CrossPack for AVR Development 20131216

Getting Started

Let's start with a simple example. We have an ATMega8 and want to blink an LED connected to Port D bit 4. To create a template project, run the following commands in a Terminal window:

bash$ cd ~/Documents bash$ mkdir AVR bash$ cd AVR bash$ avr-project Demo bash$ open Demo

We have added a new subdirectory to your Documents folder and created a project named "Demo" in it. Then we opened the newly created folder in Finder. The contents of the folder are:

bash$ cd Demo bash$ ls -l total 0 drwxr-xr-x 5 cs cs 170 Nov 19 13:58 Demo.xcodeproj drwxr-xr-x 4 cs cs 136 Nov 19 13:58 firmware

You can later create new subdirectories for the circuit diagrams, construction drawings and maybe Mac software here. If you don't have Xcode installed, you can delete Demo.xcodeproj. The subdirectory firmware is intended for the AVR firmware, it contains:

bash$ cd firmware bash$ ls -l total 24 -rw-r--r-- 1 cs cs 4139 Nov 19 13:58 Makefile -rw-r--r-- 1 cs cs 348 Nov 19 13:58 main.c

Makefile controls the build process and main.c contains the C source code for the project. We first edit Makefile. We want to configure the fuse values so that the AVR runs on an internal RC oscillator at 8 MHz and choose our programming tool. For this example we assume that you use Thomas Fischl's USBasp. We edit the options at the beginning of Makefile to look like this:

DEVICE = atmega8 CLOCK = 8000000 # 8 MHz in Hz PROGRAMMER = -c USBasp FUSES = -U hfuse:w:0xd9:m -U lfuse:w:0x24:m OBJECTS = main.o

The first two lines are obvious. The third line is avrdude's command line option for the USBasp programmer. The fourth line contains avrdude's command line options to program the fuses appropriately (see the ATMega8 data sheet for more information on fuse bits or use one of the tools in the Links section to calculate the values). And the last line lists all modules which should be compiled. That's the same as the list of source files, but with the file extension changed to .o.

Then we edit main.c, make it look like this:

#include <avr/io.h> #include <util/delay.h> int main(void) { DDRD = 1 << 4; /* make the LED pin an output */ for(;;){ char i; for(i = 0; i < 10; i++){ _delay_ms(30); /* max is 262.14 ms / F_CPU in MHz */ } PORTD ^= 1 << 4; /* toggle the LED */ } return 0; /* never reached */ }

Now we can run the build process in the firmware directory:

bash$ make avr-gcc -Wall -Os -DF_CPU=8000000 -mmcu=atmega8 -c main.c -o main.o avr-gcc -Wall -Os -DF_CPU=8000000 -mmcu=atmega8 -o main.elf main.o rm -f main.hex avr-objcopy -j .text -j .data -O ihex main.elf main.hex

If you use Xcode, you can also click the Build button to build the firmware. Make has now created the files main.o, the compiled version of main.c, main.elf, that is main.o linked with all required external libraries and finally main.hex, an Intel-Hex file ready for passing to the programmer:

bash$ ls -l total 48 -rw-r--r-- 1 cs cs 4142 Nov 19 14:05 Makefile -rw-r--r-- 1 cs cs 367 Nov 19 14:06 main.c -rwxr-xr-x 1 cs cs 3161 Nov 19 14:07 main.elf -rw-r--r-- 1 cs cs 390 Nov 19 14:07 main.hex -rw-r--r-- 1 cs cs 808 Nov 19 14:07 main.o

The final step consists of uploading the code and fuses through the programmer:

bash$ make flash avrdude -c USBasp -p atmega8 -U flash:w:main.hex:i avrdude: AVR device initialized and ready to accept instructions Reading | ################################################## | 100% 0.19s avrdude: Device signature = 0x1e9307 avrdude: NOTE: FLASH memory has been specified, an erase cycle will be performed To disable this feature, specify the -D option. avrdude: erasing chip avrdude: reading input file "main.hex" avrdude: writing flash (130 bytes): Writing | ################################################## | 100% 0.21s avrdude: 130 bytes of flash written avrdude: verifying flash memory against main.hex: avrdude: load data flash data from input file main.hex: avrdude: input file main.hex contains 130 bytes avrdude: reading on-chip flash data: Reading | ################################################## | 100% 0.15s avrdude: verifying ... avrdude: 130 bytes of flash verified avrdude: safemode: Fuses OK avrdude done. Thank you.

bash$ make fuse avrdude -c USBasp -p atmega8 -U hfuse:w:0xd9:m -U lfuse:w:0x24:m avrdude: AVR device initialized and ready to accept instructions Reading | ################################################## | 100% 0.19s avrdude: Device signature = 0x1e9307 avrdude: reading input file "0xd9" avrdude: writing hfuse (1 bytes): Writing | ################################################## | 100% 0.19s avrdude: 1 bytes of hfuse written avrdude: verifying hfuse memory against 0xd9: avrdude: load data hfuse data from input file 0xd9: avrdude: input file 0xd9 contains 1 bytes avrdude: reading on-chip hfuse data: Reading | ################################################## | 100% 0.07s avrdude: verifying ... avrdude: 1 bytes of hfuse verified avrdude: reading input file "0x24" avrdude: writing lfuse (1 bytes): Writing | ################################################## | 100% 0.20s avrdude: 1 bytes of lfuse written avrdude: verifying lfuse memory against 0x24: avrdude: load data lfuse data from input file 0x24: avrdude: input file 0x24 contains 1 bytes avrdude: reading on-chip lfuse data: Reading | ################################################## | 100% 0.07s avrdude: verifying ... avrdude: 1 bytes of lfuse verified avrdude: safemode: Fuses OK avrdude done. Thank you.

The LED connected to Port D bit 4 should blink now.