[aprssig] UI-View, Tiny2 TNC and collisions!

[John Langtry, VE3NEC]

Greetings Michael,

It's really refreshing to find someone concerned with collisions;
particularly where Level 2 (unconnected) frames are concerned.

Anyway, a place to start is to see if the hardware is really seeing
the channel busy status; granted the LED is indicating that ... but
next step is to check pin 19 (DCD A) of the UART /SIO chip is
changing state with the LED as you vary the squelch control.
This pin should go from about 0 volts DC to 5 volts as measured
with a logic probe or VOM.

If it is, it's possible (but unlikely) that the SIO chip is defective.
Or more probably that the KISS code itself is not checking the DCD
line.

If it's not changing state at the SIO, check out the path between
the front panel LED and the SIO chip. My schematic is not handy,
but as I recall, there is an option (JPD) which selects whether you
want to have the channel busy follow the the modem chip, an external
lead from the radio, or the optional digital carrier squelch circuit.
The latter will be apparent as there will be a little daughter board
underneath the 3105 chip.

Hope this helps, and please let me know if I can be of further help.

vy 73 de John VE3NEC