So, I finished my first 6S build. I will post the build in the near future.

I got some nice flights in. No cap, video is great but there is definitely some yaw twitch.

Let me get back to the problem. I crashed, everything looks fine. I tried to connect to BFC. Nothing. I tried a different cable, still nothing.  The 5V works, because the RX is powering up. The odd thing, I can get into DFU mode and flash. Even with reflash, still nothing. When I say nothing, I mean nothing even populates in device manager.  The FC looks like new, no burn components. The MCU does get hot. I have not check for short because I don't have a DMM on me at this moment.  Out at a friend's place with some acreage far from home.

Something is definitely wrong with the FC. It is likely toast, but I figure if someone have any ideas, I am open to try.

If you are able to flash via DFU then it sounds like there is maybe a fault with the VCP/MSP comms circuitry inside the STMF407 microcontroller.

I guess you've already been over the STM32 chip with a decent magnifier looking for any damage to legs of foreign debris between legs that may be affecting what the microcontroller is trying to do (?)

It's a bit of a stab in the dark but a couple of things you could try if you think it's worth the bother and haven't already done so:-

1. Completely remove ALL connectors and soldered wires from the board to eliminate any external sources that may be interfering with something for whatever reason, and then try again.
   
2. Use an USB-to-TTL adapter and try to connect through one of the other UART ports, assuming MSP is already enabled on another existing UART. If not then it will mean having to flash a version of firmware with MSP already enabled on one of the UARTs. As DFU mode seems to be working on the board, at least you can do this over the USB connector rather than having to mess around with an ST-LINK device to do that. The only hassle/challenge will be that you would have to download the Betaflight source code for your board, modify the code to enable MSP on a UART, and then compile it into a HEX file for upload.
   

It might just be easier to just get another replacement board for now so you can get it back in the air ASAP, and when you have some spare time maybe do some further diagnostics and try to get the broken board working again (if that's possible) as a spare.

Not that it makes a difference, but what make FC is it?

(31-Dec-2018, 05:01 PM)sirdude Wrote: Not that it makes a difference, but what make FC is it?

I wrote it in the title CL Racing F7

(31-Dec-2018, 02:38 PM)SnowLeopardFPV Wrote: If you are able to flash via DFU then it sounds like there is maybe a fault with the VCP/MSP comms circuitry inside the STMF407 microcontroller.

I guess you've already been over the STM32 chip with a decent magnifier looking for any damage to legs of foreign debris between legs that may be affecting what the microcontroller is trying to do (?)

It's a bit of a stab in the dark but a couple of things you could try if you think it's worth the bother and haven't already done so:-

1. Completely remove ALL connectors and soldered wires from the board to eliminate any external sources that may be interfering with something for whatever reason, and then try again.
   
2. Use an USB-to-TTL adapter and try to connect through one of the other UART ports, assuming MSP is already enabled on another existing UART. If not then it will mean having to flash a version of firmware with MSP already enabled on one of the UARTs. As DFU mode seems to be working on the board, at least you can do this over the USB connector rather than having to mess around with an ST-LINK device to do that. The only hassle/challenge will be that you would have to download the Betaflight source code for your board, modify the code to enable MSP on a UART, and then compile it into a HEX file for upload.
   

It might just be easier to just get another replacement board for now so you can get it back in the air ASAP, and when you have some spare time maybe do some further diagnostics and try to get the broken board working again (if that's possible) as a spare.

I have check the STM32F7 chip and it is pretty clean.  It was quite protected.

I have also remove all wiring, so not external sources.

Altering source code and compiling is definitely will be for another day.  Thanks for the suggestion.  Might give it a try.  I always wanted to compile my own HEX file.

Side note:  I took the components apart and my 4in1 ESC is toasted.  I think I am giving up on 4in1, even though they make for clean build.  I have had 2 go bad on me recently from crashes.  Where as individual ESC, I have not has any failure.

(31-Dec-2018, 05:28 PM)voodoo614 Wrote: I wrote it in the title CL Racing F7

Yes you did....I missed it, sorry.

The following thread just got bumped and has highlighted a similar issue with a Matek F4 board whereby flashing with "Full chip erase" switched ON can seemingly cause the VCP on the FC to get messed up.

http://intofpv.com/t-virtual-com-doesn-t...matek-f405

It's a bit of a shot in the dark and you may already have tried this, but if not, try flashing Betaflight firmware to the board with "Full chip erase" switched OFF and see if you get VCP connectivity back again. If that works you can just run the CLI "default" command afterwards to get back to vanilla Betaflight config settings.

I already tried full chip erase. Thanks for the suggestion. I really think the F7 chip is fired. Because it gets too hot.

OK, no worries. I thought you'd probably have already tried that but it was worth a stab. I guess you win some, you lose some.

If you have any motivation and/or feel inclined to try and revive your CL Racing F7 FC, I've compiled a custom version of the Betaflight 3.5.5 firmware for the CL Racing F7 which has MSP enabled on UART1. This will allow you to try and connect to the FC using a USB-to-TTL adapter hooked up to the UART1 pins on the FC if you want to (Oscar's blog post on doing that is HERE).

You can find the custom firmware in a zip file at the MEGA download link at the bottom of this post. The zip file contains two HEX firmware files:-

1. betaflight_3.5.5_CLRACINGF7.hex -> This is an original unchanged version obtained from GitHub HERE.
   
2. betaflight_3.5.5_CLRACINGF7_MSPUART1.hex -> This is a custom compiled version that has MSP enabled on UART1.
   

https://mega.nz/#!gC4wBIra!RN-ZD3SAvzcP2...7HTzp3Tc6k

Thanks Snow. I will try it.

I tried but I think the STM32 is really gone. Able to flash custom firmware. Connect FTDI to UART1. But it is still the same.

That's a bit of a bummer. Oh well, nothing ventured nothing gained. I guess the consolation prize is a parts board you can rob stuff from if you need to repair another FC.

If you have a decent heat gun, a steady hand and most importantly tons of patience you can buy an F7 chip for about $12 and replace it. I did this once, I made a functioning BFF3 board out of 2 dud ones, (I was shocked when everything worked) wouldn't try it again. - Given the number of pins and spacing on an F7 it would be a real epic, kudos to anyone who tries.

(05-Feb-2019, 12:05 PM)Jonosg Wrote: If you have a decent heat gun, a steady hand and most importantly tons of patience you can buy an F7 chip for about $12 and replace it. I did this once, I made a functioning BFF3 board out of 2 dud ones,  (I was shocked when everything worked) wouldn't try it again. - Given the number of pins and spacing on an F7 it would be a real epic, kudos to anyone who tries.

That's a good suggestion but as you say it could be a bit of a risk. It definitely requires good skills and a decent rework station (preferably one with a heating plate in addition to a hot air gun that will heat the whole board).

The cost of a complete new CL Racing F7 board is ~$40. The cost of a new STM32F722RET6 MCU which is used on that FC is ~$15 with shipping costs (on Digi-Key HERE), so just under half the cost of a complete new FC.

So you could save half the cost of a new board by replacing the F7 MCU, but if you ruin the new MCU or anything else on the board in the process, or you find afterwards that there appear to be other fried components that you weren't aware of then you may as well have just purchased a new board and saved yourself all the work and hassle.

So, whose turn is it next to roll the dice?