IoT感測器驅動程式 在樹莓派上實作
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在物联网的应用领域中，感知层是物联网发展的基础，依各种场景的需要会使用到不同的感测器来收集资讯，但每种感测器要能在嵌入式系统上正常运作，都需要由驱动程式来驱动，所以开发或移植驱动程式算是嵌入式系统必备的技术，因此几位对尝颈苍耻虫驱动程式有兴趣的同学决定一起开发感测器驱动程式，并将此感测器拿来做物联网的应用。
![Process_data() {
for( n = 0; n < 40; n++)
if(high_time[n] > 50us)
data_bit[n] = 1;
else
data_bit[n] = 0;
…
dht22_irq_handler() {
irq_counter++;
now = get_time();
if(gpio == low)
high_time[] = now – pre;
if(irq_counter == last)
WORK_QUEUE(process_data());
pre = now;
}
2-1 Linux Driver for DHT22
dht22的通訊機制：
DHT22
DHT22 signal
> 1 ms
dht22_trigger() {
gpio_set_direction(pin, out);
gpio_set_value(pin, low);
udelay(1000);
gpio_set_value(pin, high);
udelay(20);
gpio_set_direction(pin, in);
}
Interrup_setup() {
reuest_irq(pin,
dht22_irq_handler,
FALLING_And_RISING)
}
Hi_H Lo_H Hi_T Lo_T Checksum
Work_Queue
Humidity
= Hi_H x 256 + Lo_H
Temperature
= Hi_T x 256 + Lo_T
Checksum
= Hi_H + Lo_H + Hi_T + Lo_T
Trigger 40-Bit DataResponse
1. interrup_setup
2. trigger
3. interrup_irq
4. process_data](https://image.slidesharecdn.com/4iotsensordriver-191103050855/85/IoT-6-320.jpg)
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