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alec(at)alecmyers.com
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 Posted: Sun Oct 15, 2017 8:12 am Post subject: Constructing an automatic RCA video camera feed splitter |
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It’s an open offer to the group (I would enjoy contributing something) - if you’d like some PIC code along the lines I suggested - one or maybe two buttons, with or without a rotary encoder (that would be my favourite solution) I can have it done by the end of the week, if Paul doesn’t want to. That’s a 1990’s technology solution.
If the group is more comfortable with a 555 and discrete components (a creditable 70’s technology solution) then there’s no need for software.
The choice of interface - number of buttons or switches, panel mount speed control etc. really is down to the person who’s going to be installing it, we should let them pick what they want.
| Quote: | On Oct 15, 2017, at 11:50 AM, Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:
Bob,
My comment was about 'buttonology'; not building. I've got a little clock that's RF linked to Federal time broadcasts. It's totally impossible to use any of the elaborate built-in functions with out the manual, because it has two or three unmarked buttons, and to access the various functions, you need to know the "combination". No one can use the thing without the book in front of them. Same thing for most kilo-function watches, etc. Even my old Icom A-4 handheld comm is like that. I seldom use it, so even though I've owned it for over 20 years, I still don't know how to program frequencies into it. If it had a keypad, anyone could pick it up and enter '122.75', or '125.25', etc. But since it doesn't, the unwashed can only hold the up or down button until they see the freq they want. For me, a perfect example of something simplified to the point of un-usability.
Charlie
 Virus-free. www.avast.com [url=x-msg://59/#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2][/url]
On Sun, Oct 15, 2017 at 10:22 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote: | Quote: | At 07:30 AM 10/15/2017, you wrote: | Quote: | | That stuff is cool as far as programming tricks go, but who will be able to use the hardware except the original designer? I, and everyone else on this list, have owned dozens of electronic gadgets over the years that are absolutely impossible to set up and use without the English-as-a-second-language printed manual that you can't find after the 1st month of ownership. I have to use google on my desktop to explore how to get my phone apps to work like I want. |
This is amongst the simplest PIC applications we'll ever encounter . . . once the first installation has combed out the nits . . . it seems unlikely that there would be many if any software upgrades. Another consideration is flexibility. Suppose the prospective end user wants only two cameras . . . or three? Different software . . . or strapped selection on the ECB? Then there's a matter of packaging. One can easily spend more time putting a gizmo in a box and installing it than it took to build the gizmo. Certainly, packaging issues are a major component of a development project. A possibility for this project is to package in a D-sub housing. The enclosure is an off-the-shelf, inexpensive product that simply snaps onto the final assembly. An ECB can be soldered directly into the gap between rows of solder-cups on a dsub. <aabd0be.jpg> and dropped into a plastic housing that simply snaps together. A product housed in a 15 pin back shell has these dimensions. <aabd0dd.jpg> This project can probably be fitted into a 25 pin back shell. I perceive no particular advantage in taking power and signals on/off the board on RCA jacks . . . shielded wires are just as easily dropped onto d-sub pins. RCA plugs are not the most installer friendly connectors. With the extra pins, the user could intall jumpers on the connector to select 2, 3 or 4 cameras. Other jumpers might select 3, 4 or 5 seconds per step . . . etc. Then there's consideration for the constellation of end users. How many would even be willing, much less able to successfully assemble the thing? Companies I've worked for have often been very protective of details for how their product was put together . . . worries about people wanting to build it themselves. I've observed that the $cost$ to built one-off exceeds the selling price from a manufacturer who is set up to build in volume while working wayyyyyyy down on the learning curve. It seems likely that the best way to bring this project into the marketplace is to have it productionized after the initial development work is completed. Even if supported by availability of bare ecbs and programmed chips, it doesn't seem like many of these things would be built.
Bob . . .
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alec(at)alecmyers.com
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| Posted: Mon Oct 16, 2017 5:20 pm Post subject: Constructing an automatic RCA video camera feed splitter |
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It really depends on how the video display is designed. Analog video was designed to be synchronized with the mains supply frequency - 60Hz in North America, 50Hz in Europe. When I was involved on a consulting project at the BBC in the late 90’s (by coincidence, it was a microcontroller project, and got me hooked on PIC programming) I was shown the rack rooms full of cables doing nothing but acting as delay Iines to make sure each studio was exactly the same propagation delay from the transmission switching room, to maintain sync. That was before it was easier to do it digitally, of course.
