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Makefile for Embedded Programming

Summary:

    1. AVR, avr-gcc and avrdude
    1. Make and makefiles
    1. The Fab Academy example

AVR, avr-gcc and avrdude

According to Wikipedia:

The AVR is a modified Harvard architecture 8-bit RISC single-chip microcontroller, which was developed by Atmel in 1996.

Since we normally use AVR microcontrollers in the Fab Academy, we need write a C code for them, compile it with avr-gcc and send it to the microcontroller with avrdude. All the instructions on the Makefile for this exercises basically deals with almost only these two commands. But what is a Makefile?

AVR, avr-gcc and avrdude

When you need to deal with multiple configurations and commands when compiling a software, you can use the make command on Mac/Linux for automatizing this task. Furthermore, you can distribute it to other people that can therefore use it for compiling your software easily.

make reads automatically a Makefile file in the folder where you launch it (it should be the folder where your project can be found). Otherwise, you can specify it with make -f filename, especially if you have more Makefiles with different names.

The structure of a Makefile is very simple, and more tutorials about it can be found here, here or here

Let's look at a ready-made example for the Fab Academy.

The Fab Academy example

On the lecture page there is already a C program that can be compiled and uploaded to the Hello Board (with an Attiny44).

Let's say that the program is ok for your board (and that your board is ok), so we can learn from its Makefile in order to understand how to modify it or create our own Makefile. The file is called hello.ftdi.44.echo.c.make so you can download it and rename it to Makefile, so that make will automatically load it. Here is its content:

PROJECT=hello.ftdi.44.echo SOURCES=$(PROJECT).c MMCU=attiny44 F_CPU = 20000000

CFLAGS=-mmcu=$(MMCU) -Wall -Os -DF_CPU=$(F_CPU)

$(PROJECT).hex: $(PROJECT).out avr-objcopy -O ihex $(PROJECT).out $(PROJECT).c.hex;
avr-size --mcu=$(MMCU) --format=avr $(PROJECT).out

$(PROJECT).out: $(SOURCES) avr-gcc $(CFLAGS) -I./ -o $(PROJECT).out $(SOURCES)

program-bsd: $(PROJECT).hex avrdude -p t44 -c bsd -U flash:w:$(PROJECT).c.hex

program-dasa: $(PROJECT).hex avrdude -p t44 -P /dev/ttyUSB0 -c dasa -U flash:w:$(PROJECT).c.hex

program-avrisp2: $(PROJECT).hex avrdude -p t44 -P usb -c avrisp2 -U flash:w:$(PROJECT).c.hex

program-avrisp2-fuses: $(PROJECT).hex avrdude -p t44 -P usb -c avrisp2 -U lfuse:w:0x5E:m

program-usbtiny: $(PROJECT).hex avrdude -p t44 -P usb -c usbtiny -U flash:w:$(PROJECT).c.hex

program-usbtiny-fuses: $(PROJECT).hex avrdude -p t44 -P usb -c usbtiny -U lfuse:w:0x5E:m

program-dragon: $(PROJECT).hex avrdude -p t44 -P usb -c dragon_isp -U flash:w:$(PROJECT).c.hex

If you launch a simple make in the terminal, only the first part will be executed, this:

PROJECT=hello.ftdi.44.echo SOURCES=$(PROJECT).c MMCU=attiny44 F_CPU = 20000000

CFLAGS=-mmcu=$(MMCU) -Wall -Os -DF_CPU=$(F_CPU)

$(PROJECT).hex: $(PROJECT).out avr-objcopy -O ihex $(PROJECT).out $(PROJECT).c.hex;
avr-size --mcu=$(MMCU) --format=avr $(PROJECT).out

$(PROJECT).out: $(SOURCES) avr-gcc $(CFLAGS) -I./ -o $(PROJECT).out $(SOURCES)

The first four lines are for configuring the Makefile:

* Name of the file to compile
* Extension of the file to compile
* Microcontroller to program
* Frequency of the board to program

The other lines initialize the process and compile the C script with avr-gcc.

The other part of the file (and that won't be executed with a simple make command) consists of different instructions, that can be specified after make:

  • make program-bsd
  • make program-dasa
  • make program-avrisp2
  • make program-avrisp2-fuses
  • make program-usbtiny
  • make program-usbtiny-fuses

program-bsd: $(PROJECT).hex avrdude -p t44 -c bsd -U flash:w:$(PROJECT).c.hex

program-dasa: $(PROJECT).hex avrdude -p t44 -P /dev/ttyUSB0 -c dasa -U flash:w:$(PROJECT).c.hex

program-avrisp2: $(PROJECT).hex avrdude -p t44 -P usb -c avrisp2 -U flash:w:$(PROJECT).c.hex

program-avrisp2-fuses: $(PROJECT).hex avrdude -p t44 -P usb -c avrisp2 -U lfuse:w:0x5E:m

program-usbtiny: $(PROJECT).hex avrdude -p t44 -P usb -c usbtiny -U flash:w:$(PROJECT).c.hex

program-usbtiny-fuses: $(PROJECT).hex avrdude -p t44 -P usb -c usbtiny -U lfuse:w:0x5E:m

program-dragon: $(PROJECT).hex avrdude -p t44 -P usb -c dragon_isp -U flash:w:$(PROJECT).c.hex

Each section specifies the terminal commands that will be executed for each option. In this case, each option is configured for a different ISP, sometimes the programming of the fuses is separated from the programming of the board. You can even add your own section, with the name that you prefer. For example, if you insert this section called "all-in-once", you can program the fuses and the board with the FabISP with one command (make all-in-once):

all-in-once: $(PROJECT).hex avrdude -p t44 -P usb -c usbtiny -U lfuse:w:0x5E:m avrdude -p t44 -P usb -c usbtiny -U flash:w:$(PROJECT).c.hex

Original tutorial by:

Licensed under a Commons Attribution 4.0 International License