Electrical engineer William Herr has constructed what’s more likely to be the smallest useful Raspberry Pi RP2040 growth board ever, becoming fully on the tip of 1 finger: the RPDot.
“I bought the concept from Solder Get together’s RP2040 Stamp, however I assumed that it might be designed smaller, granted the RP2040 is simply 7×7mm,” Herr explains, referring to the surface-mountable sq. RP2040 module which has confirmed standard for a spread of initiatives ill-suited to a naked RP2040 chip. “I settled on 10×10mm due to the power to route traces across the RP2040 and have some room for castellated edges.”
The RPDot is an RP2040 growth board barely larger than the chip which powers it. (📷: William Herr)
Regardless of being barely bigger than the chip which drives it, the RPDot packs within the options. First is, after all, a full Raspberry Pi RP2040 microcontroller — that means two Arm Cortex-M0+ cores operating at a inventory 133MHz, 264kB of static RAM (SRAM), and a intelligent programmable enter/output (PIO) block which can be utilized to create state machines operating independently of the primary CPU cores.
To this, Herr has added a choice of 0201-footprint surface-mount gadgets (SMDs) plus an ultra-compact 3.3V low drop-out regulator, and a nearly-as-small quad-SPI flash system for program storage. Maybe essentially the most spectacular inclusion: bodily buttons for boot mode choice and reset, going above and past the options inbuilt to Raspberry Pi’s personal significantly bigger Pico growth board with its lack of reset button.
“When designing this board, I knew it must be not less than 4 layers (two for GND and energy (cut up voltage airplane) and two for indicators),” Herr says. “In hindsight it might have been significantly better as a six layer board, however the value was too exhausting for a check run, so 4 layers it was. Selecting what pins I needed to go on the castellated edges took me a very long time, too; I did SWD [Serial Wire Debug], all energy strains, USB, and all ADC [Analog to Digital Converter] pins, and the remaining are [the] digital pins closest to the sting.”
Regardless of its small dimension, the RPDot packs in every thing you must use the RP2040 — together with bodily reset and boot choose buttons. (📷: William Herr)
The result’s a surface-mountable stamp-format module which makes the already compact RP2040 Stamp look positively gargantuan. It is also assembled fully by hand, utilizing a stencil, “very, very expired” lead-free solder paste, and a scorching plate, plus a 3D-printed jig and a hot-air station for the RP2040 chip.
Extra particulars on the construct, design information for which haven’t been made public, can be found on Herr’s Hackaday.io web page; the engineer has additionally designed a service board for the half, which he guarantees to indicate off “within the subsequent few days.”
