Hotboards_temp.cpp

00001 /*
00002   Hotboards_temp.cpp - Driver to read and control a serial (i2c) temperature sensor, The Microchip
00003   MCP9808 is the digital sensor to control, can be read it, set its resolution, shutdown and also
00004   set alarms.
00005   Hotboards eeprom board (http://hotboards.org)
00006   Created by Diego Perez, March 19, 2016.
00007   Released into the public domain.
00008 */
00009 #include "Hotboards_temp.h"
00010 
00011 #define SENSOR_ADDR       (uint8_t)0x3E
00012 #define REG_CONFIG        (uint8_t)0x01
00013 #define REG_ALERT_UPPER   (uint8_t)0x02
00014 #define REG_ALERT_LOWER   (uint8_t)0x03
00015 #define REG_CRITICAL_TEMP (uint8_t)0x04
00016 #define REG_TEMPERATURE   (uint8_t)0x05
00017 #define REG_MANU_ID       (uint8_t)0x06
00018 #define REG_DEVICE_ID     (uint8_t)0x07
00019 #define REG_RESOLUTION    (uint8_t)0x08
00020 
00021 Hotboards_temp::Hotboards_temp( I2C &i2c, uint8_t address, uint8_t resolution )
00022     : _i2c(i2c) 
00023 {
00024     _address = (address<<1)|0x30;
00025     _resolution = resolution;
00026 }
00027 
00028 bool Hotboards_temp::init( void )
00029 {
00030     bool flag = 0; // lets assume device is not here
00031     uint16_t val = readReg( REG_MANU_ID );
00032     if( val == 0x0054 )
00033     {
00034         // device is presence, default set resolution
00035         writeReg( REG_RESOLUTION, _resolution);
00036         // clear configuration register (alarms included)
00037         writeReg( REG_CONFIG, 0x00 );
00038         flag = 1;
00039     }
00040     return flag;
00041 }
00042 
00043 
00044 float Hotboards_temp::read( void )
00045 {
00046     uint16_t val;
00047     float temp;
00048 
00049     // read the Ta register
00050     val = readReg( REG_TEMPERATURE );
00051 
00052     // small algorithm to calculate tmeperature in Celcius
00053     // borrowed from https://github.com/adafruit/Adafruit_MCP9808_Library/blob/master/Adafruit_MCP9808.cpp
00054     temp = val & 0x0FFF;
00055     
00056     temp /=  (float)16.0;
00057      //check if a negative temperature
00058     if( val & 0x1000 ) temp -= 256;
00059 
00060     return temp;
00061 }
00062 
00063 void Hotboards_temp::setAlarms( float lower, float upper )
00064 {
00065     // set alarm values
00066     writeAlarm( REG_ALERT_UPPER, upper );
00067     writeAlarm( REG_CRITICAL_TEMP, upper );
00068     writeAlarm( REG_ALERT_LOWER, lower );
00069 
00070     uint16_t val = readReg( REG_CONFIG );
00071     // set alarm only in comparator mode with LAERT pin set to LOW
00072     writeReg( REG_CONFIG, val | 0x0008 );
00073 }
00074 
00075 void Hotboards_temp::disableAlarms( void )
00076 {
00077     uint16_t val = readReg( REG_CONFIG );
00078     // just clear the Alert Output Control bit
00079     writeReg( REG_CONFIG, val ^ 0x0008 );
00080 }
00081 
00082 void Hotboards_temp::shutdown( bool state )
00083 {
00084     uint16_t val = readReg( REG_CONFIG );
00085 
00086     if( state == HT_SENSOR_OFF )
00087     {// shutdown, curretn under 1uA, and disable convertions
00088        writeReg( REG_CONFIG, val | 0x0100 );
00089     }
00090     else
00091     {// power on
00092        writeReg( REG_CONFIG, val ^ 0x0100 );
00093     }
00094 }
00095 
00096 void Hotboards_temp::setResolution( uint8_t resolution )
00097 {
00098     resolution &= 0x03;
00099     writeReg( REG_RESOLUTION, resolution << 8 );
00100 }
00101 
00102 float Hotboards_temp::CelsiusToFarenheit( float celsius )
00103 {
00104     return celsius * (float)9.0 / (float)5.0 + 32;
00105 }
00106 
00107 float Hotboards_temp::FarenheitToCelsius( float farenheit )
00108 {
00109     return ( farenheit - 32 ) * (float)5.0 / (float)9.0;
00110 }
00111 
00112 uint16_t Hotboards_temp::readReg( uint8_t reg )
00113 {
00114     uint16_t val;
00115     char buffer[2];
00116     
00117     _address &= 0x3E;
00118     buffer[0] = reg;
00119     _i2c.write( _address, buffer, 1, true );
00120     _address |= 0x01;
00121     _i2c.read( _address, buffer, 2, false );
00122     
00123     val = buffer[0] << 8;
00124     val |= buffer[1];
00125 
00126     return val;
00127 }
00128 
00129 void Hotboards_temp::writeReg( uint8_t reg, uint16_t val )
00130 {
00131     char buffer[3] = { reg, val >> 8, val & 0x00FF };
00132     _address &= 0x3E;
00133     _i2c.write( _address, buffer, 3 );
00134 }
00135 
00136 void Hotboards_temp::writeAlarm( uint16_t reg, float temp )
00137 {
00138     uint16_t val = 0x0000;
00139     // check if negative temp
00140     if( temp < 0 )
00141     {
00142         temp += (float)256.0;
00143         // set sign bit
00144         val = 0x1000;
00145     }
00146     // convert to binary
00147     val |= (uint16_t)( temp *= (float)16.0 );
00148     writeReg( reg, val );
00149 }