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Topic: Generate PPM pulses for radio control (Read 600 times) previous topic - next topic

rva1945

Hi

I want to convert a cheap 2.4GHz 6-channel RC radio system to a computer radio (programmable), and I think I can use an Arduino for that purpose.

I can add a LCD / TFT screen in order to have a decent interface. By reading values from the potentiometers and switches, the Arduino should produce the PPM signal that is fed into the 2.4GHz module (that is already done by the original transmitter circuitry, to be replaced by the Arduino). The Arduino EEPROM can be used to store a number of models and their settings.

First, this is how PPM works (the pulses for each channel are sent as a train of pulses):

http://www.pabr.org/pxarc/doc/opwm_ppm.gif

Second, here is a code that some say works:

https://storage.googleapis.com/google-code-archive-downloads/v2/code.google.com/generate-ppm-signal/Generate_PPM_signal_nodelay.ino

It should be as easy as changing the values of microseconds in the range of 1000 to 2000 in an array whose elements are the channels.

Does anyone have any say about this? Is it feasible?

Thanks,
Robert

rtek1000

#1
Oct 21, 2019, 07:36 am Last Edit: Oct 21, 2019, 07:37 am by rtek1000
Quote
that is already done by the original transmitter circuitry, to be replaced by the Arduino
Quote
Is it feasible?
Interestingly, if the signal is already produced by some circuit, it makes little sense to switch to a microcontroller.

Surely the Arduino can produce the signal. But what would be the point?

Increase the number of knobs / potentiometers? Or maybe perform sequential command patterns?

The code informed performs the timing via software, probably there should be some interference when reading the input, especially analog inputs. You may want to look for other examples that use timers.

https://quadmeup.com/generate-ppm-signal-with-arduino/

https://github.com/kolod/Arduino-PPM-Generator

https://oscarliang.com/build-pwm-ppm-converter-arduino-2-4ghz-receiver/

Please avoid private messages, your question may be someone's answer in the future!

Robin2

#2
Oct 21, 2019, 10:11 am Last Edit: Oct 21, 2019, 10:12 am by Robin2
I reckon it would be simpler to replace the complete RC system with an Arduino based system using nRF24L01+ transceiver modules. They are cheap, effective and easy to use - see the link below. Those modules (or their Cypress equivalent) are probably used inside the commerical RC equipment).

Using the nRF24 modules directly will give you a lot more flexibility.

...R
Simple nRF24L01+ Tutorial
Two or three hours spent thinking and reading documentation solves most programming problems.

mikb55

Does anyone have any say about this? Is it feasible?

Was that code written for the specific receiver that you are using?

rva1945

Interestingly, if the signal is already produced by some circuit, it makes little sense to switch to a microcontroller.

Of course I know the wheel already exists, I will not create it. What I want is to convert the radio to a computer radio, maybe you are not into RC, but a computer radio system is a totally new world. You can create models and each is stored in the memory, with its settings of exponential, dual rate, sub trim, channels in reverse or normal mode, channels mixing, etc. But for that purpose, I will have to send the PPM pulses and take the original circuitry out (excepto for the 2.4GHz module).

As for the nRF24L01 I don't think it will have the same transmitter power as the original radio system devised for flying RC planes.

This is my "standard" and cheap transmitter:

Cheap


this is a computer radio:

computer radio system

A TFT screen and the Arduino can do the job.

mikb55

#5
Oct 21, 2019, 05:35 pm Last Edit: Oct 21, 2019, 08:27 pm by mikb55
This transmitter uses the AFHDS over the air protocol which like many other RC protocols is a frequency hopping system designed to be more jam resistant than static channel systems such as the nRF24L01.

Robin2

#6
Oct 21, 2019, 06:28 pm Last Edit: Oct 21, 2019, 06:33 pm by Robin2
As for the nRF24L01 I don't think it will have the same transmitter power as the original radio system devised for flying RC planes.
I suspect both of the RC systems you linked to use Nordic (nRF24) or Cypress wireless systems internally. 2.4GHz wireless is not easy to develop and I doubt very much that RC companies would have the resources to create their own. I know from other stuff that Spektrum RC systems uses Cypress wireless devices.

I reckon you will have all the power you need if you use a high-power nRF24 (with external antenna) for the base unit.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

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