Posted by Chris Anderson on December 11, 2009 at 10:52pm
The best way to read RC signals is PPM, which is a sequential stream where each channel is output in turn on a single wire. But traditionally the only way you can get that is to open up your RC receiver and solder a wire to a special pin. Fortunately the Paparazzi team designed a board that will convert up to 8 channels of regular PWM servo signals to one PPM signal, with no RC hacking required. We've now modified it a bit to work with our failsfe multiplexer and released a version as a DIY Drones product ($24.95).
BTW, the forthcoming ArduPilot Mega will use this technique, as well.
From the product description:"This improved & reduced PPM encoder board, based on a Paparazzi design, plugs into the servo output ports on a R/C receiver and encodes them into a PPM pulse suitable for the paparazzi autopilot and other projects. This allows you to use any R/C equipment with the paparazzi autopilot or read up to 8 servos with a single I/O pin of your uController. Modifications to the R/C receiver are not necessary. Connect the wires from your receivers channels to the PPM and one wire to the PPM in of your system. If you decide to use the tiny board to power the receiver, make sure you put-in a jumper and plug something between the 8th channel and the receiver.
The whole project is based around the ATMEL ATMEGA168/328 AVR processor and all timing is done
within interrupts so accuracy and stability is optimized
It is now also possible to select the PPM waveform shift, negative or positive.
Firmware is free and was created by Hendrix and Moa, with tiny modifications by Jordi Muñoz that allows control an extra failsafe multiplexer.
You can always send it to home and i will check them out for you... Note that this devices are running at 16Mhz, so the compiler must know this information to work properly... By default is set to 8Mhz
Exist the possibility they are flashed incorrectly... If you have an AVRISP i can help you upload the code or just send it back to me and i will do it for you.
I have the same problem. Steady blue light.
I have all 8 channels of RX connected.
I also tried the 5V FTDI cable and no output from the board.
Yes, 4 to 6 jumped.All RX ch disconnected.
I can't load new firmware if the board is not responding.
Bad board ?
Earl
No Chris, the throttle on channel 3 is connected to channel 3 on the encoder - absolutely 110% certain on this.
Checked it with a servo on channel 3 on the rx as well...
This is what is wierd!
Thanks for the rest of the info though, I have read the manual several times! Understanding it as a newby is a different matter ;)
Thanks for the answer, Ken. I just re-soldered it, but without any success. What exactly is the channel 3 on the board? I hope one of them I used :) http://www.die-kreuzzuege.de/P1000440.JPG
Still no changes on the LED. Whatever position I move the sticks to, the LED won't start flashing. As you can see, I tried an old 35MHz receiver this time to make sure it wasn't Spektrums fault.
Since you move the stick and you have ppm output then you must have connected the aileron channel of the rx to the throttle channel (number 3) of the ppm encoder.
The PPM encoder will cut the ppm output if channel 3 has an input of more than 2025 microseconds
by default.
This is done in order to signal to the ppm encoder that the receiver has lost the signal from the tx.
This is why it is essential that you program the throttle channel failsafe of the receiver to produce more than 2025 microseconds and at the same time reduce the EPA so during normal throttle operation the throttle channel never exceeds the 2025 limit.
On Futaba radios channel 3 is reversed so the throttle channel produces more than 2025 microseconds when positioned at idle (lower position) and less than 1000 microseconds when at full throttle.
You can reprogram the failsafe channel of the ppm encoder and change its threshold value or use another channel different than the throttle channel (read the manual).
Chris
Comments
Dody, do you need my address as well?
I am sure the others will thank you also.
Earl
Exist the possibility they are flashed incorrectly... If you have an AVRISP i can help you upload the code or just send it back to me and i will do it for you.
I have all 8 channels of RX connected.
I also tried the 5V FTDI cable and no output from the board.
Yes, 4 to 6 jumped.All RX ch disconnected.
I can't load new firmware if the board is not responding.
Bad board ?
Earl
Checked it with a servo on channel 3 on the rx as well...
This is what is wierd!
Thanks for the rest of the info though, I have read the manual several times! Understanding it as a newby is a different matter ;)
http://www.die-kreuzzuege.de/P1000440.JPG
Still no changes on the LED. Whatever position I move the sticks to, the LED won't start flashing. As you can see, I tried an old 35MHz receiver this time to make sure it wasn't Spektrums fault.
The PPM encoder will cut the ppm output if channel 3 has an input of more than 2025 microseconds
by default.
This is done in order to signal to the ppm encoder that the receiver has lost the signal from the tx.
This is why it is essential that you program the throttle channel failsafe of the receiver to produce more than 2025 microseconds and at the same time reduce the EPA so during normal throttle operation the throttle channel never exceeds the 2025 limit.
On Futaba radios channel 3 is reversed so the throttle channel produces more than 2025 microseconds when positioned at idle (lower position) and less than 1000 microseconds when at full throttle.
You can reprogram the failsafe channel of the ppm encoder and change its threshold value or use another channel different than the throttle channel (read the manual).
Chris
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