Video here:


as you can see , with usb only seem there is some low tension around, led blink but rx in reality is off , when i plug battery become ready .

(13-Apr-2020, 02:41 PM)zerogravity Wrote: as you can see , with usb only seem there is some low tension around, led blink but rx in reality is off , when i plug battery become ready .

Is your receiver connected to the 4V5 pad on the FC? This is the pad you should use for the receiver because it always receives USB voltage (which is usually between 4.5V and 5V) regardless of whether or not a LiPo is plugged in. Check the output voltage on that pad with a multimeter. The RXSR-FC only needs 4V to operate, so if the 4.5V pad is outputting at least 4V with just the USB lead plugged in then it means you have a potential issue with your RXSR-FC.

If the 4V5 pad is outputting less the 3.5V then try plugging the USB cable into a 5V USB wall charger and do the same test. Maybe the USB ports on your PC aren't putting out the correct voltage.

I also assume you already tried some different USB cables?

yes, pad on fc is correct, and i've tried more usb cable and more usb port, i have to admit i haven't tried with a multimeter, by the way with lipo all works great and in flight i haven't issue.

It does seem that the voltage output to the receiver isn't getting at least the 4.5V for the receiver with just the USB. A DMM measurement will tell us if this is the case, if you choose to do it. Otherwise, happy flying.

oh well, in next days i'll check , at this point of the story i'm curious, some FC are for real a mistery !

I am using the same USB as I did when it worked so I guess it is a data cable? However I have tried other cables. When I plugged it in before a blue and a green light would be on top and a green one on the receiver (underneath). Now there is only a flashing red LED (I think this means it isn't bound- even though I have already bound it.)on the receiver.

As I use apple device manager is different, however I can't see the board appearing on it.

I am just posting what I wrote to you.


Ok Mac. When you say blue and green that sounds like the receiver and not the FC. Yes, red light on receiver means that you are not bound. So it looks like there is two problems. One, the FC is not connected and we still haven't gotten your receiver working. Let's tackle the FC first. Are the leds on the receiver? Do you see another led on the FC?

When you plug in the FC, on the upper right pull down menu, what options are available to you. You should see a long name path with USB in the path.

I'm pretty sure the green and blue weren't on receiver (however there was a solid green light-indicating it was bound on the receiver which was replaced by a blinking red light when the FC stopped connecting). 

As for the pull down menu do you mean the one in Betaflight? If so then it reads: /dev/tty.Bluetooth-Incoming-Port and the one underneaths says /dev/cu.Bluetooth-Incoming-Port 
(sorry if that's really unclear!)

so, it doesn't look like the FC is even responding when plug-in. try a different cable. also check that the USB port on the FC did not desoldered or disconnected.

if everything seems to checked out, try getting the FC into DFU mode (hold down boot button when plugging in USB). If you can get into DFU mode, try reflashing the firmware.

I've already tried putting it into DFU mode and it still doesn't connect (I tried different USBs too).

 So I think I should get rid of this FC and upgrade to an f7, but get a Frsky receiver.

The confusing part is that you confirmed in our PM exchange that with a USB cable plugged in you were getting 5V and 3V from the "5V_DC" and "3V_LDO" pads respectively, which means that both the board and MCU are getting power, so it should be possible to put the FC into DFU mode. Unfortunately I don't own a Mac so I don't know how to troubleshoot USB connection issues on that.

woody_232 Wrote:Both pads read the correct amount (5.03v for the 5v regulator and 3.29v for the 3.3v regulator), so I'm guessing the 3.3v regulator isn't fried, still no connection to Betaflight...

On the Mac, both DFU and normal are recognized by the computer without any additional driver. But things do sound weird, at least he should be able to get into DFU mode.

I assume you don't have another FC to test to see if your Mac is working.

Yes, that's why I'm so confused- I even tested it again this morning and the readings for both the 5v and 3.3v pads were the same as before. 

I'm quite new to Mac too which makes trouble shooting a bit harder; I've checked through the USB part of  "system report" and can't see the FC. 

Does anyone with Mac experience know how to get a list of USB devices plugged in?

EDIT: I do not have another FC to use for testing.