The last resort if you can't get your flight controller into DFU mode for flashing...

Download the ImpulseRC Driver fixer here: impulserc.com/pages/downloads
My video on Zadig: • Using Zadig to flash y...
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[@metrahim6478]

There is known bug that INAV configurator Chrome version can’t flash firmware in DFU mode. If GPS or other peripherals are connected to UART1 or UART3 of F4/F7/H7 chip and these peripherals are powered ON while connecting USB. FC can’t enter DFU mode. It is related to DFU protocol used in the STM32 bootloader, not hardware and PC driver issue.

[@craigcupit1917]

So, so helpful

[@DFEUERMAN]

UNPLUG GPS!!!! Thanks for doing this video. I have a Darwin129 and I was trying to flash iNav. I had the same head-scratching issues (and tearing hair out, and tears in my eyes and eventually tears of joy.) I even sent you a message at my height of frustration that I couldn't enter DFU and you said it could be a lot of things, which is true. Anyway, "unplug everything" is definitely Step 1!!! Cheers, Painless!

[@jonstante]

Thanks for this video! It worked for me on my GEPRC Cinelog 20. Nearly identical scenario.

[@stefanpynappels7959]

Thanks so much Lee, I have exactly the same issue with my Rekon7Pro Analogue, so will try this to see if that helps.

[@jedituck]

Thanks Lee, just been down virtually the same route as you with a new SpeedyBee 405 wing. Unplugged all and straight into DFU, needed ImpulseRC to allow flashing but now happily on INAV 6.1

[@Painless360]

Thanks for the info. Good to know! Happy flying!

[@kruphen79]

Thanks for making this video, really helpful. I had the same problem trying to upgrade my Rekon 7. I ended up buying a new FC and loading INAV onto it. Wish your video cam out a month earlier (for me), but this will help a lot of people. HGLRC should replace these defective units. For me, I have another spare FC so now I just have to build another quad!

[@jedkenny]

3 days of pure frustration so thank you. this helped

[@jedkenny]

now question , do you know how to get the OSD onto the new dci Googles 2 not the V2 with the same quad ?

[@hector-fpv]

This worked like a charm, thanks Lee!!! you saved my flight controller

[@RectifiedMetals]

Thanks for all the videos over the years. Helped me get off the ground with a naze32 back in the day. I had the same trouble on some f3 and 4 fc’s. I narrowed it down to how I was setting up smart port. Most of the time I would have to disconnect the smart port wire or disable it in the cli, sometimes change the pin map back to original. I had a habit of squeezing everything I could with the available uarts the stm32 would allow. Depending on the board it would give me fits. The micro emax had an f3 that just didn’t like to give you smart port, but I found a way. One day I’ll probably give my quads a go. Hope it’s like riding a bicycle.😂

[@MCsCreations]

What a weird thing to happen, Lee! That's bizarre! I'm happy you've found a way out! Anyway, stay safe there with your family! 🖖😊

[@danialfpv]

Thanks for this, Lee. It turns out mine was the very port to tbs crsf on my clracingf4. off configuring my wtfos osd now. Cheers 😁😁😁

[@robertparenton7470]

This happen to my Rekon 7, and now I know. Thank You. Frisco, TX

[@53roger]

good video and info Lee. I have ran into that scenario myself but it always seemed to be with a particular brand of fc board. Very annoying to need to uninstall the board on intermittent times that the computer could not see it. I was never able to get it to work every time but i did narrow it down to unplugging the rx and gps first which usually allowed it to work but if not, then uninstall everything else.

[@TailSpinRCSpain]

On a new build, I always configure the FC out of the box before wiring anything else up, LOL. Thanks for the info Lee.

[@Painless360]

Me too. That is exactly why I setup the FC on the bench before installation in all of my build videos. Also handy to test the FC is OK before you start soldering as vendors won't always be happy about exchanging a faulty FC with solder all over it. Happy flying!

[@Videolinquency]

Thank you. I can see no reason why problems like this should exist at all, but they do, so thanks a lot for fighting them for usl.

[@ArcticriderFPV]

I had the same problem as you! 10 usb cables, one Mac, two PC´s and a speedy bee app later, I had found someone with the same issue as me! Had to unsolder the 5v wires for my GPS and Crossfire, and suddenly it worked! So many hours spent troubleshooting. Oh well, at least I didn't have to buy a new FC. Thanks for sharing it.

[@BoondockStryker]

Wow 😯 I have the exact same fc. I couldn’t flash it to 4.4.1 either lol. I saw a video with something similar, where he just took off the gps and receiver. Then it worked! I’m waiting for the library to print your 30 to 20 board that you posted for my Walksnail pro. Something weird though, mine went into DFU mode but it wouldn’t flash. I was able to flash it before, on 10.8 beta flight to 4.3.2 no problems. I guess I won’t give up until I take everything off the board lol thanks again

[@ShinyVideoStuff]

Had same thing, GPS is spewing serial data so your DFU process uses that UART for DFU instead of the USB port, thinking that the UART is the active connection. Removing power to any peripherals sending serial data prevents this.

[@k4x4map46]

my first build (2.5") in 2017 was with an HGLRC triple stack VTX, FC, 4n1 esc --still have all the components but the FC was always dodgy...sure given I didn't know squat back then but even today it (FC) seems to still be a challenging component

[@joshmellon390]

I just bought this exact FC, and I ended up having to get a replacement because the 9v regulator was no good. I like some HGLRC stuff, but I think they have some room for improvement.

[@jeffbright7728]

So, during the pandemic, while laid off, I built a 6S beast. I used a Zeus F722 board. I just tried to update it to 6.1...NOT recognized in Windows. Once again, Lee to the rescue! I removed everything but the receiver, still wouldn't recognize it. De- soldered it, BOOM, DFU!

[@travelrideandfly8355]

I also just found out: There is a hardware-bug in F4 and F7 STM Chips. If these get any signal input through UART 1 or UART3 while in bootloader phase, they can't enter DFU mode. - the key is not to have any connection on these UARTS.

[@chuckwain5591]

I was having the same issue with a SpeedyBee F405 wing. Unplugged the receiver and GPS and was able to get into DFU mode and flash it. I had a thought, perhaps it is power. When I plug in a USB cable both the receiver and GPS light up. Maybe the power available through the USB cable is not enough to power all these devices and the FC. An interesting experiment would be to power the FC with a battery then try the flash process again. I any case thanks for the insight, I was getting pretty frustrated!

[@sunsetpark_fpv]

That's so very interesting! I wonder how/why/which device was causing the issue??

[@Painless360]

Sounds like it is more common than I thought, looking at the comments... Happy flying

[@oloendithas]

Oh. Did you tried to connecting back all the components one by one and testing, which one (or two) exactly was causing the issue?

[@Painless360]

Reciever is my guess but next time I update it, I'll test. Stay tuned

[@TechnicallyTom]

Some devices on UARTS will prevent DFU mode. It’s the first thing I check for. I’ve been told it’s certain UART numbers that do this but then have had others cause this issue as well. Some flight controllers do not have USB power on any UARTS except GPS. Although it’s a bit inconvenient that you can’t troubleshoot GPS without plugging in a batter (so having to remove props) it does prevent the DFU issue by not powering any devices that might cause DFU to not work.

[@jasonstahl73]

I've run into that problem when I had just a receiver connected. Disconnected the receiver and I was able to flash it. I usually flash the flight controller before I start the build.

[@Painless360]

I suspect the connected Rx too. Odd that I've not seen this once in all the years I've been doing this. Thanks for posting! :D

[@jameshughes4041]

I had exactly the same issue with a Skystars F7. Quite new to the hobby, wish I saw this video before I wasted so much time, but I had to unsolder the crossfire power before I could flash, I'm not sure but read somewhere it is something to do with the uart number used for the crossfire receiver.

[@Painless360]

Make sure you are subscribed and have the bell notification icon selected so you don't miss future content.. Happy flying

[@VadimBryksin]

I have the same problem with iFlight Success-D F7 board, and you know what? I found exactly what was causing it. It is ELRS, by some reason when your FC goes into DFU mode, ELRS also and then you have 2 devices on the same USB port and it doesn't know which device to connect.... Basically now for every FW flash I'm unsoldering red wire from ELRS, what is very annoying. Ah btw also after I flash the latest 4.4 BF, it asks if I want to play default stuff, if I press yes, FC goes into the brick mode and the only way to rescue it is re-flash with full wipe. Also if I apply for dif from my previous BF 4.3 it also brick FC, so i had to reset everything all my difs and re-setup from zero with this latest BF 4.4

[@Painless360]

That is really interesting. This quad has Crossfire connected via CRSF and I wonder if it is a similar issue here. Thanks for posting! Happy flying!

[@hwoekki]

I had the same problem with the same iFlight FC, i’ve installed the expresslrs receiver on uart 5 (uart1to4 have the same dfu problem) now i can in dfu mode without disconnecting receiver👍🏼

[@VadimBryksin]

@@hwoekki emmm Im on UART 2 i think, next time will be flashing will re-solder to UART5, thnx man!!!

[@hwoekki]

@@VadimBryksin I’ve also the same problem with the latest BF version that’s bricked, only the first BF 4.4 works fine on the moment

[@k4x4map46]

did you mention using STM driver to setup a virtual com port?

[@scornman]

I disconnected all the red cables from my CL racing F4 and this finally allowed impulse rc to connect the driver

[@William_NS]

Litterally this exact same thing happenedto me on a new build with my first go at a SkyStars stack. I was pulling my hair out and then my PC restarted due to an update or something. The next time I tried to flash BF, it worked perfectly! You just never know. And this isn't my first build either.

[@Jonners]

I’m having a weird scenario where my moz7 works on my pc along with all my other quads, and all my other quads work in my MacBook, but the moz7 won’t be seen at all in betaflight with my MacBook. Which is frustrating as my MacBook is what I take out with me when I go flying in case I need to make any adjustments in betaflight. Any ideas?

[@Painless360]

Sorry no, I'm a Windows fan... Happy flying

[@benjaming9835]

Had the same issue with a number of ardupilot quads. It ended up being a windows usb port number conflict. Took me weeks to work it out. Force change the port number. I did watch the whole video but I do think you probably have the same issue.

[@robinmoore3649]

It sometimes happens with receivers being powered and confusing windows. You've probably not come across it before if you flash before building rather than flashing bnfs, or maybe you don't have only a few models that you regularly update. There's also only some configurations and some flight controllers that used to do this. It would happen a lot with SPRacing F3.

[@Painless360]

That could be it. I update a lot of my stuff regularly (see my INAV6 updating video for example) but many aren't using CRSF connected recievers... Happy flying!

[@robinmoore3649]

@@Painless360 thinking back with it having GPS (being the whole point of the video), I could also be that if it's powered by the USB. Usually those are less buried and easier to just unplug

[@andrewjamez]

This was me 6 weeks ago with a iflight f7 twinG. I had to un solder the serial rx before the PC would see it. I read this in an inav troubleshooting guide somewhere.

[@hwoekki]

I had the same problem with the same iFlight FC, i’ve installed the expresslrs receiver on uart 5 (uart1to4 have the same dfu problem) now i can in dfu mode without disconnecting receiver👍🏼

[@andrewjamez]

@@hwoekki Awesome. good to know thanks

[@dukedblu]

had the same, just typing dfu in the cli seemed to do the trick, maybe I missed something?

