main.cpp

00001 /* Program demonstrating data logging to SD card 
00002     Temperature is read in from an TMP36 
00003     The time since program start and the voltage 
00004     are written to a tab-delimited data file. 
00005     TMP36 pins: left = power, middle = output (p18), right = ground 
00006     SD pins: DI = p5, DO = p6, SCK = p7, CS = p8  
00007 */ 
00008 #include "mbed.h" 
00009 #include "SDFileSystem.h" 
00010 
00011 AnalogIn tmp36(p18); 
00012 Serial pc(USBTX,USBRX); 
00013 SDFileSystem fs(p5, p6, p7, p8, "fs"); 
00014 Timer t; 
00015 Ticker sampleTime; 
00016 DigitalOut doneLED(LED1); 
00017 bool timeToRead; 
00018 
00019 void triggerCollection() { 
00020     timeToRead = true;  // flag to collect data 
00021 } 
00022 
00023 int main() { 
00024 
00025     float voltage, temperature; 
00026     // Mount the filesystem 
00027     bool mountFailure = fs.mount(); 
00028     if (mountFailure != 0) { 
00029         pc.printf("Failed to mount the SD card.\r\n"); 
00030         return -1;  // ends program with error status 
00031     }
00032 
00033     FILE* fp = fopen("/fs/log.txt","w"); 
00034     if (fp == NULL) { 
00035         pc.printf("Failed to open the file.\r\n"); 
00036         fs.unmount(); 
00037         return -1; 
00038     }    
00039 
00040     // Write a header row 
00041     fprintf(fp, "Time (s) \t Temperature (deg C)\r\n"); 
00042 
00043     // Start the timer and ticker 
00044     t.start(); 
00045     sampleTime.attach(&triggerCollection, 0.5);  // write data every 0.5 s 
00046     timeToRead = true; // collect data at t = 0 
00047 
00048     while (t.read()<20) { 
00049         if (timeToRead) { 
00050             timeToRead = false;  // reset data collection flag 
00051             voltage = 3.3*tmp36.read(); 
00052             temperature = (voltage-0.5)/0.01; 
00053             fprintf(fp,"%.2f \t %.2f\r\n", t.read(),temperature); 
00054         } 
00055     } 
00056     
00057     // Close the file and unmount the file system so the SD card is happy 
00058     fclose(fp); 
00059     fs.unmount(); 
00060     // Turn on LED to let user know it is safe to remove the SD card 
00061     doneLED = 1; 
00062 }