HX711.cpp

#include <Arduino.h>
#include <HX711.h>

HX711::HX711(byte dout, byte pd_sck, byte gain) {
	PD_SCK 	= pd_sck;
	DOUT 	= dout;

	pinMode(PD_SCK, OUTPUT);
	pinMode(DOUT, INPUT);

	set_gain(gain);
}

HX711::~HX711() {

}

bool HX711::is_ready() {
	return digitalRead(DOUT) == LOW;
}

void HX711::set_gain(byte gain) {
	switch (gain) {
		case 128:		// channel A, gain factor 128
			GAIN = 1;
			break;
		case 64:		// channel A, gain factor 64
			GAIN = 3;
			break;
		case 32:		// channel B, gain factor 32
			GAIN = 2;
			break;
	}

	digitalWrite(PD_SCK, LOW);
	read();
}

long HX711::read() {
	// wait for the chip to become ready
	while (!is_ready());

    unsigned long value = 0;
    byte data[3] = { 0 };
    byte filler = 0x00;

	// pulse the clock pin 24 times to read the data
    data[2] = shiftIn(DOUT, PD_SCK, MSBFIRST);
    data[1] = shiftIn(DOUT, PD_SCK, MSBFIRST);
    data[0] = shiftIn(DOUT, PD_SCK, MSBFIRST);

	// set the channel and the gain factor for the next reading using the clock pin
	for (unsigned int i = 0; i < GAIN; i++) {
		digitalWrite(PD_SCK, HIGH);
		digitalWrite(PD_SCK, LOW);
	}

    // Datasheet indicates the value is returned as a two's complement value
    // Flip all the bits
    data[2] = ~data[2];
    data[1] = ~data[1];
    data[0] = ~data[0];

    // Replicate the most significant bit to pad out a 32-bit signed integer
    if ( data[2] & 0x80 ) {
        filler = 0xFF;
    } else if ((0x7F == data[2]) && (0xFF == data[1]) && (0xFF == data[0])) {
        filler = 0xFF;
    } else {
        filler = 0x00;
    }

    // Construct a 32-bit signed integer
    value = ( static_cast<unsigned long>(filler) << 24
            | static_cast<unsigned long>(data[2]) << 16
            | static_cast<unsigned long>(data[1]) << 8
            | static_cast<unsigned long>(data[0]) );

    // ... and add 1
    return static_cast<long>(++value);
}

long HX711::read_average(byte times) {
	long sum = 0;
	for (byte i = 0; i < times; i++) {
		sum += read();
	}
	return sum / times;
}

double HX711::get_value(byte times) {
	return read_average(times) - OFFSET;
}

float HX711::get_units(byte times) {
	return get_value(times) / SCALE;
}

void HX711::tare(byte times) {
	double sum = read_average(times);
	set_offset(sum);
}

void HX711::set_scale(float scale) {
	SCALE = scale;
}

float HX711::get_scale() {
	return SCALE;
}

void HX711::set_offset(long offset) {
	OFFSET = offset;
}

long HX711::get_offset() {
	return OFFSET;
}

void HX711::power_down() {
	digitalWrite(PD_SCK, LOW);
	digitalWrite(PD_SCK, HIGH);
}

void HX711::power_up() {
	digitalWrite(PD_SCK, LOW);
}