Hi,

I haven’t encountered that error message before myself. Is that in a GRC flowgraph you fashioned, or when you run the sample one I have the gr-baz/samples directory?

That block output (with the ‘msg’ type) must be used with the Message Callback block (also in gr-baz) to handle auto-tuning messages sent by the FSK4 demodulator. Alternatively, you can choose to switch off that output port in the OP25 decoder block’s properties.

Hopefully that helps – let me know!

PS: Regarding running audio_p25_rx.py, I have in the past used some variant of:

sudo ./audio_p25_rx.py -a -I hw:1,0 -g 15

‘sudo’ was necessary for creating the ‘tun’ device so I could capture frames in Wireshark. ‘-I hw:1,0’ was to select the second (non-default) sound card (you could leave this off if using the default), and ‘-g’ would have been for the gain. YMMV!

I believe there is another example of a full command line you could specify on the OP25 wiki. (You can also just put an ‘-h’ on the end to explore the available options.)