main.cpp

00001 /**
00002  * Current Log-O-Matic
00003  * Author: Shawn Hymel @ SparkFun Electronics
00004  * Date: July 1, 2015
00005  *
00006  * Measures current using an INA169 breakout board. Stores current and timestamp
00007  * to an SD card.
00008  *
00009  * INA169 Vout -> Pin 15
00010  * SD Card DI -> Pin 5
00011  * SD Card DO -> Pin 6
00012  * SD Card SCK -> Pin 7
00013  * SD Card CS -> Pin 8
00014  *
00015  * This code is beerware; if you see me (or any other SparkFun 
00016  * employee) at the local, and you've found our code helpful, please
00017  * buy us a round!
00018  *
00019  * Distributed as-is; no warranty is given.
00020  */
00021  
00022 #include "mbed.h"
00023 #include "SDFileSystem.h"
00024 
00025 #define DEBUG       1       // 1 to print to console. 0 to turn off.
00026 #define MAX_FILES   100     // Maximum number of log files to store on SD
00027 #define DELAY_MS    0.02    // Time between samples (in seconds)
00028 #define NUM_SAMPLES 500     // Number of samples to collect
00029 #define RS          0.5     // Value of RS (sensing resistor) in ohms
00030 #define RL          10000   // Value of RL (output resistor) in ohms
00031 
00032 // Digital output (status LED)
00033 DigitalOut status_led(LED1);
00034 
00035 // Analog input (pin 15)
00036 AnalogIn ain(p15);
00037 
00038 // USB serial (tx, rx)
00039 Serial pc(USBTX, USBRX);
00040 
00041 // SD card (SPI pins)
00042 SDFileSystem sd(p5, p6, p7, p8, "sd");
00043 
00044 // Global variables
00045 const char file_root[] = "idata";
00046 const char file_suffix[] = ".csv";
00047 char filename[20];
00048 Timer timer;
00049 
00050 // Return true if file (or directory) 'filename' is present in directory 'root'
00051 // Based on: https://developer.mbed.org/forum/mbed/topic/463/
00052 bool exists(char * root, char *filename)
00053 {
00054     DIR *d = opendir(root);
00055     struct dirent *p;
00056     bool found = false;
00057     if ( d != NULL )
00058     {
00059         while ( !found && (p = readdir(d)) != NULL )
00060         {
00061             if ( strcmp(p->d_name, filename) == 0 )
00062                 found = true;
00063         }
00064     }
00065     closedir(d);
00066     return found;
00067 }
00068 
00069 // Main
00070 int main( void )
00071 {
00072     FILE *file;
00073     char str[5];
00074     int i;
00075     int led_state;
00076     float voltage_in;
00077     float current;
00078     float timestamp;
00079     
00080     // Debugging start
00081 #if DEBUG == 1
00082     printf("\n\r");
00083     printf("-------------------\n\r");
00084     printf("Current Log-O-Matic\n\r");
00085     printf("-------------------\n\r");
00086 #endif
00087     
00088     // Create next file in sequence
00089     for ( i = 0; i < MAX_FILES; i++ ) {
00090            
00091         // Construct filename
00092         strcpy(filename, file_root);
00093         sprintf(str, "%d", i);
00094         strcat(filename, str);
00095         strcat(filename, file_suffix);
00096     
00097         // If file exists, skip to next. If not, create it.
00098         if ( exists("/sd", filename) ) {
00099 #if DEBUG == 1
00100             printf ("%s found\n\r", filename);
00101 #endif
00102             if ( i == (MAX_FILES - 1) ) {
00103                 error("ERROR: Too many files!\n\r");
00104                 return -1;
00105             }
00106         } else {
00107 #if DEBUG == 1
00108             printf ("%s not found. Creating.\n\r", filename);
00109 #endif
00110             break;
00111         }
00112     }
00113         
00114     // Construct absolute path to file
00115     strcpy(filename, "/sd/");
00116     strcat(filename, file_root);
00117     sprintf(str, "%d", i);
00118     strcat(filename, str);
00119     strcat(filename, file_suffix);
00120     
00121     // Open file for writing
00122 #if DEBUG == 1
00123     printf("Opening %s\n\r", filename);
00124 #endif
00125     file = fopen(filename, "w");
00126     if ( file == NULL ) {
00127         error("ERROR: Could not open file for writing!\n\r");
00128         return -1;
00129     }
00130     
00131     // Write header to file
00132     fprintf(file, "Time,Current\n\r");
00133         
00134     // Start timer and begin sampling
00135     led_state = 0;
00136 #if DEBUG == 1
00137     printf("Sampling. Do not remove SD card!\n\r");
00138 #endif
00139     timer.start();
00140     for ( i = 0; i < NUM_SAMPLES; i++ ) {
00141         
00142         // Write data to csv file
00143         timestamp = timer.read();
00144         voltage_in = ain * 3.3;
00145         current = (voltage_in * 1000) / (RS * RL);
00146         fprintf(file, "%2.2f,%1.3f\n", timestamp, current);
00147 #if DEBUG == 1
00148         printf("%2.2f, %1.3f\n\r", timestamp, current);
00149 #endif
00150 
00151         // Toggle LED to show logging
00152         led_state ^= 1;
00153         status_led = led_state;
00154         
00155         // Wait until next sample cycle as defined by sample delay
00156         while ( (timer.read() - timestamp) < DELAY_MS );
00157     }
00158     
00159     // Close file
00160 #if DEBUG == 1
00161     printf("Done! Closing file");
00162 #endif
00163     fclose(file);
00164     
00165     // Turn off LED to show done
00166     status_led = 0;
00167     
00168     return 0;
00169 }