Hi,

a few weeks ago I bought a camera mount gimbal on from JMTTOP (like this one: http://www.jmttop.com/f05683-brushless-camera-mount-gimbal-full-set-tested-for-gopro-3-fpv-aerial-photography-w-motor-control-board-us-free-ship_p48484.html). It
worked fine, even the calibration with the GUI tool did not make any
problems. But then suddenly the gimbal showed a strange behavior. From
one moment to another the motors started to do some very quick and
short random movements. It seems like they don't get any informations
from the sensor anymore. The problem did not go away, so I decided to
reinstall the firmware and try to recalibrate the whole board.

The GUI tool from basecamelectronics.com shows that the current
firmware version is 2.2b2. And furthermore it shows that all sensors
and everything else on the board works fine and it does not show
errors or anything either.

So I downloaded the newest firmware from basecamelectronics.com and
tried to flash it with Xloader and AvrdudeR but without any success.
Both programs just fail while uploading. The host system was a windows
7 computer. The board was connected via USB (driver was taken from
http://www.silabs.com/products/mcu/pages/usbtouartbridgevcpdrivers.aspx).
The second attempt to flash a new firmware on the gimbal was made from
a Mac OSX 10.9 computer. USB driver was the same, connection again via
USB interface. The command line options to flash the firmware with
avrdude was as follows:

avrdude -v -C avrdude.conf -p atmega328p -c arduino -P
/dev/tty.SLAB_USBtoUART -b 115200 -D -V -U
flash:w:SimpleBGC_2_0b3.enc.hex:i

At first it looked like it was working, but then this strange error
was reported:

avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x00

So this did not seem to work either. The last attempt was then made on
a Windows 8.1 computer, same setup as before but this time avrdude was
called directly from the console. The error message was the same as
before:

avrdude: stk500_recv(): programmer is not responding ... not in sync: resp=0x00

So to sum up the problem:
- I was not able to flash a new firmware on the device from 3
different computers with Win7, Win8.1 and OSX 10.9
- None of the provided flash tools (avrdude, xloader, even the GUI
tool under the tab "Software Upgrade") was able to upload the firmware
- Even Arduino itself is not able to install a new bootloader (because
I thought it's maybe broken) it just reports the same error!

In addition the behavior of the gimbal is now like this:
- If only the battery is connected, the board does nothing at all. A
red LED is on.
- If only usb is connected, the LED blinks red and green, depending on
what action was taken in the GUI. The GUI works very well, all sensor
seem to respond fine.
- If both usb and the battery are connected, the motors do these very
quick and small random movements. It really looks like something is
extremely broken... The GUI tool just works fine in the meanwhile.

My question to you now is:
Why is it not possible for me to upload a new firmware on the device?
Can somebody maybe explain what the problem is that the gimbal does not
work anymore as expected?

Any help or hint would be very welcome.

Thank you!