜂鸣器设备：

~ >: cat /proc/bus/input/
devices   handlers
~ >: cat /proc/bus/input/devices
I: Bus=0019 Vendor=001f Product=0001 Version=0100
N: Name="pwm-beeper"
P: Phys=pwm/input0
S: Sysfs=/devices/soc0/buzzer/input/input0
U: Uniq=
H: Handlers=kbd event0
B: PROP=0
B: EV=40001
B: SND=6

~ >: ls /sys/class/input/event0/
dev        device     power      subsystem  uevent
~ >: ls /dev/input/event0
/dev/input/event0

3, 编写蜂鸣器测试应用程序

/*********************************************************************************
 *      Copyright:  (C) 2016 Guo Wenxue<[email protected]>
 *                  All rights reserved.
 *
 *       Filename:  test_buzzer.c
 *    Description:  This file
 *
 *        Version:  1.0.0(08/06/2016)
 *         Author:  Guo Wenxue <[email protected]>
 *      ChangeLog:  1, Release initial version on "08/06/2016 03:16:54 PM"
 *
 ********************************************************************************/

#include <stdio.h>
#include <unistd.h>
#include <stdint.h>
#include <fcntl.h>
#include <linux/input.h>
#include <errno.h>
#include <string.h>

#define DEV_BUZZER        "/dev/input/event0"
#define BUZZER_FREQ       2700  /* 2.7KHz */

int main(int argc, char **argv)
{
    int                   fd = -1;
    int                   version ;
    int                   rv;
    struct input_event    event;
    int                   freq = BUZZER_FREQ;

    if( argc != 2 )
    {
        printf("Usage: %s [freq<2700/0>]\n", argv[0]);
        return -1;
    }

    freq = atoi(argv[1]);

    if( (fd=open(DEV_BUZZER, O_RDWR)) < 0)
    {
        printf("open buzzer ‘%s‘ failure: %s\n", DEV_BUZZER, strerror(errno));
        return -2;
    }

    event.type = EV_SND;
    event.code = SND_TONE;
    event.value = freq;

    write(fd, &event, sizeof(struct input_event));

    close(fd);
    return 0;
}

4， 编译和测试

PC端编译：

[[email protected] utils]$ /opt/buildroot-2012.08/arm926t/usr/bin/arm-linux-gcc test_buzzer.c -o test_buzzer
[[email protected] utils]$ file test_buzzer
test_buzzer: ELF 32-bit LSB executable, ARM, version 1 (SYSV), dynamically linked (uses shared libs), not stripped

ARM端下载测试

~ >: tftp -gr test_buzzer 192.168.2.18
test_buzzer          100% |*******************************|  5712   0:00:00 ETA
~ >: chmod a+x test_buzzer 

~ >: ./test_buzzer
Usage: ./test_buzzer [freq<2700/0>]
~ >: ./test_buzzer 2700       蜂鸣器的工作频率是2.7KHz，开启蜂鸣器
~ >: ./test_buzzer 0             传参数0则关闭蜂鸣器