HoodLoader2 32u4 Usage
With HoodLoader2.0.5 you can now also use the atmega32u4. This means you can combine a Leonardo/Micro with a 2nd IO MCU like a Pro Mini or Nano. This gives you two very powerful MCUs which can perfectly work together. How they interact with each other (Serial, I2C, SPI) is up to you.
Since the Arduino Nano used baud 57600 as uploading speed and the CDC Bootloader as well it is not possible to use the default Arduino Nano bootloader. Please upgrade the Nano bootloader to the one used by the Arduino Uno board. This also gives you 3,5kb more flash and faster uploading speed. Burning a new 328 bootloader is described here
In order to upload programs to a 328 or any other MCU you need to connect a few wires:
Do not forget the capacitor or it wont work!
Pin connections:
32u4 - 328/2560/etc
GND - GND
5V - 5V
TX - RX
RX - TX
PIN 4 - 100nF Capacitor - RESET
Select HL2 Uno/Mega from the boards menu. This helps you to upload programs to the I/O MCU if the custom USB MCU code is still running. It will force the USB MCU to reset and upload the program. You need to reset the USB MCU once to restart the running program if desired. Restarting the USB MCU also always resets the I/O MCU (due to a floating reset pin for a few ms).
To upload programs to the 32u4 you may select Leonardo or Micro. Any other 32u4 board entry should also work (for example if you want to use an A-Star 32U4 Mini LV). The HoodLoader 32u4 board entry is only meant for burning the bootloader via ISP but can be used as well.