MiniCore | Arduino hardware package for ATmega8 , ATmega48 , ATmega88

This installation method requires Arduino IDE version 1.6.4 or greater. Click on the "Download ZIP" button in the upper right corner. Exctract 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 "MiniCore" will show up. PlatformIO is an open source ecosystem for IoT development and supports MiniCore. *See PlatformIO.md for more information.
Open the Arduino IDE.
Open the File > Preferences menu item.
Enter the following URL in Additional Boards Manager URLs: https://mcudude.github.io/MiniCore/package_MCUdude_MiniCore_index.json
Open the Tools > Board > Boards Manager... menu item.
Wait for the platform indexes to finish downloading.
Scroll down until you see the MiniCore entry and click on it.
Click Install.
After installation is complete close the Boards Manager window.
Note: If you plan to use the *PB series, you need the latest version of the Arduino toolchain. This toolchain is available through IDE 1.8.6 or newer. Here's how you install/enable the toolchain: 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're downloaded and installed MiniCore, but how to get started? Here's a quick 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, or simply just plut it into an Arduino UNO board. (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 MiniCore 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 clock frequency. 16 MHz is standard on most Arduino boards, including the Arduino UNO.
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 ATmega328 and the ATmega328P got different device signatures, so selecting the wrong one will result in an error.
Hit Burn Bootloader. If an LED is connected to pin PB5 (Arduino pin 13), it should flash twice every second.
Now that the correct fuse settings is sat 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 22pF capacitors if you're using the internal oscillator. If you don't want to mess with breadboards, components and wiring; simply use your Arduino UNO! Click to enlarge:.