Running TLS on a Tiny MCU – RP2040 + W5500 with Only 32 kB RAM & 128 kB Flash
A clean, real-world test showing that a full HTTPS web server (TLS 1.3) can run on an RP2040 using just 32 kB RAM and 128 kB flash when paired with the W5500.
0
Components
Hardware components
WIZnet - W5500
x 1
Raspberry Pi - RP2040
x 1
Arduino - Arduino IDE
x 1
Cesanta Software Ltd - Mongoose
x 1
platformio - PlatformIO IDE
x 1
Project description
Introduction Let’s start with the question everyone asks: How small can an MCU be and still run proper TLS? The answer is surprisingly small — an RP2040 + W5500 runs full TLS 1.3 with only 32 kB RAM and 128 kB flash. WIZnet Product Integration The W5500 is the star here. It handles the complete TCP/IP stack in hardware, so the RP2040 only communicates over SPI. Almost no RAM or CPU time is spent on networking — perfect for adding TLS on tiny microcontrollers. Technical Implementation Hardware wiring is extremely simple: Pico SPI0 → W5500 (CS=GP5, SCK=GP2, MOSI=GP3, MISO=GP4, RST=GP6) 3.3 V +…
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