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GR-KURUMI Introduction

This is a Japanese Rulz translation contents


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GR-KURUMI is a GR reference board, the 2nd in the Gadget Renesas Project. Compatible with Arduino Pro Mini, GR-KURUMI hardware (external board dimensions, external pin layout) and software both supports Arduino language and standard libraries.  Therefore your existing sample codes written for Arduino can be used as is.

The following features are unique to GR-KURUMI and not available on Arduino Pro Mini. These features are perfect for creating small, low-power gadgets!

  • Single battery operation: equipped with a voltage booster circuit providing 0.9V to 3.3V (or 5V) voltage.
  • Clock with alarm: realizing high-precision real time counter (RTC).
  • Power-saving mode: easy control of RL78 standby mode (STOP/SNOOZE) with the default library.
  • KURUMI-chan’s dazzling LED hair ornament: reference board includes an image of “KURUMI-chan” with an LED hair ornament that lights up in full-color.


  • On-board MCU: RL78/G13 (R5F100GJAFB 48-pin QFP)
  • ROM/RAM: 256KB/20KB
  • Data flash: 8KB
  • Main clock: 32MHz (embedded in MCU)
  • Sub-clock: 32.768kHz
  • Operating voltage: 2.7V ~ 5.5V*
    *Minimum operating voltage of this is 1.6V, but the library supports from 2.7V due to the 
    specification compliance.

Creating Sketches

Basically, the Renesas Web Compiler is used to create sketches but e2studio and CubeSuite+ can also be used as a local environment.

The RLduino78 library cannot be used to develop Arduino sketches in combination with CubeSuite+, as the library was created with the GNU compiler GNURL78.

Web Compiler login:

When using e2studio:

Programming a sketch in GR-Kurumi

Unlike GR-SAKURA, GR-KURUMI cannot be programmed like a USB memory. Just as with the Arduino Pro Mini, your sketch is programmed using a module manufactured by FTDI that includes a USB-to-serial conversion IC. The photo shows the connection between GR-KURUMI and the USB-to-serial module. Kurumi Writer is provided as the dedicated programming software for GR-KURUMI. It can be downloaded as a file from the project created with the Web Compiler. Both Windows and Mac versions of Kurumi Writer are available.


FTDI modules that have been tested with GR-KURUMI:

Hardware Information

Software Information

Contributors Comments


We outlined all the GR-KURUMI information here as it was difficult to figure out whether info was related to GR-SAKURA or GR-KURUMI!


KURUMI debut!


Congrats on the debut! I hope you have fun with KURUMI.


Can I use, for example, a 20-pin type G13 when developing a program for KURUMI-chan with the Web compiler?


You should be able to. According to the device UM, the functions are the same for 20 pins and 48 pins. And, sorry for the slow-as-a-turtle response!


No worries! BTW, Akizuki seems to be handling IC lead frames these days.
It got me imagining a narrow dip 28-pin Kurumi-chan!


Darn, and I was just at Akizuki yesterday. I need to go buy one!