前面已经将做一个燃气烟雾检测器需要用的主要模块介绍了一下，准备好这些模块后，就是硬件连接了，先说一下MQ-2这个模块，它有AO（模拟信号）输出和DO（TTL信号）输出，这里我是接的DO，接下来就是软件上如何去实现了，下面来看一下具体过程：
首先来看一下燃气烟雾检测模块MQ-2的底层驱动程序：
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include time.h>
#include
#include
#include
#include
#include
struct mq_data{
int dottl;
int irq;
int d;
int flag;
ktime_t last_ktime;
ktime_t now_ktime;
struct mutex data_lock;
bool data_ready;
wait_queue_head_t data_queue;
struct work_struct report_work;
struct delayed_work cmd_work;
};
static irqreturn_t mq_interrupt_handler(int irq, void *ptr){
struct mq_data* data = (struct mq_data*)ptr;
if(!gpio_get_value(data->dottl)){
data->d = 0;
}else{
data->d = 1;
}
data->flag = 1;
data-> data_ready = true;
wake_up_interruptible(&data->data_queue);
return IRQ_HANDLED;
}
static void cmd_work_func(struct work_struct* work){
struct mq_data* data = container_of(work,struct mq_data,cmd_work.work);
data-> data_ready = true;
wake_up_interruptible(&data->data_queue);
schedule_delayed_work(&data->cmd_work,msecs_to_jiffies(50));
}
static int parse_dt(struct platform_device* pdev,struct mq_data* data){
int rc;
struct device_node* node = pdev->dev.of_node;
data->dottl = of_get_named_gpio(node,"thunder,dottl",0);
if(gpio_is_valid(data->dottl)){
rc = gpio_request(data->dottl,"mq_dottl");
if(rc < 0){
pr_err("Unable to request dottl gpion");
}
gpio_direction_input(data->dottl);
}
return 0;
}
static ssize_t mq_show_value(struct device *dev,
struct device_attribute* attr,char* buf){
struct mq_data* data = dev_get_drvdata(dev);
ssize_t lenth;
wait_event_interruptible(data->data_queue,data->data_ready);
data->data_ready = false;
mutex_lock(&data->data_lock);
if(data->flag == 1){
lenth = sprintf(buf,"%dn",data->d);
}else{
lenth = sprintf(buf, "%dn", 1);
}
mutex_unlock(&data->data_lock);
return lenth;
}
static DEVICE_ATTR(value,0644,mq_show_value,NULL);
static int mq_probe(struct platform_device *pdev){
struct mq_data* data;
int result;
data = kmalloc(sizeof(struct mq_data),GFP_KERNEL);
if(!data){
pr_err("%s kmalloc errorn",__FUNCTION__);
return -ENOMEM;
}
dev_set_drvdata(&pdev->dev,data);
result = parse_dt(pdev,data);
if(result<0){
pr_err("%s error when parse dtn",__FUNCTION__);
result = -EINVAL;
goto err_parse_dt;
}
data->irq = gpio_to_irq(data->dottl);
result = request_irq(data->irq,mq_interrupt_handler,IRQF_TRIGGER_RISING|IRQF_TRIGGER_FALLING,"mq_time_count",data);
if(result<0){
pr_err("Unable to request irqn");
goto err_parse_dt;
}
INIT_DELAYED_WORK(&data->cmd_work,cmd_work_func);
mutex_init(&data->data_lock);
init_waitqueue_head(&data->data_queue);
schedule_delayed_work(&data->cmd_work,msecs_to_jiffies(50));
result=sysfs_create_file(&pdev->dev.kobj,&dev_attr_value.attr);
printk("mq-2 probe successn");
return 0;
err_parse_dt:
kfree(data);
printk("mq-2 probe failedn");
return result;
}
static int mq_remove(struct platform_device *pdev){
return 0;
}
static struct of_device_id mq_match_table[] = {
{ .compatible = "thunder,mq",},
{ },
};
static struct platform_driver mq_driver = {
.probe = mq_probe,
.remove = mq_remove,
.driver = {
.owner = THIS_MODULE,
.name = "MQ-2",
.of_match_table = mq_match_table,
},
};
module_platform_driver(mq_driver);
MODULE_AUTHOR("MQ-2");
MODULE_LICENSE("GPL v2");
节点路径：/sys/bus/platform/drivers/MQ-2/mq-2.66/value
当节点中数值为１时，表示正常，当节点中数值为０时，指示灯被点亮，表示检测到可燃气体或者烟雾。
到此燃气烟雾检测模块MQ-2的底层驱动就完成了。
