VideoHub 40x40 Leitch Server mode RS-422 communication

Hello,

I need some clarification about the format of the RS422 Communication protocol when in Leitch Server mode. For example, to the query

@ S?0<CR>

would the reply contain 2 carriage returns and a linefeed, like

S:00,D<CR><CR><LF>
S:01,F<CR><CR><LF>
......

or just 1 carriage return and a linefeed, like

S:00,D<CR><LF>
S:01,F<CR><LF>
......

Any help would be greatly appreciated!

Hi,

I only interfaced with the 16x16 but I assume it would be the same. When monitoring the port, I received multiple line ends pairs (CR/LF). Sometimes two pairs, sometimes three but always in order and in pairs.

Videohub.png (48.04 KiB) Viewed 3632 times

Regards,

Dave.

Dave,

Thanks very much for your answer. It make sense to see pairs of CR/LF. But what I'm seeing in my setup is CR/CR/LF. Any idea/suggestion why it is occurring?

Hi,

Over the years BMD have changed the documentation and/or firmware regarding the RS422 protocol line ends. Sometimes it's <CR><LF> other manuals show just <LF>. When I wrote my code (in 2012), I needed to just ignore the <CR> and key on the <LF>. My other thought is whether the baud rate is out of spec, however I'd expect more random missing characters in this situation. Do you have access to a digital storage oscilloscope to monitor the hardware signal?

Regards,

Dave.

After several days of testing, it has been very consistent in showing CR/CR/LF. I'll accept this as the norm for now. It's interesting to see that different models/firmware are displaying slightly different line ends implementing the same Leitch pass-thru protocol.

Thanks again for your help!

Hi,

I think you'd be better off not relying on a precise line ending sequence - if BMD change the specification again in updated firmware (if you load it) your code could break.

Regards,

Dave.

You're right. I'm not relying on it, especially after seeing the differences between our devices already.