led和蜂鸣器驱动广州龙芯中科1B开发板

1、1. 前言32. 硬件电路32.1. LED引脚32.2. LED原理分析42.3. 蜂鸣器引脚52.4. 蜂鸣器原理分析53. GPIO相关分析63.1. 阅读CPU手册63.2. Linux内核源码分析64. 点亮一个led94.1. 源码94.2. 运行结果135. 手动指定那个led亮135.1. 源码135.2. 运行结果196. 蜂鸣器驱动206.1. 源码207. 参考资料20修订历史版本号更新日期更新内容V1.0创建1. 前言由于龙芯资料较少，现在又有点时间，写了两句，仅供初学者入门时参考，还望高手多多指教。2. 硬件电路2.1. LED引脚先把电路图贴出来我们选择LED9作为

2、本次实验的对象。LED9接到龙芯1B的引脚T12再查龙芯1B处理器的用户手册v1.9如下图即CAN0_RX为GPIO38.，同理可得Led6接GPIO39；led7接GPIO40；led8接GPIO41。如原理图所示注意：这里有GPIO0，GPIO1，。GPIO38，GPIO39。到底表示什么意思啊？个人认为第一列的GPIO1，GPIO2，为原理图中的编号，而第三列的GPIO38，GPIO39为CPU引脚编号，可以再CPU手册中找到。如前面的led9所示。这几个引脚可以在源码中定义为宏，详细请见后面代码，这里只贴出相关部分。2.2. LED原理分析LED又叫发光二极管，有正负两个极，只要在正负

3、两极之间接上合适的正电压，LED就导通，并发光。这里只需要让CPU的GPIO引脚输出低电平，对应的LED就被点亮。比如GPIO38输出低电平，即可点亮LED9。2.3. 蜂鸣器引脚LED7接在CAN1_RX上，CAN1_RX经过电阻后接蜂鸣器，如下图所示所以LED7和蜂鸣器共用一个引脚GPIO40。2.4. 蜂鸣器原理分析蜂鸣器通过NPN三极管提供所需的大电流，当GPIO40输出低电平时，NPN三极管截止，蜂鸣器不响；当输出高电平时，NPN三极管导通，蜂鸣器响。由于LED7和蜂鸣器共用同一个引脚，并且为了开机后蜂鸣器不响（想起来烦人，哈哈）。所以引脚GPIO40必须输出低电平，恰好低电平使LE

4、D导通，所以LED7在开机后一直亮着。3. GPIO相关分析3.1. 阅读CPU手册首先看龙芯1B处理器的手册，其中对GPIO相关的寄存器有：配置寄存器，输入使能寄存器，输入寄存器，配置输出寄存器，MUX寄存器。根据经验，一般都是先配置GPIO为输入还是输出，然后读输入寄存器或者写输出寄存器实现输入输出功能。V1.9版的手册中写得还不是很清楚，我们这里也只能猜了。贴上手册中的截图作为对比参考，我把其它CPU的截图也贴上相比较而言，龙芯1B处理器手册写得太简单了，以至于没有说清楚。3.2. Linux内核源码分析现在我们来看一下linux内核中GPIO相关代码。源码路径“linux内核根目录/a

5、rch/mips/loongson/ls1x/gpio.c”。我们想实现的功能就是简单的在GPIO口输出高低电平。源文件gpio.c中有个函数ls1b_gpio_direction_output()，从函数名字上看好像能实现这个功能。具体分析一下。/* 函数功能：直接在某个GPIO输出高电平或者低电平入参：struct gpio_chip *chip 可以为空指针 unsigned gpio GPIO的序号 int level 电平值。1-高电平；0-低电平*/int ls1b_gpio_direction_output(struct gpio_chip *chip,unsigned gpio

6、, int level)u32 temp;u32 mask;/ 入参检查：判断是否超过最大的GPIO个数，即GPIO的合法性检查if (gpio >= STLS1B_N_GPIO)return -EINVAL;/ 把高低电平值写到输出寄存器中gpio_set_value(gpio, level);/ 由于寄存器是32位的，一个寄存器最多可以控制32个GPIO/ 就比如：配置寄存器，就有配置寄存器0和配置寄存器1/ 所以这里分开处理if(gpio >= 32)/ 获取锁，执行原子操作spin_lock(&gpio_lock);mask = 1 << (gpio -

