![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/4iotsensordriverontheraspberrypi-191104115744/85/IoT-IoT-Sensor-Driver-On-The-Raspberry-Pi-6-320.jpg)
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IoT感測器驅動程式在樹莓派上實作 IoT Sensor Driver On The Raspberry Pi
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