From 84cf9165d1a83ef4976423f8775bacb509ebb80f Mon Sep 17 00:00:00 2001
From: Leon Krieg <info@madcow.dev>
Date: Sat, 24 Aug 2024 22:02:52 +0200
Subject: [PATCH] Test serial data transmission on atmega32a

---
 Makefile   |  7 +++++--
 src/main.c | 47 ++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 51 insertions(+), 3 deletions(-)

diff --git a/Makefile b/Makefile
index 2be064a..9a47560 100644
--- a/Makefile
+++ b/Makefile
@@ -5,7 +5,7 @@
 # Written by Leon Krieg <info@madcow.dev>
 
 ARCH      := m32
-FREQ      := 1600000UL
+FREQ      := 8000000UL
 MCU       := atmega32a
 ASP       := usbasp
 GCC       := avr-gcc
@@ -22,7 +22,10 @@ all: flash
 
 .PHONY: flash
 flash: $(TARGET)
-	$(AVD) -c $(ASP) -p $(ARCH) -U flash:w:$(TARGET)
+	$(AVD) -c $(ASP) -p $(ARCH) \
+	       -U lfuse:w:0xff:m    \
+	       -U hfuse:w:0x99:m    \
+	       -U flash:w:$(TARGET)
 
 $(TARGET): src/main.c
 	$(GCC) -o $(ELFILE) $(CFLAGS) $(CPPFLAGS) $^ -mmcu=$(MCU)
diff --git a/src/main.c b/src/main.c
index 258b76a..85b6605 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,6 +1,51 @@
-#define UNUSED(s) (void)(s)
+#include <avr/io.h>
+#include <util/delay.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#define BAUD_PRESCALE (((F_CPU / (USART_BAUDRATE * 16UL))) - 1)
+
+void UART_Init(long USART_BAUDRATE)
+{
+	UCSRB |= (1 << RXEN) | (1 << TXEN);
+	UCSRC |= (1 << URSEL) | (1 << UCSZ0) | (1 << UCSZ1);
+	UBRRL = BAUD_PRESCALE;
+	UBRRH = (BAUD_PRESCALE >> 8);
+}
+
+unsigned char UART_RxChar()
+{
+	while ((UCSRA & (1 << RXC)) == 0);
+	return UDR;
+}
+
+void UART_TxChar(char ch)
+{
+	while ((UCSRA & (1 << UDRE)) == 0);
+	UDR = ch;
+}
+
+void UART_SendString(char *str)
+{
+	unsigned char j = 0;
+
+	while (str[j] != 0) {
+		UART_TxChar(str[j++]);
+	}
+}
 
 int main(void)
 {
+	char buf[64];
+
+	UART_Init(9600);
+
+	for (int i = 1;; i++) {
+		if (i >= 999) i = 1;
+		sprintf(buf, "BOINK #%03d\r\n", i);
+		UART_SendString(buf);
+		_delay_ms(3000);
+	}
+
 	return 0;
 }