Zoltan Hudak
Library for communication with the HX711 24-Bit Analog-to-Digital converter.
Library for communication with the HX711 24-Bit Analog-to-Digital converter.
HX711
HX711 is a precision 24-bit analog-to-digital converter (ADC) designed for weigh scales and industrial control applications to interface directly with a bridge sensor. The input multiplexer selects either Channel A or B differential input to the low-noise programmable gain amplifier (PGA). Channel A can be programmed with a gain of 128 or 64, corresponding to a full-scale differential input voltage of ±20mV or ±40mV respectively, when a 5V supply is connected to AVDD analog power supply pin. Channel B has a fixed gain of 32. On-chip power supply regulator eliminates the need for an external supply regulator to provide analog power for the ADC and the sensor. Clock input is flexible. It can be from an external clock source, a crystal, or the on-chip oscillator that does not require any external component. On-chip power-on-reset circuitry simplifies digital interface initialization.
Example program:
Import programHMC1501_Hello
Example program for the HMC1501 magnetic 90° angle sensor connected to a HX711 high precision 24-bit programmable analog-to-digital converter (ADC) .
Last commit 19 Sep 2020 by 
Zoltan Hudak
Diff: HX711.cpp
- Revision:
- 0:72a9d7812a33
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/HX711.cpp Sat Sep 19 17:54:17 2020 +0000
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+/*
+ * 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/>.
+ */
+
+#include "mbed.h"
+#include "HX711.h"
+
+/**
+ * Class for communication with the HX711 24-Bit Analog-to-Digital converter (ADC)
+ * (Developed for Weigh Scales by AVIA Semiconductor but can be used generally.)
+ * This library is based on the library at https://github.com/bogde/HX711
+ */
+
+/**
+ * @brief Sets gain
+ * @note
+ * @param gain Selected gain (128, 64 or 32)
+ * @retval
+ */
+void HX711::setGain(uint8_t gain)
+{
+ _gain = gain;
+
+ switch (gain) {
+ case 128: // channel A, gain factor 128
+ _mode = 1;
+ break;
+
+ case 64: // channel A, gain factor 64
+ _mode = 3;
+ break;
+
+ case 32: // channel B, gain factor 32
+ _mode = 2;
+ break;
+ }
+
+ _sck.write(0);
+}
+
+/**
+ * @brief Obtains digital value of measured analog input voltage.
+ * @note It's a 24-bit two's complement integer.
+ * @retval Digital value of measured analog input voltage.
+ */
+uint32_t HX711::readInt()
+{
+ uint32_t value = 0;
+ for (uint8_t i = 0; i < 24; ++i) {
+ _sck.write(1);
+ value = value << 1;
+ value |= _dout.read();
+ _sck.write(0);
+ }
+
+ // set the channel and the gain factor for the next reading using the clock pin
+ for (unsigned int i = 0; i < _mode; i++) {
+ _sck.write(1);
+ _sck.write(0);
+ }
+
+ return value;
+}
+
+/**
+ * @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 HX711::_toFloat(uint32_t dword)
+{
+ if (dword & 0x800000)
+ return(-float((~dword + 1) & 0xFFFFFF) / 8388608.0f);
+ else
+ return(float(dword) / 8388607.0f);
+}
+
+/**
+ * @brief Converts normalised value to voltage.
+ * @note
+ * @param val Normalised measured value (ranging from -1.0f to + 1.0f)
+ * @retval Input voltage in Volts [V]
+ */
+float HX711::toVolt(float val)
+{
+ return((val * _avdd) / _gain / 2);
+}
+
+/**
+ * @brief Obtains HX711's input voltage in mV.
+ * @note
+ * @retval Measured voltage in mV.
+ */
+float HX711::read()
+{
+ return(toVolt(_toFloat(readInt())) * 1000 - _drift);
+}