Added basic frontend_getpid.h

groundStation/src/frontend/frontend_common.h

 #ifndef FRONTEND_COMMON_H
 #define FRONTEND_COMMON_H
+#include <stdlib.h>
 
 struct backend_conn;
 
@@ -16,6 +17,6 @@ void ucart_backendDisconnect(struct backend_conn * conn);
 char * ucart_backendGetline(struct backend_conn * conn);
 
 /* Write a line to the backend */
-void ucart_backendWrite(struct backend_conn * backend, const char * line);
+size_t ucart_backendWrite(struct backend_conn * backend, const char * line);
 
 #endif

groundStation/src/frontend/frontend_getpid.h

+#ifndef FRONTEND_GETPID_H
+#define FRONTEND_GETPID_H
+
+#include "frontend_common.h"
+#include "pid_common.h"
+
+/* Get a specified PID.
+ *
+ * Example:
+ *
+ * struct frontend_pid_data pid_data;
+ * pid_data.pid = PITCH;
+ * if (frontend_getpid(conn, &pid_data)) {
+ * 		error
+ * } else {
+ * 		pid_data.p, pid_data.i, and pid_data.d are filled
+ * }
+ *
+ * Returns 0 on success, 1 on error
+ */
+int frontend_getpid(
+		struct backend_conn * conn,
+		struct frontend_pid_data * pid_data);
+
+
+#endif

groundStation/src/frontend/pid_common.h

+#ifndef PID_COMMON_H
+#define PID_COMMON_H
+
+enum frontend_pid {
+	PITCH,
+	ROLL,
+	YAW,
+	NUM_PIDS
+};
+
+struct frontend_pid_data {
+	enum frontend_pid pid;
+
+	float p;
+	float i;
+	float d;
+};
+
+
+#endif