Diff: main.cpp

Revision:

0:21a200b880d7

Child:

1:dd5fb735acf1

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Fri Feb 05 16:23:38 2016 +0000
@@ -0,0 +1,150 @@
+/* 
+
+2645_I2C_TMP102
+
+Sample code from ELEC2645 Week 17 Lab
+
+Demonstrates how to read the temperature from an I2C sensor
+
+(c) Craig A. Evans, University of Leeds, Feb 2016
+
+*/ 
+
+#include "mbed.h"
+
+// addresses for ADD0 connected to GND
+#define TMP102_ADD      0x48
+#define TMP102_R_ADD    0x91
+#define TMP102_W_ADD    0x90
+
+// register addresses
+#define TEMP_REG    0x00
+#define CONFIG_REG  0x01
+#define THIGH_REG   0x02
+#define TLOW_REG    0x03
+
+// I2C peripheral for temperature sensor
+I2C tmp102(I2C_SDA,I2C_SCL);  
+// UART connection for PC
+Serial pc(USBTX,USBRX);
+
+// K64F on-board LEDs 
+DigitalOut r_led(LED_RED);
+DigitalOut g_led(LED_GREEN);
+DigitalOut b_led(LED_BLUE);
+// K64F on-board switches
+InterruptIn sw2(SW2);
+InterruptIn sw3(SW3);
+
+// error function hangs flashing an LED
+void error();
+// setup serial port
+void init_serial();
+// set-up the on-board LEDs and switches
+void init_K64F();
+// initialisation function for temperature sensor
+void init_TMP102();
+// function to read temperature from sensor (in degrees C)
+float get_temperature();
+
+int main()
+{
+    // initialise the board, serial port and sensor
+    init_K64F();
+    init_serial(); 
+    init_TMP102();
+    
+    while (1) {
+        
+        // read temperature and print over serial port
+        float T = get_temperature();
+        pc.printf("T = %f K\n",T);
+        // small delay - 1s to match the update rate of the sensor (1 Hz)
+        wait(1.0);
+        
+    }
+
+}
+
+void init_serial() {
+    // set to highest baud - ensure terminal software matches
+    pc.baud(115200); 
+}
+
+void init_K64F() 
+{
+    // on-board LEDs are active-low, so set pin high to turn them off.
+    r_led = 1;
+    g_led = 1;
+    b_led = 1;   
+    
+    // since the on-board switches have external pull-ups, we should disable the internal pull-down
+    // resistors that are enabled by default using InterruptIn
+    sw2.mode(PullNone);
+    sw3.mode(PullNone);
+
+}
+
+void error()
+{
+    while(1) {  // if error, hang while flashing error message
+        r_led = 0;
+        wait(0.2);
+        r_led = 1;
+        wait(0.2);    
+    }    
+}
+
+void init_TMP102()
+{    
+    tmp102.frequency(400000); // set bus speed to 400 kHz
+
+    int ack;  // used to store acknowledgement bit
+    char config_data[2];  // array for data
+    char reg = CONFIG_REG;  // register address
+     
+    //////// Read current status of configuration register ///////
+        
+    ack = tmp102.write(TMP102_W_ADD,&reg,1);  // send the slave write address and the configuration register address
+    if (ack)
+        error();  // if we don't receive acknowledgement, flash error message
+            
+    ack = tmp102.read(TMP102_R_ADD,config_data,2);  // read default 2 bytes from configuration register and store in array
+    if (ack)
+        error();  // if we don't receive acknowledgement, flash error message
+
+    ///////// Configure the register //////////
+
+    // set conversion rate to 1 Hz - CR1 and CR2 are in the second data byte
+    config_data[1] |= (1 << 6);    // set bit 6  
+    config_data[1] &= ~(1 << 7);    // clear bit 7  
+       
+    //////// Send the configured register value to the slave config register ////////////
+    
+    // create data packet
+    char data_packet[3] = {reg,config_data[0],config_data[1]};
+        
+    ack = tmp102.write(TMP102_W_ADD,data_packet,3);  // send the data packet to the slave write address
+    if (ack)
+        error();  // if we don't receive acknowledgement, flash error message
+    
+}
+
+float get_temperature()
+{
+    int ack;  // used to store acknowledgement bit
+    char data[2];  // array for data
+    char reg = TEMP_REG;  // temperature register address
+
+    ack = tmp102.write(TMP102_W_ADD,&reg,1);  // send temperature register address
+    if (ack)
+        error();  // if we don't receive acknowledgement, flash error message
+
+    ack = tmp102.read(TMP102_R_ADD,data,2);  // read 2 bytes from temperature register and store in array
+    if (ack)
+        error();  // if we don't receive acknowledgement, flash error message
+
+    int temperature = (data[0] << 4) | (data[1] >> 4);
+
+    return temperature*0.0625;
+}
\ No newline at end of file