Hi guys. Here's a little experiment we did yesterday using Doug Weibel's spektrum-to-PPM substitute firmware for the APM's ATmega328P, an upcoming (now available here!) Spektrum Adapter accessory board, and an ArduCopter. Sorry about the lack of video, but I can assure you our resident quad pilot Jeff Taylor flew this here at the shop with good results (considering none of this is fully baked)!
The Spektrum Adapter accessory powers the Spektrum module with an on-board 3.3V regulator, takes care of level translation on the single serial line, and has an input pin to enable/disable the regulator (this is used for putting the satellite in bind mode). The four pins are GND, 5V, data, and regulator enable.
I wrote a (very) crude sketch to put the satellite in different bind modes, you can grab it here: https://gist.github.com/ef01907a5c90dd66f987. I've tested it with DSM2, DSMX, and Orange Rx satellites. I've found that "DSM2 1024/22ms" mode is the one that works with Doug's firmware. The sketch is meant to be used on any Arduino Mega style board, it uses Tx1 to enable the regulator and consequently the satellite at the right moment to then receive the bind mode pulses sent out through Rx1. Once the sat is in bind mode, Rx1 is configured as an input again to receive the serial data after binding.
The ATmega328P needs to be re-programmed with Doug's firmware. You can either Arduino-ify the chip with the right bootloader and load the sketch through an FTDI cable connected to IN1 and IN2, or take the easy way and verify the sketch, grab the .hex file, and load it with an AVR ISP programmer.
Once the sat is bound, I soldered the adapter board on to an APM as seen in the photo, directly on the three IN1 pins. IN1 is the 328's Rx and is the only pin needed to receive the satellite's channel data. The small blue wire in the photo is connecting the 5V and reg enable pins to keep the regulator on at all times. The 328's Tx line could also be set high at all times to do the same thing, maybe the binding modes can be integrated into the 328 firmware as well?
After this, all should be the same as when using the full Rx module with servo extension cables. We found no problems with this setup during the Mission Planner configuration steps.
The Spektrum Adapter boards are now in stock in the store! Feedback for future revisions is welcome, and happy hacking!
Comments
I don't think you'll get a range improvement. You'll need to add other satellites if you want reliability enhancement, but range will not rise too much.
The big advantage of using this method is the weight reduction and simplicity (less wires), and eventually smaller price of the satellite compared to a full receiver.
I you want range improvment, there are other technics :
- rise the transmission power (not possible for most country)
- use a directive antenna at the transmitter side (quite difficult to use)
- rise the height of the transmitter antenna to avoid field reduction effect because of ground reflections
Does anybody have an idea of the range you get with this compared to the standard receiver setup?
UPDATE: the Spektrum Adapter board is available now! http://store.diydrones.com/ProductDetails.asp?ProductCode=RC-SPEKTR...
Using the new Arducoder code for the Mega 328 chip, it is possible to use a Jeti satellite without hardware modification. Just read the manual in the Arducoder repository.
Tested and working here. The Rsat need to be configured in ppm 8 mode, the default one.
george, correct! looks great without all that stuff getting in the way.
Well put me down for one Chris as I hate all the cables and swaping the chanels about. But will I need to buy one of these
Alex, it will be a commercial product soon; this one was just a prototype.
So if I understand correctly I won't need the rats nest of wires between my receiver and autopilot?! That's great!
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