This library provides a convenient interface to the Si4702 and Si4703 FM radio chips from Silicon Labs. It targets the Raspberry Pi Pico and similar RP2040 based boards using the C/C SDK.

Main controls:

• FM band (87.5-108 / 76-90 / 76-108 MHz)
• channel spacing and de-emphasis
• seek sensitivity
• volume (with extended range)
• softmute (mutes noisy frequencies)
• mono / stereo output

Features:

• tune / seek the next station without blocking the CPU
• monitor signal strength and stereo signal
• RDS (only on Si4703) - decode station name, radio-text, and alternative frequencies

A test program is included. To interact with it, establish a serial connection through USB or UART.

Si470X - test program
=====================
- =   Volume down / up
1-9   Station presets
{ }   Frequency down / up
[ ]   Seek down / up
s     Toggle seek sensitivity
0     Toggle mute
f     Toggle softmute
m     Toggle mono
i     Print station info
r     Print RDS info
x     Power down
?     Print help

Follow the instructions in Getting started with Raspberry Pi Pico to setup your build environment. Then:

• clone repo
• mkdir build, cd build, cmake ../, make
• copy fm_example.uf2 to Raspberry Pico

Communication is done through I2C. An additional GPIO pin is used to reset the FM chip during powerup. The default pins are:

• pico_rda5807 is a similar library for the RDA5807 FM radio chip.

Valentin Milea [email protected]