龙芯1B开发板上实现温湿度传感器dht11的驱动

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1、1. 简介32. 硬件设计42.1. DHT11手册中的典型电路42.2. 龙芯1B开发板电路分析52.3. 实物图73. 软件设计83.1. DHT11通信协议分析83.2. 主要思路93.3. 关键函数赏析104. 运行结果124.1. 采用中断方式读DHT11124.1.1. 采集温湿度成功124.1.2. 采集温湿度失败之校验不过144.1.3. 采集温湿度失败之不符合协议164.1.4. 成功失败次数统计分析174.1.5. 加载模块后第一次采集失败194.2. 采用udelay延时方式读DHT11215. 经验245.1. 读GPIO引脚245.2. 与DHT11通信过程中不要执行

2、printk等耗时操作246. 源码清单246.1. 驱动源码246.1.1. ls1b_dht11_driver.c246.1.2. Makefile416.2. 测试程序源码426.2.1. ls1b_dht11_app.c427. 参考文档43版本更新日期更新内容V1.02014.4.9创建V1.12014.4.28增加了详细的软硬件说明1. 简介这里使用的DHT11为入门级的温湿度传感器，如果需要精度更高一点的可以选择AM2302、AM2303等，也是单总线的实现方式相似。也有I2C接口的，比如AM2321。首先，到广州奥松电子官方网站下载传感器手册和相关示例代码等。下载手册的地方为“

3、产品展示”->“数字输出型”然后选择dht11，就进入如下界面，单击“产品手册”旁边的“点击下载”按钮，进行下载。还可以在“下载中心”下载应用例程，如下2. 硬件设计2.1. DHT11手册中的典型电路DHT11的手册中已经给出了典型电路图，如下所示图中说了：信号线小于20米时需要加5.1K上拉电阻；可以采用5V或者3.3V供电。2.2. 龙芯1B开发板电路分析从DHT11手册中可以知道：只需要电源、地、一个信号线和一个5.1K上拉电阻就可以与龙芯1B开发板通信。龙芯1B开发板把3.3V、5V和GND都引出来了。具体如下信号引脚从开发板上4个LED灯中选一个。其中LED7即CAN1_RX

4、被蜂鸣器占用，这里选择LED8所在引脚，即CAN1_TX，对应龙芯1B的GPIO41。2.3. 实物图我这里采用的是3.3V供电，同时也使用了一个5.1K的上拉电阻。3. 软件设计3.1. DHT11通信协议分析其实DHT11手册中讲得很清楚，这里简单提一下要点。整个通信过程如下图首先是主机（龙芯1B开发板）发送开始信号，然后就一直读，直到读完所有数据。开始信号为至少18ms的低电平和20到40us的高电平组成，如下图所示同时DHT11也回应一个起始信号，然后就是40bit的数据。每bit数据都是以50us的低电平开始，然后根据后面高电平的持续时间来判断为0还是1。如下图所示3.2. 主要思路

5、通过对DHT11单总线协议分析，决定先将DHT11发送的40bit数据的高低电平持续时间计算出来，然后再根据DHT11手册中的说明，将高低电平持续时间转换为二进制的0和1，最后得到温湿度值。计算DHT11发出的高低电平持续时间的方法有两种：l 通过不断读取GPIO引脚的值，发现发生改变，则记录当前系统时间l 通过中断方式，当发生中断时记录当前的系统时间后来发现通过不断读GPIO引脚值得过程中，有几次电平变化都没有被识别到，很明显是驱动有被“暂停”了，即被schedule了。因为DHT11发送的40bit数据约4ms，相对linux来说太长了，不允许一直被占用。所以最后选用中断方式。3.3. 关

6、键函数赏析首先通过函数ls1b_dht11_gpio_output_level()发送开始信号，然后马上把GPIO引脚设为输入并使能中断，然后在中断发生时记录当前系统时间，同时启动（或重启）定时器用于判断是否通信完成。如果超过指定时间没有发生中断，则表明通信完成，这时将记录下来的每个中断的发生时刻，转变为相邻两个中断的间隔时间，然后根据DHT11手册将间隔时间转换为对应的二进制0和1，最后得到温湿度值。发生起始信号的函数为ls1b_dht11_communication_start()，如下中断处理函数为ls1b_dht11_irq_handler()，如下中断下半部如下定时器超时处理函数如下

