First experiments with AVR USART

diff --git a/avr/usart/Makefile b/avr/usart/Makefile
new file mode 100644 (file)
index 0000000..2012d57
--- /dev/null
+++ b/avr/usart/Makefile
@@ -0,0 +1,30 @@
+#MCU=at90s2313
+MCU=attiny2313
+PORT=/dev/ttyUSB0
+CC=avr-gcc
+OBJCOPY=avr-objcopy
+PROJECT=main
+RESET=false
+# optimize for size:
+CFLAGS=-g -mmcu=$(MCU) -Wall -Wstrict-prototypes -Os -mcall-prologues
+#-------------------
+all: $(PROJECT).hex
+#-------------------
+$(PROJECT).hex : $(PROJECT).out 
+       $(OBJCOPY) -R .eeprom -O ihex $(PROJECT).out    $(PROJECT).hex 
+$(PROJECT).out : $(PROJECT).o 
+       $(CC) $(CFLAGS) -o $(PROJECT).out -Wl,-Map,$(PROJECT).map $(PROJECT).o 
+$(PROJECT).o : $(PROJECT).c 
+       $(CC) $(CFLAGS) -Os -c $(PROJECT).c
+asm : $(PROJECT).c 
+       $(CC) $(CFLAGS) -O -S $(PROJECT).c
+# you need to erase first before loading the program.
+# load (program) the software into the eeprom:
+load: $(PROJECT).hex
+       $(RESET) && stty -F $(PORT) 19200 hupcl && sleep 2 && stty -F $(PORT) 19200 -hupcl && sleep 2 || true
+       avrdude -cstk500v1 -P$(PORT) -b19200 -p $(MCU) -Uflash:w:$(PROJECT).hex:i || $(MAKE) RESET=true MAKE=true load
+       # uisp -dlpt=/dev/parport0 --erase --upload --verify if=$(PROJECT).hex -dprog=dapa  -v=3 --hash=12
+#-------------------
+clean:
+       rm -f *.o *.map *.out *.hex
+#-------------------

diff --git a/avr/usart/main.c b/avr/usart/main.c
new file mode 100644 (file)
index 0000000..853f82a
--- /dev/null
+++ b/avr/usart/main.c
@@ -0,0 +1,27 @@
+#include <avr/io.h>
+#define F_CPU 1000000UL //1MHz default internal RC oscillator setting
+//util/delay.h and util/setbaud.h
+
+#define USART_BAUDRATE 9600
+#define BAUD_PRESCALE (((F_CPU / (USART_BAUDRATE * 16UL))) - 1)
+
+int main (void)
+{
+   char ReceivedByte;
+
+   UCSRB |= (1 << RXEN) | (1 << TXEN);   // Turn on the transmission and reception circuitry
+   //UCSRC |= (1 << URSEL) | (1 << UCSZ0) | (1 << UCSZ1); // Use 8-bit character sizes (not in attiny2313?)
+
+   UBRRH = (BAUD_PRESCALE >> 8); // Load upper 8-bits of the baud rate value into the high byte of the UBRR register
+   UBRRL = BAUD_PRESCALE; // Load lower 8-bits of the baud rate value into the low byte of the UBRR register
+
+   for (;;) // Loop forever
+   {
+      while ((UCSRA & (1 << RXC)) == 0) {}; // Do nothing until data have been received and is ready to be read from UDR
+      ReceivedByte = UDR; // Fetch the received byte value into the variable "ByteReceived"
+
+      while ((UCSRA & (1 << UDRE)) == 0) {}; // Do nothing until UDR is ready for more data to be written to it
+      UDR = ReceivedByte; // Echo back the received byte back to the computer
+   }
+}
+