max31875.cpp

00001 /*******************************************************************************
00002 * Copyright (C) 2019 Maxim Integrated Products, Inc., All Rights Reserved.
00003 *
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00009 * Software is furnished to do so, subject to the following conditions:
00010 *
00011 * The above copyright notice and this permission notice shall be included
00012 * in all copies or substantial portions of the Software.
00013 *
00014 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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00016 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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00021 *
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00025 *
00026 * The mere transfer of this software does not imply any licenses
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00032 */
00033 #include "max31875.h"
00034 #include "mbed.h" 
00035 // #include "USBSerial.h"
00036 
00037 
00038 /******************************************************************************/
00039 MAX31875::MAX31875(I2C &i2c_bus, uint8_t slaveAddress):
00040 m_i2c(i2c_bus), 
00041 m_writeAddress(slaveAddress <<1),
00042 m_readAddress ((slaveAddress << 1) | 1),
00043 m_extended_format(0)
00044 {
00045 }
00046  
00047  
00048 /******************************************************************************/
00049 MAX31875::~MAX31875(void) 
00050 {
00051   /** empty block */
00052 }
00053  
00054 
00055 /******************************************************************************/
00056 int MAX31875::read_reg(uint16_t *value, char reg) 
00057 {
00058     int32_t ret;
00059     char data[2] = {0, 0};
00060     max31875_raw_data tmp;
00061      
00062     if (reg <= MAX31875_REG_MAX) {
00063         /* write to the Register Select */
00064         ret = m_i2c.write(m_writeAddress, &reg, 1, true);
00065         /* read the two bytes of data */
00066         if (ret == 0) {
00067             ret = m_i2c.read(m_readAddress, data, 2, false);
00068             if (ret == 0) {
00069                 tmp.msb = data[0];  /* MSB */
00070                 tmp.lsb = data[1];  /* LSB */
00071                 *value = tmp.swrd;
00072                 return MAX31875_NO_ERROR;
00073             } else {
00074                 printf(
00075                     "%s: failed to read data: ret: %d\r\n", __func__, ret);
00076             }
00077         } else {                
00078             printf("%s: failed to write to Register Select: ret: %d\r\n",
00079                 __func__, ret);
00080         }
00081     } else {
00082         printf("%s: register address is not correct: register: %d\r\n",
00083                 __func__, reg);
00084     }                
00085     return MAX31875_ERROR;
00086 }
00087 
00088 
00089 float MAX31875::read_reg_as_temperature(uint8_t reg)
00090 {
00091     max31875_raw_data tmp;
00092     float temperature;
00093     if (reg == MAX31875_REG_TEMPERATURE ||
00094         reg == MAX31875_REG_THYST || reg == MAX31875_REG_TOS) {
00095         read_reg(&tmp.uwrd, reg);
00096         temperature = (float)tmp.swrd;
00097         if (m_extended_format)
00098             temperature *= MAX31875_CF_EXTENDED_FORMAT;
00099         else
00100             temperature *= MAX31875_CF_NORMAL_FORMAT;
00101         return temperature;
00102     } else {
00103         printf("%s: register is invalid, %d r\n", __func__, reg);
00104         return 0;
00105     }
00106 }
00107 
00108 
00109 /******************************************************************************/
00110 int MAX31875::write_reg(uint16_t value, char reg) 
00111 {
00112     int32_t ret;
00113     char cmd[3];
00114     max31875_raw_data tmp;
00115 
00116     if (reg >= MAX31875_REG_CONFIGURATION && reg <= MAX31875_REG_MAX) {
00117         cmd[0] = reg;
00118         tmp.uwrd = value;
00119         cmd[1] = tmp.msb;
00120         cmd[2] = tmp.lsb;
00121         ret = m_i2c.write(m_writeAddress, cmd, 3, false);
00122         if (ret == 0) {
00123             if (tmp.uwrd & MAX31875_CFG_EXTENDED_FORMAT)
00124                 m_extended_format = 1;
00125             else 
00126                 m_extended_format = 0;
00127             return MAX31875_NO_ERROR;
00128         } else {
00129             printf("%s: I2C write error %d\r\n",__func__, ret);
00130             return MAX31875_ERROR;
00131         }
00132     } else {
00133         printf("%s: register value invalid %x\r\n",__func__, reg);
00134         return MAX31875_ERROR;
00135     }
00136 }
00137 
00138 
00139 int MAX31875::write_cfg(uint16_t cfg)
00140 {
00141     return write_reg(cfg, MAX31875_REG_CONFIGURATION);
00142 }
00143 
00144 
00145 int MAX31875::write_trip_low(float temperature)
00146 {
00147     max31875_raw_data raw;
00148     if (m_extended_format)
00149         temperature /= MAX31875_CF_EXTENDED_FORMAT;
00150     else
00151         temperature /= MAX31875_CF_NORMAL_FORMAT;
00152     raw.uwrd = uint16_t(temperature);
00153     return write_reg(raw.uwrd, MAX31875_REG_THYST);
00154 }
00155 
00156 
00157 int MAX31875::write_trip_high(float temperature)
00158 {
00159     max31875_raw_data raw;
00160     if (m_extended_format)
00161         temperature /= MAX31875_CF_EXTENDED_FORMAT;
00162     else
00163         temperature /= MAX31875_CF_NORMAL_FORMAT;
00164     raw.uwrd = uint16_t(temperature);
00165     return write_reg(raw.uwrd, MAX31875_REG_TOS);
00166 }
00167 
00168 
00169 float MAX31875::celsius_to_fahrenheit(float temp_c)
00170 {
00171     float temp_f;
00172     temp_f = ((temp_c * 9)/5) + 32;
00173     return temp_f;
00174 }