Short-press BAND+ to enter band selection, then use the encoder to switch bands.
Several independent developers have optimized the code for this hardware. The two most prominent choices include: 1. PU2CLR SI4735 Library-Based Firmware
Ricardo Caratti (PU2CLR) developed a comprehensive Arduino library for the SI47XX chip family. Most custom ATS20 firmware versions are built on top of his foundational work. Firmware based directly on this library is highly stable, heavily documented, and regularly updated. 2. "All-in-One" Modified Sketches
Advanced firmware allows for better bandwidth control, helping you cut through interference on crowded bands. Popular Firmware Variants 1. The "PU2CLR" Library Based Firmware ats20 firmware
Ensure the cable supports data transfer, not just charging (usually Mini-USB or USB-C depending on your board version).
Enthusiasts have reverse-engineered and rewritten large parts of the ATS20 firmware, unlocking features the original designers never documented:
In this guide, we’ll dive into why you should update, the different versions available, and how to flash your device safely. Why Update Your ATS20 Firmware? Short-press BAND+ to enter band selection, then use
"The radio went from being a toy for SWL listening to a useful receiver for ham operations." — KL7MJ, commenting on his ATS-20+ after a firmware update.
Download a firmware version explicitly mapped for the ATS20 configuration, as generic SI4732 firmware maps pins differently. Conclusion
: Common choices include AVRDUDESS or the Arduino IDE . It's a different hardware platform
In simple terms, firmware is the operating system of the radio. It is the software permanently stored on the microcontroller (usually an ATmega328 or similar) that governs:
Custom firmware solves these problems by rewriting the control logic of the Si4732 chip.
This project is for the newer generation of "mini" ATS-style receivers that use a more powerful ESP32 microcontroller and a color display. It's a different hardware platform, but it shows the evolution of the design.
The ATS20 firmware is a quiet rebellion against planned obsolescence. A $30 radio, transformed not by new hardware, but by better ideas written in C and flashed over a serial cable. That’s the kind of engineering that makes you smile.