by Max » Sat Jun 20, 2015 12:55 am
Hello David,
There are a number of possible reasons for failure. The COM port already being open (in QGC or some other program) is the most common. The stm32flash program never reports that error very well, but the result would be similar to what you're seeing.
The attempt to "force bootloader mode" depends on the ESC firmware version, and the firmware actually working (so if a previous flashing attempt corrupted the firmware, it won't work). It also depends on the Port and Speed being selected properly in the QGC ESC32 Settings tab.
Did you try again with the BOOT pins shorted? That is the most reliable method -- as long as nothing else is using the selected COM port, it should work every time.
Also I just noticed there is nothing attached to the serial port GND pad of the ESC. Using the PWM ground might work, but it would be more reliable to hook the serial GND pad directly to your USB TTY adapter. A clean ground path is very important for serial comms.
-Max