UTC and/or Coaxitron, electrical characteristics ?

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hello

 

i am looking the electrical characteristics (plus protocol ideally) of UTC or Coaxitron protocol

and/or if exist any special IC that decodes it !

 

for those don't know , its a relative new standard to transmit PTZ control data of surveillance cameras over the same coaxial cable, video transmitted too.

thats for reducing the need for extra ptz data cables

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plouf wrote:
its a relative new standard to transmit PTZ control data of surveillance cameras over the same coaxial cable, video transmitted too.

Hardly.  Coaxitron has been around for nearly 30 years. and all it does is put the usart TX pin of a micro controller on the coax during the vertical blanking interval for PTZ controls.    Pelco has their format, and it a D format, or a P format 

 

What 'decodes' it is the PTZ itself.  Now what takes care of the timing in the transmitter, is a video sync separator like the common LM1881:

 

https://nootropicdesign.com/ve/d...

 

Usually this is tied to an interrupt pin on the micro which then send the data burst, and then HI-Z's its output driver so as not to affect the video signal.  This sync signal is also used for superimposition of graphical text information in the stream as well.

 

Hope this helps.

 

JIm

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

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Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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I looked it up guys... Pan Tilt Zoom

 

Imagecraft compiler user

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pelco d and pelco P are 485, separated 2 cable format afaik

 

so you say that during vblank the (5volt ?!) pin of usart is aplied to coax, and how fast this transmition is ?

 

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plouf wrote:
pelco d and pelco P are 485, separated 2 cable format afaik

Coaxitron also sends PelcoD and P formats.    There is also a real old version of Coaxitron that was obsoleted in the early 90's or so, but that's not important.

 

plouf wrote:
so you say that during vblank the (5volt ?!) pin of usart is aplied to coax, and how fast this transmition is ?

 

Not the +5volt levels of the common USART directly.  What is done is the USART output was connected to a digital buffer/driver with an enable input. The output was connected to the Coax through a resistor.  75 - 100 ohms if I remember.

 

Sequence of events is as follows:

 

1) sync separator vertical sync output tied to IRQ input of micro

2) IRQ fires, enabling the output buffer/driver which now is active - sitting at 0v

3) Micro sends commands to USART which outputs them to the buffer/driver which then drives the Coax

4) when transmission is complete the micro disables the buffer/driver - which now sits in a HI-Z condition

5) micro sits in holding pattern waiting for next sync interrupt

 

Keep in mind that if there is nothing to transmit to the PTZ, then the micro does nothing.

 

the speed was about 1.5megabaud  I would have to find my notes for 20+ years ago when I worked on fiber modems for Coaxitron

 

Jim

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user