# RP2040 PICAN Castellated Molecule v1

Castellated RP2040 molecule with integrated MCP251863 CAN bus controller/transceiver — 19×35 mm, 4 corner machine pins, 49 castellated machine contacts. USB-C, 16 MB QSPI flash, SWD debug, and 120 Ω CAN termination on-board.

## Overview

| Property | Value |
|---|---|
| **Molecule ID** | `rp2040-pican-castellated-v1` |
| **Board Size** | 19.0 × 35.0 mm |
| **Layers** | 2 |
| **MCU** | RP2040 (Raspberry Pi, QFN-56) |
| **CAN Controller** | MCP251863T-E/9PX (Microchip, integrated CAN FD controller + transceiver) |
| **Flash** | W25Q128JVPIQ — 16 MB QSPI |
| **Regulator** | AP2112K-3.3 (3.3V LDO from 5V input) |
| **USB** | USB-C 2.0 with USBLC6-2P6 ESD protection |
| **Crystal** | 12 MHz (RP2040), 40 MHz (MCP251863) |
| **Castellated Pads** | 49 machine contacts + 4 corner machine pins |
| **KiCad Version** | 7/8 |

## Key ICs

| Ref | Part | Package | Function |
|---|---|---|---|
| U4 | RP2040 | QFN-56 | Dual-core Arm Cortex-M0+ MCU |
| U2 | MCP251863T-E/9PX | VQFN-28 | CAN FD controller + transceiver (SPI interface) |
| U3 | W25Q128JVPIQ | WSON-8 | 16 MB QSPI flash |
| U6 | AP2112K-3.3 | SOT-23-5 | 3.3V 600mA LDO regulator |
| U1 | USBLC6-2P6 | SOT-23-6 | USB ESD protection |
| U5 | 74LVC1T45 | SOT-23-5 | Level translator (LED data) |

## Machine Contact Pin Mapping

4 corner machine pins (X1–X4) for power/ground, 49 castellated contacts for signals.

### Corner Machine Pins

| Pin | Position | Net | Function |
|---|---|---|---|
| X1 | Bottom-left (1, 7) | GND | Ground |
| X2 | Top-left (1, -25) | +3V3 | 3.3V output |
| X3 | Top-right (17, -25) | +5V | 5V input |
| X4 | Bottom-right (17, 7) | GND | Ground |

### Left Edge Contacts (bottom to top)

| Contact | Net | Function |
|---|---|---|
| X54 | STBY | CAN standby control |
| X43 | nINT0/GPIO0/XSTBY | CAN interrupt 0 / GPIO0 |
| X42 | nINT1/GPIO1 | CAN interrupt 1 / GPIO1 |
| X47 | nINT | CAN interrupt |
| X15 | GPIO10 | General purpose I/O |
| X14 | GPIO9 | General purpose I/O |
| X13 | GPIO8 | General purpose I/O |
| X12 | GPIO7 | General purpose I/O |
| X11 | GPIO6 | General purpose I/O |
| X10 | GPIO5 | General purpose I/O |
| X9 | GPIO4 | General purpose I/O |
| X8 | GPIO3 / SCL1 | I2C1 clock |
| X7 | GPIO2 / SDA1 | I2C1 data |
| X6 | GPIO1 / RX0 | UART0 RX |
| X5 | GPIO0 / TX0 | UART0 TX |

### Right Edge Contacts (bottom to top)

| Contact | Net | Function |
|---|---|---|
| X56 | CANL | CAN Low bus line |
| X55 | CANH | CAN High bus line |
| X44 | RXD | CAN RX data |
| X53 | TXD | CAN TX data |
| X23 | GPIO19 | General purpose I/O |
| X24 | GPIO20 / SDI | SPI data in |
| X25 | GPIO21 / CS | SPI chip select |
| X26 | GPIO22 / SCK | SPI clock |
| X27 | GPIO23 / SDO | SPI data out |
| X37 | GPIO24 | General purpose I/O |
| X29 | GPIO25 | General purpose I/O |
| X30 | A0 (GPIO26) | ADC channel 0 |
| X31 | A1 (GPIO27) | ADC channel 1 |
| X32 | A2 (GPIO28) | ADC channel 2 |
| X33 | A3 (GPIO29) | ADC channel 3 |

### Top Edge Contacts (left to right)

| Contact | Net | Function |
|---|---|---|
| X57 | RST | Reset |
| X36 | BOOT | Bootloader select |
| X22 | GPIO17 / LED | User LED data line |
| X41 | USB+ | USB data positive |
| X40 | USB- | USB data negative |
| X35 | SWD_IO | SWD debug data |
| X34 | SWD_CLK | SWD debug clock |

### Bottom Edge Contacts (left to right)

| Contact | Net | Function |
|---|---|---|
| X16 | GPIO11 | General purpose I/O |
| X17 | GPIO12 | General purpose I/O |
| X18 | GPIO13 | General purpose I/O |
| X19 | GPIO14 | General purpose I/O |
| X20 | GPIO15 | General purpose I/O |
| X21 | GPIO16 | General purpose I/O |
| X38 | GPIO18 | General purpose I/O |

## CAN Bus Interface

The MCP251863T provides integrated CAN FD controller and transceiver connected to the RP2040 via SPI. Features:

- CAN 2.0B and CAN FD support
- On-board 120 Ω termination resistor (R20, solder jumper configurable)
- CANH/CANL brought out to castellated pads X55/X56
- 40 MHz crystal (Y2)
- Interrupt lines (nINT, nINT0, nINT1) exposed on left edge

## Power

| Rail | Source | Regulator |
|---|---|---|
| +5V | USB-C or X3 corner pin | Input rail |
| +3V3 | AP2112K-3.3 LDO from 5V | Powers RP2040, flash, CAN controller |
| +1V1 | RP2040 internal | Core voltage |

500 mA polyfuse (F1) on USB input. Schottky diode (D3, PMEG2010BELD) for reverse protection.

## Solder Jumpers

| Jumper | Default | Function |
|---|---|---|
| JP1 | Open | USB VBUS select |
| JP2 | Bridged 1-2 | Power source select |
| JP3 | Open | CAN termination enable |
| JP4–JP9 | Bridged | GPIO routing configuration |
| JP10–JP12 | Bridged | CAN signal routing |

## Debug & Programming

- **USB-C**: Native USB bootloader (hold BOOT + reset)
- **SWD**: Test points TP1 (CLK) and TP2 (DIO), also on castellated pads X34/X35
- **BOOT button**: SW1
- **Reset button**: SW2

## Fabrication

- Gerber files: `jlcpcb/gerber/`
- Production files: `jlcpcb/production_files/`

## Issues

- No GLB 3D model included in the project — `packages3D_incomplete/` contains individual component models but no assembled board model
- Lock files present (`~*.lck`) suggest the project may have been exported while open in KiCad