Merge pull request #49 from CarletonURocketry/dev-descriptor

Fetcher now requires the device descriptor to be specified

fetcher.use

@@ -7,15 +7,19 @@ license for more details: https://www.gnu.org/licenses/
 
 DESCRIPTION:
     A command line utility for reading sensor data over I2C and providing it
-    over stdout.
+    over stdout or a message queue.
 
 SYNTAX:
-    fetcher
+    fetcher [-p -s <sensor>] /dev/i2c1
+
+ARGUMENTS:
+    device       The device descriptor of the I2C bus to use for reading sensor
+                 data.
 
 OPTIONS:
     -p           If this flag is passed, fetcher will print its sensor data to
                  stdout. Enabling this flag will take messages off the output
                  message queue.
 
-    -s           If this flag is passed, fetcher will only open and read 
+    -s <sensor>  If this flag is passed, fetcher will only open and read 
                  sensor data from the sensor whose name follows.

src/main.c

@@ -51,6 +51,9 @@ static collector_args_t collector_args[MAX_SENSORS];
 /** Buffer for reading sensor messages when print option is selected. */
 uint8_t buffer[BUFFER_SIZE];
 
+/** Device descriptor of the I2C bus. */
+char *i2c_bus = NULL;
+
 /**
  * Reads the sensor name from the board ID into a new buffer.
  * @param board_id The contents of the board ID.
@@ -137,6 +140,13 @@ int main(int argc, char **argv) {
         }
     }
 
+    /* Positional argument for device descriptor. */
+    if (optind >= argc) {
+        fprintf(stderr, "I2C bus device descriptor is required.\n");
+        exit(EXIT_FAILURE);
+    }
+    i2c_bus = argv[optind];
+
     /*
      * Open/create the message queue.
      * Main thread can only read incoming messages from sensors.
@@ -161,7 +171,7 @@ int main(int argc, char **argv) {
     }
 
     /* Open I2C. */
-    int bus = open("/dev/i2c1", O_RDWR);
+    int bus = open(i2c_bus, O_RDWR);
     if (bus < 0) {
         fprintf(stderr, "Could not open I2C bus with error %s.\n", strerror(errno));
         exit(EXIT_FAILURE);