Tait 2015 programming

[SiriusHardware]

Amateur Radio, but possibly not vintage enough (mid nineties?) - if so, mods please move to an appropriate home.

I've been asked to look into reprogramming a VHF high band Tait 2000 series PMR radio, specifically a Tait 2015 which I believe is an 'ordinary' (Not trunked) variant which supports up to 24 channels. It's already on two metres, but programmed with only eight channels to the previous owner's specific requirements. Quite a neat little thing, I've never seen one before.

The programming software (Some DOS, some early Windows) seems broadly available, although I'm not sure which exact variant applies to this radio which I think is an 'original' 2000 series rather than a 2000/II.

What I need to know is whether the serial programming cable between the PC and the radio requires an RS232-TTL level-shifter (ie, MAX232 IC or similar) or whether the level shifting is handled within the radio, allowing direct connection of RS232 to the programming port.

Also, I'm aware that the similar Tait 2020 supports up to 100 channels which would obviously make it more flexible for amateur usage: Is it possible to 'make' a 2015 into a 2020 just by changing the onboard firmware?

[Sparky67]

Hi there,

My T2000 programming cable has what looks like a level shifter in the D-type connector with a MAX232 and a 78-series device built in. It works on both the original and the series II radios.

I believe the 2015 has a 2-digit LED display and the 2020 has an LCD display, so would presume the 2020 firmware is quite different to the 2015 elsewhere than just channel availability? Might be worth cross-checking the radio and head board numbers in the manuals.

Hope this helps.

Cheers,

Martin
G4NCE

[SiriusHardware]

Sparky67, thanks - I have not seen a 2020 and assumed (incorrectly as it turned out) that the 2015 was just a firmware limited version of the 2020. Didn't realise the displays were so different.

Thanks for confirming that the lead does need a level converter in it - the radio I have here has a 15-way Sub-D female connector (9 way size, but three rows of pins like a VGA connector on a PC) on the rear panel. All the illustrations of Tait cables I have seen have a network type (RJ45?) plug on the end, so I assume this must go into the microphone socket on the radio?

[Sparky67]

Yep, via the mic socket is how I have programmed them in the past. It may be possible to use the rear connector, again a look in the book would confirm that.

I always found the T2000 (and T800) series to be very reliable with good RF and AF performance, so well worth getting going if you can.

Martin

[SiriusHardware]

Thanks, I think I can also assume, then, that the level shifter must take its power from the microphone socket as well, presumably 12V which is then regulated down to 5V by the 78xx regulator in the programming lead.

I don't have the manuals, if you have a link to them that would be handy or if you happen to know which pins on the microphone socket are 0V, power out, data in, data out that is probably all I really need to know at this stage. Unless there is a further link which needs to be made to put the radio into programming mode?

[Sparky67]

Mic socket pinout attached. Just plug the lead in, run the software and go...

[SiriusHardware]

Superb, thanks, just what I needed!

[Sparky67]

No problem. Good luck getting it running. If you would like to pm me your email address I will zip the service manual pdfs and send those over to you. Might come in useful working out what that high density D-type on the back is connected to...

[SiriusHardware]

Sparky, sorry, just saw this. Thanks for the offer.

My involvement with this radio at the moment is just with trying to reprogramme it as I don't own it, but if I may I will ask the owner if he wants to be put in touch with you regarding the service manuals. I'm not sure he will because, although he has many talents, he's not very confident when it comes to electronics.

[SiriusHardware]

All set to try programming, but... how do I release the microphone so I can plug in the RJ45 plug of the programming lead?

The 'root' of the microphone cable where it enters the front panel is completely covered by a rubber grommet which I don't want to force in any direction without further advice.

OK, got it. It just digs out and slides out along the microphone cable. But now I have discovered my lead needs to have a 6-way modular plug on it - I thought it was an 8-way one with the outer two pins not used. Back to the drawing board... (Have some 6 way plugs at work).

[G6Tanuki]

One caveat is that the programing software for these sorts of old radios frequently makes spectacular assumptions about the clock-rate of the PC on which it's running.

A lot of the first-generation flash-memories/EAROMs used to store the programing info in these radios have rather baroque timing considerations when they're being programed - by modern standards they are spectacularly-slow. Hence the programing software has timers in it so you can send each quartet/octet of data to the radio with a long delay-time between them and then send a 'save' command followed by another delay to let it be saved, before sending the next quartet/octet.

The timing is often done using simple software counting-loops [calculate a few thousand sines...] and assumes an old-style PC/XT clock-rate/cycle-time.

A software delay-loop which works just fine on an original PC with a 4.77MHz or even an 8MHz! clock-rate XT becomes hopelessly inadequate when run on a modern PC/laptop with a clock-rate closer to 3GHz.

[I had a big problem with this while trying to reprogram a Standard/Communique radio something like 15 years ago. Even then trying to find an original 4.77MHz clock-rate PC was difficult. In the end I gave up and parted-out the radio, using its PA transistor in a little 10-Watt 3.5MHz transmitter!]

[Biggles]

I remember having to use "AT-slow" with newer laptops in the nineties. Some of the radio programming software was DOS based and I believe all it did was to run routines to waste time and effectively slow the machine up a bit. I never had a problem with later Windows based software.

[SiriusHardware]

All good advice generally - the PC to be used for this is contemporary with the software which, depending on the version (I have several) is from between around 1994-1997.

The PC is a Brother laptop running Win'98 SE (originally Win '95), although it has access to 'proper DOS' if software needs it through the MS-DOS prompt.

If you are wondering why on earth I maintain such an old machine in running order it is because I myself have some very old devices, notably eprom programmer / chip testers which require old school hardware ports (COM / LPT) and are powered by DOS software. I also have the programming software for several other amateur and PMR radios which I do own... all DOS software.

