Samot2040 devboard

SamotPi2040 DevBoard

📌 Project Overview & Purpose

• What is it? A standalone development board based on the Raspberry Pi RP2040 dual-core ARM Cortex-M0+ processor.
• What does it do? It provides all essential supporting circuitry (power regulation, Li-Po 3.7V battery charging, automatic power source switching, high-speed crystal oscillator, SPI flash, USB termination, and ESD/pull-down configuration) to run MicroPython, CircuitPython, Arduino, or bare-metal C/C++ Pico SDK code.
• Why does it exist? It was created to explore custom PCB design from scratch, master 2-layer routing with fine-pitch QFN and 0402 components, and build a reliable, inexpensive, and customizable devboard for prototyping robotics and embedded electronics.

Why I Made This Project

Because I wanted to design my own RP2040 board with my own design a to be able to say "I made this" with:

1. A modern USB-C connector
2. Integrate both BOOT and RESET switches directly on board to make flashing easy.
3. Provide a full 8MB high-speed SPI Flash storage for large CircuitPython scripts, assets, and datalogging.
4. Integrated Li-Po 3.7V battery charging (MCP73831) and automatic power source switching (BAT54C Schottky diode) for portable projects.

Project Gallery

3D Render

3D Board View

PCB Layout & Routing

Schematic

Hardware Features & Specifications

Power Management & Battery Support

The board features a built-in power management circuit designed for both desktop development and portable battery-powered operation:

• 3.7V Li-Po / Li-Ion Battery Support: Connect any standard 3.7V single-cell Lithium-Polymer (Li-Po) or Lithium-Ion (Li-Ion) battery to the +BATT and GND pins/pads.
• Integrated Battery Charging: The on-board Microchip MCP73831 charge controller automatically charges the battery when connected to USB-C (5V VBUS) using constant current / constant voltage (CC/CV) up to 4.2V.
• Automatic Power Source Switching: A dual common-cathode Schottky diode (BAT54C) acts as an automatic power OR-ing switch. When USB-C is plugged in, the board runs directly from USB power while recharging the battery. When USB-C is disconnected, power seamlessly falls over to the battery without interruption or board resets.

🛠️ Step-by-Step Assembly Guide

[!IMPORTANT] I recommend using HOT airflow station or hot plate for soldering because there are really small components like the main chip or 0402 capacitors/resistors

Required Tools

• Hot air station / hot plate and soldering iron
• solder flux paste / pen and solder wick
• tweezers
• USB-C data cable

Assembly Steps

1. Solder the RP2040 chip:
   • Apply a thin layer of solder paste to the center thermal pad and other pads.
   • Align first pin of the RP2040 chip using the silkscreen dot marker.
   • Reflow using hot air (~320°C–350°C) or hot plate. Make sure the chip is centered.
2. Solder the Flash (U3), Voltage Regulator (U2), Charger (U4), and Diode (D1):
   • Solder the MX25L6433 flash chip (SOIC-8), MCP1700 (SOT-23), MCP73831 charger (SOT-23-5), and BAT54C diode (SOT-23). You can do this with normal soldering iron and plenty of flux.
3. Solder Passives (Resistors & Capacitors) and Crystal:
   • Solder the small 0402 capacitors (C1–C12, C17, C18) close to the RP2040 power pins.
   • Solder the 0603 capacitors (C13, C14), crystal load capacitors (C15, C16), and resistors (R1–R7, R9).
   • Then carefully solder the 12 MHz crystal (Y1).
4. Solder USB-C (J1):
   • Align the 16-pin USB-C receptacle (GCT USB4085). Solder the through-hole shielding legs for mechanical strength, then use a iron tip with a lot of flux to solder the other pins.
5. Solder buttons(SW1, SW2):
   • Solder the swithces for BOOT and RESET.
6. Double check :
   • Inspect all solder joidnts under magnification for solder bridges or cold joints (especially on the RP2040 and USB-C).
   • Using a multimeter in continuity/resistance mode, verify that VBUS (5V), 3V3, and GND are not shorted.
7. Solder Pin Headers (J2, J3, ):
   • Insert the 1x20 2.54mm male headers into a solderless breadboard to keep them perpendicular, place the PCB on top, and solder each pin.

How to Flash Firmware

The RP2040 has a built-in ROM bootloader that makes flashing firmware simple without requiring external programmers:

flowchart LR
    A["Hold BOOT"] --> B["Plug in USB-C"]
    B --> C["'RPI-RP2' Drive Appears"]
    C --> D["Drag & Drop .UF2 File"]
    D --> E["Auto Reboot & Run!"]

1. Enter Bootloader Mode:
   • Hold the BOOT button (SW1).
   • Connect the board to computer using a USB-C data cable
   • Release the BOOT button.
2. Flashing Firmware:
   • Drag and drop your compiled .uf2 firmware file onto the RPI-RP2 drive that should appear on PC:
     • MicroPython: Download the Official RP2040 MicroPython UF2.
     • CircuitPython: Download the Adafruit CircuitPython RP2040 UF2.
     • C/C++ SDK / Arduino: Build your project using Arduino IDE (with Earle Philhower RP2040 core) or Pico SDK and drag the resulting .uf2 file.
3. Execution:
   • Once the .uf2 file finishes copying, the board will automatically dismount and execute the program immediately.

BOM

Import quickOrder_TME.csv directly to TME.eu for fast order.

JLCPCB Cart: