Diff: main.cpp

Revision:

0:f638a5d8ddf4

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Wed Aug 02 22:10:06 2017 +0000
@@ -0,0 +1,124 @@
+#include "mbed.h"
+
+#define SAMPLES 128
+
+I2C i2c(PB_9, PB_8);                //Initialize i2c master, where PB_9 is SDA, PB_8 is SCL
+Serial pc(SERIAL_TX, SERIAL_RX);    //Init serial connection to PC
+Timer t;                            //Timing and stuff
+
+const int addr = 0x90;
+float C[SAMPLES];
+
+////////////////////////////////////////////////////////////////////////////////
+//                              FUNCTIONS                                     //
+////////////////////////////////////////////////////////////////////////////////
+
+//Initialize the AD7746
+void capInit(){             //Initialize EXC and CAP
+    char cmd[2];
+    
+    cmd[0] = 0x09;          //EXC setup
+    cmd[1] = 0b00001011;
+    i2c.write(addr,cmd,2);
+    
+    cmd[0] = 0x07;          //CAP setup
+    
+    //De-comment the integration time desired
+    //cmd[1] = 0b10000000;  //11.0ms (90.9 Hz)
+    //cmd[1] = 0b10000001;  //11.9ms (83.8 Hz)
+    cmd[1] = 0b10000010;  //20.0ms (50.0 Hz)
+    //cmd[1] = 0b10000011;  //38.0ms (26.3 Hz)
+    //cmd[1] = 0b10000100;  //62.0ms (16.1 Hz)
+    //cmd[1] = 0b10000101;  //77.0ms (13.0 Hz)
+    //cmd[1] = 0b10000110;  //92.0ms (10.9 Hz)
+    //cmd[1] = 0b10000111;  //109.6ms (9.1 Hz)
+    i2c.write(addr,cmd,2);
+}
+
+//Initialize the CAPDAC
+void capdac(){
+    char cmd[2];
+    
+    cmd[0] = 0x0B;
+    cmd[1] = 0x80 | 30;
+    i2c.write(addr,cmd,2);
+}
+
+//Check if the AD7746 is ready to do another measurement
+bool checkRdy(){
+    uint8_t donebit;
+    
+    i2c.start();            //Read register 0x00 (status), mask & shift RDY bit
+    i2c.write(addr & 0xFE);
+    i2c.write(0x00);
+    i2c.start();
+    i2c.write(addr | 0x01);
+    donebit = i2c.read(0);
+    i2c.stop();
+    donebit = (bool)((donebit & 0b00000100) >> 2);
+    return donebit;
+}
+
+//Take a single capacitance measurement
+float capRead(){
+    char cmd[2];
+    uint8_t lb1, lb2, lb3;
+    uint32_t lb;
+    float result;
+    
+    cmd[0] = 0x0A;          //Set up a single measurement
+    cmd[1] = 0b00000010;
+    i2c.write(addr,cmd,2);
+    
+    while(checkRdy()){      //Check status register if measurement is done
+        ;
+    }
+    
+    i2c.start();            //Read 3 bytes
+    i2c.write(addr & 0xFE);
+    i2c.write(0x01);
+    i2c.start();
+    i2c.write(addr | 0x01);
+    lb1 = i2c.read(1);
+    lb2 = i2c.read(1);
+    lb3 = i2c.read(0);
+    i2c.stop();
+    
+    lb = lb1*65536+lb2*256+lb3;     //Calculate capacitance
+    result = (lb-8388608)*4.096/8388608;
+    
+    //pc.printf("lb1 = %d, lb2 = %d, lb3 = %d\n",lb1,lb2,lb3);
+    //pc.printf("lb = %d\n",lb);
+    //pc.printf("C = %f\n",result);
+    
+    return result;
+}
+
+//Print over serial
+void printCap(){
+    for(uint16_t i = 0; i < SAMPLES; i++){
+        if(i == SAMPLES-1){
+            pc.printf("%f\n",C[i]);
+        }
+        else{
+            pc.printf("%f,",C[i]);
+        }
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+//                                   MAIN                                     //
+////////////////////////////////////////////////////////////////////////////////
+
+int main(){
+    pc.baud(115200);
+    capInit();
+    capdac();
+    
+    while(1){        
+        for(uint16_t i = 0; i < SAMPLES; i++){
+            C[i] = capRead();
+        }
+        printCap();
+    }
+}
\ No newline at end of file