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Programming old aviation radios with DOS software thru LPT1

October 28, 2016 at 09:24:58
Specs: Windows 7-10, n/a
Hi, I have a small job for someone if they are interested, possibly paid if that helps. This will be extremely simple for the right person with knowledge in the right fields. Unfortunately, i was only like 8 years old when this technology was around and i think i still had a mac at that age.

The company i work for has a heap of aviation FM band radio transceivers we use for ground to air comms, TFM-138B, they are so old now but still the only viable option on the market and still worth almost $15k a piece. I have to program them manually, which takes 3-4 hours and a further 3-4 hours to double check my work.
The programming software they come with is made for DOS. It is extremely simple but i cannot get it to function on a modern PC and in the isolated town i live in, that has only recently embraced electricity, I cannot get my hands on an old PC easily.

The manufacturer did make a windows programming software made for Win95 but you have to buy the $1000 module, and the company is not interested in buying it. Instead i made the LPT1 cable to specs and am trying to persevere with the DOS software option.

The software it comes with is basically allows you to save all your 120 preset stations on a file then download them to the TFM-138B via a cable from the parrellel port set as LPT1. Our company only uses 1 set of presets ever.

I have the cable, the radio, the PCI-parrellel card, DOSBox, and winXP-32bit but cannot get the signal to pass thru to the radio.

What I want is... if somebody can somehow capture that download signal that goes out through the parrellel port from the DOS software, then allow me to simulate that signal on a modern PC with just a USB-parrellel port or PCI-parrellel port and my cable connected to the radio transceiver. The signal is always the same to program it.

I'm certain this would be fairly simple if you had the right combo of knowledge and hardware, and i have the software here, it arrived on a floppy disk, its so ancient....but yet would make life so much easier.

See More: Programming old aviation radios with DOS software thru LPT1

October 28, 2016 at 16:23:33
You say you made the cable--rather than buying one, I assume. To be sure you may want to just buy an IEEE 1284 rated cable. There's ebay if you can't find one locally.

The software may be looking for a port at a particular address. If you're using an add-on card its port may be at a non-standard address. Sometimes you can change that in device manager. You may need to consult the software manual or help file to determine if that may be a factor.

Does the card have jumpers? There can be 3 parallel port settings--SPP, EPP and ECP. It sounds like you only need the basic SPP although EPP may be OK. But sometimes using the ECP setting may not work with simple devices. It's designed mainly for more sophisticed devices the scanners that before USB were often connected through the parallel port.

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October 29, 2016 at 04:01:43
Hi Snowtar,

a) are you positive the parallel port was used instead of a serial one?

b) surely a standard Parallel Printer ( LPT1) cable is easily obtainable, such that you did not need to make one - e.g. ebay?..
Although in the early days there was a choice of connectors - RS232 or Centronics.

c) I think you are making a rod for your own back.
If it were me, I would move heaven and earth to obtain a dos pc and prove everything works first before involving windows, if at all.

Would think a local pc repair shop has an old pc or maybe there is one in someones basement.

d) why DOSbox?
Free standing dos applications run ok under WXP.
However when printing, the output goes via WXP and not direct to the port.

e) under dos there was freeware around that could capture print to a file.
e.g. Check out dosprint etc.

Good Luck - Keep us posted.

message edited by Mike Newcomb

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October 31, 2016 at 11:56:35
H DAVEINCAPS, thanks for the reply.
The cables were discontinued and out of stock in the late 1990's. I had to make it by the wiring diagram its 25-pin parallel one end and 15-pin the other with a few resistors, transistors and diodes in the circuit plus a 28V power supply going in through the 15-pin plug.
I think you may be on to something with the address. The card seems to be using ECP in the device manager and i don't see where to change that. And i don't really know what this means. The specs on the PCI-parrellel card did mention all 3 ECP/SPP/EPP but I'm not sure how to adjust it.
There only seems to be settings to adjust Legacy compliance and whether to allow and interrupt to be used on the port or not.

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October 31, 2016 at 12:10:01
Hey Mike,
Thank for your help. Yes defiantly a parallel port used, and also there are no drivers when you connect the FM tranceiver to the PC. It a custom cable, 15pin one end, 25-pin the other and 28V power supply with a basic circuit inline. I had to make it from a manufacturer wiring diagram, as its unavailable to buy anymore.
Thanks for the tip on XP, i was using DOSBox because i believed that XP would not allow MS-DOS access to the LPT1, but the software does seem to function fine in XP.

These are the software specs:

2.14.6 DOS Program Requirements:
1. PC compatible computer with:
$ 486 or early Pentium one processor, 200 MHz or less
$ CD drive - If not, you can copy the software on another computer to a floppy disk.
$ Colour monitor is preferred as some of the text is colour coded.
$ Printer port (LPT1)
2. Bench power supply of 28 volts DC.
3. PC Download cable (p/n 943165-4) see figure 2.2.

Unfortunately the guy at the local PC shop decided to end the conversation after i mentioned the word floppy disc. I think he just removes viruses and sells new HP computers and prefers it that way, haha.

I have tryed capturing, but i dont know what to do with the RAW, txt, or TIF file when i have it. I need to get it sent to the LPT1 to a device without a driver.

Any ideas on that one?

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October 31, 2016 at 17:00:41
I googled that part number--943165-4--and got a few hits from a 'dallas avionics'. Is that who makes the equipment? They still show that cable on their parts site:

If that cable has a 15-pin connection on one end then likely it's proprietary and yeah, you'd either have to make it yourself or find one from the manufacturer.

I'm not sure about the card. You may be able to find some information about it online or its manufacturer's site.

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November 1, 2016 at 05:00:17
Hi Snowtar,

a) under dos, drivers were contained in the application itself and not the os.
b) think program is probably sending simple ASCII numeric characters.
At pc end, cable uses data pins 2, 3 and 4, suggesting only numeric characters 0 - 7 are being sent. Does that sound correct?
c) unsure what 14.6 dos is
d) why use a pci parallel card - most mobo's have a LPT1 port as standard.
For such projects it is best to keep things simple if possible.
e) CD drives need be slow (16x or less) otherwise may not work with old slow pc's. as too fast.

Please see PM just sent.
As a matter of interest, where are you based (City/State)?. I am in West London.

Good Luck - Keep us posted.

message edited by Mike Newcomb

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November 4, 2016 at 06:46:55
Hi Snowtar, further thoughts:-

Looking at the 'Special Cable' connections leads me to suspect the application uses
the LPT1 port, not in print, but in communication mode, using 1 connection for data in one directiion
Thought a serial port was better for this purpose, although timing and overflow could be behind using LPT1..

Think any dos pc, such as a Pentium or earlier with a LPT1 port will work.
Here in the UK, these can be found on ebay / computing / vintage

I believe one cannot access the port directly under Windows, which is why the extra Box etc. is required.


Good Luck - Keep us posted.

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