URI FAQs - DMK Engineering

URI FAQs - DMK Engineering
Q: What is URI?
A: The USB Radio Interface is the easiest and least expensive way to connect a land or mobile
radio to nearly any host computer. This allows remote connectivity and simple internet access.
Q: What type of radio can I use?
A: Virtually any type of radio may be used including, amateur, business, public service/safety
radios, plus GMRS, citizens band, and many others.
Q: What types of applications is URI suitable for?
A: Radios are often placed in inaccessible locations requiring remote access. Audio signals and
digital controls may be passed through any available channel including but not limited to VOIP
and Ethernet.
Q: Can I use URI to make a repeater?
A: Radio controllers may be replaced with a URI based system. Since URI is full-duplex, only
one URI is needed for both transmit and receive channels.
Q: How do I connect my radio to URI?
A: Many transceivers and radio systems provide an interface connector for interfacing to external
equipment. It is usually very simple to make an interconnection cable between this and the 25pin D-shell URI connector. If such a connector is not provided, internal modifications may be
required to gain access to the required electrical signals.
Q: How does the URI work?
A: The URI contains a CM119A audio controller IC made by C-Media. (Older URIs used an
equivalent CM108.) This is a high-quality full-duplex USB audio device with several general
purpose I/O channels. The CM119A provides one channel of receive audio, and two channels of
transmit audio. This allows support for many different radio configurations. The second audio
output channel may be optionally used as a line monitor.
Q: What are the functions of the I/O pins?
A: The URI has two dedicated input pins intended for carrier CTCSS presence indications and
one dedicated output pin for PTT. There are several other general purpose I/O pins that may be
controlled by software.
Q: How is audio output processed?
A: Both audio output channels are fed through a low-pass filter. This helps eliminate potential
spectral impurities, which is especially important for direct modulation. The filters are 3-pole
Chebyshev with a cutoff frequency of 4KHz. The filter outputs are AC coupled through a 10uF
non-polarized capacitor. This large coupling capacitor allows the low frequency CTCSS signals
to be passed when driving a low impedance input.
DMK Engineering Inc.
Tel: 310  544  1222
2908 Oregon Ct. H3
Fax: 310  693  0753
California 90503
Q: What is the +6dB gain amplifier used for?
A: If a radio requires high drive levels, a 6dB gain amplifier is provided. An external 12 volt
power supply must be provided with positive connected to pin 25 and negative to pin 13 in order
to use this circuit.
Q: What is the EEPROM used for?
A: Configuration and calibration data may optionally be stored in a 93C46 EEPROM. If the
EEPROM is not present the software will automatically store that data in a configuration file on
the hard drive. The EEPROM is useful in systems with multiple URIs. There is space on the
circuit board for an SOIC version of the EEPROM but it is typically not installed. Instead, the
preferred method is to solder a DIP IC directly to the DB-25 connector pins. That way if a URI is
swapped out, the stored data stays with the cable and therefore with the specific radio.
Q: What software is required?
A: You must install Asterisk and which runs under Linux. We recommend you use the latest
versions of the app_rpt modules. The easiest way to get everything you need is to download the
Allstar Centos Install Disk (ACID) ISO image from Allstar Link located at
http://dl.allstarlink.org/ .
Q: Do I need any other drivers?
A: No, not as long as you have the current ACID installation or equivalent dated 6/3/2011 or
later. You may access source code from the SVN at http://ohnosec.org/drupal/node/6 .
Q: How can I test my URI?
A: Download the uridiag program located at
Un-tar it and then ‘make’ it. Run ./uridiag and select option C. That will tell you how to make a
loop-back connector for running the diagnostics. This is the same program we use to test each
URI before it leaves the factory.
Q: How can I make a loop-back cable to test my URI?
A: Get a male DB-25 connector such as L717SDB25P from www.digikey.com . Then wire up
the following connections:
Pin 1 to Pin 7
Pin 2 to Pin 3
Pin 4 to Pin 8
Pin 23 to Pin 24
10K Resistor between Pins 21 and 22
10K Resistor between Pins 21 and 23
For URIx (CM119) only, also include the following connections:
Pin 5 to Pin 10
Pin 6 to Pin 11
DMK Engineering Inc.
Tel: 310  544  1222
2908 Oregon Ct. H3
Fax: 310  693  0753
California 90503
Q: How do I purchase URIs?
A: Go to our URI Order Page on our web site at http://www.dmkeng.com . If this is a
commercial application, click the upper Add to Cart button. If you have an amateur license, click
the lower button to get your 30% discount.
Q: How can I get technical support?
A: Please contact us by phone or email (see below), or sign up for the app_rpt mailing list at
http://ohnosec.org/cgi-bin/mailman/listinfo/app_rpt-users and post your question. There are a
great many knowledgeable and dedicated people who are ready to help.
Q: What it I don’t have a PayPal account and don’t want one?
A: You can use a credit card without a PayPal account; PayPal will process the transaction for no
fee. When you add an item to the shopping cart a new PayPal window will open. On the
checkout page click the left yellow button to “Check Out”. On the bottom right of the next page
click the link “Don’t have a PayPal account?” Fill in the appropriate information and complete
your transaction.
DMK Engineering Inc.
Tel: 310  544  1222
2908 Oregon Ct. H3
Fax: 310  693  0753
California 90503
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