There are also sorts of scenarios about how a cheap Chinesium video receiver is going to handle a short frame, or a long frame, and some of them may be very unpretty. Since someone is going to have buy some cameras and a screen, to install in their airplane, I’d feel happier knowing that they’ve tried it out, before spending a happy Sunday writing the code.
| Quote: | On Oct 16, 2017, at 9:12 PM, Charlie England <ceengland7(at)gmail.com> wrote:
It's been a really long time since I did any TV work (long before digital TV standards). But from what I remember about composite video, I'd be very surprised if sync is a problem. Both horizontal and vertical sync are embedded in the video. Here's the 1st tutorial I clicked on in 'the google':
http://www.ni.com/white-paper/4750/en/
Charlie
On 10/16/2017 7:36 PM, Alec Myers wrote:
>
>
> Actually we can combine both a set-at-install with a programmable cycle period. Fans of jumpers/resistors and buttonologists can both be happy.
> And a two-way toggle is the same as two push buttons, and if you only want one push button simply don’t install the second, and be happy with only scanning forward.
>
> Don’t worry about the number of pins on a micro controller - buy the micro controller with enough pins to do what you want. In the face of an $8 part, extra pins are free.
>
>>> Hmmm... I don't have the cameras or a monitor to test it with, and I don't have any need for them. I'm not sure what to do here other than cross my fingers but since the cost of failure is pretty low, I'm OK with that!
> Someone who’s going to build and install this system - and who is going to buy some cameras and a screen either now or later - should buy them, now, and check the idea of frequency and asynchronously switching a bunch of free-running composite video source into the choice of video monitor yields acceptable results. Before a lot of time is spent on this. The cost of failure is - a lot of wasted engineering time and resource writing code and designing circuit boards that will function perfectly and achieve nothing.
>
>
>> On Oct 16, 2017, at 7:11 PM, Eric Page <edpav8r(at)yahoo.com> wrote:
>>
>>
>>
>> Wade,
>>
>>
>> Airdog77 wrote:
>>> No, I like the one toggle or one push-button control on the panel. Simple is good. Scalability to control more cameras, if able, would be a nice feature but not a requirement.
>>
>> Got it: keep it simple. How do you like Alec's idea to have the switch work left-right and be momentary in both directions? Short press steps forward (right) or back (left), long press (2 sec?) starts scanning forward or back. Same functionality, but with the ability to move in either direction.
>>
>>
>>> Being able to set scan rate internal to/or on the box is good, however, don't need a panel mounted control.
>> OK, we'll stick with a set-it-at-installation design.
>>
>>> 5 RCA jacks would be better, much simpler hook up for my configuration.
>> OK, how about a compromise: we design it around a D-Sub and provide a mating connector with RCA pigtails you can use with the equipment you already have on hand? This gives us a ready-made enclosure in the form of the D-Sub shell, and provides a universally available connector for installations in the future.
>>
>> Eric
>>
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alec(at)alecmyers.com
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| Posted: Wed Oct 18, 2017 4:10 pm Post subject: Constructing an automatic RCA video camera feed splitter |
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I don’t think there’s an impedance problem - the inputs to the video switch IC are digital. So yes, I expect it would work fine to connect multiple pic outputs to one camera select input. You can have a camera that is displayed twice as often (or twice as long) if you really want, by using 2 PIC outputs connecting to one video select input. But you’d have to solder some green wires on the PCB to make it happen.
| Quote: | On Oct 18, 2017, at 4:19 PM, Charles Davis <charlesdavis(at)iuncapped.co.za> wrote:
Hi Guys
For the question of the number of cameras to cater for ... if you didn't include the option to change the number of inputs, and had for example 8 available, then someone who only wants 2 cameras - they could connect each camera to 4 inputs, or 4 cameras could be connected to 2 inputs each. A splitter of some sort should be able to match the impedances fairly well. or not ?
maybe not practical, just a thought that doesn't seem to have been discussed ... and I'd hate for you-all to run out of input
Charles
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alec(at)alecmyers.com
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| Posted: Sat Oct 28, 2017 12:42 pm Post subject: Constructing an automatic RCA video camera feed splitter |
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Eric, et al.
