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Configurable pullup delay time, default 55 usec

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Phillip Burgess
2019-02-14 09:24:17 -08:00
parent 1e752b12ee
commit 7cec0cb06d
3 changed files with 10 additions and 4 deletions
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9
DHT.cpp
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@ -22,7 +22,9 @@ DHT::DHT(uint8_t pin, uint8_t type, uint8_t count) {
// based on the speed of the processor.
}
void DHT::begin(void) {
// Optionally pass pull-up time (in microseconds) before DHT reading starts.
// Default is 55 (see function declaration in DHT.h).
void DHT::begin(uint8_t usec) {
// set up the pins!
pinMode(_pin, INPUT_PULLUP);
// Using this value makes sure that millis() - lastreadtime will be
@ -30,6 +32,7 @@ void DHT::begin(void) {
// but so will the subtraction.
_lastreadtime = millis() - MIN_INTERVAL;
DEBUG_PRINT("DHT max clock cycles: "); DEBUG_PRINTLN(_maxcycles, DEC);
pullTime = usec;
}
//boolean S == Scale. True == Fahrenheit; False == Celcius
@ -179,8 +182,10 @@ bool DHT::read(bool force) {
// End the start signal by setting data line high for 40 microseconds.
pinMode(_pin, INPUT_PULLUP);
// Delay a moment to let sensor pull data line low.
delayMicroseconds(pullTime);
// Now start reading the data line to get the value from the DHT sensor.
delayMicroseconds(40); // Delay a bit to let sensor pull data line low.
// Turn off interrupts temporarily because the next sections
// are timing critical and we don't want any interruptions.