New Backend: "Bevin"

[oubiwann]

@gbevin has a couple of open source CLI tools for sending/receiving MIDI:

• https://github.com/gbevin/SendMIDI
• https://github.com/gbevin/ReceiveMIDI

For situations where these are the only thing needed by a user, Extempore would be overkill (and the bevin backend would thus be quite welcome).

Ideally, we'd be able to start up two OS processes, one for each, put them in the supervision tree, and then pipe (using Erlang ports) commands as needed to these ... will have to look at the tools more to see what's possible. Even without that, though, it might still be worth the cost of an OS process for every command as a tradeoff for the increased simplicity of a backend like this.

Branch:

• epic/80/bevin-backend

Tasks/features (some of this might get broken out into separate tickets):

• [x] Download & install the tools and explore their capabilities
• [x] Add configuration for new backend
• [x] Decide upon module prefix (maybe bv?)
• [x] Update the supervisor to only start the backend that's active
• [x] Create gen_servers for each, with spawned ports for the OS process
• [x] Select appropriate restart strategy(ies)
• [ ] #87 - Add health checks for ports/processes
• [ ] #83 - Add utility functions for converting from beats, tempo, notes timings, etc., to time strings (of the form HH:MM:SS.mmm)
• [ ] #84 - Add utility functions for quantizing notes
• [ ] #85 - Adapt xt.midi:cc, xt.midi:cc-ramp, etc. for use with this backend
• [x] Display banner after backend starts
• [x] Add utility functions for getting CLI tool versions
  • [x] done during system setup, so only one call to get the versions is ever made
  • [x] os:cmd call should probably go in sysconfig module
  • [x] update system state upon bring-up
  • [x] add state-based API call for getting version info from cached data
• [x] #88 - Properly kill OS processes upon exit
• [x] #89 - Capture ^C and ^D to exit (and kill OS processes) on interrupt
• [ ] Display the appropriate / configured REPL prompt after banner display
• [ ] Add examples

Also:

• [x] #92 - Updates to Extempore required as a result of these changes

[oubiwann]

Video for setup on Mac:

• https://www.youtube.com/watch?v=_o1kg0IbetY

First 1/3rd is for beginners. Notes on the rest:

• an Erlang port can read receivemidi's output
• multiple ccs can be sent at the same time
• Bidule might be nice to put in the docs to help users more easily set up MIDI on their systems
• yes! sendmidi -- is supported!

[oubiwann]

If this goes well, I might demo this at the next conference! (CodeBEAM in March).

[oubiwann]

Downloaded:

• https://github.com/gbevin/SendMIDI/releases/tag/1.0.15
• https://github.com/gbevin/ReceiveMIDI/releases/tag/1.1.0

[oubiwann]

Added a question at https://github.com/gbevin/SendMIDI/issues/29 for guidance in adding MIDI time clock & code support in the backend.

[oubiwann]

Basic reading and writing to the open Erlang ports for the OS process is working quite well (as expected). One problem so far, is that exiting the server doesn't seem to be causing the receivemidi process to exit. sendmidi exits just find, though.

[oubiwann]

Basic reading and writing to the open Erlang ports for the OS process is working quite well (as expected). One problem so far, is that exiting the server doesn't seem to be causing the receivemidi process to exit. sendmidi exits just find, though.

This has its own ticket now: #88