drivers/sensors/ds18b20/ds18b20.c

   1 /**************************************************************************/
   2 /*!
   3     @file     ds18b20.c
   4     @author   Albertas Mickenas (mic@wemakethings.net)
   5     @date     8 August 2012
   6     @version  1.0
   7
   8     @section DESCRIPTION
   9     Driver for DALLAS DS18B20 temperature sensor.
  10
  11     @section Example
  12
  13     @code
  14      #include "core/cpu/cpu.h"
  15      #include "drivers/sensors/ds18b20/ds18b20.h"
  16
  17      int main(void) {
  18          cpuInit();
  19
  20          int32_t temp = 0;
  21
  22          // Initialise the DS18B20
  23          ds18b20Init(3, 0, &IOCON_PIO3_0);
  24          while (1) {
  25              temp = ds18b20GetTemperature();
  26
  27              // Use modulus operator to display decimal value
  28              printf("Current Temperature: %d.%d C\n", temp / 10000, temp % 10000);
  29          }
  30      }
  31     @endcode
  32
  33     @section LICENSE
  34
  35     Software License Agreement (BSD License)
  36
  37     Copyright (c) 2010, microBuilder SARL
  38     All rights reserved.
  39
  40     Redistribution and use in source and binary forms, with or without
  41     modification, are permitted provided that the following conditions are met:
  42     1. Redistributions of source code must retain the above copyright
  43     notice, this list of conditions and the following disclaimer.
  44     2. Redistributions in binary form must reproduce the above copyright
  45     notice, this list of conditions and the following disclaimer in the
  46     documentation and/or other materials provided with the distribution.
  47     3. Neither the name of the copyright holders nor the
  48     names of its contributors may be used to endorse or promote products
  49     derived from this software without specific prior written permission.
  50
  51     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ''AS IS'' AND ANY
  52     EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  53     WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  54     DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY
  55     DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  56     (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  57     LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  58     ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  59     (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  60     SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  61 */
  62 /**************************************************************************/
  63
  64 #include "ds18b20.h"
  65 #include "core/gpio/gpio.h"
  66 #include "core/timer16/timer16.h"
  67
  68 #define CMD_CONVERTTEMP 0x44
  69 #define CMD_RSCRATCHPAD 0xbe
  70 #define CMD_WSCRATCHPAD 0x4e
  71 #define CMD_CPYSCRATCHPAD 0x48
  72 #define CMD_RECEEPROM 0xb8
  73 #define CMD_RPWRSUPPLY 0xb4
  74 #define CMD_SEARCHROM 0xf0
  75 #define CMD_READROM 0x33
  76 #define CMD_MATCHROM 0x55
  77 #define CMD_SKIPROM 0xcc
  78 #define CMD_ALARMSEARCH 0xec
  79 #define DECIMAL_STEPS_12BIT 625 //.0625
  80
  81 uint32_t portNum = 0;
  82 uint32_t bitPos = 0;
  83
  84 inline void pullLineLow() {
  85     gpioSetDir(portNum, bitPos, gpioDirection_Output);
  86     gpioSetValue(portNum, bitPos, 0);
  87 }
  88
  89 inline void releaseLine() {
  90     gpioSetDir(portNum, bitPos, gpioDirection_Input);
  91 }
  92
  93 inline void delayUs(uint16_t us) {
  94     timer16DelayUS(1, us);
  95 }
  96
  97 inline uint32_t readLineState() {
  98     return gpioGetValue(portNum, bitPos );
  99 }
 100
 101 void writeBit(uint8_t bit){
 102         //Pull line low for 1uS
 103     pullLineLow();
 104         delayUs(1);
