Connecting Usb data input to Receiver IC - RC Groups
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Dec 02, 2012, 10:25 AM
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Connecting Usb data input to Receiver IC

I've been looking all over the internet for a data sheet so I can find the pinout on this IC to no avail. I want to see if I can solder in the data and power lines from usb to the futaba FP-R122JE maybe it will be possible to control the servos from coding/generic software.

I'm using these servos for a camera pan/tilt bot and needed some control. I'm eventually going to get some 6 servo controllers but for now want to fiddle with this so if anyone has any idea's it would be very much appreciated!

Here is the circuit board top and bottom and then a schematic someone made:

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Dec 02, 2012, 10:34 AM
An itch?. Scratch build.
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You need to ask this sort of question in the - , it's the DIY Electronics forum, they have loads of knowledge and expertise.

In the top right hand corner of your post is the 'Report', this allows you to get the thread moved to another forum if you require.
Dec 02, 2012, 12:03 PM
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Thank you!
Dec 02, 2012, 01:36 PM
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I don't know whether this helps, but the servo output signals come out on pins 7, 8.

Although the schematic is labelled CH1, CH2, CH3 it appears that CH3 may not exist and Pin 15 is brought out to the battery connector for another purpose.

There is the possibility that Pin 15 is the raw PPM receiver output before it goes into the channel decoder.
Last edited by Martyn McKinney; Dec 02, 2012 at 08:24 PM.
Dec 02, 2012, 02:05 PM
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Interesting, maybe I can get it wired up and do a diagnostic to test what signals I'm getting.. only problem is that I don't have the controller transponder so it might be hard for me to stimulate a signal. I'm thinking maybe its a generic IC with a different label printed on it, if so I can figure out the pin signature for most of the pins then more than likely match it to something similar or identical.

Where did you find that?

Nvm I see what traces you followed.. Pin 15 could be channel 3.. but goes to a grounded cap, maybe for voltage buffer.
Last edited by jpb0801; Dec 02, 2012 at 02:09 PM. Reason: mistake
Dec 02, 2012, 02:09 PM
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A standard 27MHz car transmitter on the correct frequency will likely control this receiver.

The pulses on pins 7 and 8 will repeat 50 times per second with an amplitude of about 5V and will vary in width from between 1 and 2 ms. depending on transmitter stick positions.

Why are you stuck with this receiver if you don't have a transmitter?.

Almost any radio control system will give you what you need without any soldering by simply plugging connectors into the servo channel outputs.

You can also simulate a signal with an inexpensive servo tester.
Last edited by Martyn McKinney; Dec 02, 2012 at 02:22 PM.
Dec 02, 2012, 03:16 PM
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My initial goal was to harvest the servos from this system (old rc sail boat that was given to me without handheld unit) to use with a Texas Instrument Stellaris ( Micro-controller, unfortunately that controller has proven somewhat difficult to debug/code the timers for PWM and its new so the community support isn't there just yet not to mention I'm some what of a novice when it comes to circuit design and programming. My next option was to maybe try turn over the RF receiver to usb control just needing the 2 servos for pan and tilt function for webcam.. making a servo controlled telescope mount for astronomy.

Btw I like the idea for car radio transmitter, very simple. I'd like to keep it all in one system seeing how I need a comp for the webcam anyways. really just having fun modifying stuff and maybe save a buck along the way.

and servos are Futaba S3003
Dec 02, 2012, 10:42 PM
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Something like this would be handy, anyone in here have experience with what pinning usb debug should be connected to in 24 pin PWM IC?

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