So on to something different.  I needed to build something else, but what.  So I have a Crazybee 3.1 with some pads still left on it (after some crap soldering problems some months back).  Can I put the FlyFish 1303.5 motors on to this frame, get ELRS to work and have a working VTX with OSD.  Challenge set.

Parts

JMT Eyas 100 2.5" Frame
Happymodel Crazybee V3.1 2-4S 12A AIO FC
FlyFishRC 1303.5 5500kv motors
Happymodel EP2 Receiver (ELRS)
Happymodel Diamond VTX
Caddx Ant Nano 4:3
RushFPV Cherry 2 RHCP u.fl
BetaFPV Micro Light Canopy
Azure 2540 or HQ 2.5x3.5x3 Props
3-4S Lipos

The Build

So this board has no T2/R2 pads left, so i have one UART available.  It turned out the LED pad was toast as well, which is what i was going to use for smartaudio.  So I researched.  I have a T1, R1 and IR1.  R1 is a bad place to solder, so IR1 it has to be.  So first thing lets sort out the pads/ports/resources.



So initially my resource lists looks this.


This board uses 4.2.11 and yes I could put 4.3.1 on it since I am no longer limited by the SPI FrSky Rx that doesn't work with 4.3.1, but I don't want to add in more possible problems, so lets do it on 4.2.11. Don't fix what isn't broken.

So initially i was going to set LED_STRIP as a softserial.  But then i soldered a wire on it and the pad came off. :/  Seems I screwed this board up big time last time.  So what to do now.  I decided on BEEPER, but that wouldn't work for some reason.  Then I remembered Oscar had mentioned about splitting the UART's in his softserial article, so I looked up that and thought why not ELRS on IR1 and smartaudio on T1 (as a softserial).  So lets remap.

First lets clear what we don't have or need.



Now lets make a softserial using SERIAL_TX 1.


So I then soldered everything up.

Next was ELRS.  As usual this was problematic.  Turned out I needed to update my platformio udev rules file.  I maybe didn't have the entry that covered Happymodel EP2.  Once I updated it everything started working.  I soldered it to an old 5A FC with a bricked gyro and then configured it in betaflight so i could use passthrough.  I then flashed it with ELRS 2.5 and setup bindphrase, wifi, inverted receiver, etc.  This will never be updated again beyond this. I then desoldered it from the 5A FC and soldered it to the Crazybee FC.  Then fired it up in Betaflight.  No connection to the radio initially, but after power cycling the FC, it started working.  My guess is your radio needs to be switched on before you power up.  If I power up the radio after the FC it won't connect.

So now I have a working FC, VTx (and Smartaudio) and ELRS Rx.  Next will be mounting it on the frame and soldering the motors to it.

Nice, guess it is an old AIO? Not sure from the photo, but if there is still gunk on the board you may want to scrub off with some alcohol. Sometimes AIOs do fine caked in gunk, but other times just the tiny piece of debris is enough to wreak havoc. No more fireballs

It's the same one I used on the Flea 3.0 build. It's always been twitchy on FrSky D8. The other one flew on a single antenna for six months and never missed a beat, this one flies 25m away and failsafes.

I did try and do this a while back, but my soldering level was still too low, hence why it looks kind of bad in the picture. I need to try and find some isopropyl alcohol and scrub the board a bit. The stuff I have at the minute is only 70% (hand wash from Covid times). Also there's a ton of flux on it. I wasn't taking any chances when i soldered it up earlier so i let rip with the flux. I might have a go with the 70% stuff if needs be and put it on a window outside, it's pretty warm here at the minute so will probably dry pretty quickly.

Tomorrow I will solder the motor wires. Beyond that it's all plug and play. I built the frame earlier and mounted the FC on it, but need to do a big battery strap since the 4S 450's are as big as the 3S 650's. Probably going to try it on both of those. But it's primarily a 4S build.

I'm glad to learn the remapping stuff. I always wanted to do it, but never had a good reason to do so. Not to mention that EP2 that has sat in the parts box for two years. Yes it's a ceramic antenna, but i'm unlikely to fly this more than a couple hundred metres. Going to try and mount it in some way so the antenna is on the outside of the canopy, but I don't think it will have an issue if I fly inside 500m. I forgot to put a camera on the parts list, but it will be my favourite, the Ant Nano since that's all I have.

Hoping to get it in the air by Friday, weather is currently holding, but the possibility of rain is increasing daily i think. Would be cool to get out and fly for a couple of hours.