Following several friends recommendations I purchased a FR Sky Taranis radio to control my quad copter. I wanted more channels of communication than what my original transmitter supplied, as well as the ability to choose which switches controlled which activities on my UAV. The Taranis was fairly inexpensive for its feature set, but has been in limited supply. I had myself put on a waiting list from http://www.alofthobbies.com/ to be notified when they had them in stock. I received mine about a month ago, and while I took pictures and have used it in the past month, this is the first time I’ve sat down and consolidated that information. I purchased the Taranis & X8R combination that includes both the transmitter and receiver. It included the protective carrying case, rechargeable battery, AC adapter, neck strap and balancing clip, as well as the transmitter and receiver. A small zip-lock bag contained keys for the carrying case and two pin jumpers for configuring the receiver outputs. There is a green LED visible between the battery compartment and the charger port that blinks when the battery is being charged and goes solid when it is completely charged. I wish that the LED was visible on the front because everything else is on the front, and I don’t really want to lay the device in its front during the charging period but would like to know when it’s done charging.
The X8R receiver has 8 standard PWM channel outputs as well as a Futaba compatible SBus output. The standard outputs can be configured as either outputting channels 1-8 or channels 9-16. The X8R is capable of receiving 16 channels and sending controls for those 16 channels over the single SPort connection. I am connecting it to my Pixhawk using the single SBus connection. Arducopter running on my Pixhawk currently only pays attention to the first 8 channels. I may configure the standard outputs on my X8R to output channels 9-16, and connect my camera gymbal controls directly to the X8r, allowing me to utilize all the channels currently.
The Pixhawk is designed with a single input control set of pins, using PPM instead of PWM. PWM stands for Pulse Width Modulation. PPM stands for Pulse Position Modulation. Pulse Position Modulation allows for packing multiple channels into a single signal. There are plenty of good examples describing the technology as it related to RC devices, if you know the right terms to search for. I started learning RC airplanes last summer, and understanding what was going on didn’t seem as easy as it should be. The APM board that I was originally using had 8 PWM inputs, and 8 PWM outputs. The inputs were connected to the receiver and the outputs were connected to the ESCs, Electronic Speed Controls, for the motors. Now I’m using the Pixhawk and it’s got a single three wire cable connecting to the receiver but still 4 three wire cables connecting to the 4 ESCs. http://www.endurance-rc.com/ppmtut.php is one description of PPM vs PWM.
The Taranis itself runs OpenTX operating system which accounts for a large portion of its flexibility compared to its cost. It reports data back from the receiver as well, so technically both the transmitter and receiver are transceivers, sending data as well as receiving data. A simple bit of data that it constantly reported back at the transmitter is RSSI, the receiver signal strength. This is useful simply to recognize before you fly your model out of range of your transmitter. This return data path should also be able to carry all of the telemetry back and display it directly on the transmitter. I’ve not figured out if the pixhawk needs to be connected to two ports on the x8r to accomplish this feature.
What follows is a link dump of many of the items I’ve been saving up in understanding my configuration of the taranis radio, using the 16 channels, using the pixhawk, my Tarot GoPro gymbal, and references to the APM as well.
- New Features to play with: http://diydrones.ning.com/forum/topics/arducopter-3-1-released?commentId=705844%3AComment%3A1574300