From bc14a5653ca23b50e127d7ff4e3a731e349a7a8c Mon Sep 17 00:00:00 2001
From: Leon Krieg <info@madcow.dev>
Date: Tue, 1 Oct 2024 00:16:20 +0200
Subject: [PATCH] Burn fuse for external crystal at 16K CK and 65ms

---
 Makefile        |  4 ++--
 src/bus/usart.c |  2 +-
 src/main.c      | 15 ++++++++++++++-
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/Makefile b/Makefile
index c854174..a48e271 100644
--- a/Makefile
+++ b/Makefile
@@ -57,8 +57,8 @@ flash: $(TARGET)
 	$(E) "[AVD] Flashing..."
 	$(Q) $(AVD) -l $(LOGFILE)    \
 	       -c $(ASP) -p $(ARCH)  \
-	       -U lfuse:w:0xff:m     \
-	       -U hfuse:w:0x91:m     \
+	       -U lfuse:w:0xFF:m     \
+	       -U hfuse:w:0xD2:m     \
 	       -U flash:w:$<
 
 .PHONY: clean
diff --git a/src/bus/usart.c b/src/bus/usart.c
index 7f15677..156bf7d 100644
--- a/src/bus/usart.c
+++ b/src/bus/usart.c
@@ -27,7 +27,7 @@ int USART_Init(void)
 
 	UCSR0B = BIT(RXCIE0); // Handle RXC interrupts
 	UCSR0B |= BIT(RXEN0) | BIT(TXEN0); // Enable RX and TX circuitry
-	UCSR0C = BIT(USBS0) | BIT(UCSZ00) | BIT(UCSZ01); // 8-bit data, 2-bit stop
+	UCSR0C = BIT(UCSZ01) | BIT(UCSZ00); // 8-bit data, 1-bit stop, no parity
 	UBRR0H = (USART_BAUD_PRESCALE >> 8); // Set baud rate upper byte
 	UBRR0L = USART_BAUD_PRESCALE; // Set baud rate lower byte
 
diff --git a/src/main.c b/src/main.c
index a9a01d3..ed56b0b 100644
--- a/src/main.c
+++ b/src/main.c
@@ -57,6 +57,16 @@ static int Init(void)
 
 	Info("Initializing...");
 
+	// FIXME: Something is wrong here:
+	// - AVRDUDE sometimes fails to verify flash.
+	// - UART sometimes stops working.
+	// - External crystal problems?
+	// - Power supply problems?
+	// - Wrong fuses? Unlikely.
+	// - Bootloader problems?
+
+	return 0;
+
 	// The watchdog timer is clocked from a separate
 	// on-chip oscillator which runs at 1 MHz. Eight
 	// different clock cycle periods can be selected
@@ -232,10 +242,13 @@ int main(void)
 
 	for (;;) {
 		WDT_Reset();
-		Update();
+		Info("UPDATE");
+		continue;
+		// Update();
 		WDT_Reset();
 		Sleep(1000);
 	}
 
+	UNUSED(Update);
 	return 0;
 }