[App_rpt-users] Manually key ASL from command-line

[Kevin Custer]

James,

 From your description, and my extensive knowledge of the CM119, CM119A 
and its variants, I believe the chip is bad.  You can try to add a 10k 
pull-up externally to 3.3V from pin 48, but I doubt it'll work.  
Hopefully you are using protection diodes on these hardware inputs, 
otherwise, that's what blew it up.  Why?  Here's why....

There is much confusion surrounding the COS and CTCSS inputs to the 
CM1XX chipsets.  Here is a dissertation I wrote some time ago, that 
hopefully explains the situation well:

The COS and PL "hardware" logic inputs on CM1XX based radio adapters 
were originally the volume-up and volume-down functions, actuated by 
manual (push button tactile) switches in a standard audio adapter 
(FOB).  These inputs are internally pulled high, to 3.3 V, and have to 
be pulled low enough to become valid.  As such the push-button switches 
made a good ground when depressed, as that's what the other side of the 
switch was tied to - ground. Most AllStar radio adapters use protection 
diodes (BAT-43's) that don't allow voltage to be sent into the CM1XX 
chip.  If voltage is allowed to be inputted to these pins, the chip is 
destroyed. So - with the diodes in place, it doesn't matter what voltage 
is present on the COS or CTCSS hardware inputs, because voltage on these 
pins doesn't make anything happen, and because of the protection diodes, 
doesn't hurt anything if voltage is present. Pull-up resistors are 
totally unnecessary, because we need a ground to assert the condition.

Okay, so the CM108/119's logic inputs are looking for a ground to be 
valid.  This "active low" condition is required NO MATTER if the setting 
in the conf file is upright or inverted.  So - the setting in the 
configuration file doesn't change the fact that the adapter needs an 
active low to be valid and assert the condition. All this software 
setting does is change if the low condition exists when the radio is 
hearing a valid signal, or when it's not.  Using a DMM, you can read the 
voltage on the CM119 side of the BAT-43 diodes to see if the logic level 
is properly changing from 3.3V (2.4 in some instances) to 0.0 (or a few 
tenths of a volt).

Not all radio logic signals are created equal.  Some logic circuits can 
source current, but lack the ability to sink. Sometimes active high 
circuits (circuits that provide a voltage when the state becomes active) 
don't have the ability to pull to ground very well. These circuits may 
not have the capability to pull the COS and CTCSS inputs low enough on 
the radio adapter to become valid/active.  A pull-down resistor can 
help, but nothing beats a real active low circuit.  A 2N2222 (or similar 
NPN transistor) with the emitter grounded usually works well.

Hope this helps...

Kevin



On 5/2/2019 4:07 PM, James WD0JB wrote:
> All,
>
> Is there a way to manually key from the Asterisk command-line, or 
> other, to transmit when using a USB fob without the COS activated?  I 
> have a fob that I cannot key with pin48 on CM119, but I still want to 
> use the fob, possibly as a radio-less node with a headset / 
> microphone. I cannot key with pin48 on the CM119 because there is not 
> the proper voltage on that pin to pull down.
>
> If anyone has any suggestions, I am using the SYBA UAUD compact fob.  
> This Amazon link: https://www.amazon.com/dp/B001MSS6CS
>
> Also, these fobs (I've tried 2 so far) have an eeprom chip on them 
> (FT93C46A).  Any others I've seen used in this manner from forum posts 
> do not appear to have this chip, however, removing the chip does not 
> resolve the issue.  One fob has 200mv the other has about 1volt.  
> Nothing else connected to the pin.
>
> Thanks in advance for any help.
>
> James