I pulled mine apart to try to see if there was a label that would provide a clue about which version to write it it - there isn't. A tip: you can just undo the top screws front and back to get the lid off. Watch the speaker connected by short wires
On power on, it displayed V1.1.5 of the library by PU2CLR. After upgrade it now shows 3.04.
I followed the instructions on swling.com but used Arduino 1.8.13 on macOS just fine.
Basically the steps are:
- Select Arduino Nano
- Select ATMega 328P (Old boot loader)
- Install libraries:
- TinyOLED-Fonts (it's a dependent)
In the source code of the sketch there are some settings to adjust if you like such as default volume.
Before upgrade here's the splash screen:
It's quite a sensitive receiver and sideband works pretty well. Here's an example.