7、驱动的read接口如下关键寒暑浏览完毕。4. 运行结果4.1. 采用中断方式读DHT114.1.1. 采集温湿度成功Algorithmics/MIPS FPU Emulator v1.5#mount all.#Starting mdev.Processing /etc/profile.Done!LOONSONLoongson-gz:/#echo 8 > /proc/sys/kernel/printkLOONSONLoongson-gz:/#cd test/LOONSONLoongson-gz:/test#lsls1b_dht11_app ls1b_dht11_driver.koLOONS

8、ONLoongson-gz:/test#insmod ls1b_dht11_driver.ko ls1b_dht11_init: ls1b_dht11 device installed with major 253LOONSONLoongson-gz:/test#mknod /dev/dht11 c 253 0LOONSONLoongson-gz:/test#./ls1b_dht11_app 首先打开调试开关“echo 8 > /proc/sys/kernel/printk”，然后插入模块“insmod ls1b_dht11_driver.ko”，根据打印的主设备号创建设备节点“mkno

9、d /dev/dht11 c 253 0”，最后运行应用程序“./ls1b_dht11_app”。-dht11 high and low level info begin-timeval=625926197s,789833us interval= 0 binary=timeval=625926197s,790014us interval=181 binary=Etimeval=625926197s,790083us interval= 69 binary=0timeval=625926197s,790153us interval= 70 binary=0timeval=625926197s,7

10、90274us interval=121 binary=1timeval=625926197s,790353us interval= 79 binary=0timeval=625926197s,790477us interval=124 binary=1timeval=625926197s,790600us interval=123 binary=1timeval=625926197s,790679us interval= 79 binary=0timeval=625926197s,790755us interval= 76 binary=0timeval=625926197s,790835u

11、s interval= 80 binary=0timeval=625926197s,790911us interval= 76 binary=0timeval=625926197s,790988us interval= 77 binary=0timeval=625926197s,791065us interval= 77 binary=0timeval=625926197s,791143us interval= 78 binary=0timeval=625926197s,791222us interval= 79 binary=0timeval=625926197s,791300us inte

12、rval= 78 binary=0timeval=625926197s,791377us interval= 77 binary=0timeval=625926197s,791454us interval= 77 binary=0timeval=625926197s,791532us interval= 78 binary=0timeval=625926197s,791611us interval= 79 binary=0timeval=625926197s,791733us interval=122 binary=1timeval=625926197s,791812us interval=

13、79 binary=0timeval=625926197s,791935us interval=123 binary=1timeval=625926197s,792059us interval=124 binary=1timeval=625926197s,792185us interval=126 binary=1timeval=625926197s,792261us interval= 76 binary=0timeval=625926197s,792340us interval= 79 binary=0timeval=625926197s,792416us interval= 76 bin

14、ary=0timeval=625926197s,792495us interval= 79 binary=0timeval=625926197s,792573us interval= 78 binary=0timeval=625926197s,792648us interval= 75 binary=0timeval=625926197s,792727us interval= 79 binary=0timeval=625926197s,792806us interval= 79 binary=0timeval=625926197s,792882us interval= 76 binary=0t

15、imeval=625926197s,793008us interval=126 binary=1timeval=625926197s,793085us interval= 77 binary=0timeval=625926197s,793161us interval= 76 binary=0timeval=625926197s,793240us interval= 79 binary=0timeval=625926197s,793317us interval= 77 binary=0timeval=625926197s,793441us interval=124 binary=1timeval

16、=625926197s,793563us interval=122 binary=1timeval=0s,0us interval=206437 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=E-dht11 high and low level info end-ls1b_dht11_irq_buff_calc_temp_humidity: result0=44ls1b_dht11_irq_buff_calc_temp_humidity: result1=0ls1b_dht11_irq_

17、buff_calc_temp_humidity: result2=23ls1b_dht11_irq_buff_calc_temp_humidity: result3=0ls1b_dht11_irq_buff_calc_temp_humidity: result4=67humidity= 44, temp= 23main: dht11 collect successhumidity=44, temp=23打印中有三列分别是timeval、interval和binary。其中timeval为每次中断发生时的系统时间，interval为相邻两次中断的时间间隔（单位us），binary为根据DHT11