I think there is - because I used it to solve a similar problem on a 'fast' Win98 PC at work - a way to slow down the serial ports on that OS - I don't mean by changing the baud rate, which is obviously fixed on the radio, but by playing with the buffering and other Windows settings for the com port. The fact that the comms between the radio and the PC (in the case of the Tait and most others) does not use hardware flow control may make things more tricky. The protocol of the traffic between the radio and PC may include software flow control (Xon / Xoff, etcetera) - I really have no idea.

With the PC, the radio and the software all approximately the same age in this case, I'm hoping it will be relatively straightforward.

[Sparky67]

The laptop I used to prog the T2000s was a 486 DX4 (Tosh 2130CT) with Win98SE and it worked faultlessly. I *think* an early Pentium machine may also have been used in the past.

Martin

[SiriusHardware]

That's what this is, a P133 with an enormous 64MB of memory.

I'm itching to get on with it and see if it works but I'll just have to wait until I've located the proper plugs at work. I'll be ready to have another go at it tomorrow evening.

[SiriusHardware]

Back again. I now have the right 6-pole plug connected up correctly according to my initial idea of how the programming lead should work but, the software does not see the radio.

Sparky67, I asked you what your programming lead had in it, you mentioned a regulator and a MAX232 level-shifter. Does it also contain a logic device which could be used as two inverters?

The reason I'm asking is this: Here's an interesting version of a multi-radio programming lead where the initial level shifting is done by transistors, as it happens. I used a MAX232 but the function of the main part of the circuit is the same, to level shift and invert the data going to and from from RS232 - TTL - RS232.

http://www.cqham.ru/uniprog2_eng.html

To the basic main circuit you then add the specific bit for your radio. The add on section for the T2000 series is some way down the page.

The add-on bit for the T2000 radios clearly includes a logic IC used as two inverters, one to invert the TTL-Level signal coming out of the level converter, and the other to invert the TTL-Level signal coming out of the radio and going to the level converter.

It looks to me as though I am going to have to do the same and invert the data at TTL level on the way to and from the radio so it is in effect the 'same way up' as the RS232 data.

[G6Tanuki]

In the past I've had 'issues' seeing the radio with level-shifters that try to steal their power from CTS/RTS/DSR/CI/DCD/RI pins of the RS232/V.24 serial port: particularly with laptops, many of which used custom chips that - to save power - didn't deliver the full RS232/V.24-spec current/voltage.

hooking-up a proper full-current +/- 12V supply might be worth trying?

[SiriusHardware]

A good thought, but not an issue here as the microphone socket outputs a handy full-fat 13.8V supply for anything which might need it, see Sparky's excerpt from the circuit diagram in #6. That powers the 5V regulator within my programming cable, on which, in turn, the MAX232 level converter is running. In case you're not familiar with the MAX232, this IC runs from a single 5V supply and has onboard voltage generators to provide the +/- 9V or so required on the RS232 output side of the IC.

Having looked around at more circuits nominally aimed at Tait radios it does look as though I need to invert the TTL level data.

Normally the 'Standby/Inactive' voltage on a TTL-Level serial line (such as might be found coming out of the TX data pin of a UART IC) is Logic 1, with this being inverted and level shifted / translated to minus 9V or so on the RS232 side.

Measuring on the RXD and TXD pins of the Tait's microphone socket with the radio powered on, I see that the quiescent level on the TX data output pin is 0V, rather than the expected 5V: That also supports the idea that the data needs to be inverted on the way to and from the MAX232.

It will be simple enough to try, although it will require another trip back to my bench at work to insert almost any inverting logic gate IC wired as a pair of inverters into the TTL-level data lines.

Unfortunately I have other demands on my time for the next week or so, so I'm going to have to put this on pause until the other stuff is sorted out.

[Sparky67]

Here are the innards of the 25w serial connector on the lead I used for progging T2000s.

And just to muddy the waters....a lead diagram I found on an old PC here... I had a vague recollection that direct connection to the serial port was supported on some T2000-series radios? Whether this is just for the series II sets and my initial comment on the lead supporting both the initial and the later versions was wrong I'm not sure, and unfortunately I no longer have the sets to test it on.

Out of interest what software are you using?

Later edit... Found another lead diagram on this old PC (shown in the .pdf). This seems to match the interface in the 25w connector.

[SiriusHardware]

I have come across all sorts of conflicting information.

Some diagrams show a direct connection from RS232 to Tait. Your lead certainly doesn't include a separate inverter IC, just the textbook MAX232 + 5 capacitors and a 5V regulator. I wonder if the third and fourth (in theory unused) elements of the MAX232 are somehow being used to perform inversion of the TTL level data?

If the port on this Tait I have here was directly compatible with R232 (as some sources suggest it is) then it would be outputting a standby output level of ~ minus 9V on the transmit data out pin, which it is not. For that reason, I don't think this particular variant supports direct RS232 connection.

On the diagram, from what / to what do the RXD and TXD pins on the microphone socket go on the inside of the radio? (your excerpt in #6 shows the immediate area around the microphone socket, what I need to know now is where / at what sort of device do those signals end up inside the radio? Do they go to a MAX232 or similar? Or directly to the pins of a logic-level device (a microprocessor or dedicated UART)?

Edit: Just caught your edit, where you included the diagram. That's fascinating, as they have cascaded two elements of the MAX232 in each direction so that what is coming in from the PC at RS232 is inverted and converted to TTL level, and then inverted again and converted back to RS232 level!

I was not expecting that, and it does explain why some schemes just use a direct RS232 connection to the radio. The interface only seems to serve to buffer the RS232, not to level convert or invert it.

Edit #2: Various versions of DOS software, but I think the problem is the data inversion in my circuit, which is currently only using one element of the MAX232 each way.