 105         //If we want to write 1, release the line (if not will keep low)
 106         if(bit) {
 107         releaseLine();
 108     }
 109         //Wait for 60uS and release the line
 110         delayUs(60);
 111         releaseLine();
 112 }
 113
 114 uint8_t readBit(void){
 115         uint8_t bit = 0;
 116         //Pull line low for 1uS
 117         pullLineLow();
 118         delayUs(1);
 119         //Release line and wait for 14uS
 120         releaseLine();
 121         delayUs(14);
 122         //Read line value
 123         if(readLineState()){
 124         bit=1;
 125     }
 126         //Wait for 45uS to end and return read value
 127         delayUs(45);
 128         return bit;
 129 }
 130
 131 uint8_t readByte(void){
 132         uint8_t i = 8, n = 0;
 133         while(i--){
 134                 //Shift one position right and store read value
 135                 n >>= 1;
 136                 n |= (readBit() << 7);
 137         }
 138         return n;
 139 }
 140
 141 void writeByte(uint8_t b){
 142         uint8_t i = 8;
 143         while(i--){
 144                 //Write actual bit and shift one position right to make the next bit ready
 145                 writeBit(b & 1);
 146                 b >>= 1;
 147         }
 148 }
 149
 150 uint32_t reset(){
 151         uint32_t i;
 152         //Pull line low and wait for 480uS
 153         pullLineLow();
 154         delayUs(480);
 155         //Release line and wait for 60uS
 156         releaseLine();
 157         delayUs(60);
 158         //Store line value and wait until the completion of 480uS period
 159         i = readLineState();
 160         delayUs(420);
 161         //Return the value read from the presence pulse (0=OK, 1=WRONG)
 162         return i;
 163 }
 164
 165 /*!
 166  @brief Initializes DS18B20 sensor driver.
 167 */
 168
 169 void ds18b20Init(uint32_t portNumber, uint32_t bitPosition, volatile uint32_t *ioconReg) {
 170     portNum = portNumber;
 171     bitPos = bitPosition;
 172     timer16Init(1, TIMER16_DEFAULTINTERVAL);
 173     timer16Enable(1);
 174     gpioSetPullup(ioconReg, gpioPullupMode_Inactive);
 175 }
 176
 177 /*!
 178     @brief Returns temperature read from BS18B20
 179
 180     @note Reading is returned mutiplied by 10000 i.e.
 181           for 25.8750 degrees the result will be 258750
 182 */
 183 uint32_t ds18b20GetTemparature(){
 184         //Reset, skip ROM and start temperature conversion
 185         if(reset()) {
 186         printf("DS18B20 is not responding%s", CFG_PRINTF_NEWLINE);
 187         return 0;
 188     }
 189         writeByte(CMD_SKIPROM);
 190         writeByte(CMD_CONVERTTEMP);
 191
 192     //Wait until conversion is complete
 193     uint16_t timeout = 0xFFFF;
 194         while(!readBit() && timeout > 0) {
 195         timeout--;
 196     }
 197     if(0 == timeout) {
 198         printf("BS18B20 temperature conversion has timed out%s", CFG_PRINTF_NEWLINE);
 199         return 0;
 200     }
 201
 202         //Reset, skip ROM and send command to read Scratchpad
 203         if(reset()) {
 204         printf("DS18B20 is not responding%s", CFG_PRINTF_NEWLINE);
 205         return 0;
 206     }
 207         writeByte(CMD_SKIPROM);
 208         writeByte(CMD_RSCRATCHPAD);
 209
 210         uint8_t scratchpad[2] = {0, 0};
 211     //Read Scratchpad (only 2 first bytes)
 212         scratchpad[0] = readByte();
 213         scratchpad[1] = readByte();
 214
 215     //Store temperature integer digits and decimal digits
 216         int8_t digit = scratchpad[0] >> 4;
 217         digit |= (scratchpad[1] & 0x7) << 4;
 218         //Store decimal digits
 219         uint16_t decimal = scratchpad[0] & 0xf;
 220         decimal *= DECIMAL_STEPS_12BIT;
 221
 222     return digit * 10000 + decimal;
 223 }
 224