hx711: Initial implementation HX711 24bit ADC module

Signed-off-by: Rafael Neri <rafael.neri@gmail.com>
Signed-off-by: Mihai Tudor Panu <mihai.tudor.panu@intel.com>

src/hx711/CMakeLists.txt

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+set (libname "hx711")
+set (libdescription "HX711 24bit ADC")
+set (module_src ${libname}.cxx)
+set (module_h ${libname}.h)
+upm_module_init()

src/hx711/hx711.cxx

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+/*
+*
+* Author: Rafael da Mata Neri <rafael.neri@gmail.com>
+* Copyright (c) 2015 Intel Corporation.
+*
+*
+* Permission is hereby granted, free of charge, to any person obtaining a copy of
+* this software and associated documentation files (the "Software"), to deal in
+* the Software without restriction, including without limitation the rights to
+* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+* the Software, and to permit persons to whom the Software is furnished to do so,
+* subject to the following conditions:
+*
+* The above copyright notice and this permission notice shall be included in all
+* copies or substantial portions of the Software.
+*
+* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+*/
+#include <iostream>
+#include <fstream>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include "hx711.h"
+
+using namespace upm;
+using namespace std;
+
+struct HX711Exception : public std::exception {
+    std::string message;
+    HX711Exception (std::string msg) : message (msg) { }
+    ~HX711Exception () throw () { }
+    const char* what() const throw () { return message.c_str(); }
+};
+
+HX711::HX711(uint8_t data, uint8_t sck, uint8_t gain) {
+    mraa_result_t error = MRAA_SUCCESS;
+    
+    this->m_dataPinCtx = mraa_gpio_init(data);
+    if (this->m_dataPinCtx == NULL) {
+        throw HX711Exception ("Couldn't initilize DATA pin.");
+    }
+    
+    this->m_sckPinCtx = mraa_gpio_init(sck);
+    if (this->m_sckPinCtx == NULL) {
+        throw HX711Exception ("Couldn't initilize CLOCK pin.");
+    }
+    
+    error = mraa_gpio_dir (this->m_dataPinCtx, MRAA_GPIO_IN);
+    if (error != MRAA_SUCCESS) {
+        throw HX711Exception ("Couldn't set direction for DATA pin.");
+    }
+    
+    error = mraa_gpio_dir (this->m_sckPinCtx, MRAA_GPIO_OUT);
+    if (error != MRAA_SUCCESS) {
+        throw HX711Exception ("Couldn't set direction for CLOCK pin.");
+    }
+
+    this->setGain(gain);
+}
+
+HX711::~HX711() {
+    mraa_result_t error = MRAA_SUCCESS;
+    
+    error = mraa_gpio_close (this->m_dataPinCtx);
+    if (error != MRAA_SUCCESS) {
+        mraa_result_print(error);
+    }
+    
+    error = mraa_gpio_close (this->m_sckPinCtx);
+    if (error != MRAA_SUCCESS) {
+        mraa_result_print(error);
+    }
+}
+
+unsigned long HX711::read() {
+    unsigned long Count = 0;
+    
+    while (mraa_gpio_read(this->m_dataPinCtx));
+                                  
+    for (int i=0; i<GAIN; i++)
+    {
+        mraa_gpio_write(this->m_sckPinCtx, 1);
+        Count = Count << 1;
+        mraa_gpio_write(this->m_sckPinCtx, 0);
+        if(mraa_gpio_read(this->m_dataPinCtx))
+        {
+            Count++;
+        }
+    }
+
+    mraa_gpio_write(this->m_sckPinCtx, 1);
+    Count = Count ^ 0x800000;
+    mraa_gpio_write(this->m_sckPinCtx, 0);
+
+    return (Count);
+}
+
+void HX711::setGain(uint8_t gain){
+    switch (gain) {
+        case 128:       // channel A, gain factor 128
+            GAIN = 24;
+            break;
+        case 64:        // channel A, gain factor 64
+            GAIN = 26;
+            break;
+        case 32:        // channel B, gain factor 32
+            GAIN = 25;
+            break;
+    }
+
+    mraa_gpio_write(this->m_sckPinCtx, 0);
+    read();
+}
+
+unsigned long HX711::readAverage(uint8_t times){
+    unsigned long sum = 0;
+    for (uint8_t i = 0; i < times; i++) {
+        sum += read();
+    }
+    return sum / times;
+}
+
+double HX711::getValue(uint8_t times){
+    return readAverage(times) - OFFSET;
+}
+
+float HX711::getUnits(uint8_t times){
+    return getValue(times) / SCALE;
+}
+
+void HX711::tare(uint8_t times){
+    double sum = readAverage(times);
+    setOffset(sum);
+}
+
+void HX711::setScale(float scale){
+    SCALE = scale;
+}
+
+void HX711::setOffset(long offset){
+    OFFSET = offset;
+}

