A new open-source hardware board called Bells&Whistles puts a complete development setup on a single PCB, built around the Raspberry Pi RP2350B and a second Raspberry Pi RP2040 that acts as a built-in debug probe. The developer, who goes by riktw, has published the KiCad schematics, PCB layout files, and a PDF schematic under an MIT license on GitHub, so the entire design can be inspected, modified, or fabricated from scratch.
The onboard RP2040 runs Picoprobe firmware and behaves like a standalone Raspberry Pi debug probe, handling programming and UART monitoring over its own dedicated USB Type-C port without any extra hardware. A second USB-C port connects to the main RP2350B, and both the target and the debugger get their own reset and boot buttons. That separation makes for a tidy flash-and-monitor loop on a single 87 x 26.5 mm (3.4 x 1.0 inches) board, with UART routed internally to the debugger on GPIO0 and GPIO1.
The RP2350B is the wide variant of Raspberry Pi's dual-architecture microcontroller, shipping in a QFN-80 package that exposes up to 46 GPIOs across two 30-pin headers. Each chip carries dual Arm Cortex-M33 cores with TrustZone and dual RISC-V Hazard3 cores, both clocked at 150 MHz, though only two of the four cores can run at once. The board adds 4 MB of on-board SPI flash, a MicroSD slot wired to GPIO20 through GPIO23, and an optional factory-soldered 8 MB PSRAM chip on top of the SoC's 520 KB of SRAM. An HDMI connector provides DVI video output and deliberately reuses the GPIO12 to GPIO19 pin mapping of the Adafruit DVI Sock, so existing code written against Luke Wren's PicoDVI library runs unchanged.
On the toolchain side, the open-source path is mostly there but still settling. The Pico SDK supports the RP2350, and the debugprobe firmware works with OpenOCD, but full RP2350 support landed after OpenOCD 0.12.0, so a current build (or Raspberry Pi's fork) is needed, and RISC-V core debugging remains less polished than the Arm flow. For prototyping with the Arm cores, the integrated probe covers the common case out of the box.
The RP2350's Hazard3 RISC-V cores have also attracted community effort as a no-MMU Linux target. Jesse Taube's pi-pico2-linux project runs a minimal Buildroot-based Linux image on the RP2350's RISC-V cores by staging the kernel in external PSRAM, since the chip's 520 KB of on-die SRAM cannot hold it. The optional 8 MB PSRAM on the Bells&Whistles satisfies that hardware requirement. The fruitjam-linux project has extended a similar Buildroot stack to the Adafruit Fruit Jam, another RP2350B board with PSRAM, reflecting growing community interest in adapting this class of no-MMU Linux configuration to specific RP2350B hardware.
The Bells&Whistles ships as a fully assembled and tested PCBA, with headers sold separately, at a starting price of $30 (€28). Standard ground shipping from the Netherlands starts at $7 (€6), and the extra PSRAM is offered as a factory-installed add-on.
