In order to make a custom controller that knows what strips Ardour has, the controller needs to be able to query Ardour for that information. These set of commands are for smarter control surfaces That have the logic to figure out what to do with the information. These are not of value for mapped controllers like touchOSC and friends. The controller will need to send these queries to ardour as often as it needs this information. It may well make sense to use regular feedback for things that need to be updated often such as position or metering. Here are the commands used to query Ardour: (added in Ardour 5.5)

A list of strips

/strip/list asks Ardour for a list of strips that the current session has. Ardour replies with a message for each strip with the following information:

• Strip type
• Strip name
• Number of inputs
• Number of outputs
• Muted (bool)
• Soloed (bool)
• Ssid (strip number)
• Record enabled (bool)

• The text end_route_list
• The session frame rate
• The last frame number of the session

A bus will not have a record enable and so a bus message will have one less parameter than a track. It is the controllers responsability to deal with this.

A list of sends

/strip/sends ssid asks Ardour for a list of sends for strip number ssid. The reply is sent back to the controller as one message with the following information:

• Ssid that information is for
• Each send's information:
• The send's target bus ssid
• The send's target bus name
• The send id for this strip
• The send gain as a fader possition
• The Send's enable state

The controller can tell how many sends there are from the number of parameters as each send has 5 parameters and there is one extra for ssid.

A list if tracks that send audio to a bus

/strip/receives ssid will return a list of tracks that have sends to the bus at the ssid. The reply will contain the following information for each track conntected to this bus:

• The ssid of the track sending
• The name of the sending track
• The id of the send at that track
• It's gain in fader possition
• The send's enable state

A list of plug-ins for strip

/strip/plugin/list ssid will return a list of plug-ins that strip ssid has. The reply will contain the following information:

• Ssid that information is for
• Each plugin's information:
• The plug-in's id
• The plug-in's name

A list of a plug-in's parameters

/plugin/descriptor ssid piid will return the plug-in parameters for ppid plug-in on the ssid strip. The reply will contain the following information:

• Ssid of the strip the plug-in is in
• The plug-in id for the plug-in
• The plug-in's name
• Information about each parameter
• The parameter id
• The parameter's name
• A bitset of flags (see below)
• Data type
• Minimum value
• Maximum value
• The number of scale points
• zero or more scale points of one value and one string each
• The current parameter value

The flag bitset above has been defined as (from lsb):

• 0—enumeration
• 1—integer step
• 2—logarithmic
• 3—max unbound
• 4—min unbound
• 5—sample rate dependent
• 6—toggled
• 7—controllable

While this seems complex, it is really not that bad. Minimum, maximum and value will in most cases give you all you need.