[App_rpt-users] GE Mastr III and DMK USB-URI

Kevin Custer kuggie at kuggie.com
Mon Mar 11 12:32:19 UTC 2019 

I apologize - this is long, but it's necessary (I think)?

The COS and PL "hardware" logic inputs on the radio adapter 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.

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 3.3 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. Use the 
collector to feed logic to the radio adapter and use a suitable bias 
resistor to the base.  Of course, if you happen to find a place that 
goes to ground when the receiver is active (or vice versa), it should 
work as-is, again, as long as it's active low. The resistor can be any 
wattage 1/8 watt or higher. Its value isn't critical either, a 1k to 47k 
would likely be acceptable.

Is the radio adapter a URI, URIx, or URIxB?

Hope this helps..

Kevin W3KKC


On 3/11/2019 8:19 AM, Bret Taylor wrote:
> Marshall is correct, and Marshall has helped me with this project as 
> well.... Thank you Marshall.
>
> I suspect there has to be an underlying configuration file still. It's 
> still Debian under the hood. If I can get to it, and modify it... that 
> is still to be seen.
>
> What wattage does the 47k ohm resistor need to be? 1/8, 1/4, 1/2, 1, 
> 2? Does it matter? Ditto on the NPN transistor. It sucks radio shack 
> doesn't exist anymore, it's now a pain to find the components locally.
>
> Thanks
>
> --Bret Taylor
> Olympia School District
>
>
> On Sun, Mar 10, 2019 at 10:54 PM Marshall Oldham <ke6pcv at cal-net.org 
> <mailto:ke6pcv at cal-net.org>> wrote:
>
>     FYI,
>
>     He is not using app_rpt software with the URI, he is using the
>     Bridgecom MV-iL hardware with a URI to interface to his GE Mastr III
>
>     So he can not set CORFROM=uisbinvert in software config.
>
>     73
>
>     Marshall
>
>     *From:*App_rpt-users
>     [mailto:app_rpt-users-bounces at lists.allstarlink.org
>     <mailto:app_rpt-users-bounces at lists.allstarlink.org>] *On Behalf
>     Of *REDBUTTON_CTRL
>     *Sent:* Saturday, March 09, 2019 5:24 PM
>     *To:* app_rpt-users at lists.allstarlink.org
>     <mailto:app_rpt-users at lists.allstarlink.org>
>     *Subject:* Re: [App_rpt-users] GE Mastr III and DMK USB-URI
>
>     Bret, one thing to know about the URI is that the COR input line
>     (pin 8) requires a signal transition to pull to ground. This is
>     different that a signal that sources voltage and goes low. the URI
>     has internal pullup resistors so it doesn't look for voltage change.
>
>     So what this means is if the CAS/COR out line on the Master III
>     does not pull to ground when it goes low, the URI will not see a
>     signal change. The URI has a dc blocking diode on its input. So it
>     needs to see a signal that either goes low when the receiver is
>     active or when it is inactive.
>
>     If the Master III CAS/COR is active hi then I suggest you connect
>     the CAS/COR through a 47K resistor then to the base of an NPN
>     transistor. Then connect the collector to pin 8 on the URI and
>     connect the emitter to gorund. This will invert the CAS/COR signal
>     and give an open collector that goes to ground on receiver activity.
>
>     Then in the Allstar node set the CORFROM=usbinvert.
>
>     This means the URI will be looking for a signal to ground pin 8.
>     then audio will be sent through the system.
>
>     Hope this helps.
>
>     Regards,
>
>     Jon VA3RQ
>
>     On 3/9/2019 8:26 AM, Bret Taylor wrote:
>
>     "What channel driver are you running?  This will determine what
>     sort of audio
>     you need from the system and where squelch is performed."
>
>     I'm using a Bridgecom MV-i1 to drive the URI -
>     https://www.bridgecomsystems.com/collections/tl-net/products/mv-1
>
>     I don't know exactly what is under the hood. Their "OS" is called
>     TL-Net. But under that is Raspbian. I have a network of TRBO
>     repeaters that the MV-i1 taps into through IP Site Connect.
>
>     I'm trying to bridge the TRBO repeaters to this Mastr III base
>     station. I've already created a cable using the info from
>     http://www.repeater-builder.com/ge/mastr3/m3-ctrl/m3-ctrl.html
>
>     I created a bridge group in TL-Net to bridge the analog interface
>     to IPSC masters. I can PTT on a DMR programmed to the correct Call
>     Group, and hear it on a Analog radio tuned to the Mastr III
>     frequency.  But I can not hear the Analog radios return, it
>     doesn't seem to trigger the URI.
>
>     If I use pin 8 on the URI (active low) and connect it to P5-17, or
>     P5-20 (COR & CTCSS both Active High) on the Mastr III backplane,
>     the URI goes into a broadcast storm. Using any of the optional
>     pins for COR (2 & 3 both listed as active high) nothing happens. I
>     suspect since these are GPIO, the configuration (for the URI?) is
>     incorrect.
>
>     I know the URI works, as I was able to use it to drive an XPR5550e
>     programmed to the analog frequency of the Mastr III. It's just not
>     the best situation to run it like that. You clearly hear dispatch,
>     but since I'm not tapped onto the return path of the antenna
>     connected to the Mastr III, the mobiles response clarity is
>     dependent on the proximity to the antenna of the XPR5550e.
>
>     "Double check your programing too, as the Mastr III IO is based on
>     programing.
>
>      You'll need to ensure you have your de-empahsis and pre-emphasis
>     setup
>     properly too."
>
>     I do not have the Mastr III programming software (and can't seem
>     to find it anywhere). Another user in this list says he has it,
>     but it searching for it. So, I have no idea how it's programmed.
>     It's possible the backplane connecters for audio out are disabled?
>
>     Thanks for your help.
>
>     --Bret Taylor
>
>     Olympia School District
>
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