Electrical engineer William Herr has constructed what’s more likely to be the smallest useful Raspberry Pi RP2040 growth board ever, becoming solely on the tip of 1 finger: the RPDot.
“I acquired the concept from Solder Social gathering’s RP2040 Stamp, however I believed that it may very well be designed smaller, granted the RP2040 is simply 7×7mm,” Herr explains, referring to the surface-mountable sq. RP2040 module which has confirmed in style for a spread of tasks 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 greater 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, in fact, 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 principle CPU cores.
To this, Herr has added a collection 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 machine 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 at the very least 4 layers (two for GND and energy (break up voltage aircraft) and two for indicators),” Herr says. “In hindsight it could have been a lot better as a six layer board, however the worth was too onerous for a take a look at 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 remainder are [the] digital pins closest to the sting.”
Regardless of its small measurement, the RPDot packs in every little thing you have to 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 solely by hand, utilizing a stencil, “very, very expired” lead-free solder paste, and a sizzling 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.”