Now, I have written a first attempt at the software for this. It uses 220 instructions, 9 bytes of RAM, and two bytes of non-volatile memory.
It’s coded for the 16f18323, which costs about $1. All 14-pin PICs use pretty much the same pinout, as far as I can tell.
Pinout as it stands is
A0 - right button - momentary short to ground
A1 - left button - momentary short to ground
A4,5, C0-5 video selects, active low
The pins can change easily, on this PIC they’re all equivalent, except I thought it best not to use A3 as that’s Vpp which goes to something high for ICSP.
If you want active high for the video select we can do that too, but that means we can’t hack about with bit-or’ing the outputs, as Bob discussed.
Operation:
Right button short push (<1 sec): advance to next camera and stop sequencing
Right button long push (>1 sec): advance to next camera and continue automatic sequencing forward
Left button short push: previous camera and stop sequencing
Left button long push: previous camera and automatic sequence in reverse
If power is applied with the left button held down:
Left button: reduce camera count by 1
Right button: increase camera count by 1
If power is applied with the right button held down:
Left button: decrease sequence delay by one second (to a maximum of 1 seconds, wraps around to 16 seconds)
Right button: increase sequence delay by one second (to a maximum of 16 seconds, wraps around to 1 second)
If power button is applied with both buttons held down:
Reset to 4 cameras, and 3 second sequence period
I have to check if the EEPROM memory can be programmed along with the code.
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Eric Page
Joined: 15 Feb 2017
Posts: 247
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| Posted: Sat Oct 28, 2017 4:03 pm Post subject: Re: Constructing an automatic RCA video camera feed splitt |
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Alec, I think my last post on this subject (on Fri 10/20) must not have been echoed out via email, as it drew no reply at the time.
To sum it up, I found another, better option for the video switch IC. That was the CD4051B, but I've since found an even better one. The CD74HC4051E has high bandwidth, is a true 8:1 mux in a single IC instead of two 4-channel switches, and it requires only 3 control lines to select one of 8 inputs.
http://www.ti.com/lit/ds/symlink/cd74hc4051.pdf
Since just 3 control lines are used, an 8-pin PIC is all we need, so I went back to the PIC12F683. For ease of layout, the pin assignments work best like this:
1: Vdd
2: Control B
3: Control A
4: Vpp
5: Control C
6: Switch (Left) / ICSPCLK
7: Switch (Right) / ICSPDAT
8: Vss
With the CD74HC4051E and PIC12F683, I was just able to make everything fit in the space of a DB-25 backshell I found on Digi-Key (not necessarily the biggest one, but the only one I could find with a drawing that shows interior dimensions)...
https://www.digikey.com/product-detail/en/norcomp-inc/983-025-010R031/925PE-ND/858537
To save a bit of space, I used a two-position male pin header instead of a tactile switch for the duplicate left switch on the board. It can be closed with one of these little shorting jumpers...
https://www.digikey.com/product-detail/en/sullins-connector-solutions/SPC02SYAN/S9001-ND/76375
I hope it isn't a big pain to alter the code for different PICs. I'm sorry you didn't see my earlier post -- it's the last one in this thread...
http://forum.matronics.com/viewtopic.php?t=16767494
For some reason I don't understand, the Matronics server has split this discussion into more than a dozen separate threads, some with just one or two posts. I emailed Matt Dralle about it, but he must be away or busy, as he didn't reply.
Bob, I presume you must have missed my post last week also. I asked about the DB-25 backshell you posted a picture of. Do you have a part number so I can get a dimensioned drawing, or do you know the interior dimensions? It looks like it might be bigger than the one I found, and a bit more room for video signal trace routing would be welcome.
Cheers,
Eric
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Eric Page
Joined: 15 Feb 2017
Posts: 247
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| Posted: Sat Oct 28, 2017 4:09 pm Post subject: Re: Constructing an automatic RCA video camera feed splitt |
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| alec(at)alecmyers.com wrote: | | I have to check if the EEPROM memory can be programmed along with the code. |
I would be surprised if it isn't. The PICAXE chips I've played around with are based on PICs, and their EEPROMs are loadable during programming. Of course, that might be a function of the PICAXE bootloader and not a native capability of the bare silicon...
Eric
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