[@toolmakerdave5287]

had same issue flashing inav on a holybro f7. found a bardwell vid if something is on uart 1 or 3 it won't go into dfu disconnected the power to my crossfire on uart 3 and bingo

[@Raven187FPV]

So something was pulling that uart low and locking up the fc?

[@Painless360]

Yep, looks like it. I've not had it before here but others have seen similar stuff... Happy flying

[@GhostRyderFPV]

I'm 3 minutes in, and wondering if you've removed all the serial and I2C devices.... Leaning on the edge of my seat, I've also had this happen to me, and my resolution was to remove GPS and sometimes SBUS/Serial Reveivers and ESC's. I guess pass-through capabilities bit me in the -ass- arse

[@Painless360]

Thanks for the comment. I'm loving all the ideas and stories from others.. Happy flying!

[@GhostRyderFPV]

@@Painless360 I've got one for 'ya Lee, maybe something you'd be interested in. Alternative iNav firmware for a Matek board, to enable features? In my Dragonfly V2 (aka Skipper) is a Matek F411-Wing, a board that only has 2 UARTs, and 1 SoftSerial, at least according to 'the tin'. I've installed a GPS and FrSky X8R using SBus, that's both UARTs. But I was able to get SmartAudio sent out over SS and analog RSSI piped in, even though there's no pin. The F411-Wing has 3 different iNav hex's, the stock one, and two that enable either 2x SS, or SS and RSSI on the LED pad. Of course, you lose the LED pad, but this is almost like being able to map resources BF style. I didn't know at the time when I bought the board - I just needed something skinny that would fit in my Dragonfly, but love the fact that I've been able to add SA, so I can run a strong VTx and not worry about it cooking my seaplane while I wait for GPS.

[@Painless360]

A number of the Matek flight controllers have multiple targets. I made a video for the Matek F405WSE and DJI HD fpv a while back. Seems that LED pin is a common sacrifice! Happy flying!

[@sullytrny]

A crushed servo cable drove me nuts for two days. And i only found it because it finally magic smoked

[@Painless360]

Where did you damage the cable?

[@sullytrny]

@@Painless360 I built the kit up and pinced the elevator cable in the lower plastic, I even multi metered it but it took a while to short and the elevator just quit working. I havent figured out logging yet. First Arduplane, VTOL too. I got lucky, the day before it would arm but the weather stank Happily vexed Ps. T1 ranger

[@Charl-Viljoen]

3rd Day struggles. Just managed to install INAV 6.1 to align version to SpeedyBee405. Still no DFU mode. Nothing is connected and never was. New out of box. Have tried all computers in the house and different USB cables. Will try again the weekend. 😡

[@Painless360]

Best of luck!

[@upnorthFPVandEUC]

I had the exact same problem.. wouldn’t work on Mac or windows. When I downloaded Impulse and ran is said there was multiple devices detected. The only thing I could think of was that it was picking up either my ELRS RX that lights up with usb or my gps that also lights up with usb. I unplugged the gps and it flashed perfectly using Impulse. The trick with impulse is you must start it BEFORE plugging into the FC. Let impulse do its thing and if it says drivers fixed you then go and flash new firmware…. Hope this helps someone. I think this is why when you unsoldered everything on your board it worked for you.. I think you could have just unplugged your gps??

[@Painless360]

What I cover in the video is a known issue with some flight controllers. Happy flying...

[@grampafpv8013]

the receiver cant be on uart 1 it can be on any other uart and it will work i dont know why this is happening but that is what i found after hours of messing with it.

[@crizzisz745]

This is a problem especially with hglrc fcs. And the reason I buy no more. Who wants to mess around for hours just because your FC won't get into DFU? I had to sent in my recon5 cause no help from support. When I bought a second hglrc fc for another quad I had to go through the pain again try to use an USB port on you Mainboard. Unplug everything. Start immersion rc. Plug FC with button pressed in. Pain, pain pain. Other fcs no issues at all .

