Day/date/time onto cassette ... ??

[McGuinn]

John1,

It's been a while since I posted here, and I hope I'm not coming in late and OT on this subject.

As mentioned by a previous poster, DTMF is something you would want to look at. It's a method of using audiable tones to pass data down a phone line typically. It is the basis of tone dialing. It stands for Dial Tone Something Something... sorry... but I do have a link for you...

Decoder:
**broken link removed**

Encoder:
**broken link removed**

The only thing I am unsure of is whether it will allow anything more than 0-9 adn star and pound (hash) to be produced/decoded... you could develop a sort of protocol if you need... A PIC will do this for you.

Enjoy!

 

[john1]

Hi McGuinn,

Thanks for your interest, and i did look up that stuff about
tones. I had thought that the major problem would be making
something that could put the date/time on to tape (or whatever
medium). It now turns out that creating the date/time needed
such a high level of technology that turning it back to audio
in order to record it to cassette is effectively a backward
step, using the arrangement necessary to create the date/time
to further create additional control mechanisms is more in
keeping with the desired end result.
That is, a record of events and actions around my home, having
this in an electronic form for my PC and also printed on an
old printer (maybe later on a till roll). Using a PIC and also
some support chips running from the supply and the box that
would have to be made to create the date/time information, is
i now think a much more practical proposition.

So really the nature of this project has actually altered by
discussing it here on these forums. Unfortunately i cannot
alter the thread title, but now its more a case of me stumbling
along into PICs, a direction that i did not foresee.
Now that i am starting to realise what they are, i am getting
more and more fascinated by them.


Hi Nigel,


Well ive been reading up on these PIC devices, the more i read
about them, the more they remind me of the Zilog 8080-A, they
seem to be rather like a slow running PC chip, i may be wrong
but i think they use clock speeds of one microsecond, okay its
not that slow i spose.

Years ago i went through a phase of trying to program an 8080
in assembler, i did a little bit of moving letters around on
the monitor, then i got frightened off cos i didn't really
follow the architecture.

Now i find that these PIC chips use a 'Reduced Instruction Code
Set' so maybe i could get to grips with the PIC system of
shuffling 'words' between registers till it comes out right.
Apparently the instruction set is thirty odd instructions,
i wonder if its not too difficult to learn how to use it, at
a machine code level.

Your mention of 'allocate a pin for each input' has me quite
confused, unless you mean on the integers (2,4,8,) i'm still a
bit lost on that ...
And i am a bit concerned about the overlap of incoming signal
times. As it stands, the incoming signals light lamps, and some
ring bells. If two come in close together, thats ok, two lights
is ok. But for the electronics it might not be ok. Maybe i
should arrange that any incoming signal would only feed a mille
second pulse to the electronics, in the unlikely event that two
such signals arrive together, then one would be lost.
Unless there is a way to respond that i haven't thought of.
The lights or bells would still work anyway, so it wouldn't get
missed.

I would like to ask about the programming of the PIC, i assume
that is erasable and not permanent?
And would i need to make some kind of rig to 'implant' the
programming?
I had to make a 'rom' unit years ago for programming rom chips
i used to run seven segment displays off them directly on the
output lines, i think i coded the inputs for the 8+2 binary
from early counting chips. It made for an easy count and display.

I am still reading up on these PICs but basic info is not
easy to find.

John

 

[Nigel Goodwin]

Well ive been reading up on these PIC devices, the more i read
about them, the more they remind me of the Zilog 8080-A, they
seem to be rather like a slow running PC chip, i may be wrong
but i think they use clock speeds of one microsecond, okay its
not that slow i spose.

It all depends on what speed you need, a 4MHz PIC runs at one instruction cycle per uS - that's a million instruction per second. This is actually pretty fast, far more so than most of the early home computers, most don't execute instructions at only one quarter of their clock speed (and the 8080 certainly doesn't). Going back to the early days, the 6502 running at 1MHz had the same sort of performance as Z80's running at far higher clock speeds, due to it's more efficient design.

BTW, a 20MHz PIC gives one instruction cycle every 200nS.

Years ago i went through a phase of trying to program an 8080
in assembler, i did a little bit of moving letters around on
the monitor, then i got frightened off cos i didn't really
follow the architecture.

Now i find that these PIC chips use a 'Reduced Instruction Code
Set' so maybe i could get to grips with the PIC system of
shuffling 'words' between registers till it comes out right.
Apparently the instruction set is thirty odd instructions,
i wonder if its not too difficult to learn how to use it, at
a machine code level.

It's a lot easier, there are only 35 instructions, and out of the 35 there's a fair few you only rarely use.

