New Scratch Build Project

[DroneCartel]

Hi All,

I'm new to drones, embarked on building my own with zero knowledge or experience, think it's going ok so far..
Bare in mind I'v come over from SlotCars, and 1:1 Drifting before that, I can make most things.. However Iv zero RC knowledge other than 23yrs ago when I had a Tamiya buggy, so it's all pretty new to me.. Nothing like jumping off the deep end..

I'm building this for shits'n'giggles, I'd also like to race when I find a club or like minded people to race with.

The spec is as follows..

FC - Matek F722 STD
PDB - Matek FCHUB 6S
ESC - Spedix GS30A
Motor - iFlight 2306 - 2450kv
Cam - RunCam Split 2S WiFi
VTX - TBS Unify Pro32 HV
Transmitter is going to be Turnigy Evolution(which I'm happy to modify if I need more functions)
I also got a SpeedyBee Bluetooth dongle, hoping this will work ok with this FC and stuff?
The frame is a cheap eBay special, as I guess I'll break quite a few.. Its 215mm. Iv chopped bits off, made holes, big air ducts to cool the boards..
I may even design a new frame to suit my build, at least then I can machine a whole load of extra arms..

I havnt got FPV Goggles yet.. don't know which to buy, and waiting for more slot cars to sell to fund them..
Same goes for Batteries, it'll be 4S of somesort, havnt decided and don't have the spare cash just yet. In the meantime, can I power it up with a bench test power supply to 14v?
Also unsure on what Antennas to get.. I'm thinking TBS Triumph Pro MMCX as it'll poke straight out the back nicely with a straight fit to the VTX. And a TBS Triumph Pro SMA for whatever headset I get..

Question time..

1) What I need help with is understanding CRSF/Smartaudio stuff, I literally have zero clue what the difference is or what it does. And how to wire up these 2 pins from the VTX to FC. Iv currently wired them like so.. CRSF RX1(Smartaudio) -> TX3(on FC). Then CRSF TX1 -> RX3(on FC). Is this correct?

2) I also need help on LEDs, of all things.. In my naivety, I bought a roll of SMD LED 12v strip light, with the intention of cutting them on the cut lines and soldering wires on, which has worked a charm, they are things of beauty and weigh little more than paper... Now I look at how to wire them up and I'm stumped.. all I see is Matek LED controllers and big heavy LEDs on beefy circuit boards. Wired to the LED pin on the FC board, which I think I need to use a proper LED controller for, and the way I read it, those only activate for "lost drone" situations.
Is there a way to power them and switch them through the FC rather than having an additional LED controller? (I can run them off as little as a 3v output if I rewire them so they are no longer in series) I take it I can't use a UART to power or ground them, and presumably the 3v-5v-10v outputs are permanent lives and can't be remotely switched? Is there tiny Relays that a UART could switch on/off? Or is there just a tiny LED controller with simple +/- pinout? In the meantime, Iv bought a tiny Lipo 3.7v battery and a bag of PCB mount switches, so I'm going to rewire the individual LEDs and run them independently of the drone's Battery.

3) Does the Camera Angle have a bearing on the FC and it's calculations? ie, I read that setting the cam angle/pitch is critical to how fast the thing goes, but then said nothing of any help in setting the angle.

4) Props, so many to choose from.. all the guides say different things, I need something slow, and robust.. and preferably pink/purple in colour..

5) I'll save the programming questions for when I'm ready to power up, Warning- I'm a complete moron when it comes to computers.. try to do everything on iPad where at all possible, including CAD. I will dust off the old laptop when the time comes and see how far I get..


Any help on the questions above would be greatly appreciated 

Regards
MrD

[ched]

I haven't got time now to reply fully but the bits you have so far look ok.
I will try and reply later today.
One thing, flying is megga difficult, so get a sim like fpvfreerider or velocidrone and hook up your evo tx ( i have one and i do like it) and get some stick time in. It's not perfect simulation of actually flying but the controls work correctly and give you a great idea of fpv flying.

[ched]

1. CRSF RX1(Smartaudio) to RX3(on FC). As long as rx3 is not used for usb port! You really need to install BetaFlight configurator and connect up the FC. Just so you know it's working and you can then check which uart ports the usb is using. Also most sellers wont accept a fauty fc back if you have soldered to it!
2. LEDs. FC can control WS2512B LEDs but just standard LEDs can't be controlled by the FC, unless you get some add on bit that enables them to be switched on or off. I have one of these LED and Buzzer board. This can be controlled by the FC and has a buzzer.
3. Camera angle has no bearing on FC. Start with lowish angle say 15 degrees and when you notice you are flying and only seeing the ground tilt up a bit.
4. Props lots of different options as you say. I use DAL T5040C Cyclone props and they are quite robust. I have also used these 5" 40pitch props and they took lots of crashes.
5. Just ask away, we will try and help.

