bool DHTRead(DHT_Sensor *sensor, DHT_Sensor_Data* output)
{
int counter = 0;
int laststate = 1;
int i = 0;
int j = 0;
int checksum = 0;
int data[100];
data[0] = data[1] = data[2] = data[3] = data[4] = 0;
uint8_t pin = GPIO_ID_PIN(sensor->port);
// Wake up device, 250ms of high
GPIO_OUTPUT_SET(pin, 1);
sleepms(250);
// Hold low for 20ms
GPIO_OUTPUT_SET(pin, 0);
sleepms(20);
// High for 40ns
GPIO_OUTPUT_SET(pin, 1);
os_delay_us(40);
// Set DHT_PIN pin as an input
GPIO_DIS_OUTPUT(pin);
// wait for pin to drop?
while (GPIO_INPUT_GET(pin) == 1 && i < DHT_MAXCOUNT) {
os_delay_us(1);
i++;
}
if(i == DHT_MAXCOUNT)
{
DHT_DEBUG("DHT: Failed to get reading from GPIO%d, dying\r\n", pin);
return false;
}
// read data
for (i = 0; i < DHT_MAXTIMINGS; i++)
{
// Count high time (in approx us)
counter = 0;
while (GPIO_INPUT_GET(pin) == laststate)
{
counter++;
os_delay_us(1);
if (counter == 1000)
break;
}
laststate = GPIO_INPUT_GET(pin);
if (counter == 1000)
break;
// store data after 3 reads
if ((i>3) && (i%2 == 0)) {
// shove each bit into the storage bytes
data[j/8] <<= 1;
if (counter > DHT_BREAKTIME)
data[j/8] |= 1;
j++;
}
}
if (j >= 39) {
checksum = (data[0] + data[1] + data[2] + data[3]) & 0xFF;
DHT_DEBUG("DHT%s: %02x %02x %02x %02x [%02x] CS: %02x (GPIO%d)\r\n",
sensor->type==DHT11?"11":"22",
data[0], data[1], data[2], data[3], data[4], checksum, pin);
if (data[4] == checksum) {
// checksum is valid
output->temperature = scale_temperature(sensor->type, data);
output->humidity = scale_humidity(sensor->type, data);
//DHT_DEBUG("DHT: Temperature = %d *C, Humidity = %d %%\r\n", (int)(reading.temperature * 100), (int)(reading.humidity * 100));
DHT_DEBUG("DHT: Temperature*100 = %d *C, Humidity*100 = %d %% (GPIO%d)\n",
(int) (output->temperature * 100), (int) (output->humidity * 100), pin);
} else {
//DHT_DEBUG("Checksum was incorrect after %d bits. Expected %d but got %d\r\n", j, data[4], checksum);
DHT_DEBUG("DHT: Checksum was incorrect after %d bits. Expected %d but got %d (GPIO%d)\r\n",
j, data[4], checksum, pin);
return false;
}
} else {
//DHT_DEBUG("Got too few bits: %d should be at least 40\r\n", j);
DHT_DEBUG("DHT: Got too few bits: %d should be at least 40 (GPIO%d)\r\n", j, pin);
return false;
}
return true;
}
// return values:
// DHTLIB_OK
// DHTLIB_ERROR_CHECKSUM
// DHTLIB_ERROR_TIMEOUT
int dht_read_universal(uint8_t pin)
{
// READ VALUES
int rv = dht_readSensor(pin, DHTLIB_DHT_UNI_WAKEUP);
if (rv != DHTLIB_OK)
{
dht_humidity = DHTLIB_INVALID_VALUE; // invalid value, or is NaN prefered?
