MightyCore | Arduino hardware package for ATmega1284 ATmega644

This installation method requires Arduino IDE version 1.6.4 or greater. Click on the "Download ZIP" button. Extract the ZIP file, and move the extracted folder to the location "~/Documents/Arduino/hardware". Create the "hardware" folder if it doesn't exist. Open Arduino IDE, and a new category in the boards menu called "MightyCore" will show up.
Open the Arduino IDE.
Open the File > Preferences menu item.
Enter the following URL in Additional Boards Manager URLs: https://mcudude.github.io/MightyCore/package_MCUdude_MightyCore_index.json
Separate the URLs using a comma ( , ) if you have more than one URL
Open the Tools > Board > Boards Manager... menu item.
Wait for the platform indexes to finish downloading.
Scroll down until you see the MightyCore entry and click on it.
Click Install.
After installation is complete close the Boards Manager window.
Open the Tools > Board > Boards Manager... menu item.
Wait for the platform indexes to finish downloading.
The top is named Arduino AVR boards. Click on this item.
Make sure the latest version is installed and selected
Close the Boards Manager window.
Ok, so you've downloaded and installed MightyCore, but how do you get the wheels spinning? Here's a quick start guide:. Your code should now be running on your microcontroller! If you experience any issues related to bootloader burning or serial uploading, please use this forum post or create an issue on Github.
Hook up your microcontroller as shown in the pinout diagram. If you're not planning to use the bootloader (uploading code using a USB to serial adapter), the FTDI header and the 100 nF capacitor on the reset pin can be omitted.
Open the Tools > Board menu item, and select a MighyCore compatible microcontroller.
If the BOD option is presented, you can select at what voltage the microcontroller will shut down at. Read more about BOD here.
Select your prefered pinout. Personally I prefer the standard pinout because it's "cleaner", but the Bobuino pinout is better at Arduino UNO pin compatibility. Read more about the different pinouts here.
Select your prefered clock frequency. 16 MHz is standard on most Arduino boards.
Select what kind of programmer you're using under the Programmers menu.
If the Variants option is presented, you'll have to specify what version of the microcontroller you're using. E.g the ATmega1284 and the ATmega1284P have different device signatures, so selecting the wrong one will result in an error.
Hit Burn Bootloader. If an LED is connected to pin PB0, it should flash twice every second.
Now that the correct fuse settings is set and the bootloader burnt, you can upload your code in two ways: Disconnect your programmer tool, and connect a USB to serial adapter to the microcontroller, like shown in the minimal setup circuit. Then select the correct serial port under the Tools menu, and click the Upload button. If you're getting some kind of timeout error, it means your RX and TX pins are swapped, or your auto reset circuity isn't working properly (the 100 nF capacitor on the reset line). Keep your programmer connected, and hold down the shift button while clicking Upload. This will erase the bootloader and upload your code using the programmer tool.
Here is a simple schematic showing a minimal setup using an external crystal. Skip the crystal and the two capacitors if you're using the internal oscillator. Click to enlarge:.