File content as of revision 0:72a9d7812a33:

/*
 * Copyright (c) 2020 Zoltan Hudak <hudakz@outlook.com>
 * All rights reserved.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef _HX711_H_
#define _HX711_H_
#include "mbed.h"

/**
 * Class for communication with the HX711 24-Bit Analog-to-Digital converter (ADC)
 * (Developed for Weigh Scales by AVIA Semiconductor.)
 * This library is based on the library at https://github.com/bogde/HX711
 */
class   HX711
{
public:
    /**
     * Creates an HX711 object
     * @param avdd Analog power supply voltage [V]
     * @param sck PinName of the clock pin (digital output)
     * @param dout PinName of the data pin (digital input)
     * @param drift Chip's input offset drift [V]
     * @param gain Channel selection is made by passing the associated gain:
     *      128 or 64 for channel A, 32 for channel B
     */
    HX711(float avdd, PinName sck, PinName dout, uint8_t gain, float drift = 0) :
    _avdd(avdd),
    _sck(sck),
    _dout(dout, PullUp),
    _drift(drift)
    {
        setGain(gain);
    }

    /**
     * Check if the sensor is ready.
     * From the datasheet: When output data is not ready for retrieval,
     * digital output pin _dout is high. Serial clock input _sck should be low.
     * When _dout goes low, it indicates data is ready for retrieval.
     * @return true if _dout.read() == 0
     */
    bool isReady() { return _dout.read() == 0; }

    /**
     * Returns a raw int reading
     * @return int sensor output value
     */
    uint32_t readInt();

    /**
     * Obtains input voltage in mV biased by chip's input offset drift
     * @return float
     */
    float read();

    /**
     * Puts the chip into power down mode
     */
    void powerDown() { _sck.write(0); _sck.write(1); }

    /**
     * Wakes up the chip after power down mode
     */
    void powerUp() { _sck.write(0); }

    /**
     * Set the gain factor; takes effect only after a call to read()
     * channel A can be set for a 128 or 64 gain; channel B has a fixed 32 gain
     * depending on the parameter, the channel is also set to either A or B
     * Ensures that gain_ = 128, 64 or 32
     * @param gain 128, 64 or 32
     */
    void setGain(uint8_t gain = 128);

    /**
     * Obtain current gain
     * @return gain_
     */
    uint8_t getGain() { return _mode; }

    /**
     * Get sensor's analog power supply voltage
     * @return power supply voltage
     */
    float getAvdd() { return _avdd; }

    /**
     * Sets the chip's input offset drift
     * @param drift The input offset drift [mV]
     */
    void setDrift(float drift = 0) { _drift = drift; }

    /**
     * Gets chip's input offset drift
     * @return Chip's input offset drift [mV]
     */
    int getDrift() { return(_drift); }

private:
    float       _avdd;      // analog power supply voltage [V]
    DigitalOut  _sck;       // HX711 clock input line
    DigitalIn   _dout;      // HX711 data output line
    uint8_t     _gain;      // amplification factor of HX711
    uint8_t     _mode;      // operating mode of HX711
    float       _drift;     // chip's input offset drift [mV]

    /**
     * @brief   Converts a 32-bit signed fixed point integer to floating point value
     * @note    The 32-bit unsigned integer argument represnts actually a 24-bit signed fixed point value:
     *          two’s complement and the LSB of the 24-bit binary number represents 1/8,388,608th of a unit).
     * @param   32-bit unsigned integer
     * @retval  Floating point value ranging from -1 to +1
     */
    float       _toFloat(uint32_t dword);

    /**
     * Converts floating point value to input voltage
     * @param val Floating point value ranging from -1.0 to +1.0
     * @return Voltage at input [V]
     */
    float toVolt(float val);
};
#endif