7、 32);/ 配置GPIO引脚为GPIO功能temp = LOONGSON_GPIOCFG1;temp |= mask;LOONGSON_GPIOCFG1 = temp;/ 配置GPIO引脚为输出temp = LOONGSON_GPIOIE1;temp &= (mask);LOONGSON_GPIOIE1 = temp;/ 释放锁spin_unlock(&gpio_lock);elsespin_lock(&gpio_lock);mask = 1 << gpio;temp = LOONGSON_GPIOCFG0;temp |= mask;LOONGSON_GP

8、IOCFG0 = temp;temp = LOONGSON_GPIOIE0;temp &= (mask);LOONGSON_GPIOIE0 = temp;spin_unlock(&gpio_lock);return 0;/*函数功能：把高低电平值写到输出寄存器中入 参：unsigned gpio GPIO编号 int state 高低电平。1-高电平；0-低电平*/void gpio_set_value(unsigned gpio, int state)u32 val;u32 mask;/ 判断GPIO是否有效、合法if (gpio >= STLS1B_N_GPIO) _

9、gpio_set_value(gpio, state);return ;/ 对不同GPIO操作不同的寄存器if(gpio >= 32)mask = 1 << (gpio - 32);/ 获取锁spin_lock(&gpio_lock);/ 把高低电平值写到输出寄存器中val = LOONGSON_GPIOOUT1;if (state)val |= mask;elseval &= (mask);LOONGSON_GPIOOUT1 = val;/ 释放锁spin_unlock(&gpio_lock);elsemask = 1 << gpio;s

10、pin_lock(&gpio_lock);val = LOONGSON_GPIOOUT0;if(state)val |= mask;elseval &= mask;LOONGSON_GPIOOUT0 = val;spin_unlock(&gpio_lock);经过以上分析，要让GPIO输出高低电平，首先写输出寄存器，然后把引脚配置为GPIO，最后设置为输出。4. 点亮一个led4.1. 源码源码包含一个驱动源程序、一个应用源程序和一个Makefile。rootlocalhost led# cat Makefile # if KERNELRELEASE is define

11、d, we've been invoked from the# kernel build system and can use its language.ifneq ($(KERNELRELEASE),) obj-m := ls1b_led_driver.o# otherwise we were called directly from the command# line; invoke the kernel build system.else KERNELDIR = /home/dev/develop/1b-linux-3.0-d8b47bb PWD := $(shell pwd)d

12、efault: $(MAKE) -C $(KERNELDIR) M=$(PWD) modules cp ./ls1b_led_driver.ko /nfsramdisk/LS1Brootfs/test mipsel-linux-gcc ls1b_led_app.c -o ls1b_led_app cp ls1b_led_app /nfsramdisk/LS1Brootfs/testclean: rm *.o *.mod.c *.order *.symvers *.koendif这个Makefile是参考linux device driver修改的。也是比较通用的，只需要修改一个linux内核路

13、径和驱动模块文件名就可以了。这里把应用程序的编译也放在了一起。这样执行make时，驱动和应用一起编译。rootlocalhost led# cat ls1b_led_driver.c #include <linux/module.h>#include <linux/fs.h>#include <linux/cdev.h>#include <linux/init.h>#include <linux/kernel.h>#include <linux/slab.h>#include <linux/errno.h>#i

14、nclude <linux/types.h>#include <linux/delay.h>#include <linux/device.h>#include <asm/uaccess.h>#include <asm/mach-loongson/gpio.h>#define LS1B_LED_1_ON (0)#define LS1B_LED_1_OFF (1)int ls1b_led_major = 0;int ls1b_led_minor = 0;struct cdev ls1b_led_devs;int ls1b_led_open

15、(struct inode *inode, struct file *filp) printk(KERN_DEBUG "%s: openn", _FUNCTION_); return 0;int ls1b_led_release(struct inode *inode, struct file *file) printk(KERN_DEBUG "%s: closen", _FUNCTION_); return 0;ssize_t ls1b_led_set(struct file *filp, const char _user *buff, size_t

16、count, loff_t *offp) ls1b_gpio_direction_output(NULL, 38, 0); printk(KERN_DEBUG "%s: led 9 onn", _FUNCTION_); return 0;struct file_operations ls1b_led_ops = .owner = THIS_MODULE, .open = ls1b_led_open, .release = ls1b_led_release, .write = ls1b_led_set,;MODULE_AUTHOR("caogos caogos&qu

17、ot;);MODULE_LICENSE("Dual BSD/GPL");int ls1b_led_init(void) int result; dev_t devno; struct cdev *dev = &ls1b_led_devs; struct file_operations *fops = &ls1b_led_ops; result = alloc_chrdev_region(&devno, 0, 1, "ls1b_led"); if (0 > result) printk(KERN_WARNING "l

