Using a PC to Decode MDC 1200

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Postby MicorRT » Sun Mar 03, 2002 1:27 pm

Is there software out that will use a dataslicer or a soundcard to decode MDC 1200 or other ANI? Comspec and a few others have a "special" interface. I would think that it could be done with a dataslicer. Thanks,
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Postby wavetar » Sun Mar 03, 2002 2:52 pm

We developed a DOS program to decode & display MDC ID's onto a computer screen for a Taxi company, coming from a Motorola BSC-II (Base Station Controller). I don't see why a dataslicer wouldn't work for it, although I've never tried it.

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Postby MicorRT » Sun Mar 03, 2002 7:45 pm

I interested... Is this shareware? What are the system requirements 386 or 486? Thanks! My email is mailto:n3ita@hotmail.com
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Postby wavetar » Mon Mar 04, 2002 2:49 pm

You aren't the only one to express interest :smile: While not copyrighted, it was developed by my company. It could only be done after paying a LOT of money to Motorola for the "white sheets" on the MDC protocol. Therefore, I cannot share the program as it would likely land me in some serious hot water with my employer. They may be willing to part with a copy for a price, I've never thought to ask until now. Perhaps it would be a nominal fee...I'll keep you posted.

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Postby jim » Mon Mar 04, 2002 7:35 pm

Visit http://www.midelec.com

They have a CAD program that does it. While not cheap, it does work.
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Postby Nickdap » Mon Mar 04, 2002 8:35 pm

Wavetar,
I never even thought i should ask. But I've been hoping it would come up somtime. I remember a past post of yours talking about what you did. If you can find out if its possible. even just the protocal infomation. For educational purposes only of course.
:razz: anyway thanks for jump starting my interest in mdc again
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Postby MicorRT » Tue Mar 05, 2002 7:54 am

I am still interested in your software... Also the source code if possible but I respect you postion... If the price is resonalable... My email is mailto:n3ita@hotmail.com
If the answer is no I understand. Thank you for you response. -MicorRT
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Postby Alan » Tue Mar 05, 2002 8:30 am

On 2002-03-03 17:52, wavetar wrote:

We developed a DOS program to decode & display MDC ID's onto a computer screen for a Taxi company, coming from a Motorola BSC-II (Base Station Controller). I don't see why a dataslicer wouldn't work for it, although I've never tried it.

Todd


As Wavetar wrote, he used a BSC-II. This device does all of the MDC1200 decode/encode functions and spits out a serial data steam that contains the ID/ststus information.
He them took that serial data and brought it into his dispatch software. A data slicer would not work as the decode functions are not in the software, but in the BSCII module.

I think your question is "How do I decode MDC1200 over-the-air data".

I have never seen anyone do this. It is a highly protected protocol, but over the last couple of years Motorola has licensed it out to a few companies (Midian, SSC, cimeron).

With the Midian product, the software is only 1/2 the picture. The other part is a radio adapter that connects to the base station and does the decode function much like the Motorola BSCII. The radio adapter then feeds serial data to the computer and the software takes the ID information and displays it.

Good luck, but I think you may need to look at a device like a BSCII or Midians decoder.

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Postby MicorRT » Tue Mar 05, 2002 9:14 am

Alan I think you may have hit the nail on the head. I'm not familiar with the BSCII but I wanted to do away with the "magic black box" with the special price. It would also be handy to be able to hook a dataslicer up to a laptop and my R2000 demod out when checking out subscriber units... something small inexpensive and handy. It looks like its not going to happen at least inexpensively. Thanks guys for you input.
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Postby xmo » Tue Mar 05, 2002 10:36 am

"and my R2000 demod out when checking out subscriber units... "

Don't you find it strange that after having MDC for all these years Motorola never put it into a service monitor - R2001, R2600, 2670 - even the new R2590? They never had an outboard test encoder/decoder either.

Now that Motorola doesn't make service monitors any more we will probably never get one that knows how to do MDC.

