I have been having this issue (maybe non-issue) for some time.
Here is my set up:
Teensy 2.0 MIDI Device
Late 2013 Macbook Pro
I am using a Teensy MIDI device in Pd.
If I connect the Teensy device, then launch Pd, I get the following error message:
could not open midi input 0 (Teensy MIDI): PortMidi: 'Invalid device ID'
could not open midi output 1 (Teensy MIDI): PortMidi: 'Invalid device ID'
Under my MIDI settings I have "Teensy MIDI" selected both as my input and output.
If I re-select "Teensy MIDI" in both dialogs of the MIDI preferences menu, and hit OK the same error message will reappear in Pd's print window.
Though I get this error, it seems to not effect the use of the device in any way.
When I connect the device to a windows machine, I don't have this PortMidi error message.
I have also connected this device to my iPhone using MobMuPlat, no issues.
Any advice would be helpful.
On startup, Pd-Extended 0.43.4 reports that it is unable to load several libraries. PureData's site explains that getting errors like these means X11 is not installed, see here.
However, X11 IS installed on my MBP, and works fine when using it to remote into my Raspberry Pi, for example.
Has anyone experienced this issue?