[@alainassaf]

my solution to 'usb not recognized' is try every usb port of every computer available in the house.... and it works ! Oddly enough not all usb ports are created the same for flashing our FCs

[@phillip7047]

I found a while back that if you disconnect the receiver from the flight controller it will go into DFU.

[@grampafpv8013]

The receiver needs to be dissconected i found this with the skystar fc as well

[@dfgaJK]

I find it is often something disturbing the ftdi chip when there is driver issues, like too high baud rate or nosy power or high current draw

[@Raven187FPV]

Another troubleshooting step is to try to use your phone/speedybee. It can rule out the PC as the issue.

[@Painless360]

I did that, I mention it in the video. It's a great way to rule out all of the possible PC issues at once... Happy flying!

[@Raven187FPV]

@@Painless360 oh crap, not sure how I missed that. Sorry mate! You're too good 😅

[@Painless360]

😁 No worries. Great minds think alike!

[@loc4725]

It a little bit of a shame you didn't try it on Linux. It still wouldn't have worked (most likely) but the output from the diagnostic messages ('dmesg' command) would have been interesting and potentially useful at a later date. Still, it's a good bit of advice. I usually flash mine 'naked' for just this reason; there's always the chance _something_ will interfere with the boot loader or worse, the flashing process.

[@Painless360]

Nice idea! This is exactly why I flash the FC naked before install in all my build series here on the channel. If it doesn't flash up, you can return it... Happy flying

[@icp-trek]

Yea, it's annoying. Had to desolder some stuff on an Iflight controller to get DFU recognized.

[@hwoekki]

I had the same problem with the same iFlight FC, i’ve installed the expresslrs receiver on uart 5 (uart1to4 have the same dfu problem) now i can in dfu mode without disconnecting receiver👍🏼

[@icp-trek]

@@hwoekki Manufacturers should not sell flight controllers with this problem. Period.

[@matiasbrollo6871]

StmCUBE TAMBIEN ES BUENO PARA FLASHAR ESTOS CHIPS.

[@p.i.engineer398]

it was your gps, unplug your gps and you would've been good. i've been through this a few times.

[@Painless360]

Thanks for the comment. Happy flying

[@craigcupit1917]

With Inav you can flash without pushing the DFU button :)

[@Painless360]

I was flashing INAV ;)

[@rolliseventeen]

i just HATE this stm usb stuff.. driverfixer, zadig, ..... I had something similar the last weeks. iflight twinG mini F7 on 4.4.1 loading broken defaults. i spent 8hrs or more and i was not able to reflash to old or 4.5 nightlies. i also had to disconnect all stuff in my flywoo explorer 4 and everybody who upgraded it knows it. its a full PITA. ok, then i had the problem, that just one of 20 attempts it will load a new firmware. finally i got it running again. i´m in this hobby since 2004 and still wonder what cheap crap they sell us around 100$ for a fc. is it maybe possible to connect to it without any driver fixer and other tools in the future? why is there still this monster analog chip on the board? we can use this place for a dual bootloader thing like on motherboards. my idea is to have access to the fc no matter what i stupid did to it, to reflash the correct target or change it to last stable..... i wonder also, is it always me who is angry about that?

[@rolliseventeen]

i still like my iflight fc, not their fault. ;-)

[@Painless360]

There is a very good reason that I recommend the kit that I do here on the channel. Some stuff works. Some stuff can be a pain to setup and troubleshoot. It can be a false economy sometimes.. Happy flying!

[@rolliseventeen]

@@Painless360 i hope, some time we have a new generation of controllers....

[@BigMeanyVids]

Ug. They need to get a better flight controller if they want me to consider this quad then. If I had to take it apart just to flash it I would not be happy.

[@fklotaloi]

Hi, What does """ flash "" exactly mean, formating or installing nrw firmwire in the FC?? Thnx.

[@Painless360]

To 'flash' means to copy the operating instructions to the hardware flight controller. In the hobby this is things like Betaflight, INAV, Ardupilot and EdgeTX... Happy flying