Makefiles

OS autodetection

Note that not all copies of the Makefile include this at the moment (see section "Use" below).

Motivation

The name of the serial port depends on the operating system:
  • Windows: COM4:
  • All others (?): /dev/ttyUSB0

The port to use is selected automatically to avoid having to modify the Makefile every time a different machine is used.

Use

The Makefile contains a line starting with AVRDUDE_PORT =. Replace that line with:

AVRDUDE_PORT = $(shell if uname -s |grep -i w32 >/dev/null; then echo 'COM4:'; else echo '/dev/ttyUSB0'; fi)

Requirements

  • uname
  • sh

Both are standard on unix machines and included in the mingw32 distribution.

Principle of operation

Algorithm

The OS is determined by looking at the output of the uname -s (kernel name) command. If the output contains, case insensitively, the string "w32", a Windows system is assumed and COM4: is used. If not, /dev/ttyUSB0 is used.

Implementation

The switch is not implemented by means of make but relies on a shellout. The output from grep is redirected to /dev/null to avoid printing the port name to stdout.

Alternative methods

  • Instead of looking at the output of uname, the existence of /dev/ttyUSB0 could be checked. However, it would try to access COM4: on Linux when the robot is not plugged in (which is not a real problem, but might lead to confusion).
  • The system wide AVRdude configuration file (/etc/avrdude.conf) could be used to set the default port for a given machine (where is this file located on Windows systems?). However, this would have to be set up for every machine used for programming.

Extensions

A more complex selection scheme can be implemented in case the name of the port may be different on a given machine (for example COM1: or /dev/ttyS0).

Enhancements

  • Multi-user main function (problems with the current solution: preprocessor black magic, main function not called main, main file not recompiled when different makefile chosen)
  • Single Makefile (included)
  • Change target name "main"
  • Output files not clean up?