TMP102.cpp

00001 // library implemtation file
00002 
00003 // obviously need to include the header
00004 #include "TMP102.h"
00005 
00006 // we now implement each of the methods listed in the header
00007 
00008 // note the TMP102:: at the beginning of the method name
00009 TMP102::TMP102(PinName sda, PinName scl)
00010 {
00011     // in the constructor, we create the mbed API objects using 'new'
00012     i2c_ = new I2C(sda,scl);
00013     led_ = new DigitalOut(LED_RED);
00014 }
00015 
00016 void TMP102::init()
00017 {
00018     i2c_->frequency(400000); // set bus speed to 400 kHz
00019 
00020     int ack;  // used to store acknowledgement bit
00021     char config_data[2];  // array for data
00022     char reg = CONFIG_REG;  // register address
00023 
00024     //////// Read current status of configuration register ///////
00025 
00026     ack = i2c_->write(TMP102_W_ADD,&reg,1);  // send the slave write address and the configuration register address
00027     if (ack)
00028         error();  // if we don't receive acknowledgement, flash error message
00029 
00030     ack = i2c_->read(TMP102_R_ADD,config_data,2);  // read default 2 bytes from configuration register and store in array
00031     if (ack)
00032         error();  // if we don't receive acknowledgement, flash error message
00033 
00034     ///////// Configure the register //////////
00035 
00036     // set conversion rate to 1 Hz - CR1 and CR2 are in the second data byte
00037     config_data[1] |= (1 << 6);    // set bit 6
00038     config_data[1] &= ~(1 << 7);    // clear bit 7
00039 
00040     //////// Send the configured register value to the slave config register ////////////
00041 
00042     // create data packet
00043     char data_packet[3] = {reg,config_data[0],config_data[1]};
00044 
00045     ack = i2c_->write(TMP102_W_ADD,data_packet,3);  // send the data packet to the slave write address
00046     if (ack)
00047         error();  // if we don't receive acknowledgement, flash error message
00048 
00049 }
00050 
00051 void TMP102::read_temperature()
00052 {
00053     int ack;  // used to store acknowledgement bit
00054     char data[2];  // array for data
00055     char reg = TEMP_REG;  // temperature register address
00056 
00057     ack = i2c_->write(TMP102_W_ADD,&reg,1);  // send temperature register address
00058     if (ack)
00059         error();  // if we don't receive acknowledgement, flash error message
00060 
00061     ack = i2c_->read(TMP102_R_ADD,data,2);  // read 2 bytes from temperature register and store in array
00062     if (ack)
00063         error();  // if we don't receive acknowledgement, flash error message
00064 
00065     int temperature = (data[0] << 4) | (data[1] >> 4);
00066 
00067     temperature_ = temperature*0.0625F;
00068 }
00069 
00070 // temperature accessor method
00071 float TMP102::get_temperature() 
00072 {
00073     read_temperature();
00074     return temperature_;    
00075 }
00076 
00077 void TMP102::error()
00078 {
00079     while(1) {  // if error, hang while flashing error message
00080         led_->write(0);
00081         wait(0.2);
00082         led_->write(1);
00083         wait(0.2);
00084     }
00085 }