RP2040-ETH Documentation

Overview

The Waveshare RP2040-ETH is a compact microcontroller board that combines the Raspberry Pi RP2040 chip with built-in Ethernet connectivity. It provides a powerful dual-core processor with integrated networking capabilities in a small form factor.

Hardware Specifications

Processor

Chip: Dual-core Arm Cortex M0+ processor
Clock Speed: Flexible clock up to 133 MHz
Memory: 264KB SRAM
Storage: 4MB onboard Flash memory (W25Q32JVSSIQ NOR-Flash)

Ethernet

Ethernet Chip: CH9120 with integrated TCP/IP protocol stack
Capabilities:
- TCP Server/Client modes
- UDP Server/Client modes
Connector: RJ45 Ethernet port

I/O and Interfaces

GPIO: 14 multi-function GPIO pins
USB: Type-C connector (USB 1.1 host/device support)
Special Features:
- 8 Programmable I/O (PIO) state machines
- Temperature sensor
- Castellated module design for board integration
- Compatible with some Pico HATs

Power

Regulator: RT9013-33GB 500mA Low Dropout LDO
Programming: Drag-and-drop via USB mass storage

Programming the RP2040-ETH

Development Options

C/C++ SDK
MicroPython
Arduino IDE

What We've Learned

From our WS2812 LED control implementation:

PIO Usage: The RP2040's PIO (Programmable I/O) is excellent for timing-critical operations like WS2812 LED control. We used PIO0 with state machine 0 to generate precise timing signals.
Clock Configuration: The default system clock works well for most applications. We commented out set_sys_clock_48() as it wasn't necessary for our WS2812 implementation.
Pin Mapping: GPIO 25 was used for WS2812 data output in our example, demonstrating the flexibility of pin assignment on the RP2040.
Timing Precision: The PIO handles the 800kHz timing requirement of WS2812 LEDs perfectly, showing the RP2040's capability for real-time signal generation.
Memory Efficiency: With 264KB of SRAM, there's plenty of room for complex applications beyond simple LED control.

Code Structure Example

Our WS2812 implementation demonstrates key RP2040 programming patterns:

// PIO initialization
PIO pio = pio0;
int sm = 0;
uint offset = pio_add_program(pio, &ws2812_program);
ws2812_program_init(pio, sm, offset, 25, 800000, true);

// Color data formatting (GRB format for WS2812)
uint32_t mask = (green << 16) | (red << 8) | (blue << 0);
put_pixel(mask);

Key Takeaways

Hardware Abstraction: The Pico SDK provides excellent hardware abstraction layers, making it easy to work with complex peripherals.
PIO Power: The programmable I/O blocks are one of the RP2040's strongest features, enabling precise timing without CPU intervention.
Development Workflow: The USB mass storage programming mode makes development iteration very fast - just drag and drop the UF2 file.
Ethernet Integration: While our example doesn't use Ethernet, the CH9120 chip provides a straightforward path to network connectivity without complex TCP/IP stack implementation.

Future Considerations

The Ethernet functionality via CH9120 opens possibilities for IoT applications
The dual-core processor allows for concurrent tasks (e.g., LED animation on one core, network communication on the other)
The castellated edges make this board ideal for integration into custom PCBs
PIO state machines can be used for various protocols beyond WS2812 (SPI, I2C variants, custom protocols)

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