18、s1b_led: unable to get amjorn"); return result; ls1b_led_major = MAJOR(devno); printk(KERN_DEBUG "ls1b_led: major = %dn", ls1b_led_major); cdev_init(dev, fops); dev->ops = fops; result = cdev_add(dev, devno, 1); if (result) printk(KERN_NOTICE "Error %d adding ls1b_led", r

19、esult); return result; printk(KERN_DEBUG "ls1b_led device installed. with major %dn", ls1b_led_major); return 0;void ls1b_led_exit(void) cdev_del(&ls1b_led_devs); unregister_chrdev_region(MKDEV(ls1b_led_major, 0), 1); printk("ls1b_led device uninstalledn");module_init(ls1b_le

20、d_init);module_exit(ls1b_led_exit);这个驱动程序必linux device driver中的Hello World Module要稍微复杂点。不过已经是非常简单的字符设备驱动了。这个驱动程序的核心就是函数ls1b_led_set（）。其中的ls1b_gpio_direction_output(NULL, 38, 0);的功能是让GPIO38输出低电平。然后把函数ls1b_led_set（）作为该驱动struct file_operations ls1b_led_ops的写函数，即应用程序中调用write（）函数，就会对应调用驱动的函数ls1b_led_set（

21、）。注意：函数ls1b_led_set（）没有对入参进行分别处理，只要应用程序调用write（）函数，不管write什么内容，都执行GPIO38输出低电平的操作。rootlocalhost led# cat ls1b_led_app.c #include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <fcntl.h>#include <string.h>#include <sys/types.h>#include <sys/stat.h>int

22、 main(void) int dev_fd; char buff2 = 0; dev_fd = open("/dev/led", O_RDWR | O_NONBLOCK); if (-1 = dev_fd) printf("Cann't open file /dev/ledn"); return -1; write(dev_fd, buff, 1); close(dev_fd); return 0;这个应用程序简单来说就是打开设备文件，并执行写操作。即调用驱动中的函数ls1b_led_set（）点亮LED。友情提示：内核顶层配置中* Enabl

23、e loadable module support -> 一定要选上。4.2. 运行结果/test # lsls1b_led_app ls1b_led_driver.ko/test # echo 8 > /proc/sys/kernel/printk/test # insmod ls1b_led_driver.ko ls1b_led: major = 253ls1b_led device installed. with major 253/test # mknod /dev/led c 253 0/test # ./ls1b_led_app ls1b_led_open: openl

24、s1b_led_set: led 9 onls1b_led_release: close/test # 当然开发板上的LED9肯定被点亮。经过前面分析可知，打印信息“ls1b_led_set: led 9 on”为驱动程序打印出来的。命令“echo 8 > /proc/sys/kernel/printk”是将内核打印级别调到最低。为了能把所有驱动中的printk打印信息打印出来。命令“mknod /dev/led c 253 0”新建设备节点。否则，应用中open（）会失败。253为主设备号，根据前面的打印“ls1b_led device installed. with major 25

25、3”获得的。5. 手动指定那个led亮5.1. 源码在前面led驱动的基础上改进了一下，现在可以手动输入led序号，然后制定序号的led被点亮。驱动程序源码ls1b_led_driver.c#include <linux/module.h>#include <linux/fs.h>#include <linux/cdev.h>#include <linux/init.h>#include <linux/kernel.h>#include <linux/slab.h>#include <linux/errno.h>

26、;#include <linux/types.h>#include <linux/delay.h>#include <linux/device.h>#include <asm/uaccess.h>#include <asm/mach-loongson/gpio.h>/ led正极接3.3v，负极接cpu引脚/ cpu输出低电平，led导通，亮#define LS1B_LED_ON (0)/ cpu输出高电平，led截止，灭#define LS1B_LED_OFF (1)/ led引脚#define LS1B_PIN_LED_9 (38

27、) / gpio38#define LS1B_PIN_LED_6 (39) / gpio39#define LS1B_PIN_LED_7 (40) / gpio40#define LS1B_PIN_LED_8 (41) / gpio41/ led主次设备号，动态申请int ls1b_led_major = 0;int ls1b_led_minor = 0;struct cdev ls1b_led_devs;int ls1b_led_open(struct inode *inode, struct file *filp)printk(KERN_DEBUG "%s: openn"

28、;, _FUNCTION_);return 0;int ls1b_led_release(struct inode *inode, struct file *file)printk(KERN_DEBUG "%s: closen", _FUNCTION_);return 0;/*功 能: 将led序号转换为对应的引脚入 参: unsigned int led_index led序号出 参: 无返 回 值: unsigned int led_gpio led引脚*/ unsigned int ls1b_led_index_to_pin(unsigned int led_inde

29、x) switch (led_index) case 9: return LS1B_PIN_LED_9; case 6: return LS1B_PIN_LED_6; case 7: return LS1B_PIN_LED_7; case 8: return LS1B_PIN_LED_8; default: return 0; /*功 能: 熄灭指定led入 参: unsigned int led_index led序号出 参: 无返 回 值: 无*/ void ls1b_led_off(unsigned int led_index) ls1b_gpio_direction_output(NU

30、LL, ls1b_led_index_to_pin(led_index), LS1B_LED_OFF);/*功 能: 点亮指定led入 参: unsigned int led_index led序号出 参: 无返 回 值: 无*/ void ls1b_led_on(unsigned int led_index) ls1b_gpio_direction_output(NULL, ls1b_led_index_to_pin(led_index), LS1B_LED_ON);/*功 能: 关闭所有led入 参: 无出 参: 无返 回 值: 无*/ void ls1b_led_off_all() ls

31、1b_led_off(9); / 关闭led9 ls1b_led_off(6); ls1b_led_off(7); ls1b_led_off(8);ssize_t ls1b_led_set(struct file *filp, const char _user *buff, size_t count, loff_t *offp) char inputbuff10 = 0; unsigned int led_index = 0; unsigned int tmp = 0; / 关闭所有led ls1b_led_off_all(); / 打开指定led copy_from_user(inputbu

32、ff, buff, 1); / 一次只处理一个led led_index = (unsigned int)(inputbuff0); ls1b_led_on(led_index); printk(KERN_DEBUG "%s: led %d onn", _FUNCTION_, led_index); return 0;struct file_operations ls1b_led_ops = .owner = THIS_MODULE,.open= ls1b_led_open,.release = ls1b_led_release,.write= ls1b_led_set,;

33、MODULE_AUTHOR("caogos caogos");MODULE_LICENSE("Dual BSD/GPL");int ls1b_led_init(void)int result;dev_t devno;struct cdev *dev = &ls1b_led_devs;struct file_operations *fops = &ls1b_led_ops;result = alloc_chrdev_region(&devno, 0, 1, "ls1b_led");if (0 > resul

34、t)printk(KERN_WARNING "ls1b_led: unable to get amjorn");return result;ls1b_led_major = MAJOR(devno);printk(KERN_DEBUG "ls1b_led: major = %dn", ls1b_led_major);cdev_init(dev, fops);dev->ops = fops;result = cdev_add(dev, devno, 1);if (result)printk(KERN_NOTICE "Error %d add

35、ing ls1b_led", result);return result;printk(KERN_DEBUG "ls1b_led device installed. with major %dn", ls1b_led_major);return 0;void ls1b_led_exit(void)cdev_del(&ls1b_led_devs);unregister_chrdev_region(MKDEV(ls1b_led_major, 0), 1);printk("ls1b_led device uninstalledn");modu

36、le_init(ls1b_led_init);module_exit(ls1b_led_exit);应用程序源码#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <fcntl.h>#include <string.h>#include <sys/types.h>#include <sys/stat.h>int main(void)int dev_fd;char buff2 = 0; unsigned int tmp = 0;dev_

37、fd = open("/dev/led", O_RDWR | O_NONBLOCK);if (-1 = dev_fd)printf("Cann't open file /dev/ledn");return -1; / 根据用户输入，点亮指定的led buff0 = getchar()-'0'write(dev_fd, buff, 1); / 由于led7和蜂鸣器接在同一个引脚上 / 避免蜂鸣器一直响，最后把蜂鸣器关了 sleep(1); buff0 = 7;write(dev_fd, buff, 1); close(dev_fd)

38、;return 0;Makefilerootlocalhost led# cat Makefile # if KERNELRELEASE is defined, we've been invoked from the# kernel build system and can use its language.ifneq ($(KERNELRELEASE),) obj-m := ls1b_led_driver.o# otherwise we were called directly from the command# line; invoke the kernel build syste

39、m.else KERNELDIR = /home/dev/develop/1b-linux-3.0-d8b47bb PWD := $(shell pwd)default: $(MAKE) -C $(KERNELDIR) M=$(PWD) modules cp ./ls1b_led_driver.ko /nfsramdisk/LS1Brootfs/test mipsel-linux-gcc ls1b_led_app.c -o ls1b_led_app cp ls1b_led_app /nfsramdisk/LS1Brootfs/test/clean: rm *.o *.mod.c *.order