Controller Area Network (CAN) Bus has been around since the 1980’s. It was developed byBOSCH as a rugged and reliable way to move data around in automobiles. It has maturedover the years, gaining new features and popularity. Flight Display Systems uses BASICCAN 2.0B (ISO11898). It has remained virtually unchanged since the early 1990’s. Usersfamiliar with RS-485 busses popular with many Avionics vendors will find the CAN busfamiliar as it shares many of the same physical features for wiring and connectors. Theyboth use shielded/twisted pair wires as their communication backbone. They both requiresome attention to wiring practices and have similar termination requirements. The CAN busis designed specifically for “distributed master” or “peer to peer” networking compared to thenecessary “Master/slave” systems required for fast data transfers on RS-485 busses.
Sample CAN Commands
CAN Command 110
This message is typically sent by the Audio Crosspoint Switch (FD-ACS).
Payload 1 holds the pause command. Transmission of this command will cause all IFE under CMS control to pause for one second upon recipt of this message. If a long pause is intended, this message must be repeated at least each .99 seconds. Pause may be terminated immediatly upon issuance of pause command 2. PA in progress broadcasts the status of pilot PA activity. Receiving devices will assume that a PA is no longer in progress 1 second after recipt of this message. This message must be repeated at least each .99 second during a long announcement. PA may be terminated immediatly upon issuance of PA status 2.
CAN Command 160
If command = 1, connect the downstream port specified with payloads 2 and 6 to the upstream ports specified in payloads 3 and 7.
If command = 2, set the volume control to the percentage specified with payload 4. (only downstream channel 9/18/27 is affected by volume control)
if command = 3, enable compression on the the upstream port specified with payload 3
if command = 4, disable compression on the the upstream port specified with payload 3
When using the zone for switching audio and/or video set payload 1 = 0×01 then place the desired zone to be affected in payload 5. Then all that needs to be specified is the requested audio/video channel to switch to. Leave the output channel set to 0×00.
CAN Command 161
High Definition Video Crosspoint Switch
Payload 1, HD Video Output port = Which Output port to affect
Payload 2, Requested HD Video input port = Which input port to connect to.
CAN Command 170
CAN commands for front panel and remote are:
0 = STOP, 1 = EJECT, 2 = REWIND, 3 = PLAY, 4 = FFWD, 5 = OK
Payload 1 – Which Blue Ray player,
Payload 2 – Front Panel command,
Payload 3 – 8 unused
Command 168 offers more functionality than this one. Either command may be used.
CAN Command 230
Payload 1 – Command, 0 = None, 1 = raise, 2 = lower, 3 = halt
Payload 2 – Which group. Up to 8 groups can be individually affected at the same time.
Payload 3-8 Unused
Up to 8 Window Shade groups are supported. Groups are defined in a project by project basis. Group examples: Left side shades, right side, left side fore, left side aft, lav, fore cabin, aft stateroom.
Hardware that supports shades will time the activation of each interface switch. Once the Full Raise or Full lower command is issued, then the receiving device will power the window shade appropriatly for each make and model number shade that we support.
We do not expect that all window shades will raise and lower at the same rate, so user must expect mixed results with using this command to get all shades to be precisly half open.
A CAN command to halt motion is also supported.