I ordered this FC to replace my Skystars on which the 10V power (used for DJI O3) went kaput: Amazon.com: GoolRC GF30F722-ICM F722 F7 HD Baro OSD 5V 10V Dual BEC Flight Controller 3-8S 30.5X30.5mm. It doesn't connect to betaflight with just USB power, as all of my other FCs do.

I rewired the FC to ESC harness so the pins match up, connected a battery, and I got full startup tones. I then plugged in USB to betaflight, it connects, and everything looks OK with a quick check.

Is it normal for some FCs to require battery power to connect to Betaflight? Not only have I never had to do it before, but I've never seen it in any BF configuration videos I've watched, other than of course if I want to do something with the motors.

This is going to be a bit of a pain with the quad assembled, as the O3 gets quite hot with battery connected, so I have to put a fan on it whenever I do that, and I try to limit the time I have the battery connected. Or I can disconnect the O3, but that also is a bit of a hassle.

Is this just part of the deal for a cheapo FC, or is there something I'm missing?

Although rare, some FC do require external power to run power the 5V rail. But I don't recall any FC needing external power just to flash or change settings.

I don't know of any FC that doesn't power up when a USB cable is plugged in. Are you getting any LED activity on the FC when you plug in the cable?

I'm going to assume that you've already tried a different USB cable.

The 5V supply from the USB cable runs through a Schottky diode before it then enters the FC circuit (see the crude diagram below), so if your FC isn't getting any power from the USB cable then my guess is that you have one or more of the following issues:

1. The 5V pin on the USB connector isn't soldered properly to the FC board.
   
2. There is a short to ground on the 5V rail from the USB connector before it goes through the Schottky diode (maybe caused by a fried capacitor that has gone short circuit).
   
3. The Schottky diode has a fault whereby it has gone open circuit and so isn't letting any voltage through it.
   

You would need to do some circuit tracing, continuity testing, and voltage measurements on the FC to confirm which of the above is the root cause of your issue.


USB / LiPo voltage Schottky Diode circuit schematic:



Note: Sometimes a single 3-pin Schottky diode IC package is used, and sometimes two individual Schottky diodes are used with the output from each one just joined together via circuit board traces.

(20-Oct-2023, 08:27 AM)SnowLeopardFPV Wrote: I don't know of any FC that doesn't power up when a USB cable is plugged in. Are you getting any LED activity on the FC when you plug in the cable?

I'm going to assume that you've already tried a different USB cable.

I assumed it wasn't a cable problem since I used the cable I use to connect other FCs to BF.
This morning I randomly plugged it into a USB cable on my bench, and the FC lighted up! The difference: it's powered by USB A instead of USB C. Upon further experimentation, any of my cables with USB A on the power end work, and any with USB C on the power end don't work.

USB-C has a much more complex and sophisticated power management. There is a configuration pin that must be set either by the connecting device or on the cable connectors before the host will supply the correct power, so seems in your case the C-to-C cable and your FC both do not have this. Probably easiest just to use the C-to-A cable with this FC, but if you really want to use C-to-C this document details USB-C and may help you get the right setup.
http://ww1.microchip.com/downloads/en/ap...01953a.pdf

I found the same problem about a month ago as detailed in another post at the link below. I don't have many FC's with a USB-C socket on so that was a new problem for me, and the issue only surfaced when the host also had a USB-C connector on it (so a USB-C to USB-C cable). I just reverted to using a USB-A to USB-C cable and everything then worked as expected.

https://intofpv.com/t-gps-warmup-with-us...#pid205116