This module was born out of solving real-world problems I encountered while working on my own projects. I needed a compact charger with a UPDI programmer for a 3D-printed night lamp, a USB-C battery charger for another 3D-printed device, and a reliable USB-UART converter for my random hacking. This design combines all these features, with the added bonus of a good quality 3D model for easy integration into custom enclosures.

Key points:

• 1S Li-Ion/Li-Po Battery Charging: The built-in charger supports single-cell Li-Ion or Li-Po batteries with a default charging current of 200 mA, which can be easily adjusted by changing the resistor at position R7.
• USB to UART: The converter provides RX, TX, CTS, DTR, and RTS signals, enabling seamless communication with microcontrollers, sensors, or other devices.
• Selectable Output Voltage: Choose between 3.3V and 5.0V output to match your device requirements. The output current supports up to 1 A at 5V or 1.5 A at 3.3V.
• Compact and Practical Design: The board has dimension 43×25 mm and is equipped with a 4-pin JST-SH connector (1 mm pitch) for UART, a 2-pin JST-PH connector (2 mm pitch) for battery connection and two mounting holes for easy integration into your project using M3 screws.

Whether you are developing IoT devices, testing embedded systems, or building prototypes, this module is an excellent choice for combining battery management and UART communication into a single compact solution.

Usage

The board serves multiple purposes and can adapt to various use cases:

USB-to-UART Converter: The CH340K chip is compatible with Windows, Linux, and macOS, making it a reliable tool for communication between your computer and embedded devices. If no battery is connected, the charging indicator (red LED) might occasionally blink, which does not affect functionality.

Microcontroller Programming: With CTS, DTR, and RTS signals, the board can program devices like Arduino, ESP32, or other MCUs supporting UART programming.

UPDI Programmer: By connecting RX and TX pins together with a 1 kΩ resistor, the converter transforms into a UPDI programmer for certain AVR ATtiny and ATmega MCUs. This includes models such as ATtiny424/426/427/824/826/827, ATtiny212/214/412/414, megaAVR 0 series, AVR Dx, AVR Ex, and many others. Use pymcuprog from Microchip.

Battery-Powered Applications: When a battery is connected, the board can be integrated into standalone projects requiring a 3.3V or 5.0V power supply. Charging is then possible by the USB-C connector. A 3D model is available for easy integration into your design.

Alternative Power Inputs: If USB-C is not preferred, you can supply power via the VUSB pins on connector J4. The output voltage is available on the VOUT pins, and the battery voltage on the VBAT pins.

Connector Options: TX, RX, and GND signals are accessible through two connectors: J1 (2.54 mm pitch) and a 4-pin JST-SH connector (1 mm pitch). You can choose whichever suits your setup best.

Configurable Output Voltage: The output voltage (3.3V or 5.0V) is set via solder jumpers JP1 and JP2, located above the USB connector. Only one jumper should be soldered at a time; soldering both results in a 5.2V output, while none leaves the output at 0.5V. The output voltage setting does not affect UART functionality, which always operates from USB power.

Adjustable Charging Current: The default charging current is set to 200 mA but can be modified by soldering an appropriate resistor at position R7 (SMD 0603) near the USB connector. The charging current is calculated as follows: I_CHRG = (5 * R7) / (5 + R7) [mA] where R7 is value of your resistor. For example:

• R7 = 10 kΩ → 300 mA
• R7 = 3 kΩ → 1 A
• R7 = 30 kΩ → 100 mA

Package Contents

• USB-C charger with UART, Revision A
• 100 mm cable with 4-pin JST-SH-1 mm connectors on both ends
• 1×40 pin header (2.54 mm pitch)

Downloads

• Schematics (PDF)
• 3D model (STEP)
• Board layout (Kicad PCB)
• Bill of material (CSV)

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Shipping Times: Typically under 2 weeks for the European Union.

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