I reused the Raspberry Pi Pico board originally designed for my R909-tester project as the CPU board for my R909-DSP airband receiver.

The existing receiver firmware required only minor modifications, and the receiver is now working.

The R909-DSP project is my ongoing DIY development of an airband receiver.
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For the R909-tester, I designed a PCB using a **Raspberry Pi Pico Zero module from Waveshare**. I made a mistake when placing the I2C connector for the OLED, so the first PCB was not assembled as intended.

https://hackaday.io/project/206070-r909-tester-a-modular-rp2040-zero-instrument/log/249589-r909-tester-pcb-is-ready-but-found-a-bug-during-assembly

Instead of throwing it away, I decided to reuse it as an experimental CPU board for the R909-DSP.

I ported the existing R909-DSP receiver sketch to the Pico.

It now works with the existing TA2003 + Si5351A + Si4732 RF front-end.

The R909 CPU has evolved through several platforms:

ATmega328P → ESP32-C3 → Raspberry Pi Pico

One pleasant surprise is the amount of memory available on the Pico. Compared with the ATmega328P, there is plenty of room left, so I can even add Japanese character display support.

For the next step, I need to tune the RF front-end for better **sensitivity and stability**.

I will continue this development as R909-DSP6.