18、手册中的协议将电平持续时间转换为对应的二进制数据0和1。第一个timeval是记录的第一次中断，之前没有中断，所以对应的interval为0，binary没有。第二个timeval是记录的第二次中断，即DHT11响应的开始信号产生的中断，该信号有80us低电平和80us高电平组成，所以对应的interval约160us。因为binary只是针对后面的数据的，所以这里为Error，简写E。后面的第三、四、五个中断分别为40bit数据的中断，其中数据0由50us低电平和26-28us高电平组成，即间隔为77us左右的表示数据0,；数据1由50us低电平和70us高电平组成，即间隔为120us左右的

19、表示数据1。最后得到5字节的数据。如这里的44,0,23,0,67，其中第一个值“44”表示湿度为44%，第三个值“23”表示温度为23摄氏度；第五个值“67”表示校验和为67。4.1.2. 采集温湿度失败之校验不过-dht11 high and low level info begin-timeval=625926222s,922134us interval= 0 binary=timeval=625926222s,922291us interval=157 binary=Etimeval=625926222s,922363us interval= 72 binary=0timeval=62

20、5926222s,922439us interval= 76 binary=0timeval=625926222s,922562us interval=123 binary=1timeval=625926222s,922638us interval= 76 binary=0timeval=625926222s,922762us interval=124 binary=1timeval=625926222s,922886us interval=124 binary=1timeval=625926222s,922965us interval= 79 binary=0timeval=62592622

21、2s,923042us interval= 77 binary=0timeval=625926222s,923121us interval= 79 binary=0timeval=625926222s,923198us interval= 77 binary=0timeval=625926222s,923276us interval= 78 binary=0timeval=625926222s,923351us interval= 75 binary=0timeval=625926222s,923432us interval= 81 binary=0timeval=625926222s,923

22、508us interval= 76 binary=0timeval=625926222s,923586us interval= 78 binary=0timeval=625926222s,923664us interval= 78 binary=0timeval=625926222s,923741us interval= 77 binary=0timeval=625926222s,923818us interval= 77 binary=0timeval=625926222s,923896us interval= 78 binary=0timeval=625926222s,924021us

23、interval=125 binary=1timeval=625926222s,924099us interval= 78 binary=0timeval=625926222s,924222us interval=123 binary=1timeval=625926222s,924347us interval=125 binary=1timeval=625926222s,924471us interval=124 binary=1timeval=625926222s,924549us interval= 78 binary=0timeval=625926222s,924627us interv

24、al= 78 binary=0timeval=625926222s,924703us interval= 76 binary=0timeval=625926222s,924782us interval= 79 binary=0timeval=625926222s,924857us interval= 75 binary=0timeval=625926222s,924935us interval= 78 binary=0timeval=625926222s,925012us interval= 77 binary=0timeval=625926222s,925093us interval= 81

25、 binary=0timeval=625926222s,925171us interval= 78 binary=0timeval=625926222s,925294us interval=123 binary=1timeval=625926222s,925372us interval= 78 binary=0timeval=625926222s,925448us interval= 76 binary=0timeval=625926222s,925527us interval= 79 binary=0timeval=625926222s,925639us interval=112 binar

26、y=1timeval=625926222s,925734us interval= 95 binary=0timeval=625926222s,925851us interval=117 binary=1timeval=0s,0us interval=74149 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=E-dht11 high and low level info end-ls1b_dht11_irq_buff_calc_temp_humidity: result0=44ls1b_d

27、ht11_irq_buff_calc_temp_humidity: result1=0ls1b_dht11_irq_buff_calc_temp_humidity: result2=23ls1b_dht11_irq_buff_calc_temp_humidity: result3=0ls1b_dht11_irq_buff_calc_temp_humidity: result4=69ls1b_dht11_irq_buff_calc_temp_humidity: check sum error.ls1b_dht11_irq_buff_analytical: calc temp humidity f

28、ail. ret=6main: dht11 collect fail. ret=-1这是校验不过的情况，正确的校验和应该是44+0+23+0然后取低8位=67，而不是这里的69。4.1.3. 采集温湿度失败之不符合协议-dht11 high and low level info begin-timeval=625926216s,649827us interval= 0 binary=timeval=625926216s,650001us interval=174 binary=Etimeval=625926216s,650070us interval= 69 binary=0timeval=6