src/hx711/hx711.h

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+/*
+*
+* Author: Rafael da Mata Neri <rafael.neri@gmail.com>
+* Copyright (c) 2015 Intel Corporation.
+*
+*
+* Permission is hereby granted, free of charge, to any person obtaining a copy of
+* this software and associated documentation files (the "Software"), to deal in
+* the Software without restriction, including without limitation the rights to
+* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+* the Software, and to permit persons to whom the Software is furnished to do so,
+* subject to the following conditions:
+*
+* The above copyright notice and this permission notice shall be included in all
+* copies or substantial portions of the Software.
+*
+* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+*/
+#pragma once
+
+
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <mraa/gpio.h>
+
+namespace upm {
+
+     /**
+      * @brief HX711 24bit ADC library
+      * @defgroup hx711 libupm-hx711
+      */
+
+     /**
+      * @brief C++ API for HX711
+      *
+      * [HX711](http://www.dfrobot.com/image/data/SEN0160/hx711_english.pdf) 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. This module was tested on the Intel Galileo Gen2.
+      *
+      * @ingroup hx711 hx711
+      * @snippet hx711.cxx Interesting
+      * @image html hx711.jpeg
+      */
+      class HX711 {
+      public:
+            /**
+            * HX711 module constructor
+            *
+            * @param data define the data pin
+            * @param sck define the clock pin
+            * @param gain define the gain factor
+            * Valid values are 128 or 64 for channel A; channel B works with 32 gain factor only
+            */
+            HX711(uint8_t data, uint8_t sck, uint8_t gain = 128);
+
+            /**
+            * HX711 module Destructor
+            */
+            ~HX711();
+
+
+            /**
+            * Waits for the chip to be ready and returns a reading
+            *
+            * @return raw adc read
+            */
+            unsigned long read();
+
+            /**
+            * 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
+            * @param gain define the gain factor
+            */
+            void setGain(uint8_t gain = 128);
+
+            /**
+            * Returns an average reading
+            * @param times define how many times to read
+            * @return the avarage reading
+            */
+            unsigned long readAverage(uint8_t times = 10);
+
+            /**
+            * Returns (readAverage() - OFFSET)
+            * @param times define how many readings to do
+            * @return the current value without the tare weight
+            */
+            double getValue(uint8_t times = 10);
+
+            /**
+            * Returns getValue() divided by SCALE
+            * @param times define how many readings to do
+            * @return the raw value divided by a value obtained via calibration
+            */
+            float getUnits(uint8_t times = 1);
+
+            /**
+            * Set the OFFSET value for tare weight
+            * @param times define how many times to read the tare value
+            */
+            void tare(uint8_t times = 10);
+
+            /**
+            * Set the SCALE value 
+            * This value is used to convert the raw data to "human readable" data (measure units)
+            * @param scale value obtained via calibration
+            */
+            void setScale(float scale = 1.f);
+       private:
+            mraa_gpio_context m_sckPinCtx; // Power Down and Serial Clock Input Pin
+            mraa_gpio_context m_dataPinCtx; // Serial Data Output Pin
+            
+            uint8_t GAIN; // amplification factor
+            unsigned long OFFSET; // used for tare weight
+            float SCALE; // used to return weight in grams, kg, ounces, whatever
+
+            
+            /**
+            * Set the OFFSET value 
+            * The value that's subtracted from the actual reading (tare weight)
+            * @param scale value obtained via calibration
+            */
+            void setOffset(long offset = 0);
+     };
+
+}

src/hx711/jsupm_hx711.i

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+//! [Interesting]
+%module jsupm_hx711
+%include "../upm.i"
+
+%{
+    #include "hx711.h"
+%}
+
+%include "hx711.h"
+//! [Interesting]

src/hx711/pyupm_hx711.i

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+%module pyupm_hx711
+%include "../upm.i"
+%include "stdint.i"
+
+%feature("autodoc", "3");
+
+%include "hx711.h"
+%{
+    #include "hx711.h"
+%}