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process input from radio control receiver plus other sensors — Parallax Forums

process input from radio control receiver plus other sensors

roedjroedj Posts: 6
edited 2011-09-13 20:21 in Propeller 1
To All,

This is my first post on this forum. I want build a system that does the following:

1) Be able to receive 8 channels of PWM signal (0.5 ms to 2.5ms) from a standard Futaba PWM receiver. Convert them to digital data that I can examine and change.

2) At the same time I also want to connect perhaps as many as 6 other sensors to this same system. These sensors would sense such things a sound, light, temperature, or pressure.

3) If necessary, change the value of the digitized PWM signal data depending on the input from the sensors, and

4) Covert all the data from the processed 8 channels into and ASCII string to be output as an TTL level serial communication. This data would be fed into a Parallax servo control board which can handle as many as 16 servos.

This is part of an underwater autonomous craft.

I'm not sure an Propeller can do all this. I'm also investigation Microchip PIC's and Arduino.

I could really use your help and guidance. Thanks for your time,

Dan in Michigan, USA

Comments

  • RS_JimRS_Jim Posts: 1,773
    edited 2011-09-13 05:59
    Hi Dan,
    First welcome to the Forum. Next in answer to your question the answer is YES the prop can do all that you have requested. Next go to the main Parallax web site and check out the Nuts and Volts articles as I believe there is one that involves reading the PWM from an RC receiver. 1 cog for serial coms, 1 cog for PWM, 1 cog for sensors,1 master cog, now I count 4 left to do whatever you need. I just looked in Nuts and Volts myself and the Sept 2010 article describes the process of reading a VEX data stream.
    Jim
  • roedjroedj Posts: 6
    edited 2011-09-13 17:45
    Jim,

    I don't think I explained my design properly. Let me try again.

    Basically, I need to monitor upwards of 16 channels simultaneously. 8 of the channels will be PWM signals from a radio control receiver and the other 4 to 8 will be either analog or digital outputs from various types of sensors. Then, depending on the various inputs, I massage the data and output an ASCII string to a Parallax Proto Servo Control board to control up to 16 servos.

    Dan
  • Zap-oZap-o Posts: 452
    edited 2011-09-13 17:49
    I think that this would be child's play for the prop. You could use a ADC for the analog signals and run the 8 PWM signals into the prop directly, if they are 0 - 3.5 Volts signals. Sky is the limit.
  • RS_JimRS_Jim Posts: 1,773
    edited 2011-09-13 18:36
    Dan,
    Looking through the OBEX, I found an object that would read multiple servos and store the data as integer values in micro seconds. It was written in spin and would be worth your while to study it.
    Jim
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-09-13 20:21
    Dan,

    This is just the type of project the Propeller is really good at. Other's on the forum have already done a lot of these type of things with the Prop (including myself).

    Learn how to control a servo then learn how to listen in on the signal line.

    An external analog to digital converter will probably make your life easier (when reading your analog sources). A MCP3208 has eight 12-bit channels. It is a common ADC used with the Prop (and other uCs). (I personally like them.) There are several objects written for MCP3208 chips (there are also objects for other ADC chips).

    Your radio's signals will likely be closer to 5V than 3.3V which is fine. You'll just need to add a series resistor on each signal line to protect the Propeller (I usually use 10K resistors with my RC receivers).

    This sounds like a really fun project.

    Duane
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