Your best be for something cheap is either a B1667 encoder/decoder box or a T5620 remote with MDC - T5600's sometimes sell for less than $50 on ebay.
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Postby MicorRT » Tue Mar 05, 2002 10:41 am

Thanks xmo. I will look into those options.
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Postby Kosh » Sun Mar 24, 2002 6:28 pm

Haven't anyone reversed engineered the MDC1200 protocol ? Seems to be a not so hard task.

I know it is patented, but what is its patent number ?
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Postby xmo » Sun Mar 24, 2002 6:48 pm

Look @ U.S. Patent 4,590,473

Let us know when you get that decoder program written.
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Postby xmo » Sun Mar 24, 2002 6:58 pm

Here is another MDC decoder - the C100 remote.

This was listed on ebay with a $400 buy it now, but didn't sell.

Motorola MDC 1200 Tone Remote C100
Item # 1336108997


Maybe he'll relist - or you could contact him direct.
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Postby Kosh » Mon Mar 25, 2002 5:12 am

Thanks, I have seen the 4,590,473.
There are also the 4,518,068 and 4,517,561 that may be related.

What I would like to know :

- What are the interleaver used ?
- What are the convolutional code polynomials used ?
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Postby xmo » Mon Mar 25, 2002 4:28 pm

The signaling is encoded at 1200 baud using FFSK (MSK) @ 1200Hz/1800Hz. First there is a 56 bit preamble, then a 40 bit word sync, and then either 1 or 2 112 bit codewords for a packet length of 173 ms for one codeword or 267 ms for two codewords.

The 112 bit codeword starts as 32 bits of data (the actual MDC data payload) this is expanded from 32 to 112 bits with error detection and correctional algorithms (rate 1/2 convolutional threshold decoder and 16 bit inverted-CCITT CRC respectively).


Get busy coding.
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Postby Kosh » Tue Mar 26, 2002 12:53 pm

>The signaling is encoded at 1200 baud using
>FFSK (MSK) @ 1200Hz/1800Hz. First there is a
>56 bit preamble, then a 40 bit word sync,
>and then either 1 or 2 112 bit codewords for
>a packet length of 173 ms for one codeword
>or 267 ms for two codewords.

Seems to be the same as MDC4800.

>The 112 bit codeword starts as 32 bits of
>data (the actual MDC data payload) this is
>expanded from 32 to 112 bits with error
>detection and correctional algorithms (rate
>1/2 convolutional threshold decoder and 16
>bit inverted-CCITT CRC respectively).

Actually, the CRC16 is appended to the original 32 bits plus 8 status bits. Now you have 56 bits for the rate 1/2 encoder.

Assuming the same interleave as MDC4800, the only "unknown" is the convolutional encoder.

Ideas ?
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Postby xmo » Tue Mar 26, 2002 5:19 pm

Once you get the MDC into your computer as 1's & 0's, you should to have enough to go on now.

Just send your development program a known MDC payload & try convolutional decoders until you decode the same data.

For example, program a radio to send PTT ID (beginning of trasmission) for unit ID 1234 and the payload will be 01801234(Hex).

Go for it.
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Postby Kosh » Tue Mar 26, 2002 5:56 pm

>For example, program a radio to send PTT ID >(beginning of trasmission) for unit ID 1234 and >the payload will be 01801234(Hex).

Do you have a description of these two bytes ?
(0180) I haven't found any.

Thanks.
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Postby OX » Tue Mar 26, 2002 6:18 pm

Fleet & group? Group is a 3 digit ID.
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Postby xmo » Tue Mar 26, 2002 7:01 pm

0180 is the MDC 'opcode'

Reference to the term opcode is found is some motorola manuals. Actually the 'opcode' is comprised of 3 flag bits that determine data/command, direction, and ack/no ack, followed by an operation code specifing the particular operation (ID, status, message, emergency, etc) and then an arguement (which might for example contain the status number in a status packet)

Once you get your decoder working, you can reverse engineer the opcode table by recording the data sent by various units. Program radio #1234 to send emergency and you will see 00801234. Program RTT (Request To Transmit) and you get 40011234, etc.
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Postby MicorRT » Mon Oct 07, 2002 8:49 am

Using a PC to decode MDC 1200.
Just curious if anyone has chased this anymore?