As for powering from a bench supply that should be OK. REMEMBER NEVER power the quad up on the bench with props on.

As for goggles do you have a budget in mind? Box goggles can be bought for £30, Fatshark style from £80, all the way to the FatShark HDO plus Rapid Fire module totalling £550!

Batteries are an interesting one, 4S (4 cell) is what you want and probably 1500mAh capacity. The 'C' rating is VERY important but cheap brands exaggerate the C ratings. The C rating is supposed to be the maximum current the battery can give out. i.e. a 50C rating is 50 x capacity in amps so for a 1500mAh battery (1.5Ah) 50 x 1.5 = 75 Amps. Now check your motor specs and see whet the max amp draw is with a 5" prop. Times that by 4 and you get max amp draw. So for your iFlight 2306 - 2450kv on a 5" 43 pitch (5043) prop max current is 36Amps. So 36 x 4 = 144Amps!!! So using a 1500mAh (1.5Ah) battery the C rating should be 144/1.5 = 96C!
You need a reputable brand of battery like Tattu, GNB, Acehe, or RDQ and a high C version. Be aware that your esc can't handle the max current your motors can pull!!! So be very very careful going towards max throttle and maybe stick to 5040 props, the 40 is the pitch, the higher the pitch the more current motors need to spin props!

Hope that helps?

[DroneCartel]

Ched, you sir, are a legend.. thank you muchly for your help and advice, it's very much appreciated. Amazon kindly delivered a who load of bits and bobs over the last few days, just sat down to have another fiddle, with the drone.

Hopefully the transmitter will arrive tomorrow, if so, I'll have everything other than goggles, batteries and antenni. May get round to plugging it in by end of the weekend if time allows.

Re original questions..
1) I think I can set the uarts to do what ever, other than rx2 which share PPM, not that I know what PPM is..
Iv just checked the diagrams on Matek site, and they have it drawn that the Receiver SBUS connects to RX2 and SmartAudio to TX3, I'm pretty sure I can change what each UART does though.

2) I will look into the LED situation in due course, for now, I'm going to run the 'Look at me' LEDs independently to the main battery/fc/pdb..

4) Can you get lower pitch props, or is 40 where it starts?

Batteries) I was thinking MaxAmps, Graphene 1450mah, 170C, however the weight puts me off a little.

As someone who has no idea what kind of things people race with, what sort of total weight is normal?


Thanks again

[Six6siX]

I'm currently new to this world too, and I second the sim recommendation. After hours and days of sim flying, I took my quad out for a spin and can vouch it's a lot harder in the real world.

Also take some pictures of your build if you can, it's always nice to see !

Six.

[DroneCartel]

Hey Six,
I will indeed get some pics up, it's in a million pieces again at the moment, I'm doing a few bits before it starts going back together, then I'll get some pics up.

I will also look into the simulators, I'm usually a 'jump in deep end' guy, however, everywhere I read things, it tells me to use sims..

Another question..
Weight distribution? Is it preferably to have weight forwards, backwards, or equal? (I have 4 sets of scales for corner weighting Slot Cars, so to a certain extent I can balance it)

[ched]

40 pitch is probably lowest pitch.
Your motors are powerful, they create something like 1.4kg of thrust per motor. So at a guess of an all up weight including battery of about 500 to 600gms you are looking at a thrust ratio of 10:1 which is quite high!!!! Seasoned racers will be running higher thrust ratio but at 10:1 it will be powerful, very powerful!
What you have to remember is that you only have so much throttle movement, so your hover throttle maybe only about 15% of throttle!!! That is LOW. It might be worth setting up Betaflight to limit the throttle as otherwise I doubt your fingers are good enough to make the very small movements that will be needed. This is where a sim comes in, I assume you realise that racing or acrobatics have to be flown in rate/acro mode!! This means that when you let go of the sticks it doesn't level it's self but carries on doing what it was doing.

Do not power the vtx without an antenna you will kill it within a few seconds!!!

Matek do good diagrams so if possible follow the diagram.

