[OZAPRS] Questions about tncs

Matthew Cook vk5zm at bistre.net
Tue Jul 10 11:22:56 AEST 2018

Hi Max,

Check your TNC code for Software DCD detection or similar, you need some
form of DCD to do CSMA properly.



On 6 July 2018 at 11:50, Max Bainrot <mbainrot at gmail.com> wrote:

> Hi Matt
> I will definitely check that out, I have both the radios on open squealch
> because it seemed like the squealch control on the wuexon handheld was a
> bit slow to open.
> I haven’t implemented the leds as they weren’t in the schematic I used but
> looking in the source there was allocation for some indicator leds (one of
> the tncs uses a different ptt pin because of the non 0.1” header offset so
> had to tweak the pin allocations as initially I had stuck ptt issues) I’ll
> check tonight
> It is sending the acknowledgment though, I had a rtlsdr setup with basic
> decoder and I can see the two way traffic but the open squelch might be
> what’s slowing it down enough to miss the fast ACK
> 73s
> Max - VK2NMF
> On Fri, 6 Jul 2018 at 9:40 am, Matthew Cook <vk5zm at bistre.net> wrote:
>> Max,
>> Check how your TNC is detecting if the channel is busy.
>> Not many TNC's worked well in the day with open mute, in fact we used to
>> retrofit a small board to TNC's that would detect the AFSK tones and drive
>> the carrier SQ input on our TNC's.    What you describe is classic CSMA
>> "hold off" due to a busy channel.  I think you'll find that your TNC thinks
>> that the channel is busy, so it's not transmitting.  Since there is no way
>> for Xastir or Yaac to know if the packet has left, it retries.
>> Does your TNC have a carrier squelch input or software DCD (data carrier
>> detect), it may even have a DCD (or RX decoded) LED  if so what is it
>> telling you ?
>> I'm not familiar with your TNC per se, but can remember back to the time
>> where small fury creatures from alpha centari were real small furry
>> creatures from alpha centari.
>> 73
>> Matthew
>> VK5ZM
>> On 6 July 2018 at 08:02, Max Bainrot <mbainrot at gmail.com> wrote:
>>> Hi all,
>>> I’m fairly new to the whole packet radio shenanigans and been tinkering
>>> away for the past couple of days and have been running into gremlins
>>> I’m currently using a mobilinkd tnc2 firmware on a home brew shield on a
>>> 16mhz Arduino which works o.k. but it seems like it has a really long delay
>>> between transmitting and receiving, like long enough for default settings
>>> xastir (more on that later) to get impatient and retransmit like 6 times
>>> before entropy has it that the acknowledgement makes it through.
>>> Is this just because the firmware is asking too much of the poor little
>>> atmega328p or is it something else? Doesn’t appear to be the radio(s) as I
>>> have two radios, wuxeon handheld and a tyt md380 (working 439.100 as there
>>> is no local digipeter) and switched radios between the sender and receiver,
>>> updated firmware on both Arduinos, the tncs where crashing before I
>>> attached ferrites to the cables but that appears to have fixed the issue.
>>> I haven’t confirmed beyond all doubt if the tnc is still randomly
>>> rebooting or not, going to hook the bus pirate (it has high z serial mode)
>>> up to the tnc’s serial lines to see if it’s singing it’s song of it’s
>>> people every time it transmits.
>>> The reset on connect jumper is enabled btw, is it xastir closing and
>>> reopening the serial port?
>>> I’m also using default settings in xastir for kiss tnc which could be
>>> another mistake I’ve made?
>>> Now onto the topic of xastir :) does anyone know where I can find the
>>> setting to slow it right down??? It resends wayyyyy too quickly which is
>>> both bad form and severely aggrevates the problem. I’m also thinking of
>>> rocking YAAC as it’s java based so I can use the latest version on all
>>> operating systems and I can slow it right down.
>>> Reason I am running down the open hardware and/or diy route is I am
>>> intending on cooking up a raspberry pi zero hat/cape, so want to leave
>>> options open for my future shenanigans.
>>> Many thanks in advance,
>>> VK2NMF
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