RP2040

Everything about RP2040 controllers.

Overview #

This new chip by the Raspberry Pi foundation finally replaces the outdated AVR microcontrollers and expensive/hard-to-get STM32 chips. It’s low cost coming in at just 1$ p.p. and most importantly it’s available in high volume!

The RP2040 features two ARM Cortex-M0+ 32-bit CPUs that operate at 133MHz, along with 264Kb of SRAM. For comparison the atmega32u4 chips used in Pro Micros only feature a single 8-bit RISC core operating at 16MHz, along with 2.5KB SRAM (they also have onboard flash, but sadly only 32KB).

So as you can tell it’s a pretty big upgrade from the 32U4 and I/O wise it’s also a beast:

• 2 × UART, 2 × SPI controllers, 2 × I2C controllers, 16 × PWM channels
• 1 × USB 1.1 controller and PHY, with host and device support
• 8 × Programmable I/O (PIO) state machines for custom peripheral

The main star is the PIO making the use cases endless. Some options are ethernet, PIO USB host and much, much more.

Power #

The rp2040 needs 3.3V power instead of 5V like the 32u4.

3.3V #

The easiest way to archive this is by using a 3.3V LDO to step down the 5V from the USB port.

1.1V #

You might have spotted the voltage regulator in the floorplan image. it provides 1.1V for the cores.

Flash #

Because the RP2040 doesn’t have built-in storage you need an external 3.3V (Q)SPI flash and you may use up to 128Mb / 16MB of it.

Recommended Flash Chips #

For assembly/reflow soldering:

• W25Q128JVPIQ | 16MB | WSON-8-EP(5x6mm)
• W25Q64JVXGIQ | 8MB | XSON-8-EP(4x4mm)
• W25Q32JVUUIQ | 4MB | USON-8(3x4mm)
• W25Q16JVUXIQ | 2MB | USON-8-EP(2x3mm)

For hand soldering:

• W25Q128JVSIQ | 16MB | SOIC-8-208mil
• W25Q64JVSSIQ | 8MB | SOIC-8-208mil
• W25Q32JVSSIQ | 4MB | SOIC-8-208mil
• W25Q16JVSSIQ | 2MB | SOIC-8-208mil

Bootloader #

The RP2040 comes with a bootloader etched into ROM (Read Only Memory).

After that, a second-stage bootloader takes over and runs code from the flash.

Entering the bootloader #

To enter the bootloader you have to disable the flash chip on startup:

pull and hold QSPI_SS_N low and reset the controller by pulling RUN low.

You will see a new flash drive appear on your computer and you can drag and drop .uf2 files onto it to flash them.

Pinout #

GPIO functions #

Every GPIO can serve multiple functions thanks to the PIO fabric.

This for example enables you to place full duplex split transport almost anywhere on the chip (see col. F2):

QMKs naming for GPIO #

To reference the RP2040s GPIO you use GP* where * is the GPIO number (not the pin number).

Die Shot #

Look at this beauty: