The Frood

The Frood is a high-performance and affordable Pro Micro drop-in replacement based on a Raspberry Pi RP2040. It is physically and electrically compatible with Elite-C/nice!nano as much as possible.

It follows the SparkFun Pro Micro RP2040 pinout with 5 more pins (GPIO12-GPIO16) added along the bottom edge (like on Elite-C), and USB data lines broken out in the top corners.

Features

• Powerful dual-core Raspberry Pi RP2040 MCU
• 4 MB of on-board flash memory
• Only 3.2 mm thick thanks to a mid-mounted USB-C socket
• 500 mA linear regulator and resettable fuse
• Combined Pro Micro / Elite-C / nice!nano / SparkFun Pro Micro RP2040 compatible pinout
• 5 more I/O pins (GPIO12-GPIO16) added along the bottom edge
• 2 more I/O pins (GPIO10, GPIO11) can be converted from left-hand side GND pins by cutting a jumper
• 23-25 total available digital pins for a maximum of 11x12 = 132 (or even 12x13 = 156) switches
• 4 pins configurable as analogue inputs
• USB D+/D- broken out for use with an external USB socket/daughterboard
• USB power sensing on GPIO19 for split keyboard side detection
• UF2 bootloader for drag & drop programming with no extra software required
• Orange indicator LED on pin GPIO17
• Now with official CircuitPython support

Availability

The Frood is available from 42keebs.eu.

Revision history

Rev9 (03/01/2024)

• Allows converting left-hand side GND pins into GPIO pins (GPIO10, GPIO11) by cutting PCB jumpers
• VBUS IN/OUT solder jumper dropped, the RAW pin is now connected to VBUS after a Schottky diode/input of linear regulator before a resettable fuse
• Uses a different (but equivalent) USB-C socket due to component shortage
• Routing and silkscreen tweaks/improvements

Rev8 (10/10/2023)

• Add a 2-way solder jumper to select VBUS OUT or VBUS IN on the RAW pin
• Use orange indicator LED again

Rev7 (23/06/2023)

• Use a different 4 MB flash chip (Winbond W25Q32JVUUIQ) which will hopefully not need a special config
• Use a higher-quality Panasonic reset/boot switches
• Some routing tweaks
• Bug: uses red indicator LED by mistake

Rev6 (28/12/2022)

• Use a 4 MB (32 Mbit) flash chip (needs a special configuration in QMK config.h: #define RP2040_FLASH_GD25Q64CS)
• Tweak a few tracks

Rev5 (26/10/2022)

• Improve USB socket position to match nice!nano
• Add BOOT/RESET pads on the bottom of the PCB (when the buttons are not accessible)
• Use a smaller crystal to gain some valuable space
• Add an orange indicator LED on pin GPIO17 (inspired by the 0xB2)

Rev4 (28/09/2022) - Confirmed working

• Use a 2 MB flash with correct supply voltage rating
• Switch to GT-USB-7014C USB-C socket and a standard 1.6 mm PCB
• Improve pin labels
• Improve routing

Rev3 (18/08/2022) - DO NOT USE!

• Rename to "Frood"
• Use HRO-TYPE-C-31-M-14 for a fully mid-mounted socket with a 1.0 mm PCB
• Use 500 mA fuse instead of 350 mA one
• Improve layout (move USB termination resistors closer to MCU)
• Still uses the same flash chip with an incorrect supply voltage (1.8-2.6 V)

Rev2 (16/08/2022) - DO NOT USE!

• Rename to "PiMicro2040"
• Fix crystal routing
• Use Elite-C/nice!nano-like outline
• Use mid-mounted USB-C connector (HRO-TYPE-C-31-M-13)
• Use a "standard" Sparkfun Pro Micro-compatible pinout
• Add 350 mA resettable fuse
• Add VBUS sensing
• Break-out USB data lines
• Contains a critical error - flash chip with an incorrect supply voltage (1.8-2.6 V)

Rev1 (08/08/2022) - DO NOT USE!

• Initial version with a top-mounted USB-C socket, a shorter outline and a custom pinout
• Contains a critial error - incorrect crystal routing due to a mismatch between a 2-pin symbol and a 4-pin footprint