Using ExpressLRS receiver. ExpressLRS site says to use channel 5 for Arm/Disarm, yet Ardupilot channel 5 “default” for copters is modes.
I think (not sure) I can change channel 5 to Arm/Disarm through a switch on transmitter by using this parameter RC5_OPTION = 41 and setting up the switch in the transmitter on channel 5 (Mixes Page). Will this work?
If so, is it then possible to put “Modes” on a different channel (such as channel 6) and use a 3-position switch on that one channel to change between 3 different Modes? If so, what parameter do I need to change and to what value? Is it FLTMODE_CH = 6?
I’m also having a confusion regarding this channel 5 arming on ELRS:
ELRS devs say that I “would better have channel 5 at high when armed” and it’s something beyond my understanding. Along with this channel 5 on ELRS is a 1 bit and it’s sent on every frame? frequently. I feel much safer arming by throttle, and also I have on my Radiomaster TX16S a 6-pos button ideal for mode switch, but I can’t set it on channel 5, because it’s 1 bit. Also my quad arms fine while channel 5 at low.
Maybe it’s some old time superstition, but still a mysterious religious fear keeps me from setting rings and bells on this switch.
What should I do with it?
You definitely want to set channel 5 high during flight, at least under present ELRS firmware. It sets some flags for transmission as well. You can probably just set a global function as Ch5 high and let ArduPilot ignore it as an arming command.
ELRS 3.0 brings some improvements to this mess and is the chief reason I’m considering switching over to ELRS in the near future.
From everything I’ve read/seen, Ch5 should be high when in a ready-for-flight mode. I was trying to find some more specific documentation on the rationale yesterday and came up empty. Some of the videos by the likes of Painless360 and RC Reviews discuss it in some detail.
Actually, here is the one of the ELRS dev team tells that even in 3.0 RC channel 5 still has to be high for the “link optimization be active”. I suppose, that means that otherwise ELRS will think that the aircraft is on the ground with some magic circumstances.
I stand corrected! Re-watched that video last night and realized I must’ve been too excited about the other features to recognize the continued importance of Ch5. Still, 15 full resolution channels with one wonky one is pretty good stuff, and the lower transmission rate certainly works for most, if not all of my use cases.
I got an R9M module + R9MM working with 3.0-rc tonight, and the results are so far pretty good. Even with the RX still on my desk amidst USB cables, monitors, and lots of sources of interference, I was able to get 260m away at 100mW through multiple obstacles before signal strength started to suffer badly. With direct line of sight and good antenna placement, I imagine the range would increase by an order of magnitude.
There’s also a little mention of MAVLink in that video which sounds promising!
TLDR; Set Ch5 high in-flight for all ELRS versions to date if you want to take full advantage of its capabilities.