I have noticed a slight change in the MCS2000 MDC word from the word created from Maxtracs... I believe this was to throw off any "unlicensed MDC1200 developers" :( Old Maxtracs will still decode the MCS2000 and vice a versa through...
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Postby alex » Mon Oct 07, 2002 9:35 am

I've also noticed that there is a distinct difference in sound that comes from a MTX/MTS/MT2000 based controler when it comes to MDC... Not as loud or as crisp sounding as the Maxtrac/Spectra/Waris MDC bursts. I wonder if the extra "word" causes this.

-Alex
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Postby doi » Mon Oct 07, 2002 12:23 pm

micorrt:

wouldn't it be easier just to have a modem that converts the FSK signal into a bitstream for your pc?
a modem could be easily built.
or if i am mistaking please correct me someone.

i am very interested in developing a mdc monitor with some microcontroller and i think that a modem with a controller will do it. am i right?
see you
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Postby Nickdap » Mon Oct 07, 2002 8:08 pm

Thats exactly how you do it. You can figure out what the bit stream "means" by using the info on bat labs and the US patant documents, and writing a Basic program to present the binary out put to you on screen. Once you have this down, you can write a program to understand the different mdc signals, and better still feed it back in to the modem and into your radio. (instant console for 1/100th the price) I hear the MSK modem chips are around $30 AUD. MDC is at 1200 bps, so you can hook it into the mic and spk audio with out degredation.

Using a soundcard to decode it is not an option, I could explain this but it would take to long. It's all to do with the modulation.

I'm in the process of moving, so I'll need to track down my papers on this subject.

Good luck to you in the mean time.
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MDC1200 receiver IC

Postby Kosh » Thu Nov 21, 2002 2:31 pm

A good one is the CMX469 from CML.
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Postby tom IL » Thu Nov 21, 2002 3:38 pm

What motorola produts will decode and display MDC1200??? Do any HT's do it? Thanks
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Postby Pj » Thu Nov 21, 2002 5:47 pm

To my knowledge:
HT1250
HT1550
LS verions of the above
MT2000? (may need proper flash)
MTS2000? (may need proper flash)
Certain Maxtrac's

With the proper flash:
Astro Saber
Astro Spectra
XTS series

Basically any of the newer display radio's will support unit ID. Some will only show the unit number, others will display text in place of the unit id if programmed.
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Postby Paul » Thu Nov 21, 2002 7:44 pm

Very interesting analysis...
Some time ago I was also 'playing' with MDC1200 and CMX469.
It works just fine and I think that the decoding code could fit even
inside the MC68HC705J1. The best place to 'tap' MDC1200 is inside
the transmitting radio, just before the modulator, no noise at all.
The MaxTrac is a nice example of a 'roomy' radio to play with.
I can't check it out again soon, since I'm getting married this Saturday,
I'm leaving for a 7-day honeymoon to London and then I have to finish
my Select-5/PL encoder board project to begin production.
So, by mid-December -if I still have a Maxtrac available- I'll post my
results.

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Postby ASTROMODAT » Thu Nov 21, 2002 9:26 pm

Is MDC Unit ID functionality over XTS 3000 and ASTRO Spectra mobile radios only applicable when operating in the analog mode? Is there a similar function available in the ASTRO digtial mode for Unit ID and/or short message service?

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Postby Bob » Fri Nov 22, 2002 6:58 am

Pj wrote:To my knowledge:
HT1250
HT1550
LS verions of the above
MT2000? (may need proper flash)
MTS2000? (may need proper flash)
Certain Maxtrac's

With the proper flash:
Astro Saber
Astro Spectra
XTS series

Basically any of the newer display radio's will support unit ID. Some will only show the unit number, others will display text in place of the unit id if programmed.


