TMP102.cpp

00001 /* * Print String
00002 *
00003 * Prints a string of characters to the screen buffer, string is cut off after the 83rd  pixel.
00004 * @param x - the column number (0 to 83)
00005 * @param y - the row number (0-5) - the display is split into 6 banks - each bank can be considered a row
00006 * @author - David Leaming - 25574043
00007 * @ Date - December 2021
00008 *
00009 * Acknowledgements 
00010 * Craig A. Evans, University of Leeds, TMP102 Library ,Feb 2016
00011 * Dr Edmond Nurellari, University of Lincoln, Joystick & N5110 Libraries
00012 *
00013 */ 
00014 
00015 // library implemtation file
00016 
00017 // obviously need to include the header
00018 #include "TMP102.h"
00019 
00020 // we now implement each of the methods listed in the header
00021 
00022 // note the TMP102:: at the beginning of the method name
00023 TMP102::TMP102(PinName sda, PinName scl)
00024 {
00025     // in the constructor, we create the mbed API objects using 'new'
00026     i2c_ = new I2C(sda,scl);
00027     led_ = new DigitalOut(LED_RED);
00028 }
00029 
00030 void TMP102::init()
00031 {
00032     i2c_->frequency(400000); // set bus speed to 400 kHz
00033 
00034     int ack;  // used to store acknowledgement bit
00035     char config_data[2];  // array for data
00036     char reg = CONFIG_REG;  // register address
00037 
00038     //////// Read current status of configuration register ///////
00039 
00040     ack = i2c_->write(TMP102_W_ADD,&reg,1);  // send the slave write address and the configuration register address
00041     if (ack)
00042         error();  // if we don't receive acknowledgement, flash error message
00043 
00044     ack = i2c_->read(TMP102_R_ADD,config_data,2);  // read default 2 bytes from configuration register and store in array
00045     if (ack)
00046         error();  // if we don't receive acknowledgement, flash error message
00047 
00048     ///////// Configure the register //////////
00049 
00050     // set conversion rate to 1 Hz - CR1 and CR2 are in the second data byte
00051     config_data[1] |= (1 << 6);    // set bit 6
00052     config_data[1] &= ~(1 << 7);    // clear bit 7
00053 
00054     //////// Send the configured register value to the slave config register ////////////
00055 
00056     // create data packet
00057     char data_packet[3] = {reg,config_data[0],config_data[1]};
00058 
00059     ack = i2c_->write(TMP102_W_ADD,data_packet,3);  // send the data packet to the slave write address
00060     if (ack)
00061         error();  // if we don't receive acknowledgement, flash error message
00062 
00063 }
00064 
00065 void TMP102::read_temperature()
00066 {
00067     int ack;  // used to store acknowledgement bit
00068     char data[2];  // array for data
00069     char reg = TEMP_REG;  // temperature register address
00070 
00071     ack = i2c_->write(TMP102_W_ADD,&reg,1);  // send temperature register address
00072     if (ack)
00073         error();  // if we don't receive acknowledgement, flash error message
00074 
00075     ack = i2c_->read(TMP102_R_ADD,data,2);  // read 2 bytes from temperature register and store in array
00076     if (ack)
00077         error();  // if we don't receive acknowledgement, flash error message
00078 
00079     int temperature = (data[0] << 4) | (data[1] >> 4);
00080 
00081     temperature_ = temperature*0.0625F;
00082 }
00083 
00084 // temperature accessor method
00085 float TMP102::get_temperature() 
00086 {
00087     read_temperature();
00088     return temperature_;    
00089 }
00090 
00091 void TMP102::error()
00092 {
00093     while(1) {  // if error, hang while flashing error message
00094         led_->write(0);
00095         wait(0.2);
00096         led_->write(1);
00097         wait(0.2);
00098     }
00099 }