As for people who race and the weight I don't really know. Bottom line is lightest possible weight as the quad can then turn and accelerate as fast as possible but it's a trade off. If the quad is not able to take a few crashes then you might not have a change. When I have watched races it's not all about ultimate speed as you have to actually go through all the gates and not crash!!! A bit tortoise and hare type thing. That said if you crash in a race and have a strong enough quad to not suffer any damage you might be able to use turtle mode to flip back over and carry on.
As you are learning don't worry about weight as you will be crashing lots. I can still remember the first time I managed to fly a complete battery pack without crashing, and that was only about 6mins of flight time!!! It took me a long time to learn, OK so I am 50 now and had not really had any RC experience other than ic boats about 20 years earlier. Also I don't play computer games so my eye hand co ordination isn't great. You might be OK but a sim with your tx (the evolution plugs straight into a pc via usb) is the way to go. FPVFreerider has a free version with just 1 scene and limited adjustments but it would get you going. Also have a look at Josh Bardwell's youtube learning to fly fpv videos as he uses FPVFreerider to teach.

Weight balance wise, always best, if you can, to have a reasonable balance as that way the motors are not having to work harder at one end to the other. It's not critical but main thing is try and put battery on so it's balanced front to back as that is the heaviest single thing.

I would guess that your quad will be capable of doing speeds in excess of 80mph!!! and as the weight is fairly low it will be able to do 0-80 within a second or so!!!!!!! So you need a big area with zero people. Don't think flying rate mode is easy you need to respect the quad as it's spinning razor sharp props at tens of thousands of rpm!!!! Make sure your failsafe works, check on bench with props off that when you switch the tx off the motors stop.
Building and flying is a bit of a steep learning curve but there are lots of great vids on youtube about setting up quads on Betaflight from Josh Bardwell, Painless360, CurryKitten, UAVFutures, ProjectBlueFalcon, and Albert Kim to name but a few. Then there is Oscar Laing who has a great web site with lots of info and explanation of things.
Sorry for long post but lots to say. Have fun and take it easy.

[ched]

No idea where you live but there is a meet up tomorrow close to Aylesbury/Watford. Details here: https://www.multi-rotor.co.uk/index.php?topic=24068.msg218233;topicseen#new
You would be welcome and be able to see how people do things and what kit they use. I am sure someone would let you watch a few flight on their goggles if you ask.

[DroneCartel]

Sadly couldn't have made it, despite not being too far away. I'm on the Surrey/Hampshire border, so only an hour and a half away from Watford.

I made a little progress with the LEDs, Iv wired 8x LEDs straight to battery, no resistors. The battery is 3.7v, it weighs around 6grams. The rest of the wiring/lights/switch etc weigh 1.56grams. They are self adhesive, cut off the roll and 30awg wires soldered directly to the terminals. I could have made it lighter if I used a higher voltage battery and wired them in series, but without knowing what voltage range they work with I had to try wiring them differently until they worked. They are Black Light LEDs by the way. £8 for a 5m roll.
So all in all, its way cheaper than buying LED kits, lighter than an LED controller and boards with LEDS on, and doesn't draw power from the main battery, win win in my book. 

Pics coming in a mo if the uploaded works with iPad..

The soldering isn't up to scratch I'm afraid, my soldering experience on this scale is quite limited.
Also, most is just placed in position, a lot of work left to do..
And, most the wires have been left long because in unsure if I'll stick with this frame which is on the small side. I put stress release loops on the Motor wires to give me the option to change to a bigger frame with longer arms.

The last picture with the top part mounted, has my first go at making Air Ducts to cool the components, I will make some more that look nicer and scoop more air.. 


I also have another question, if I may..
Telemetry, for ESC? Is it worth trying to wire on to the tiniest contact in the world(without frying the board or disturbing the signal wire right next to it) for ESC Telemetry?

[DroneCartel]

[Six6siX]

That build is coming along I see. Will you be reducing some of the cable lengths once you got it to a powered state? Thanks for the photo's I like the colour of those LED's.

[DroneCartel]

That build is coming along I see. Will you be reducing some of the cable lengths once you got it to a powered state? Thanks for the photo's I like the colour of those LED's.

Yip she's coming along.. Yes and no on the cable lengths, I'm leaning towards designing my own frame and buying a CNC Router/Mill. In which case, a fair amount of the wire will be used up in a bigger frame, it will all need rerouting and trimming though.
Yes the LEDs are pretty intense, my once concern is the Black Light may interfere with the cameras.

