Interface your PC to an RC Radio
Recently I built a couple of projects where I interfaced a PlayStation controller to a microcontroller. While this works fine in many situations there are times when you want to use an RC radio for its extended range or reliability. In this article we are going to create a very accurate and reliable interface to any RC radio with up to 6 channels. To perform this interface we will create a Coprocessor using a microcontroller. Once complete we can then connect other devices or even a PC to this interface.
The RC Radio
An RC receiver has multiple connectors that allow you to connect to servos or speed controllers. Each of these connectors has three leads. Two of the leads provide power and the third is a signal lead. The signal lead provides a positive pulse once every 20 milliseconds. It is the width of this pulse that each servo or speed controller uses to determine its position or speed. On average the pulse will range from 1000 to 2000 microseconds. The neutral or center position is at, or close to 1500 microseconds.
As you change the positions of the joysticks or knobs on the transmitter the pulse width will change in proportion to the amount of movement. When it is all said and done it is these pulse widths that we are going to measure with our interface.
The Objective
When I started the interface project I came up with a list of objectives.
1.Must support 1 to 6 channels
2.Must cover the pulse range from 1000us to 2000us at a resolution of 10us.
3.The interface must support the PC and microcontrollers.
Since the pulse repeats one every 20 milliseconds you will never be able to measure the pulses any faster than that. If we take the time to measure each pulse independently one after another it would take as long as 120 milliseconds to measure 6 pulses. This is much too slow. What we have to do is measure all the pulses at once. We need a real fast chip to do this. This is where the DiosPro comes in. In order to obtain the resolution we need for 6 channels we need to use assembly language. The DiosPRo chip supports inline assembly language with the KRAssmebler. The DiosPro chip also has a built-in UART so we can add a serial interface that just about any chip, device or PC can talk to.

download full report
http://kronosroboticsProjects/RCRadioInterface.pdf