Prevent redundant writes and start implementing parser timeout

src/common/common.c

@@ -3,21 +3,8 @@
 
 #include <stdio.h>
 
-static void Puts(const char *str)
-{
-	while (*str != '\0') {
-		USART_Putc(*str++);
-	}
-}
-
-static void PrintArgs(const char *fmt, va_list ap)
-{
-	char msg[256];
-
-	vsnprintf(msg, sizeof(msg), fmt, ap);
-
-	Puts(msg);
-}
+static void Puts(const char *str);
+static void PrintArgs(const char *fmt, va_list ap);
 
 void Print(const char *fmt, ...)
 {
@@ -51,3 +38,19 @@ void Error(const char *fmt, ...)
 
 	// XXX: Force reset?
 }
+
+static void Puts(const char *str)
+{
+	while (*str != '\0') {
+		USART_Putc(*str++);
+	}
+}
+
+static void PrintArgs(const char *fmt, va_list ap)
+{
+	char msg[256];
+
+	vsnprintf(msg, sizeof(msg), fmt, ap);
+
+	Puts(msg);
+}

src/common/parser.c

@@ -3,27 +3,44 @@
 #include <stdlib.h>
 #include <ctype.h>
 #include <errno.h>
+#include <avr/io.h>
 
 #define CMD_MAX_LEN 128
 
 // TODO: Write documentation.
 // TODO: Implement start and stop commands.
-// TODO: Reset command buffer on timeout?
+// TODO: Reset command buffer on timeout.
 
 static char cmdbuf[CMD_MAX_LEN + 1];
 static char *tail = cmdbuf + CMD_MAX_LEN - 1;
 static char *head = cmdbuf;
 
 static bool ParseLine(cmd_t *out);
+static void StartTimer(void);
+static bool IsTimedOut(void);
+static void StopTimer(void);
 
 bool CMD_Parse(char ch, cmd_t *out)
 {
 	bool is_valid;
 
-	if (ch == '\n' || ch == '\r') {
+	// FIXME: Reset command buffer on timeout:
+	// No newline character is received if the serial
+	// buffer is full and the ending is discarded. This
+	// means that after a command that is too long, the
+	// next command will not be parsed properly.
+
+	if (head == cmdbuf) {
+		StartTimer();
+	}
+
+	if (IsTimedOut() ||
+	   (ch == '\n' || ch == '\r')) {
 		is_valid = ParseLine(out);
 		tail = cmdbuf + CMD_MAX_LEN - 1; 
 		head = cmdbuf;
+		StopTimer();
+
 		return is_valid;
 	}
 
@@ -70,3 +87,20 @@ static bool ParseLine(cmd_t *out)
 
 	return false;
 }
+
+static void StartTimer(void)
+{
+	TCNT0 = 0x00;
+	TCCR0 = BIT(CS00) | BIT(CS02);
+}
+
+static bool IsTimedOut(void)
+{
+	return false; // TIFR & BIT(TOV0)
+}
+
+static void StopTimer(void)
+{
+	TCNT0 = 0x00;
+	TIFR = BIT(TOV0);
+}