PPM interface Issues - Airtronics VR400

[warren]

I have solved my ppm interface problem. Briefly: I had built an interface cable which had the VR400 connected directly to the Parallel Connector. I solved the voltage level problem by using 5V from pin 8 of the game port to power the VR400. This worked fine on and older socket 7 mother board. It will not work on a newer socket 7 board with AGP support. I finally found that the newer board required the VR400 to sink more current than it was capable of to get the logic 0 level. I had to add a 2n2222 transistor (I think I have seen Futaba interfaces describing this) between pins 10 and 18 of the parallel lport connector, with a 2.2K resistor between the signal source and the base of the transistor. I'm still using the 5V from the game port to power the modulator of VR400. All works fine now.

I changed the computer to get AGP Video support. WOW. 17 frames per second at 1280x1024. I think the graphics are excellent. Good job!