CN0216.cpp

00001 /**
00002 *   @file     cn0216.cpp
00003 *   @brief    Source file for CN0216
00004 *   @author   Analog Devices Inc.
00005 *
00006 * For support please go to:
00007 * Github: https://github.com/analogdevicesinc/mbed-adi
00008 * Support: https://ez.analog.com/community/linux-device-drivers/microcontroller-no-os-drivers
00009 * Product: www.analog.com/EVAL-CN0216-ARDZ
00010 * More: https://wiki.analog.com/resources/tools-software/mbed-drivers-all
00011 
00012 ********************************************************************************
00013 * Copyright 2016(c) Analog Devices, Inc.
00014 *
00015 * All rights reserved.
00016 *
00017 * Redistribution and use in source and binary forms, with or without
00018 * modification, are permitted provided that the following conditions are met:
00019 *  - Redistributions of source code must retain the above copyright
00020 *    notice, this list of conditions and the following disclaimer.
00021 *  - Redistributions in binary form must reproduce the above copyright
00022 *    notice, this list of conditions and the following disclaimer in
00023 *    the documentation and/or other materials provided with the
00024 *    distribution.
00025 *  - Neither the name of Analog Devices, Inc. nor the names of its
00026 *    contributors may be used to endorse or promote products derived
00027 *    from this software without specific prior written permission.
00028 *  - The use of this software may or may not infringe the patent rights
00029 *    of one or more patent holders.  This license does not release you
00030 *    from the requirement that you obtain separate licenses from these
00031 *    patent holders to use this software.
00032 *  - Use of the software either in source or binary form, must be run
00033 *    on or directly connected to an Analog Devices Inc. component.
00034 *
00035 * THIS SOFTWARE IS PROVIDED BY ANALOG DEVICES "AS IS" AND ANY EXPRESS OR
00036 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, NON-INFRINGEMENT,
00037 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
00038 * IN NO EVENT SHALL ANALOG DEVICES BE LIABLE FOR ANY DIRECT, INDIRECT,
00039 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
00040 * LIMITED TO, INTELLECTUAL PROPERTY RIGHTS, PROCUREMENT OF SUBSTITUTE GOODS OR
00041 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
00042 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
00043 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
00044 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
00045 *
00046 ********************************************************************************/
00047 
00048 #include "mbed.h"
00049 #include "AD7791.h"
00050 #include "CN0216.h"
00051 extern Serial pc;
00052 
00053 /**
00054  * CN0216 constructor
00055  * @param CSAD7791 - Chipselect of the AD7791
00056  * @param MOSI - MOSI line of the SPI bus
00057  * @param MISO - MISO line of the SPI bus
00058  * @param SCK - SCK line of the SPI bus
00059  */
00060 CN0216::CN0216(PinName CSAD7791, PinName MOSI, PinName MISO, PinName SCK) : ad7791(1.2, CSAD7791, MOSI, MISO, SCK)
00061 {
00062     _cal_weight = 0;
00063     _zero_scale_value = 0;
00064     _full_scale_value = 0;
00065     _weight_units_per_bit = 0;
00066 }
00067 
00068 /**
00069  * Initializes the mode and filter values of the AD7791 and sets the weight to be used in calibration
00070  * @param cal_weight - weight used in calibration
00071  * @param mode_val - value of the mode register
00072  * @param filter_val - value of the filter register
00073  */
00074 void CN0216::init(float cal_weight, uint8_t mode_val, uint8_t filter_val)
00075 {
00076     _cal_weight = cal_weight;
00077     ad7791.frequency(500000);
00078     wait_ms(50);
00079     ad7791.reset();
00080     wait_ms(50);
00081     ad7791.write_mode_reg(mode_val);
00082     wait_us(2);
00083     ad7791.write_filter_reg(filter_val);
00084     wait_ms(50);
00085 }
00086 
00087 /**
00088  * Calibrates the CN0216 weigh scale
00089  * @param cal - calibration step.
00090  * Step CN0216::ZERO_SCALE_CALIBRATION will take CN0216::_NUMBER_OF_SAMPLES samples and use the minimum as value for the zero scale
00091  * Step CN0216::FULL_SCALE_CALIBRATION will take CN0216::_NUMBER_OF_SAMPLES samples and use the average as value for the full scale
00092  * Step COMPUTE_UNITS_PER_BIT will compute the grams per bit used in weight computation.
00093  */
00094 void CN0216::calibrate(CalibrationStep_t  cal)
00095 {
00096     uint64_t sum = 0;
00097     uint32_t min = 0xFFFFFFFF;
00098     uint32_t sample = 0;
00099     switch(cal) {
00100         case ZERO_SCALE_CALIBRATION:
00101         case FULL_SCALE_CALIBRATION:
00102             for(int i = 0; i < _NUMBER_OF_SAMPLES; i++) {
00103                 sample = ad7791.read_u32();
00104                 min = (min < sample) ? min : sample;
00105                 sum += ad7791.read_u32();
00106                 wait_us(5);
00107             }
00108             if(cal == ZERO_SCALE_CALIBRATION) {
00109                 // pc.printf("ZERO SCALE VALUE = %x",sum);
00110                 _zero_scale_value = min;
00111             } else {
00112                 //  pc.printf("FULL SCALE VALUE = %x",sum);
00113                 sum = sum / _NUMBER_OF_SAMPLES;
00114                 _full_scale_value = sum;
00115             }
00116             break;
00117 
00118         case COMPUTE_UNITS_PER_BIT:
00119             _weight_units_per_bit = _cal_weight / (static_cast<float> (_full_scale_value - _zero_scale_value));  /* Calculate number of grams per LSB */
00120             // pc.printf("GRAMS/LSB = %f", _grams_per_bit);
00121             break;
00122         default:
00123             break;
00124     }
00125 
00126 }
00127 
00128 /**
00129  * Computes the weight based on the formula
00130  * weight = (data - zeroscale) * weight_units_per_bit
00131  * @param data read from the ADC
00132  * @return weight based on data
00133  */
00134 float CN0216::compute_weight(uint32_t data)
00135 {
00136 //  pc.printf("\r\nFULL_SCALE_VALUE = %x\r\nZERO_SCALE_VALUE = %x\r\nDATA READ = %x\r\nGRAMS/LSB = %f\r\n",_full_scale_value,data,_zero_scale_value,_grams_per_bit);
00137     if(data < _zero_scale_value)
00138         data = _zero_scale_value; // clamp data to 0
00139     float weight_in_grams =  (static_cast<float>((data) - _zero_scale_value)) * _weight_units_per_bit;         /* Calculate weight */
00140     return weight_in_grams;
00141 }
00142 
00143 /**
00144  * Reads the AD7791
00145  * @return value read by the ADC
00146  */
00147 uint32_t CN0216::read_u32()
00148 {
00149     return ad7791.read_u32();
00150 }
00151 
00152 /**
00153  * Reads the ADC and computes the weight based on the formula described above.
00154  * @return weight
00155  */
00156 float CN0216::read_weight()
00157 {
00158     uint32_t weight =  read_u32();
00159     return compute_weight(weight);
00160 }
00161