Dan Gliebe wrote:

> Does anybody here know anything about camera blocks and sending serial 
> data to them?  I have a Hitachi VK-S274 color camera block, commonly 
> used in PTZ Dome cameras.  I have the datasheet with the serial protocol 
> here..  http://ip.gliebetronics.com:800/hitachi/S274R_Comm_E11.pdf  It 
> is simple enough, but I just can't seem to get the camera to do anything 
> when I send commands.
> 
> A friend and I have tried sending data to the camera block using a PC 
> com port and using a BS2.

BS2 with or without an RS232 level translator?

>  I found that I can successfully capture data 
> at 4800 baud 8,n (non-inverted)

N stands for NO PARITY, not 'non-inverted'.
Your other 4 choices are Mark/Space/Even/Odd parity.
Only even or odd are useful for error detection.
Anything other than N gives you only 7 data bits.

> that is sent to this camera from a 
> SpeedDome Ultra V dome camera.  I just can't seem to send data to the 
> camera and make it do anything.  We're rather confused and any tips or 
> advice would be greatly appreciated.  Can a PC Com port send 
> non-inverted data?

No.

>  Maybe I need some sort of serial interface chip?  

Maybe.
Seems more likely that you have the wrong parity chosen.

Maybe the camera requires that you send it an address before
you can send it commands.

> What does non-inverted really mean?.. since inverted captured only garbage.

Non-inverted means exactly that. NO INVERSION.
RS232 transceivers invert the signal polarity.
Mark is -12V. Space is +12V.
TTL mark is 5V. Space is 0V.
An idle line sits at Mark level. Start bit is a space. Stop is mark.
All RS232 interface chips invert the data.

4800,N,8,1 means 4800 baud, NO parity, 8 bits 1 stop bit.
The N does NOT mean 'no inversion'.


Hopefully this gets you pointed in the right direction.

Robert

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