29、25926216s,650146us interval= 76 binary=0timeval=625926216s,650271us interval=125 binary=1timeval=625926216s,650346us interval= 75 binary=0timeval=625926216s,650470us interval=124 binary=1timeval=625926216s,650593us interval=123 binary=1timeval=625926216s,650673us interval= 80 binary=0timeval=6259262

30、16s,650750us interval= 77 binary=0timeval=625926216s,650828us interval= 78 binary=0timeval=625926216s,650907us interval= 79 binary=0timeval=625926216s,650981us interval= 74 binary=0timeval=625926216s,651061us interval= 80 binary=0timeval=625926216s,651205us interval=144 binary=Etimeval=625926216s,65

31、1296us interval= 91 binary=0timeval=625926216s,651371us interval= 75 binary=0timeval=625926216s,651449us interval= 78 binary=0timeval=625926216s,651527us interval= 78 binary=0timeval=625926216s,651603us interval= 76 binary=0timeval=625926216s,651728us interval=125 binary=1timeval=625926216s,651806us

32、 interval= 78 binary=0timeval=625926216s,651929us interval=123 binary=1timeval=625926216s,652053us interval=124 binary=1timeval=625926216s,652177us interval=124 binary=1timeval=625926216s,652255us interval= 78 binary=0timeval=625926216s,652332us interval= 77 binary=0timeval=625926216s,652411us inter

33、val= 79 binary=0timeval=625926216s,652488us interval= 77 binary=0timeval=625926216s,652566us interval= 78 binary=0timeval=625926216s,652644us interval= 78 binary=0timeval=625926216s,652721us interval= 77 binary=0timeval=625926216s,652800us interval= 79 binary=0timeval=625926216s,652875us interval= 7

34、5 binary=0timeval=625926216s,653002us interval=127 binary=1timeval=625926216s,653079us interval= 77 binary=0timeval=625926216s,653156us interval= 77 binary=0timeval=625926216s,653233us interval= 77 binary=0timeval=625926216s,653311us interval= 78 binary=0timeval=625926216s,653434us interval=123 bina

35、ry=1timeval=625926216s,653558us interval=124 binary=1timeval=0s,0us interval=346442 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=E-dht11 high and low level info end-ls1b_dht11_irq_buff_calc_temp_humidity: result0=44ls1b_dht11_irq_buf

36、f_calc_temp_humidity: *binary=E, byte_index=1, bit_index=4ls1b_dht11_irq_buff_analytical: calc temp humidity fail. ret=-1main: dht11 collect fail. ret=-1打印信息已经提示了，第二字节的第二个bit的值不合法，其interval为144，超过了二进制数据1的最大电平持续时间（140us）。4.1.4. 成功失败次数统计分析LOONSONLoongson-gz:/test#rmmod ls1b_dht11_driverls1b_dht11_exit

37、: ls1b_dht11 device uninstalled.LOONSONLoongson-gz:/test#insmod ls1b_dht11_driver.ko LOONSONLoongson-gz:/test#./ls1b_dht11_app main: dht11 collect fail. ret=-1main: dht11 collect fail. ret=-1main: dht11 collect successhumidity=45, temp=23main: dht11 collect successhumidity=45, temp=23main: dht11 col

38、lect successhumidity=45, temp=23main: dht11 collect successhumidity=45, temp=23main: dht11 collect fail. ret=-1main: dht11 collect fail. ret=-1main: dht11 collect successhumidity=45, temp=23main: dht11 collect successhumidity=45, temp=23main: dht11 collect successhumidity=45, temp=23main: dht11 coll

39、ect fail. ret=-1main: dht11 collect successhumidity=45, temp=23main: dht11 collect fail. ret=-1main: dht11 collect successhumidity=44, temp=23main: dht11 collect successhumidity=45, temp=23main: dht11 collect successhumidity=45, temp=23main: dht11 collect successhumidity=45, temp=23main: dht11 colle

40、ct fail. ret=-1main: dht11 collect fail. ret=-1main: dht11 collect fail. ret=-1main: dht11 collect successhumidity=45, temp=23main: dht11 collect successhumidity=45, temp=23main: dht11 collect successhumidity=45, temp=23main: dht11 collect successhumidity=44, temp=23main: dht11 collect fail. ret=-1m

