#SSTV interface
8 messages in this thread
Kelly – careful, you have my PPN wrong! Take note of the one in this message,
and use it in the future, ok?
DB0-DB5 go to DB0-DB5 on the PARALLEL PORT – this is NOT in ANY way
connected to the Amiga's internal circuitry. -BR goes to DB6 on the
PARALLEL port, and -BA goes to DB7 on the PARALLEL port. THe whole thing is
interfaced to the Amiga thru the parallel port! The mode bus, for the
purposes of this particular project (Which is 8 second sstv, b&w only) does
not need to be used. If you DO elect to use it, what it does is tell the
outside world what MODE the terminal unit (which is what you are building)
is in. THis is so that pre-selctor filters can be applied according to the
mode. For instance, if the mode bus = 010, then the terminal unit is in
RTTY mode, and a 170hz filter is appropriate. If the Mode bus is 011, then
the TU is in SSTV mode, and a 2khz filter is appropriate. The terminal unit
will function very well w/o any extra filtering, so don't worry about this
yet.
The mode indicators are: (0-7) CW, 170rtty, 425rtty, 800rtty, Originate,
Answer, Rx SSTV, TX SSTV.
Yes – the terminal unit will do ALL of those things. <grin>
I do not have the print in front of me (and alas, I have not enuf memory to
bring up scheme while telecomming… the D0-D7 lines of the EPROM go to the
D0-D7 lines of the 6809 and the RIOT chip… so if the print says
otherwise, then it's wrong. And I apologize – thanks for pointing it out.
Also – kelly, I have plans for a FAR more elaborate SSTV scheme – this will
be full color, robot modes and otherwise. The hardware is being prototyped
now, and will be MUCH easier to build than the terminal unit. Care to wait?
Let me know! –Ben–
Thanks for the reply, Ben.
Needles to say, all production on the SSTV interface has come to a stand
still! How long do you think it will be before the NEW and IMPROVED
interface will be ready? Will it use any of the same parts that were in
the original interface, like the RIOT chip or the 6809 (seeing as I now
have them on hand)? Will this new interface also do AM WEFAX? If it
doesn't, I will go ahead and build that interface. Will this new interface
still interface via the parallel printer port? Will there be LED
indicators on it for tuning indicators?
Does the program for the current interface support all the modes the
interface can do, or just the 8 second SSTV? Will the new software for the
new interface?
Looking forward to seeing the new interface about as much as I am waiting
for the next issue of the Amiga Transactor!
I understand you may be providing PCBoard layout with this one, and even
going commercial with it. I will just wire wrap it up, much quicker and I
got no plotter to make pcboard patterns! My usual way of building anything
to this point has been point to point wiring (messy), and am now giving
wire wrapping a good try.
Batteries all charged up for the wire wrap gun and nothing to wrap!!
73, Kelly
P.S. The LEDs are also backwards in the current interface schematic, and
thanks for pointing out the new PPN.
Well – the interface design should be ready tonight or tomorrow; It's
being build this very second (sat nite). It does NOT use the same parts
that the first did, so you might as well build the first one, too;
especially since the first one has many modes that this one will not. This
is a high-precision one intended strictly for use with the video modes such
as sstv and wefax. It will NOT work for Am wefax, as that has entirely
different characteristics – namely, it's an FM audio signal as opposed to
an AM one. It still interfaces via the parallel port. There will NOT be LED
indicators on it – instead, there will be a tuning indicator on screen
(much more fun, anyway). The program for the current interface supports
only 8, 17a, 17b, and 34 second B&W, as well as being able to receive the
12 second color and 36 second color images as B&W. The new program will
(eventually) support all of those modes, plus in full color, and wefax mode
a and mode b. As for how you build it, no problem; as you please.
As to the mistakes on the print, yeah, there you have it. The LEDs _are_
backwards, now that I look at em…. <grin> But I failed to find any
problems with the data bus – care to be more specific on that one? (and
thanks for examining it so closely)
If you would like to get the parts together for the new interface, I can
tell you what they are as of now:
1-74ls00, 1-74ls86, 1-LM311, 3-74ls93, 2-74ls374, 2-74ls74
In addition, you'll need a 4 mhz crystal, and a 5-50pf capacitor.