[ched]

I wouldn't worry about esc telemetry at the moment, you will have enough to be dealing with learning to fly so extra esc data won't help 
It's not a problem leaving wires long but make sure they are all cable tied/taped down. With the quad flying wires will flex and can be caught by props and then things go pear shaped as spinning props will yank cables off the circuit board!!!
As for the cooling ducts, don't worry at all. The spinning props create so much air things will be cool. That said don't run vtx without antenna and not on high power on bench as that will get hot!!!!

[DroneCartel]

Progress has been slow.. The Radio and Receiver never arrived so hoping I'll get a refund..

Now looking at the FrSky X-Lite S. Looks like it's pretty good I think.. What I need help with is understanding what all the modules on the back do, and which I'd need.
The radio has ACCESS protocol, what ever that means..
I'm also looking at the TBS Crossfire Module, and wondering what the difference is and whether they'll work together or not?
I need to get a receiver chosen and ordered before I can do any more on it really..


I now have Antenna so hopefully won't cook the VTX.
I also have a battery, went for tattu r-line 1550mah 120c. Still need a charger, any suggestions for a decent/safe but competitively priced chargers will be appreciated.
And got a selection of different pitch props

[ched]

The FrSky X-Lite S is good as it has inbuilt charging but you will need to buy the 2 batteries! FrSky are very good tx and have some great small rx. I believe ACCESS is the new encrypted communications protocol between tx and rx and ACCST is the older non encrypted version. If you don't have any tx/rx then go for the ACCESS stuff as it is supposed to be slightly faster (not that many people would notice at all).
As for the TBS Crossfire Module I am not sure if the Firmware on the FrSky X-Lite S supports TBS Crossfire yet or maybe ever. Basically TBS Crossfile is a long range/high penetration control system. It sort of depends on what you want to fly and where. If you want to fly in and out of concrete buildings then crossfire will be better or if you want to fly 'long distance' like over 500m then crossfire might be for you. Otherwise don't worry use standard tx/rx and see you you get on. By the way FRSky have their own version of long range stuff that will work with the X-Lite S called R9M lite and then you get a corresponding rx.

My opinion would be just get the x lite and a rx and learn to fly and work out what sort of flying you like then decide if you need to extend your range.

As for batt charger this one is good 300 watt lipo charger but it does need a mains power supply like this one 600watt 24v psu. This battery charger can  charge most batteries you can think of from 1 to 6 cell and can even charge your car battery if needed :-)
Hope that helps?

[DroneCartel]

Had a little time to do a little more on it over the weekend..

Got myself a FrSky R-XSR Micro Receiver, can't believe how small they make these things..
As Iv kind of used up all the space inside the main frame, I have mounted this receiver on top of the top frame. Iv made a tasty little cover for it to protect it from damage. It also incorporates another piece which is holding the Antenna Tubes, and this piece also doubles up as mounting points for the frame spacers. I had to ditch the original mounting holes to accommodate the battery XT60 connector on the PDB. Alos made bottom plate to move the mounting posts out a little, only problem is that they are very close to the props, ie 1mm clearance.
The antenna tubes were melted a little and pushed through the hole and then squeezed up to make them stay in place, they can still rotate and move if needed.
Made using 1mm thick L section carbonfibre, and 1.5mm carbonfibre sheet.

As you can see, I don't have a Stack, it's all mounted seperatly, Iv done this because the frame accommodated it, and I thought it'd be easier to assemble and service. Everything on the top frame can be unplugged from the bottom frame so separating it to work on is easy.

Iv still got various things to sort out, trying to find somewhere to mount things like the buzzer, battery for LEDs, the main Battery, etc..

Last pic is my connections to FC, does it look about right?

[DroneCartel]

terminator 2 plot

[ched]

Looks good, it's always good to see different ways people put things together.
Couple of things, the antenna needs a cable tie to secure it to the frame. Reason being you don't want any impacts being put on the vtx or it being pulled out.
The other hing is make sure all wires are cable tied down so they can't catch on props etc. When you have a crash it does put a fair bit of momentum on the cables and they can fly into the props.
Battery should be great on top, there are 2 strap slots for battery straps there. Hopefully the battery will fit between the go pro mount at front and your antenna/rx carbon box at rear. If you do mount battery on top try and put some rubber to stop the battery sitting on the bolt heads as it might punch a hole in the battery!
If not you could mount the battery under neath again a bit of rubber to stop bolt heads hitting the battery.

