Controller Area Network (CAN) Bus has been around since the 1980’s. It was developed by BOSCH as a rugged and reliable way to move data around in automobiles. It has matured over the years, gaining new features and popularity. Flight Display Systems uses BASIC CAN 2.0B (ISO11898). It has remained virtually unchanged since the early 1990’s. Users familiar with RS-485 busses, popular with many Avionics vendors, will find the CAN bus familiar as it shares many of the same physical features for wiring and connectors. They both use shielded/twisted pair wires as their communication backbone. They both require some attention to wiring practices and have similar termination requirements. The CAN bus is designed specifically for “distributed master” or “peer to peer” networking compared to the necessary “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.