dht_temperature = DHTLIB_INVALID_VALUE; // invalid value
return rv; // propagate error value
}
#if defined(DHT_DEBUG_BYTES)
int i;
for (i = 0; i < 5; i++)
{
DHT_DEBUG("%02X\n", dht_bytes[i]);
}
#endif // defined(DHT_DEBUG_BYTES)
// Assume it is DHT11
// If it is DHT11, both bit[1] and bit[3] is 0
if ((dht_bytes[1] == 0) && (dht_bytes[3] == 0))
{
// It may DHT11
// CONVERT AND STORE
DHT_DEBUG("DHT11 method\n");
dht_humidity = dht_bytes[0]; // dht_bytes[1] == 0;
dht_temperature = dht_bytes[2]; // dht_bytes[3] == 0;
// TEST CHECKSUM
// dht_bytes[1] && dht_bytes[3] both 0
uint8_t sum = dht_bytes[0] + dht_bytes[2];
if (dht_bytes[4] != sum)
{
// It may not DHT11
dht_humidity = DHTLIB_INVALID_VALUE; // invalid value, or is NaN prefered?
dht_temperature = DHTLIB_INVALID_VALUE; // invalid value
// Do nothing
}
else
{
return DHTLIB_OK;
}
}
// Assume it is not DHT11
// CONVERT AND STORE
DHT_DEBUG("DHTxx method\n");
dht_humidity = (double)COMBINE_HIGH_AND_LOW_BYTE(dht_bytes[0], dht_bytes[1]) * 0.1;
dht_temperature = (double)COMBINE_HIGH_AND_LOW_BYTE(dht_bytes[2] & 0x7F, dht_bytes[3]) * 0.1;
if (dht_bytes[2] & 0x80) // negative dht_temperature
{
dht_temperature = -dht_temperature;
}
// TEST CHECKSUM
uint8_t sum = dht_bytes[0] + dht_bytes[1] + dht_bytes[2] + dht_bytes[3];
if (dht_bytes[4] != sum)
{
return DHTLIB_ERROR_CHECKSUM;
}
return DHTLIB_OK;
}
static void
dht_read(void)
{
PIN_SET(DHT);
_delay_us(30);
DDR_CONFIG_IN(DHT);
/* Read in timingss, which takes approx. 4,5 milliseconds.
* We do not disable interrupts, because a failed read is outweighed
* by a non-serviced interrupt. Please never enclose the for-loop
* with an ATOMIC_BLOCK! */
uint8_t last_state = PIN_BV(DHT);
uint8_t j = 0;
uint8_t data[5];
for (uint8_t i = 0; i < MAXTIMINGS; i++)
{
uint8_t counter = 0;
uint8_t current_state;
while (last_state == (current_state = PIN_HIGH(DHT)))
{
_delay_us(5);
if (++counter == 20)
{
DHT_DEBUG("read timeout, edge=%u", i);
return; /* timeout in conversation */
}
}
last_state = current_state;
/* ignore first three transitions */
if ((i >= 4) && (i % 2 == 0))
{
/* shift each bit into the storage bytes */
data[j / 8] <<= 1;
if (counter > 7) /* 7*5=35us */
data[j / 8] |= 1;
j++;
}
}
/* check we read 40 bits and that the checksum matches */
if ((j < 40) ||
(data[4] != ((data[0] + data[1] + data[2] + data[3]) & 0xFF)))
{
DHT_DEBUG("read failed, bits=%u, %02X %02X %02X %02X %02X",
j, data[0], data[1], data[2], data[3], data[4]);
return;
}
int16_t t;
#if DHT_TYPE == DHT_TYPE_11
t = data[2];
t *= 10;
dht_global.temp = t;
t = data[0];
t *= 10;
dht_global.humid = t;
#elif DHT_TYPE == DHT_TYPE_22
t = data[2] << 8 | data[3];
if (t & 0x8000)
{
t &= ~0x8000;
t = -t;
}
dht_global.temp = t;
t = data[0] << 8 | data[1];
dht_global.humid = t;
#endif
DHT_DEBUG("t=%d, h=%d%%", dht_global.temp, dht_global.humid);
}