41、ain: dht11 collect successhumidity=45, temp=23main: dht11 collect successhumidity=45, temp=23main: dht11 collect successhumidity=45, temp=23main: dht11 collect successhumidity=44, temp=23main: dht11 collect successhumidity=44, temp=23main: dht11 collect fail. ret=-1main: dht11 collect fail. ret=-1ma

42、in: dht11 collect successhumidity=44, temp=23main: dht11 collect successhumidity=44, temp=23main: dht11 collect successhumidity=44, temp=23main: dht11 collect fail. ret=-1main: dht11 collect fail. ret=-1main: dht11 collect successhumidity=44, temp=23main: dht11 collect fail. ret=-1main: dht11 collec

43、t successhumidity=44, temp=23CLOONSONLoongson-gz:/test#从上面的打印初步估计成功率为50%左右，应用程序采集温湿度的间隔时间为5s，也就是说一分钟要采集12次，大概五六次成功，也就是一分钟成功采集一次还是有保障的。4.1.5. 加载模块后第一次采集失败LOONSONLoongson-gz:/test#rmmod ls1b_dht11_driverls1b_dht11_exit: ls1b_dht11 device uninstalled.LOONSONLoongson-gz:/test#insmod ls1b_dht11_driver.ko

44、 LOONSONLoongson-gz:/test#echo 8 > /proc/sys/kernel/printkLOONSONLoongson-gz:/test#./ls1b_dht11_app -dht11 high and low level info begin-timeval=625927467s,681933us interval= 0 binary=timeval=0s,0us interval=318067 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etime

45、val=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval=

46、 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0

47、s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 bi

48、nary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us

49、 interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=Etimeval=0s,0us interval= 0 binary=E-dht11 high and low level info end-ls1b_dht11_irq_buff_calc_temp_humidity: *binary=E, byte_index=0, bit_index=0ls1b_dht11_irq_buff_analytical: calc temp humidity fail. ret=-1

50、main: dht11 collect fail. ret=-1-dht11 high and low level info begin-timeval=625927467s,681933us interval= 0 binary=timeval=625927467s,864862us interval=182929 binary=Etimeval=625927467s,865028us interval=166 binary=Etimeval=625927467s,865099us interval= 71 binary=0timeval=625927467s,865179us interv

51、al= 80 binary=0timeval=625927467s,865401us interval=222 binary=Etimeval=625927467s,865505us interval=104 binary=1timeval=625927467s,865630us interval=125 binary=1timeval=625927467s,865704us interval= 74 binary=0timeval=625927467s,865785us interval= 81 binary=0timeval=625927467s,865861us interval= 76

52、 binary=0timeval=625927467s,865936us interval= 75 binary=0timeval=625927467s,866014us interval= 78 binary=0timeval=625927467s,866089us interval= 75 binary=0timeval=625927467s,866170us interval= 81 binary=0timeval=625927467s,866247us interval= 77 binary=0timeval=625927467s,866321us interval= 74 binar

53、y=0timeval=625927467s,866405us interval= 84 binary=0timeval=625927467s,866480us interval= 75 binary=0timeval=625927467s,866556us interval= 76 binary=0timeval=625927467s,866636us interval= 80 binary=0timeval=625927467s,866762us interval=126 binary=1timeval=625927467s,866836us interval= 74 binary=0tim

54、eval=625927467s,866966us interval=130 binary=1timeval=625927467s,867091us interval=125 binary=1timeval=625927467s,867219us interval=128 binary=1timeval=625927467s,867286us interval= 67 binary=0timeval=625927467s,867368us interval= 82 binary=0timeval=625927467s,867444us interval= 76 binary=0timeval=6

55、25927467s,867518us interval= 74 binary=0timeval=625927467s,867596us interval= 78 binary=0timeval=625927467s,867711us interval=115 binary=1timeval=625927467s,867752us interval= 41 binary=Etimeval=625927467s,867867us interval=115 binary=1timeval=625927467s,867907us interval= 40 binary=Etimeval=6259274

56、67s,868043us interval=136 binary=1timeval=625927467s,868120us interval= 77 binary=0timeval=625927467s,868192us interval= 72 binary=0timeval=625927467s,868271us interval= 79 binary=0timeval=625927467s,868350us interval= 79 binary=0timeval=625927467s,868474us interval=124 binary=1timeval=625927467s,868621us interval=147 binary=E-dht11 high and low level