Arduino R4 Minima uses a Renesas R4 Microcontroller and someone from Renesas (Leonardo Afonso) ported NuttX to this microcontroller.

The process to get NuttX working on this board is straight-forward:

Get the source code (I’m assuming you already have the git tool and arm-none-eabi toolchain installed on your Linux)

Configure the board:

$ ./tools/configure.sh arduino-r4-minima:nsh

Compile:

$ make -j
...
LD: nuttx
Memory region         Used Size  Region Size  %age Used
           flash:      139768 B       256 KB     53.32%
            sram:        7064 B        32 KB     21.56%
          idcode:          16 B         32 B     50.00%
CP: nuttx.hex

There is a trick to flash the firmware: you need to use a male-male wire and connect BOOT to GND and reset the board, the

$ ./rfp-cli -device ra -port /dev/ttyACM0 -p /tmp/nuttx.hex
Renesas Flash Programmer CLI V1.11
Module Version: V3.18.00.000
Load: "/tmp/nuttx.hex" (Size=393264, CRC=678FB20E)

Connecting the tool (COM port)
Tool: /dev/ttyACM0
Interface: 2 wire UART

Connecting the target device
Speed: 115,200 bps
Connected

Erasing the target device
  [Code Flash 1]       00000000 - 000227FF
Writing data to the target device                                               
  [Code Flash 1]       00000000 - 000221F7
  [Config Area 1]      01010018 - 01010027                                      
                                                                                

Disconnecting the tool

Operation successful

Remove the BOOT to GND wire and reset the board.

Connect a USB/Serial (3.3V) to GND, pin 0 (RX) and pin 1 (TX), use minicom at 115200 8N1

You will see:

NuttShell (NSH) NuttX-12.8.0
nsh> uname -a
NuttX 12.8.0 c2309b6e03 Mar 28 2025 16:21:09 arm arduino-r4-minima
nsh>