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);
+}

src/main.c

@@ -6,8 +6,8 @@
 
 #include <avr/interrupt.h>
 
+// TODO: Implement command parser timeout for large input.
 // TODO: Config header for chip specifics like EEPROM size.
-// TODO: Only update EEPROM if value differs from previous.
 // TODO: Check thermistor conversion results /w thermometer.
 // TODO: Implement primary state machine for update loop.
 // TODO: Migrate to ATMega 1284P-PU for 2nd 16-bit timer.
@@ -31,7 +31,8 @@ static float relh;
 
 static int   Init(void);
 static void  Update(void);
-static void  UpdateSensors(void);
+static void  SetTarget(float t, float td);
+static void  GetSensorState(void);
 
 static int Init(void)
 {
@@ -85,7 +86,7 @@ static int Init(void)
 
 	if (MEM_Read(&mem) == 0) {
 		Info("Found persistent configuration in EEPROM!");
-		Info("Setting targets TEMP='%.2fC', DEWP='%.2fC'.",
+		Info("Using targets TEMP='%.2fC', DEWP='%.2fC'.",
 			mem.temp, mem.dewp);
 
 		temp_target = mem.temp;
@@ -139,7 +140,6 @@ static void Update(void)
 {
 	char ch;
 	cmd_t cmd;
-	mem_block_t mem;
 
 	// Parse serial commands
 	while ((ch = USART_Getc()) >= 0) {
@@ -148,18 +148,14 @@ static void Update(void)
 			continue;
 		}
 		switch(cmd.type) {
-		case T_SET: // Configure new persistent target
-			Info("Setting new target TEMP='%.2fC'...", cmd.args[0]);
-			Info("Setting new target DEWP='%.2fC'...", cmd.args[1]);
-			mem.temp = temp_target = cmd.args[0];
-			mem.dewp = dewp_target = cmd.args[1];
-			MEM_Write(&mem);
+		case T_SET: // Set new persistent target
+			SetTarget(cmd.args[0], cmd.args[1]);
 			return;
 		}
 	}
 
 	// Poll sensor values
-	UpdateSensors();
+	GetSensorState();
 
 	// Handle state
 	switch (state) {
@@ -174,7 +170,33 @@ static void Update(void)
 	}
 }
 
-static void UpdateSensors(void)
+static void SetTarget(float t, float td)
+{
+	mem_block_t mem;
+
+	Info("=======================================");
+	Info("Setting temperature target to '%.2fC'.", t);
+	Info("Setting dewpoint target to '%.2fC'.", td);
+	Info("=======================================");
+
+	if (MEM_Read(&mem) == 0) {
+		if (t == mem.temp && td == mem.dewp) {
+			return; // Nothing to do
+		}
+	}
+
+	mem.temp = t;
+	mem.dewp = td;
+
+	// Keep in EEPROM
+	MEM_Write(&mem);
+
+	// Update state
+	temp_target = t;
+	dewp_target = td;
+}
+
+static void GetSensorState(void)
 {
 	word raw;
 	float t[6], rh[3], dp[3];