documentation updated

Author: michpro

README.md

@@ -0,0 +1,148 @@
+# **Arduino Pro Mini XL**
+
+- [**Arduino Pro Mini XL**](#arduino-pro-mini-xl)
+  - [**Overview**](#overview)
+    - [**Features**](#features)
+  - [**Schematic diagram**](#schematic-diagram)
+  - [**Module visualisation**](#module-visualisation)
+  - [**Assembly**](#assembly)
+  - [**Production files**](#production-files)
+  - [**Software Compatibility**](#software-compatibility)
+    - [**Installing MightyCore**](#installing-mightycore)
+  - [**Getting Started**](#getting-started)
+    - [**Burning the Bootloader**](#burning-the-bootloader)
+  - [**Troubleshooting**](#troubleshooting)
+  - [**Physical Specifications**](#physical-specifications)
+  - [**Reporting bugs**](#reporting-bugs)
+  - [**Acknowledgments**](#acknowledgments)
+  - [**License**](#license)
+  - [**Support**](#support)
+
+---
+
+## **Overview**
+The **Arduino Pro Mini XL** is a compact microcontroller board based on the **ATmega1284P**, designed to extend the capabilities of the standard Arduino Pro Mini while retaining its familiar form factor. With increased memory, additional I/O pins, and enhanced features, this board is well-suited for embedded applications requiring greater processing power and connectivity than the ATmega328P-based Arduino Pro Mini can provide. It integrates seamlessly with the Arduino ecosystem, making it accessible to hobbyists, engineers, and developers alike.
+
+### **Features**
+* **Microcontroller**: ATmega1284P
+* **Flash Memory**: 128KB
+* **SRAM**: 16KB
+* **EEPROM**: 4KB
+* **Digital I/O Pins**: 22
+* **Analog Input Pins**: 2
+* **Analog Comparator**: 1
+* **PWM Channels**: 8
+* **UARTs**: 2
+* **SPI**: 1
+* **I2C**: 1
+* **Operating Voltage**: 5V
+* **Clock Speed**: 20/16/8MHz
+* **Form Factor**: Compatible with Arduino Pro Mini
+
+---
+
+## **Schematic diagram**
+<p align="center"><img src="./docs/schematic.png" alt="wiring diagram" width="80%"/></p>
+
+
+## **Module visualisation**
+(click on the image to see the 3D model)
+<p align="center"><a href="https://3dviewer.net/#model=https://github.com/michpro/Arduino_Pro_Mini_XL/blob/master/docs/Arduino_Pro_Mini_XL.wrl"><img src="./docs/Arduino_Pro_Mini_XL.png" alt="Arduino Pro Mini XL" width="50%"/></a></p>
+
+## **Assembly**
+[Interactive BOM and placement](https://michpro.github.io/Arduino_Pro_Mini_XL/ibom.html)
+
+## **Production files**
+Production files can be found [**here**](./production/).
+
+---
+
+## **Software Compatibility**
+
+The Arduino Pro Mini XL is supported by the Arduino IDE through the [**MightyCore**](https://github.com/MCUdude/MightyCore) board package, which provides board definitions for the ATmega1284P.
+
+### **Installing MightyCore**
+
+To configure the Arduino IDE:
+
+1. Open the Arduino IDE.
+2. Navigate to `File` > `Preferences`.
+3. Add the following URL to the `Additional Boards Manager URLs` field:  
+   ```
+   https://mcudude.github.io/MightyCore/package_MCUdude_MightyCore_index.json
+   ```
+4. Click `OK`.
+5. Go to `Tools` > `Board` > `Boards Manager`.
+6. Search for "MightyCore" and install the package.
+
+After installation, select **"ATmega1284P"** under `Tools` > `Board`, and configure the variant and clock settings as needed.
+
+## **Getting Started**
+
+1. **Connect the Board**: Attach an FTDI-compatible cable or adapter to the 6-pin programming header.
+2. **Configure the IDE**: Select the ATmega1284P board and the appropriate serial port in the Arduino IDE.
+3. **Upload a Sketch**: Use a simple sketch, such as "Blink," to test functionality.
+   ```cpp
+   void setup()
+   {
+      pinMode(PIN_PC6, OUTPUT); // Onboard LED 
+                                // Don't forget to close JP1.
+   }
+
+   void loop()
+   {
+      digitalWrite(PIN_PC6, HIGH);
+      delay(1000);
+      digitalWrite(PIN_PC6, LOW);
+      delay(1000);
+   }
+   ```
+4. **Verify Operation**: Confirm that the onboard LED blinks, indicating successful setup. **Don't forget to close JP1.**
+
+### **Burning the Bootloader**
+
+To burn the bootloader using an ISP programmer:
+
+1. Connect the ISP programmer to the board’s pins.
+2. In the Arduino IDE, select the ATmega1284P board and your programmer.
+3. Choose `Tools` > `Burn Bootloader`.
+
+Consult the MightyCore documentation for correct fuse settings.
+
+## **Troubleshooting**
+
+- **Upload Failures**: Verify board and port settings; check FTDI connections and drivers.
+- **Power Issues**: Ensure input voltage is 5V (VCC); inspect for shorts. *Board has no RAW input*
+- **Pin Mapping**: Confirm pin assignments, as they differ from the ATmega328P.
+
+## **Physical Specifications**
+
+- **Dimensions**: Comparable to the Arduino Pro Mini (18.5mm x 33mm).
+
+---
+
+## **Reporting bugs**
+
+[Create an issue on GitHub](https://github.com/michpro/Arduino_Pro_Mini_XL/issues)
+
+---
+
+## **Acknowledgments**
+
+Thanks to the Arduino community and the [**MightyCore**](https://github.com/MCUdude/MightyCore) developers for enabling support for the ATmega1284P.
+
+---
+
+## **License**
+Copyright © 2020-2025 Michal Protasowicki
+
+This project is released under CERN Open Hardware Licence Version 2 - Permissive.
+
+[![License: CERN-OHL-P-2.0](https://img.shields.io/badge/License-CERN--OHL--P--2.0-blue.svg)](./LICENSE)
+
+---
+
+## **Support**
+If You find my projects interesting and You wanted to support my work, You can give me a cup of coffee or a keg of beer :)
+
+[![PayPal Direct](https://badgen.net/badge/icon/Support%20me%20by%20PayPal?icon=kofi&label&scale=1.5&color=blue)](https://www.paypal.me/michpro)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[![ko-fi](https://badgen.net/badge/icon/Support%20me%20on%20Ko-fi?icon=kofi&label&scale=1.5&color=red)](https://ko-fi.com/F1F24CEW1)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[![Coinbase](https://badgen.net/badge/icon/Support%20me%20with%20cryptocurrencies?icon=kofi&label&scale=1.5&color=blue)](https://commerce.coinbase.com/checkout/ec299320-cbed-475d-976e-fdf37c1ac3d0)