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/hx711.cxx

@@ -0,0 +1,148 @@
+/*
+*
+* 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;
+}