mustang-midi-bridge

Allow Fender Mustang series guitar amplifiers to be controlled by MIDI messages

What's New

The command line parameter for MIDI controller port is now assumed to start at 0 rather than 1 in order to match the way Linux ALSA enumerates devices (see 'Run' below).

The program has been updated to run as a non-privileged daemon process. You can still invoke it on the command line, but there will be no output to the console and it no longer responds to keypress input. Enter Ctrl-C (SIGINT) to exit.

I have added the first version of a runtime framework that starts and stops the program automatically based on attached MIDI devices. This seems to be working on a Beaglebone SBC, but has not been extensively tested or documented yet. There is a small amount of customization required to account for your specific amp model and MIDI controller interface. Technically oriented users can probably work this out, otherwise wait a bit until I can refine the packaging and arrange to have the various pieces configured from a common setup file.

Support added for amp and effects models specific to the Mustang v2 products. This has had only limited testing.

Added a python script to exercise the bridge.

Introduction

The intent is to implement the published MIDI spec for the Fender Mustang Floor pedal with whatever extensions are necessary to expose features added to the 'v2' series.

I am developing on a Ubuntu Precise desktop machine, but the code is routinely tested on a Raspberry Pi 'B' and Beagelbone Green to ensure these remain viable deployment targets. At this point I'm still experiencing issues with USB latency on the RPi and am currently recommending the BBG for real-world use.

A special thanks to the original developer and contributors to 'PLUG', from whence the Mustang USB interface code is stolen.

For the non-techies

I have written a Wiki page here:

https://github.com/snhirsch/mustang-midi-bridge/wiki/Install

that attempts to walk less technical users through the installation and build process on Raspberry Pi or Beaglebone. It's hard to know what level of detail to hit and suggestions or comments would be appreciated if I've omitted or glossed over something critical.

Status

The Mustang Floor MIDI spec is about 99% implemented, with only the following exceptions:

• Tuner On/Off

  Will require substantial rework of the program to make this work reliably.

• Amp Bypass

  It's possible to turn the amp "off" with CC#68 0, but this mutes all sound rather than acting as a bypass. I don't think the combo amps support signal bypass, but haven't given up yet.

• Pedal Volume

  I'm not sure why this is needed, since all continuous controllers are directly accessible through CC messages. Since the FUSE application cannot issue these commands it will be guesswork to figure out the protocol - if it's even supported on the combo amps.

• FX Insert

  Not supported on the combo amps

• Tap Tempo

  If I can figure out how to do this from FUSE I can code it.

I'm using USBPcap and tshark to snoop communication and plan to implement all features accessible from the Fender FUSE application. However, some targets listed in the MIDI spec (e.g. amplifier on/off, tuner mode) are not controllable from FUSE and it may take some time and luck to figure out the protocol.

Prerequisites

• For Ubuntu Precise or Debian Jessie:

  • libasound2
  • librtmidi-dev
  • libusb-1.0-0-dev
  • libjack0 (Precise)
  • libjackQ (Jessie)

Would appreciate feedback on requirements for other distributions.

OS Configuration

• Add the id of the user who will be running the bridge to the 'audio' and 'plugdev' groups. That user should then log out and back in to make the groups effective.

• As root, copy the file '50-mustang.rules' to /etc/udev/rules.d and refresh the system with 'udevadm control --reload'.

There may be slight differences in requirements for other distributions.

Build

$ make opt

or

$ make debug

as appropriate

Run

Both the amplifier and MIDI source should be connected first, then:

$ mustang_midi  midi_port#  midi_listen_channel#

NOTE1: I'm not sure about other platforms, but on Linux the MIDI port number is equivalent to the ALSA card index. I had originally treated port as 1..n, but since ALSA (and JACK? Not sure..) starts at 0, this has now been changed. You can find the card index for your controller by connecting it to the computer and examining the pseudo-file, e.g.:

$ cat /proc/asound/cards 0 [PCH ]: HDA-Intel - HDA Intel PCH HDA Intel PCH at 0xf7530000 irq 30 1 [Interface ]: USB-Audio - USB MS1x1 MIDI Interface M-Audio USB MS1x1 MIDI Interface at usb-0000:00:14.0-1, full speed

To accept MIDI messages from devices behind the M-Audio interface you would now specify '1' as the MIDI port value.

NOTE2: RPi and BBG are a bit fussy about enumeration of new USB devices. If you are not getting proper communication, quit the program and try replugging both the Fender amp and MIDI controller after those devices are powered up.

NOTE3: I've had success using a passive USB hub with the single USB on the BBG, but YMMV since most USB<->5Pin MIDI converters draw some degree of bus power. A powered hub might be necessary in some situations.