FWIW, I've never seen an MT2000 decode and display MDCIDs. It will decode an incoming call alert though. I've also heard people complain (though I've never verified myself) that the LS versions won't decode and display MDCIDs either, but the XLS will. You can add to the list of radios that will decode and display: the CDM1250 and CDM1550, and I believe the MCS2000 if flashed properly.
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Postby ASTROMODAT » Fri Nov 22, 2002 9:40 am

Is MDC Unit ID and/or short messages/status functionality over XTS 3000 MIII and/or ASTRO Spectra mobile radios possible when operating in the ASTRO digtial mode?

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Postby xmo » Fri Nov 22, 2002 1:17 pm

The answer is yes - sort of.

MDC is a digital overlay for analog systems. With APCO 25 systems the CAI specification defined similar functions (PTTID, Status, etc) as embedded signalling.

In a Motorola Astro25 system the maximum fuctionality is achieved with a Centracom Gold Elite console. You put an interface card in the CEB which connects to the DIU. The DIU connects to your Quantar repeater or control station. All of that communicates the data functions to/from the mobiles & portables.
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Postby ASTROMODAT » Fri Nov 22, 2002 2:34 pm

Xmo, is the Motorola Centracom Gold Elite console manufactured by GAI (who bought Instrument Associates, Inc.) some time ago?

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Postby xmo » Fri Nov 22, 2002 2:38 pm

The Centracom Gold Elite is manufatured by Motorola.
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Postby nmfire10 » Fri Nov 22, 2002 3:04 pm

We have the centracom gold console at my center. We don't do trunking but for the multi-channel system we have, it is VERY NICE!!!
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Postby ASTROMODAT » Fri Nov 22, 2002 3:14 pm

Xmo, regarding the ASTRO Quantar and DIU 3000:

Can I simply connect my existing Zetron Model 280 Tone Remote Desk sets (control tones are fully programmable, including Motorola emualtion) to the DIU 3000 via local 4 wire (desk sets and DIU are in my home), and then connect the DIU 3000 to my mountain top ASTRO Quantar repeater via the ASTRO modems at each end (over 4-wire dedicated Telco 3002 private line circuit), and support the following functions:

PTT
Repeater Set Up/Knock Down
Clear vs. Coded (DES-OFB) Operation
Analog vs. Digital ASTRO Operation
MRTI Enable vs. Inhibit

I'm tryiong to re-use my Zetron Model 280 desk sets, as they cost $2,000 each and are 2 years old.

Can I support these functions with my Tone Remote desk sets without the need to introduce a Motorola Centracom Gold Elite console, with a CEB, etc.? I understand that my set-up will NOT support Unit ID, etc. but I'd like to avoid the expense and complexities of a full blown Motorola console system.

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Postby xmo » Fri Nov 22, 2002 5:15 pm

The DIU supports standard tone remote signalling on the console side so you should be fine with your Zetrons. Since the Zetron remotes are programmable and the DIU is programmable (as to what it does in response to various tone sequencies) you should be able to configure any functionality you need. The only thing you won't have is the 'signalling' functions.

If you want to try to understand the whole thing from the Motorola manuals, here are some #'s:

68-02924C15 DIU RSS
68P02949C65 DIU3000 Owner's Manual
68P02949C70 DIU3000 Centracom Signalling Link Option

WARNING! This stuff will muddle your head! My associate and I couldn't make sense of it until we actually set up the equipment to play with it. We will be learning about that Centracom option later...
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Postby xmo » Fri Nov 22, 2002 5:27 pm

"We have the centracom gold console at my center..."
--------------------------------------------------------------

Matt, when you were asking about trunking systems you had us all believing you were paupers.. Now the truth comes out!

I really like the product and the many things you can do with it (but then I have been configuring and optimizing Centracom II consoles since they came out).

Our 911 director does have one good point - he says since most of these things are sold to government customers they should have picked a better name.

Going to our County Commissioners and telling them we are buying the "Gold Elite" model gets us off on the wrong foot! He says they should have called it the "Centracom Standard" or better yet "Centracom Economy"
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