ASL run simpleusb-tune-menu

I think you are on the right track… sorry I can’t help more with this at this point you are in front of it and looks like you are thinking of it logically.
Thanks for posting all your trials and errors as I am sure it will lend favor to others.

Keep posting and I and or others will help where we can.
When you are certain your circuits are correct and still not working, let us know.

I’m not sure there is any published threshold values for the moded sound fob as I think they can all be a bit different somewhat. You will need to do some trial and error to judge for yourself.

Used another schematic that showed a 10k resistor with 5V and calculated 6.6K with 3.3V .
I had a 6.8k resistor that actually measured 6.6k and tried it. Still no audio. Have to examine source, HTX-202, mic input on FOB and if those look good get into Asterisk settings. Time to drag out the oscilloscope.

I found this after a search and am chewing on it!

kuggie

Board Member

May '15

All FOB’s, including the URI, but the exception of a RIM, require a
logic signal capable of sinking to near ground potential on the COS
and CTCSS inputs (active low). No matter if you choose a upright
logic or inverted (in software) the hardware needs to provide a
signal that goes nearly to ground. In other words, it needs to sink
to ground potential. Many radios provide a voltage when the logic
state is valid (active high), these don’t interface to a FOB or URI
well. A pull-down resistor can help in these situations, but it’s
best to use the right type of logic circuitry to feed these logic
inputs. Since the CM119 IC is internally pulled up, changing its logic state
requires a ground. This was originally done by mechanical switches
in a FOB, but must now be done with transistors or whatever logic is
available from the radio. Protection diodes on these inputs help to
complicate the situation because they have a voltage drop. The
hardware inputs of the CM119 require that the voltage drop to about
1V or less to become valid. While Schottky diodes keep this to a
minimum (because their voltage drop is about 2/3 that of a silicon
diode), you still need a solid pull to ground logic signal for a
valid COS or CTCSS signal for a URI or simple FOB.
Some radios are difficult to properly interface the COS and CTCSS
logic to a FOB or URI. I have a board that I designed just for the
occasion:
My suggestion is to use a NPN transistor or FET to invert the active
high TKR-850 logic for a solid pull to ground. A 2N2222 or 2N7000
can work well.
Kevin

This is the only configuration I get a Busy on the HTX-202.
I get audio and RX on my EchoLink connection intermittently when I use a portable on my simplex node frequency. It’s not software.
I’m missing something in this circuit design?