All other parts are things like .1 caps, and some common resistors, the
cable to the parallel port, and (possibly) a power supply (5v) for it.
Depending on the amount of power it draws (havent even thought about it
yet) we may run oit from the parallel port.
–Ben– N4EJI
Er….. last minute update – it will NOT use an LM311 – it will use a
TLO-82. Darned front end just wasn't sensative or accurate enough. A 2
stage limiter/comparitor works well, though. Same thing that's in the
terminal unit, actually. <grin>
You will also need a 2n3904 or equivalent NPN switch.
–Ben–
Hi Ben,
I should have the currently released interface done tomorrow (if not
tonight). Now if you could be so kind as to upload the eprom contents to
your data library, I could burn the eprom and give it the smoke test – then
hook it up to the printer port and try it out.
Sounds like your new circuit will use the same input circuit as the current
interface, so I may just share that part of the circuit. Could probably get
the 4 Mhz clock from the 6809 if that doesn't load down the oscillator
circuitry in the 6809 too much. I will figure out what all I have to order for
parts when you finalized the design and released it.
Do you think the interfaces would work alright if they had to talk through a
CD4066 to get to the Amiga's parallel port? If I use a few of them, I should
be able to put all three interfaces in one box and have a selector switch to
determine which gets to talk to the Amiga. (Plus route the audio as necessary)
Regarding the eprom's data lines – it is where the lines come off the bus and
go to the D0-D2 pins of the eprom that they get reversed. You have to look
pretty close and trace them out.
This wire wrapping isn't going too bad (so far). It's a shame the sockets are
so expensive.
73, Kelly
KElly, I honestly don't know if you could tap the 6809's crystal taps; I bet
you can, IF you use a cmos buffer… nice idea, if it workes… heh heh. Upload
the EPROM? Ech! That means I'll have to connect the eprom programmer to the
system…. hmmmm… Or, it means I'll have to type in the code and assemble it
in here, which is kind of a waste of time. On the other hand, if I connect the
programmer to the system, then I'll have to write an interface program for
it…. which would NOT be a waste of time. On the other hand, I don't _have_
any time! <grin> I would MUCH rather send you one – is that alright with you?
Hope so.
The new circuit does NOT use the same type of input circuit… that is, it uses
all 8 data lines and the PC flag (whatever they called it on the parallel port,
I dunno right off) as well as (of course) lot's of grounds. I wouldn't use
4066's, I think – no drive capability. We are currently planning to make the
thing a pass-thru device; it uses the parallel port to get data into the
system, and it uses an audio channel to get it back out again (transmit AFSK).
There will be a button (10-pole switch) that makes the thing a pass thru, then
you can just plug your regular stuff into the rear of it.
I'll look at the EPROM. Thanks again!
BY the way – I have the interface here; I think it may be done. Works
outragously on black and white sstv and fax…. working on color now.
–Ben–
In the new interface, will there be a mode bus for optionally switching receive
filters, too? It seems like a good idea, especially when you try to do
anything on 20 meters!
Have you tried to use your FRG-9600 for the wefax satellites at 137.5? I
wonder if the bandwith might be too narrow for this mode.
In your message in the AmigaTech forum to somebody about wefax reception,
you mentioned Dr. Ralph Taggart's books. The third edition of this is
supposedly only available from the author at a cost of $15.00/copy (an
extra dollar if outside the U.S.) at:
Dr. Ralph E. Taggart WB8DQT
602 S. Jefferson
Mason, MI 48854
You may already know that, but you could send it to who ever you were
chatting with about wefax. I don't have the third edition, only the first
and second when it was handled by Wayne Green Press.
73, Kelly
Thanks for the info – I'll just direct him over here.
As for the mode bus, no – because this interface only handles video modes,
and they are ALL 1000-2300hz input frequencies – one filter would handle
them all. For the other interface, which supports many operating modes of
differing bandwidth, it WAS a good idea – and thanks for saying so. I'm
rather fond of that design, even if there ARE errors in the print. That's
what I get for transferring a print from paper to screen…. without the
normal draw/build/debug cycle, things just aren't checked as well. <sigh>.
–Ben–