Does anyone have (or is there available) a Processing source file (*.pde) for the Firmata_test.exe file?
The one that comes with Firmata_test.tar.gz is an *.cpp file. Can it be used by Processing?
I don't exactly know if the code posted at Firmata's SF repository is directly related to the one you mentioned earlier. However, I think it would be worth to give it a try. 