I do like the prop colours, they look great with the motors.

[DroneCartel]

Hi Ched,

As always, thanks for your advice. It's just occurred to me what the little slots at the back are for, cable tieing the antenna...
I will indeed tidy up all the loose wires and shield them from danger.

I'm going to mount the battery underneath, Iv soldered the connector onto the PDB facing downward so kinda have to now..
I'm toying with the idea of making a carbon enclosure for the battery to go in, seeing as they don't look like they take impact well, and they are pretty expensive.



At the end of the day though, you are correct, the colour of the props is clearly the most important factor at play, they're from Quadcopters.co.uk.

[Six6siX]

Looking good with the build there DroneCartel. Some very nice tech you've chosen! When do you think you'll be airborne? Keep those pic's coming.

Six

[ched]

Making a carbon battery box is probably a bit overkill. OK so lipos are not cheap, maybe just an under battery carbon plate like this .
With some of the impacts I have had, just on grass, I would be surprised if you could make a carbon box to stand up to the impact!!! It's not just gravity you have against you sometimes it's the throttle     
Gets lots of sim time in and it will help much more than a carbon box 
Keep the updates coming, great to see a build.

[DroneCartel]

Hi Chaps,

Six, I'm not sure when it'll be airborne, I'm a bit skint at the mo so waiting for some more slot cars to sell before I can afford the Goggles and Radio. Hoping it won't be long..

Ched, you're probably right, although I have some resin which will stick the carbon together pretty well.. Anyway, I'm not sure this frame will even fly, I'v started designing a new frame, similar to this design, but a true X format, longer Arms, longer frame, arms attach to top plate of frame with electronics below and battery on top, this should be optimal for weight distribution and balance, and it means the ESCs and wiring can be mounted under the arms so they'll be protected from breaking props. It's pretty simple, all the arms are identical so you won't need paired spares, and there is many mounting positions for the electronics boards. I'm about half way through designing it, looking good if I do say so myself.

[DroneCartel]

Evening All,

Iv got the goggles and radio on their way.. might get round to having a go with the sims over the weekend if I can make it work..
Went with the FrSky X-Lite Pro, and FatShark Scout goggles.. Iv got a TBS antenna, do I also need a patch antenna, or are they optional?

This is probably a daft question, only available from numpty noobies.. What happens if I let go of the controls? Does the drone stop and hover, or does it continue with its last instruction, or simply fall to its death?

[ched]

Goggle/Quad antenna - The goggles you have only have 1 antenna I think? If so then if you have  a TBS TRIUMPH then it's probably a RHCP antenna (Right Hand Circular Polarised) and so ideally you need a RHCP antenna on your goggles.
If you had 2 antennas on your goggles then a RHCP plus a patch would be good but a patch is very directional. Patches are poor when you say fly behind your self or to the extreme left or right of where it is pointing.

Seriously I can't stress enough how valuable a sim is. You need to get some practice on a sim before you head out otherwise you will at best crash and damage your quad or worse loose your quad!!! When I first started I had my first flights on a very quite beach. On second flight I lost orientation and the quad ended up about 400m away in the sand dunes within a few seconds!!! It took me about an hr to find it!

The last question, worries me a little, so even more get some sim time in!!!!!!
OK so simplistically there are basically 3 flight modes (setup in BetaFlight) Angle, Horizon, Acro.
Angle - self levelling - so letting go of right stick will level the quad, left stick controls throttle (speed/height) plus yaw (Spin left/right).
Horizon - self levelling same as Angle but when sticks are pushed towards their extremes it allows flips and rolls.
Acro aka Rate - NO self levelling!!!!!! If you let go of right stick quad will carry on doing what it was doing. i.e. if it was pitched forward going at 30mph it would carry on going at 30mph forward and the throttle would control height and a bit of speed.
Rate/Acro mode is megga difficult as the stick movement translates to the rate of pitch, roll, yaw movement not the actual angle. So the further towards the ends of travel of your sticks the faster the rotation happens!!! I have my max rotation set at about 1000 degrees per second, so in 1 second at max stick it will roll or flip almost 3 times!!!!!!
Don't have your rates that high to start with!!!!

So have a look at Josh Bardwell youtube on learning with a sim and your tx. He uses FpvFreerider (the free version) and his tutorials are very very good to start with.

I can't urge you enough to get some sim time in, it will save you money, time and will be safer!!!!!

