Gadget Renesas

Linking Ideas and Electronics



GR-CITRUS tiny board enables easier to program with Ruby language. You can create Ruby programs with Visual Studio Code. See VSCode Extension "Rubic". You can also develop with "Rubic" on chrome app.


Of course you can program like Arduino sketch on Renesas Web compiler and IDE for GR.
By connecting with WA-MIKAN that has ESP8266 module for Wi-Fi, you can prototype a system using Wi-Fi and micro SD card.

Renesas 32-bit RX63N Group MCU is on board.
Compatible pin array with Arduino Pro Mini.
-FULL product attached long pin socket for WA-MIKAN.
(The image describe normal type)
Wi-Fi module "ESP8266" and micro SD socket.
-FULL has a pin socket for GR-CITRUS connection
(The image describe full type)

Pin Map


Item Description
Microcontroller RX631(R5F5631FDDFP 100pin QFP)
Data flash 32KB
Main clock 96MHz (internal)
Sub clock 32.768kHz
Operating voltage 3.3V
Board function Reset Switch, 20 expanding pin, User LED 1

Boards Distributor

Technical Support

Technical Information
Related Web Site


Schematic / Design


How to program

Ruby firmware

It is a link to GR-CITRUS's latest firmware for Ruby. To write the firmware, please press the reset button of GR-CITRUS and recognize it as USB memory, then copy the bin file. About the latest firmware, refer to Github.

GR-CITRUS Ruby firmware V2.35


Project file for e2studio

Project file for sketching in Eclpse-based development environment e2studio. For downloading and installing e2studio please refer to the product page.

Click to download. Import the archive file (zip) as an existing workspace from the menu 'File' -> 'Import' in e2studio.

Note: This is a project exported in e2studio version 5.4. It can not be imported successfully in Version 6.0. For later versions please check that the import is compatible.

USB mass storage firmware

It is a link to GR-CITRUS's USB mass storage firmware written at manufacturing. To write the firmware, it's necessary to use Renesas Flash Programmer. And close MD jumper on GR-CITRUS to change to programming mode with USB direct connection.
At version b, the volume label becomes "GR-CITRUS_b". Version b expands the bin write area from 528 KB to 960 KB. Depending on the OS of the PC, hidden files may be written to the storage, and the actual writing area may be reduced.

GR-CITRUS USB mass storage firmware (version b, Nov 7th 2017)