Take a look to the Kidogo project, by Dilshan R Jayakody, an engineer from Sri Lanka; it is a very useful digital signal injector with 8 channels:
The project is composed by two elements:
- a board, with Microchip’s PIC18F2550 and USB interface;
- a software (Kidogo Player) running on a PC that allows to “draw” digital signals.
Kidogo Player has a very nice and user-friendly interface:
All the project files (schematics, software, documentation) has been published on author’s GitHub repository.
Source: Hack a Day