Make sure your failsafes are set to ditch the quad if signal lost (props off on bench to test).
That said, take your time, enjoy and fly safe.

[DroneCartel]

Hi Ched,

Thanks again for taking the time to help me out, your advise is very much appreciated.

Goggles and radio turned up, All is lovely..
You are correct, the goggles have 1 antenna, and a built in patch antenna, apparently. I have a matching TBS Triumph antennas for VTX and Google's, this should be fine then.

I still havnt got a battery charger, I'm waiting on inquiries Iv made to buy a load of transformers, it pains me to pay big bucks for one from the likes of banggood, eBay, Amazon, etc when I can buy them for next to nothing straight from the manufacturers in China. I'll probably buy 10 if anyone's interested? I'm happy to do them cheap to like minded people in the community, equally happy to stick them on eBay and make a few bob.


Regarding sims, I will, I promise..
First flights on the beach are a bit sketchy arnt they? what if you ditched in the sea? Lol..
I live in the bum hole of nowhere with many fields, I also rent a workshop from a farmer who'll let me on his fields and probably let me use the big(really big, like hangers) sheds.
I've taken the precaution of purchasing a cheap pet tracker device, I'll have that taped on somewhere so hopefully I'll be in the right ball park when searching for the pieces of my drone..


Which mode do people generally use for racing? Guessing this will depend on type of racing and how badass you are?


I have watched several of Bardwells videos, not that one though, so I will check it out. Also seen a video about setting failsafes, hopefully I'll be able to sort it, otherwise the good old pet tracker will come in handy again..lol

[DroneCartel]

Oh, and this be my first draft frame.. I'm going to change a few bits yet.. The battery goes on top, sits on the pink piece which will be spaced off by 2.5mm to allow strap to go under it.

[DroneCartel]

Hi Chaps,

Progress has been slow, or should I say, it stopped...
Been waiting for some parts to arrive, and sort out charging battery, headset, controller, etc..

This evening Iv wired up power source for my SpeedyBee dongle, plugged it in, and it works.. It powers up the FC and connects to my iPad, the app seems to be working ok. I havnt yet made any changes, but I can see the quad on screen moving as I move the actual quad.

Iv had a look through all the hundreds of options, and it's baffling to say the least. I clicked the drop down options for the uarts, the options I want are not displayed so I don't know what to do there.

Any tips on getting this thing configured would be much appreciated.. heading to YouTube now, but last time I looked, I could not find anything helpful related to F7 FCs, or speedybee.

[ched]

Have a look on youtube for Josh Bardwell or Project Blue Falcon. Don't be too concerned about F7 fc as f3 & f4 are not really much different. They all have uarts, vtx, camera connections etc. Every FC is slightly different but the principals all apply.
One thing to watch on ports tab (uarts) is you don't disable the usb connection!!!
As for options, normally you decide which uart you are going to connect your rx to (if using Sbus use the recommended one, that said on F7 it's not critical). Then set that to be serial rx in ports tab. Then in config set rx to serial and brand then type (can't remember the exact boxe names).

SpeedyB (only used android app via usb cable) is basically BetaFlight Configurator on a mobile device. The layout and names of things seems same as PC/Mac version of BF Configurator. So you should be able to follow youtube vids.
Hope that helps? If not come back with what FC you are using and what the issue is.

[DroneCartel]

Jeez this is a long process..
SpeedyBee can't flash FW, so got betaflight on my laptop thing, then got all the drivers which was a nightmare.. obviously my laptop need a million updates, then antivirus needed updating, then not enough storage on hard drive so had to do some clean up malarkey, it's been long..
Also had problems with the first 2 usb leads I tried, it was powering up the fc but not being seen by pc. Third cable was a charm.
Iv noticed that the drop down in betaflight which says Manual or comm3 etc, is sketchy, i have to plug in and out and close and reopen betaflight several times before comm3 becomes visible.

So I got the FC plugged in, couldn't find the exact firmware for my FC in the drop down options, so i took a gamble on the one most similar. Flashed it, opened betaflight, model moves on screen as I move the quad, so maybe it's the right FW after all.
Any thoughts??
My #version is MatekF722 (MKF7)
The FW version I went for is MatekF722 (legend)

The Bardwell vid says to next pair the transmitter & receiver, it's a new transmitter so I need to get an SD card and do yet more downloading of stuff to make it work.

Another thing I'm pleased I eventually plucked up the balls to do, was to plug the battery in... and NO smoke came out.. win