20 | Ceiling DocCam II — Appendix |
RS-232 control information
Note: For best performance of the VISCA commands, set DIP switches to the ClearOne configuration when the camera is connected to the control port of a codec.
Overview of VISCA
In VISCA a device that sends commands,such as a computer, is called the controller.The device that receives commands such as a camera is called the peripheral device.The parameters of
Communication speed: 9.6 kbps/19.2 kbps/38.4 kbps
•Data bits: 8
•Start bit: 1
•Stop: 1
•Non parity
Flow control using XON/XOFF and RTS/CTS, etc., is not supported.
VISCA Communication Specifications
Command and inquiry
•Command
Sends operational commands to the camera.
•Inquiry
Used for inquiring about the current state of the camera.
| Command Packet | Note |
Inquiry | 81 QQ RR ... FF | QQ1) = Command/Inquiry |
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| RR2)= Category code |
1)QQ = 01 (Command), 09 (Inquiry)
2)RR = (Interface), 04 (camera 1), 06 (Pan.Tilter), 07 (camera 2)
Responses for commands and inquiries
•ACK Message
Returned by the camera when it receives a command. No ACK message is returned for inquiries.
•Completion message
Returned by the camera when execution of commands or inquiries is completed. In the case of inquiry commands, it will contain reply data for the inquiry after the 3rd byte of the packet. If the ACK message is omitted, the socket number will contain 0.
| Reply Packet |
Ack | 90 41 FF |
Completion (commands) | 90 51 FF |
Completion (inquiries) | 90 51 FF |
Ceiling DocCam II — Appendix |
| 21 |
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•Error message
When a command or inquiry command could not be executed or failed, an error message is returned instead of the completion message.
90 61 01 FF | Message length error (>14 bytes) |
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90 61 02 FF | Syntax Error |
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90 61 03 FF | Command buffer full |
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90 61 04 FF | Command Cancelled |
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90 61 05 FF | No socket (to be cancelled) |
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90 61 41 FF | Command not executable |
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Command execution cancel
To cancel a command which has already been sent, send the IF_Clear command as the next command.To cancel one of any two commands which have been sent, use the cancel message.
| Cancel Packet |
Cancel | 81 21 FF |
An error message will be returned for this command, but this is not a fault. It indicates that the command has been cancelled.
VISCA Command/ ACK Protocol
Command | Command Message | Reply Message | Comments |
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General Command | 81 01 04 38 02 FF | 90 41 FF (ACK)+90 51 FF | Returns ACK when a command has been |
| (Example) | (Completion) | accepted, and Completion when a |
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| 90 42 FF 90 52 FF | command has been executed. |
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| 81 01 04 38 FF | 90 60 02 FF (Syntax Error) | Accepted a command which is not |
| (Example) |
| supported or a command lacking |
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| parameters. |
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| 81 01 04 38 02 FF | 90 60 03 FF | There are two commands currently being |
| (Example) | (Command Buffer Full) | executed and the command could |
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| not be accepted. |
| 81 01 04 08 02 FF | 90 61 41 FF | Could not execute the command in the |
| (Example) | (Command Not Executable) | current mode. |
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| 90 62 41FF |
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Inquiry Command | 81 09 04 38 FF | 90 50 02 FF (Completion) | ACK is not returned for the inquiry command. |
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| 81 09 05 38 FF | 90 60 02 FF (Syntax Error) | Accepted an incompatible command. |
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Address Set | 88 03 01 FF | 88 30 02 FF | Returned the device address to +1. |
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IF_Clear(Broadcast) | 88 01 00 01 FF | 88 01 00 01 FF | Returned the same command. |
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IF_Clear (for x) | 81 01 00 01 FF | z0 50 FF (Completion) | ACK is not returend for this command. |
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Command Cancel | 81 21 FF | z0 61 04 FF | Returned when the command of the socket |
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| (Command Canceled) | specified is cancelled. |
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| Completion for the command cancelled is |
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| not returned. |
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| z0 61 05 FF | Returned when the command of the specified |
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| socket has already been completed or when |
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| the scoket number specified is wrong. |
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