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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