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DHT11/DHT22 library fixes.

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Fixed temperature below zero.
Fixed checksum overflow verification.
Fixed inconsistent reading of DHT11.
This commit is contained in:
sheinz 2016-07-06 21:01:44 +03:00
parent a41407e3d1
commit 6ff78f802d
2 changed files with 8 additions and 7 deletions
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8
examples/dht_sensor/dht_sensor.c
View file

@ -15,7 +15,7 @@
* to read and print a new temperature and humidity measurement * to read and print a new temperature and humidity measurement
* from a sensor attached to GPIO pin 4. * from a sensor attached to GPIO pin 4.
*/ */
uint8_t const dht_gpio = 12; uint8_t const dht_gpio = 4;
void dhtMeasurementTask(void *pvParameters) void dhtMeasurementTask(void *pvParameters)
{ {
@ -29,9 +29,9 @@ void dhtMeasurementTask(void *pvParameters)
while(1) { while(1) {
if (dht_read_data(dht_gpio, &humidity, &temperature)) { if (dht_read_data(dht_gpio, &humidity, &temperature)) {
printf("Humidity: %d.%d%% Temp: %d.%dC\n", printf("Humidity: %d%% Temp: %dC\n",
humidity / 10, humidity % 10, humidity / 10,
temperature / 10, abs(temperature) % 10); temperature / 10);
} else { } else {
printf("Could not read data from sensor\n"); printf("Could not read data from sensor\n");
} }

7
extras/dht/dht.c
View file

@ -64,13 +64,14 @@ static bool dht_await_pin_state(uint8_t pin, uint32_t timeout,
bool expected_pin_state, uint32_t *duration) bool expected_pin_state, uint32_t *duration)
{ {
for (uint32_t i = 0; i < timeout; i += DHT_TIMER_INTERVAL) { for (uint32_t i = 0; i < timeout; i += DHT_TIMER_INTERVAL) {
// need to wait at least a single interval to prevent reading a jitter
sdk_os_delay_us(DHT_TIMER_INTERVAL);
if (gpio_read(pin) == expected_pin_state) { if (gpio_read(pin) == expected_pin_state) {
if (duration) { if (duration) {
*duration = i; *duration = i;
} }
return true; return true;
} }
sdk_os_delay_us(DHT_TIMER_INTERVAL);
} }
return false; return false;
@ -135,7 +136,7 @@ static inline int16_t dht_convert_data(uint8_t msb, uint8_t lsb)
data = msb & 0x7F; data = msb & 0x7F;
data <<= 8; data <<= 8;
data |= lsb; data |= lsb;
if (msb & BIT(15)) { if (msb & BIT(7)) {
data = 0 - data; // convert it to negative data = 0 - data; // convert it to negative
} }
#elif DHT_TYPE == DHT11 #elif DHT_TYPE == DHT11
@ -169,7 +170,7 @@ bool dht_read_data(uint8_t pin, int16_t *humidity, int16_t *temperature)
data[i/8] |= bits[i]; data[i/8] |= bits[i];
} }
if (data[4] != (data[0] + data[1] + data[2] + data[3])) { if (data[4] != ((data[0] + data[1] + data[2] + data[3]) & 0xFF)) {
debug("Checksum failed, invalid data received from sensor\n"); debug("Checksum failed, invalid data received from sensor\n");
return false; return false;
} }