# ZephyrOS weather app ported from Arduino GIGA R1 to UNO R4

> **Key takeaway:** A resource-intensive ZephyrOS-based weather station app was successfully optimized to run on the much more constrained UNO R4 WiFi board.

**Published:** 2026-10-09T10:54:54+00:00 
**Source:** Arduino Official Blog 
**Category:** open-hardware 
**Canonical URL:** https://fosswire.org/news/zephyros-weather-app-ported-from-arduino-giga-r1-to-uno-r4.html 

## Summary
Arduino Forum users KurtE and Merlin513 have demonstrated that a ZephyrOS-based weather station application can run on the UNO R4 WiFi. Originally developed for the high-performance GIGA R1 WiFi, the app required significant optimization to fit the UNO R4's much smaller memory and storage limits. The porting process involved switching display libraries and simplifying GUI elements to accommodate the hardware constraints.

## Optimization for constrained hardware
- The original GIGA R1 WiFi uses a dual-core **STM32H747XI** (480 MHz, 1 MB RAM, 2 MB Flash).
- The target UNO R4 WiFi uses a single-core **Renesas RA4M1** (48 MHz, 32 kB RAM, 256 kB Flash).
- The application runs on **ZephyrOS** (Arduino Core on Zephyr 0.90.0).
- Optimization techniques included switching display libraries, reducing the color palette, and minimizing image sizes to fit within the 256 kB flash and 32 kB RAM limits.

## Why it matters
The successful port demonstrates the viability of using ZephyrOS on lower-spec Arduino boards, moving away from the discontinued Mbed development.