Upgrading FuriousFPV True-D module to 3.6 firmware on MacOS and Linux made Easy :

- download 3.6 firmware from furiousfpv.com website and uncompress it
- connect module with usb cable
- make sure avrdude utility is installed (Brew, Arduino IDE, etc.)

in terminal app run the following command :

avrdude -c arduino -p atmega328p -b 57600 -P /dev/tty.SLAB_USBtoUART -U flash:w:True_D_V3.6_Release.ino.hex


Install log on my machine :

grizz@mbpg:~/Downloads$ avrdude -c arduino -p atmega328p -b 57600 -P /dev/tty.SLAB_USBtoUART -U flash:w:True_D_V3.6_Release.ino.hex

avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.00s

avrdude: Device signature = 0x1e950f (probably m328p)
avrdude: NOTE: "flash" memory has been specified, an erase cycle will be performed
         To disable this feature, specify the -D option.
avrdude: erasing chip
avrdude: reading input file "True_D_V3.6_Release.ino.hex"
avrdude: input file True_D_V3.6_Release.ino.hex auto detected as Intel Hex
avrdude: writing flash (30718 bytes):

Writing | ################################################## | 100% 8.29s

avrdude: 30718 bytes of flash written
avrdude: verifying flash memory against True_D_V3.6_Release.ino.hex:
avrdude: load data flash data from input file True_D_V3.6_Release.ino.hex:
avrdude: input file True_D_V3.6_Release.ino.hex auto detected as Intel Hex
avrdude: input file True_D_V3.6_Release.ino.hex contains 30718 bytes
avrdude: reading on-chip flash data:

Reading | ################################################## | 100% 6.08s

avrdude: verifying ...
avrdude: 30718 bytes of flash verified

avrdude: safemode: Fuses OK (E:00, H:00, L:00)

avrdude done.  Thank you.