[aprssig] usb - serial

[Wes Johnston, AI4PX]

The only problems I've heard of with usb serial adapters are on the transmit
side of things.  Many prolific usb adapters won't send a packet out until
they see a CR or LF... of course when you are in KISS mode, the packets
terminate with $c0, so they usually end up getting sent when the next
packets comes along, so they stay one packet behind.  The reason for this I
think is that the packet _data_ actually ends with CR, but the packet
_frame_ ends with $c0... so the serial adapter sends the packet out when it
sees the CR, but that's not enough to make the TNC transmit since the KISS
protocol is awaiting for the $c0 that denotes the end of the frame.  So the
TNC is essentially sitting on go, waiting for that next $c0 to come along.
When the next frame is sent, the data portion of the packet once again ends
in CR, the usb serial adapter sends it, and in doing so, the TNC finally
gets to see the $c0 it needs to go ahead and TX the previous packet.  Hope
this makes sense.

In normal CONVerse TNC mode this isn't a problem since each packet ends with
a CR and/or LF.

I'm not aware of any receiving problems with USB adapters though.

Wes
---
God help those who do not help themselves.


On Sat, May 1, 2010 at 17:54, Ben Lindner-VK5JFK <vk5jfk at activ8.net.au>wrote:

> Hi All,
>
> Is anyone using a Vantage Pro2 serial unit with the APRS data logger (
> different to standard data logger ) with a USB-Serial cable.
>
> If so, have you encountered any problems
>
> cheers
> Ben
> VK5JFK
>
>
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