Does anyone know how to interact with a 5-wire servo? I would like to be able to read the commands to this servo (with my parallax propeller) and either pass through the signal or modify it. (I'm using the propeller to interface with standard 3-wire servos just fine.) I have not been able to find a good resource describing the operation of 5-wire servos.

If anyone has any information (or better yet, spin code!) I would appreciate it very much!!


-Jason

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Marcus,

Wow, thanks for that direction to pxarc software. To answer your question, I just prodded around with my USB-oscilloscope until I found something that looked promising.

I can post some pictures (O-scope screenshots, or the pins I pulled the signal from) this weekend if anyone is interested?

-Jason
No need for pictures.
I just probed around on my 4-wire board, found the chinese data-sheet for the rc-receiver with 2 outputs
CH1 and CH2 but both are going into a Risong Microelectronics RS2681RA that seems to have no data-sheet.
These 2 may be the decoded pwm-data (there is even a third pin called "data" that may be the ppm) but I am
stuck at finding a way to verify this.
My problem is, that I do not have a usb-osci or anything to sample a time-dependent signal with ;)
Marcus,

I'm not sure what type of processor you are using for you application (Propeller, PIC 16 or 18 series, basic Stamp, or something else entirely), but it seems to me you could program up something to monitor these pins relatively easily without so much as an A/D channel.

Perhaps measure (for a given 20 ms period, for instance) how many pulses you have (over a 1.65 volt logic threshhold). If the results seem like nonsense, try another pin. Maybe you could throw in some rudimentary logic to discriminate between noise and true pulses that last longer than 10 to 100 us. The output could be simple, via an lcd, hyperterminal, or even LED's. Just a thought, good luck!
I am using a PXA270 on a gumstix-board.
My i2C-ADC chip will not arrive for a few days and I don't want to connect some unknown wire to
an expensive linux-computer (400MHz ARM running a modified paparazzi-autopilot and communicating
via wireless-lan with olsr ad-hoc routing) I had to import across the atlantic.

ARGH...I found a way. It's a PWM-signal after all.
I switched it on and meassured the voltage on that pin while moving the servo.
It changed from 0.4 to 0.15 and back every time and linear with my motions on the RC.
So it is the signal and I can cut that trace and inject the servo-pwm-output of my autopilot there.

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