Let's start from designing schematics. As an electronic design automation tool called gEDA
is chosen (http://www.geda-project.org
). Despite its enormous popularity Eagle system was eventually rejected as the dimensions of main PCB are not covered by Eagle's free license and the cost of license of substantial. At the same time, gEDA has enough capabilities to allow us design this project.
Two circuit diagrams need to be designed - one for main module and one for GSM transport module.