Reading 'whatever ís received'

Forum 2005-2010 (read only) Hardware Interfacing
1

Hi,
This might sound very noobish (as 99% of my posts) but i'd like to know if someone has already experience with this.
I have wired the old RC Car of my brother onto my arduino. One of the receivers'channels is being wired to +5V GND and DATA to Analog IN2 (the other way arround it is possible to steer it with the servo library) and now i tried to read what exactly comes from the arduino to the motor driver when i use the RC Controller. But its more frustrating than i thought. I somewhat read only Values of 5xx - with a noise of +-40..
My first thought was that i would get some sort of analog signal ranging from 0 to 255 with about 128 as middle value to control forwards and backwards, but this doesnt seem to be that since all i ever receive is 500+-40

So, does anyone know if there is some way of controlling an RC car with the Arduino the way that is not just giving full throttle or nothing but to replicate the actual stuff that is coming from the receiver?

Thanks in advance
Nachtwind

2

An R/C receiver outputs PPM digital servo commands, not analog voltages. There are routines in the Arduino site that will drive servos and speed controllers directly from the Arduino without needing a R/C receiver. Does that help?

Lefty

3

Try using pulseIn to read the pulse width coming out of the receiver. It should vary from around 1000 to 2000 us.

4

ok, thanks for your suggestions. PulseIn looked nice and i think i may try to build something on my own.. if i dont find anything useful on the site ;0)

Thanks again

5

Alright.. after spending a few hours on this i would like to ask if someone here has an idea of how to use a library to control the speed controller of an RC Car... When i try to use the servo libraries i find here i can only control the the motor in a very binary way - either it is off or at full speed..

6

That really depends on the speed controller. You may want to look at the signal that the receiver is sending the speed controller on a scope. If you don't have access to one, you may want to look at dlownloading one of the many sound card oscilloscope programs

This one has German instructions: http://zeitnitz.de/Christian/Scope/Scope_ger.html

7

uff that is way beyond my understanding i think.. gonna read into that quite much at first.

Isnt there some simple way of receiving PPM signals and somehow seeing "ok, they range from 1490 to 8000 with a zero value of 4500"?

and then of course replicate this?

8

did you try measuring the signal using pulseIn?

9

yes, but this is quite strange.. i get noise with periodically biases.
Lets say it ranges arround 9500 all the time, no matter if i steer or not, but every 4 or 5 seconds it gets peaks above 15000 to about 11000. The strange thing is that if i connect it at the same time (Line from receiver channel to breadboard -> pin 3 and into the cable to the speed controller) i have variing pulsein durations, but yet again quite random... guess that has to do with the power drain.. anyhow.. that is all quite strange. maybe i wire something wrong? all i connect is the data line with pin 3 on the arduino - no data or V+ ?