Your mention of 'allocate a pin for each input' has me quite
confused, unless you mean on the integers (2,4,8,) i'm still a
bit lost on that ...
And i am a bit concerned about the overlap of incoming signal
times. As it stands, the incoming signals light lamps, and some
ring bells. If two come in close together, thats ok, two lights
is ok. But for the electronics it might not be ok. Maybe i
should arrange that any incoming signal would only feed a mille
second pulse to the electronics, in the unlikely event that two
such signals arrive together, then one would be lost.
Unless there is a way to respond that i haven't thought of.
The lights or bells would still work anyway, so it wouldn't get
missed.

As I see it, you've got a number of wires, they normally sit at 0V, but when an event triggers one of them the particular wire goes high. It could work the other way round - going from high to 0V, it makes no difference really.

A PIC has I/O (Input/Output) pins, you would obviously set some of them as inputs for this application. The pins are arranged in Ports, where a Port has up to 8 pins (as it's basically an 8 bit processor). You can refer to these pins as 'PortB, 0', 'PortB, 1' up to 'PortB, 7' - so for you using 8 incoming wires you could simply connect them each to a pin of PortB.

All you do then is 'polling', which simply means testing each I/O pin in turn, the PIC is designed to do this and has simple instructions for testing an individual pin - which full micro-processors usually don't.

So you would simply test pin 0, if it's triggered then jump to a routine that deals with it - if it's not triggered, then carry on and test pin 1. Do exactly the same with pin 1, then pin 2, then pin 3 etc. - when you've tested all pins, loop back to the beginning and start again.

If you need more than 8 inputs, simply use more than one port.

I would like to ask about the programming of the PIC, i assume
that is erasable and not permanent?
And would i need to make some kind of rig to 'implant' the
programming?
I had to make a 'rom' unit years ago for programming rom chips
i used to run seven segment displays off them directly on the
output lines, i think i coded the inputs for the 8+2 binary
from early counting chips. It made for an easy count and display.

I am still reading up on these PICs but basic info is not
easy to find.

You need both a programmer, and software to run it. There are basically three different types of PIC's:

1) OTP (One Time Programmable), as the name suggests, these can only be programmed once - so a manufacturer would usually use these after all development has finished.

2) UV Eraseable, these are essentially OTP, but have a quartz window in the top, which allows you to erase them. These are VERY! expensive, normally only used for development work.

3) EEPROM/FLASH, these are electrically eraseable and take only a few seconds to program - the programmer erases them and reprograms them in one simple operation. These are by far the best type to learn on, if not to use all the time.

If you visit my website at http://www.winpicprog.co.uk there are quite a few details about PIC's, including programmer software, programmer hardware diagrams, and a PIC tutorial - which if you study the early ones, may help you a little.

 

[john1]

I'm guessing thats why 'simulator' programs are so helpful, cos you
can check out the reaction before setting the PIC chip, that saves
having to erase the chip if it doesn't work as you expect.

I seem to remember that the assembler code on the 8080A did not
always do what i expected, and sometimes did extra unexpected
things too!

Anyway i have obtained an old VHS Video Cassette machine and i am
going to start checking it out.
It is a 'SHARP' model: VC-7300H
So i will return with details of what i find.

Cheers, John

 

[john1]

Well it flashes 0:00 at about one second intervals.
Its a green quite large number display,
it looks like one of those thermionic filament
vacuum phosphor type displays.

Haven't got it to do anything else yet ...

still trying, John

 

[john1]

OK, you have to hold down the button marked 'clock'
then you can use the other clock buttons.

The clock seems to work fine.

I'm going to take the case off and have a look now.

John

 

[john1]

Its got lots of stuff in there,
more than most VCRs,
including a rather beefy looking power supply unit.

Well i better start looking for the clock board.
And try to find that crystal.

Wish me luck, this old thing might
have a balance wheel.

John

 

[john1]

Hi,

Well this thing is like a Mechano set gone mad, there are
about four electric motors, many pulleys and belts, some
belts have deteriorated badly, and four or five solenoids
of various sizes, an assortment of gears and mechanisms,
and lights with light sensors.
I had thought the smaller boards were not plugged in very
well cos they seemed a bit loose, but its not that, they
are slotted neatly into guides, they have flying cables
with multi way plugs and sockets, they don't have connections
along one edge so they don't feel firm.
I found my way to the clock board.
It is a filament vacuum phosphor display unit, but i see no
crystal on this board.
Some of these early digital clocks used a counting sequence
from the 50 cycle mains, it might be made like that.
And ive just noticed, it has no day/date/month only the time,
so i think i will just continue pulling this apart for any
spares that i find interesting.

John