avrdude commands for Pro Micro (ATMega32U4)

commands.sh

# Using bootloader
# To enter bootloader, connect the board to the computer and connect briefly the GND and RST pins. 
# Some boards may require this connection to be done twice.
# When the bootloader is running, a virtual serial connection is created and so we can read/write to the device

# Checking connection and fuses
avrdude -c avr109 -p m32u4 -P /dev/ttyACM0 -n

# It should write something like the example below
# Connecting to programmer: .
# Found programmer: Id = "CATERIN"; type = S
#    Software Version = 1.0; No Hardware Version given.
# Programmer supports auto addr increment.
# Programmer supports buffered memory access with buffersize=128 bytes.

# Programmer supports the following devices:
#    Device code: 0x44

# avrdude: AVR device initialized and ready to accept instructions

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

# avrdude: Device signature = 0x1e9587 (probably m32u4)

# avrdude: safemode: Fuses OK (E:FB, H:D8, L:FF)

# avrdude done.  Thank you.

# Explaining the command:
# -c avr109 set the programer as avr109. It's the protocol which will be used
# -p m32u4 set the target, which is an atmega32u4
# -P /dev/ttyACM0 set the serial port. On Windows it would be something like COM1, COM7, etc...
# -n disables any writes, it's safe option

# Arduino as ISP
# Flasing using Arduino as ISP
avrdude -v -p m32u4 -P /dev/ttyUSB0 -c stk500v1 -b 19200 -U flash:w:caterina.hex:i -U lfuse:w:0xff:m -U hfuse:w:0xd8:m -U efuse:w:0xfb:m

# Arduino has an autoreset feature which resets the device when a serial connection is opened, so avrdude will fail because Arduino will be reseting and not ready. 
# To prevent this, one option to use a capacitor in some pins (google it, dont remember) or cut some traces on the board.
# In Linux there's a simple option. It's possible to use the following command
stty -F /dev/ttyUSB0 -hupcl
# It will prevent the autoreset by not sending the hangup (something like that, I dont understand much about serial connections).