3 files changed, 136 insertions, 0 deletions
diff --git a/atxswitch/Makefile b/atxswitch/Makefile
new file mode 100644
index 0000000..db8a005
--- /dev/null
+++ b/atxswitch/Makefile
@@ -0,0 +1,35 @@
+# settings for arduino nano v3
+DEVICE     = atmega328p
+CLOCK      = 16000000
+PORT=/dev/serial/by-id/usb-FTDI_FT232R_USB_UART_A9SBZLHD-if00-port0
+#AVRDUDE=avrdude -V -F -p m328p -c arduino -b 115200 -P$(PORT)
+#AVRDUDE=avrdude -p $(DEVICE) -c arduino -b 115200 -P $(PORT)
+AVRDUDE=avrdude -p $(DEVICE) -c arduino -b 57600 -P $(PORT)
+
+DEFS    = -DF_CPU=$(CLOCK)UL
+LIBS    = -Wl,--relax,--gc-sections,--print-gc-sections,--entry=main
+LIBS = -Wl,--entry=main,--gc-sections,--rela
+CFLAGS  = -Wall -Werror -pedantic -std=c99
+CFLAGS += -Os -funsigned-bitfields -fpack-struct -fshort-enums
+CFLAGS += -mmcu=$(DEVICE) $(DEFS)
+#LDFLAGS = $(LIBS)
+
+all: main.hex size
+
+main.hex: main.c
+	avr-gcc -o main.elf $? $(CFLAGS) $(LDFLAGS)
+	avr-objcopy -j .text -j .data -O ihex main.elf main.hex
+
+f: flash
+flash: all
+	$(AVRDUDE) -U flash:w:main.hex:i
+
+clean:
+	rm -f *.o *.elf *.hex
+
+size:
+	avr-size --mcu=$(DEVICE) -t -A main.elf
+	avr-size --mcu=$(DEVICE) -C main.elf
+	avr-nm --size-sort main.elf
+
+
diff --git a/atxswitch/main.c b/atxswitch/main.c
new file mode 100644
index 0000000..2e9ff5c
--- /dev/null
+++ b/atxswitch/main.c
@@ -0,0 +1,25 @@
+#include <avr/io.h>
+#include "uart.h"
+
+int main(void)
+{
+    /* serial */
+    uart_init();
+
+    /* D4 = output and high (=> atx down) */
+    PORTD |= 0x10;
+    DDRD  |= 0x10;
+
+    for (;;)
+    {
+        switch(uart_getchar()) {
+            case '?': break; /* useful for auto documentation */
+            case '0': PORTD |=  0x10; break;
+            case '1': PORTD &= ~0x10; break;
+            case 'T': PORTD ^=  0x10; break;
+        }
+        uart_putchar((PORTD & 0x10) ? '0' : '1');
+    }
+
+    return 0;
+}
diff --git a/atxswitch/uart.h b/atxswitch/uart.h
new file mode 100644
index 0000000..22e0655
--- /dev/null
+++ b/atxswitch/uart.h
@@ -0,0 +1,76 @@
+/* #define F_CPU 16000000UL <= defined in Makefile */
+#define BAUD 9600
+
+/* This file is *highly* inspired from:
+ * http://www.appelsiini.net/2011/simple-usart-with-avr-libc
+ */
+
+#include <util/setbaud.h>
+
+#if 0
+static inline void uart_init()
+{
+    UCSRB |= (1 << RXEN)  | (1 << TXEN);
+    UCSRC |= (1 << UCSZ0) | (1 << UCSZ1);
+#define BAUD 115200
+#include <util/setbaud.h>
+    UBRRH = UBRRH_VALUE;
+    UBRRL = UBRRL_VALUE;
+#if USE_2X
+    UCSRA |= (1 << U2X);
+#else
+    UCSRA &= ~(1 << U2X);
+#endif
+}
+#endif
+
+void uart_init(void)
+{
+    UBRR0H = UBRRH_VALUE;
+    UBRR0L = UBRRL_VALUE;
+
+#if USE_2X
+    UCSR0A |= _BV(U2X0);
+#else
+    UCSR0A &= ~(_BV(U2X0));
+#endif
+
+    UCSR0C = _BV(UCSZ01) | _BV(UCSZ00); /* 8-bit data */
+    UCSR0B = _BV(RXEN0) | _BV(TXEN0);   /* Enable RX and TX */
+}
+
+void uart_putchar(char c)
+{
+    UDR0 = c;
+    loop_until_bit_is_set(UCSR0A, TXC0); /* Wait until transmission ready. */
+}
+
+char uart_getchar(void)
+{
+    loop_until_bit_is_set(UCSR0A, RXC0); /* Wait until data exists. */
+    return UDR0;
+}
+
+#if 0
+/* alternatives for stream uses */
+void uart_putchar(char c, FILE *stream)
+{
+    if (c == '\n') {
+        uart_putchar('\r', stream);
+    }
+    loop_until_bit_is_set(UCSR0A, UDRE0);
+    UDR0 = c;
+}
+
+char uart_getchar(FILE *stream)
+{
+    loop_until_bit_is_set(UCSR0A, RXC0); /* Wait until data exists. */
+    return UDR0;
+}
+#endif
+
+#if 0
+FILE uart_output = FDEV_SETUP_STREAM(uart_putchar, NULL, _FDEV_SETUP_WRITE);
+FILE uart_input = FDEV_SETUP_STREAM(NULL, uart_getchar, _FDEV_SETUP_READ);
+FILE uart_io FDEV_SETUP_STREAM(uart_putchar, uart_getchar, _FDEV_SETUP_RW);
+#endif