design requirements

tblunt

Im in the process of designing a comm system for use in theatre and need to know if the propeller will be able to handle my requirments. I think it will but i want to be sure.

What i need is a box with a qwerty keyboard attached and a screen LCD/TFT and another box exactly the same and on one box i type a message and then press enter it gets displayed on the other box's screen.
They can only communicate by 2 wires at this stage if I find a suitable RF device that wont intifer with any other current systems ten i may upgrade to a wireless link.

I would also like the ability to add more boxes in the future and heve then display on 1 master screen only.

If this all possable with the propeller or would i need to get another chip? also has anything like this been done before I have done some searching but I havent found anything like it so far.

thanks

Mike Green

The Propeller can certainly do this. You'll need a PS/2 keyboard and some kind of display. A TV that accepts standard video will work fine. You can also use a VGA display. A nice RF device that will work is a pair of xBee transceivers which Parallax is carrying. You'll need a pair of Propeller Demo Boards. The Demo Board has the connectors already for both TV and VGA as well as a PS/2 keyboard. You'll also need a pair of xBee Adapter Boards to mount them on the Demo Boards since the xBee pin spacing won't fit the Demo Board without the Adapter.

tblunt

Thanks Mike.
I was more thinking of a small LCD screen (2*16) or a few osram DLG1414's for the output.

What is the best place to start for someone that knows nothing abuot this particular chip or language?

rjo_

I think this is a classic. It is a very early document and very sparse but it is just beautiful.

Mike Green

The Propeller Education Kit Labs tutorials is another good starting place. It's all downloadable. There are links on this page:

www.parallax.com/StoreSearchResults/tabid/768/List/0/SortField/4/ProductID/541/Default.aspx?txtSearch=propeller+education+kit

There are all sorts of programming tools available from Spin and the Propeller Tool to Catalina, a C compiler and 12Blocks, a graphical programming system. There's also PropBasic which is a Basic subset based on SX/B for the SX microcontroller just recently released in "beta" form ... still under development.

A Propeller could handle either a generic small LCD screen or some DLG1414s. Rather than the Demo Board, I'd suggest a Protoboard with the Accessory Kit to give you the PS/2 connectors. There's also a VGA connector, but you don't have to use that.

Forest Godfrey

Hmm, this sounds like a nifty project! Would be very useful for me as a sound board operator to communicate with the stage manager since, at least for me, wearing a Clearcom while trying to mix a musical is not really a good option.

The nice thing about most electronics wireless gear is that it is well out of the way of wireless mics. There are some, though, in the 433MHz area that may interfere with cheap walkie-talkies (and at least one audience hearing assisted device that I've seen is in that band).

If you wanted to stay with wired communication, you could use XLR and have a male and female jack on each box and create two serial ports on the Prop. Then you could form a daisy-chain in the same way as a ClearCom. If you went the wire route, though, I'd suggest building in some electrical protection so nothing fries if it accidentally gets plugged into a mic feed with phantom power, a ClearCom feed, or a DMX feed...

tblunt

yeah thats almost my intended use. its to communicate with my mic tech backstage so if a mic dies i can talk to them with out using 2way in the really quiet scenes.

The reason i've chosen 2 wire is some places i work in only have pins 2 & 3 wired up in there sound cabling. go figure. Eventually I will get 2 boxes either side of stage for cast to pass on messages to the mic tech and also one for the SM for me.

VIRAND

It would be easy for a Propeller.

On Youtube, a video called "Home Make Keyboards" shows some old junk including a pair of terminals
based on old 1KB (?) PIC15C54. They look like calculators but can also be QWERTY and have 40x2 display.
Designed as universal interactive remote controls and communicators, many extra features packed into a chip
that barely can be a watch or calculator. Many ctrl characters including BEEP, clear, 4-direction cursor.

Chips might be available VERY CHEAP within USA. Mostly posted to show it has been done and how it works.

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VIRAND, If you spent as much time SPINNING as you do Trolling the Forums,
you'd have tons of awesome code to post! (Note to self)

Forest Godfrey

Hmm, this is more complicated than I thought then. If you only have 2 & 3 (the two signal pins), then you don't have a common ground. That's fairly common in audio cables (to lift the ground), but a habit I really hate (if I need the ground lifted, I'll do it myself!). So, if you use one of the pins for ground or you go for differential signaling, then you don't have one TX pin, one RX pin, and a ground, which is what I was assuming with the XLR connector.

However, what you could do is make the male XLR connector be a slave and the female connector be a master (or vice-versa). The master transmits 10 bits while the slave receives, then there's a gap, then the slave transmits 10 bits while the master receives. That gives you the 8 bits for a character, one bit for parity, and one "valid" bit. The master would *always* transmit a 10 bit chunk when it has its turn. If it has nothing to transmit, it clears the valid bit. That way, the slave always knows when it has a turn to transmit. That way, you can use differential signaling, which will increase your max cable length significantly and still only requires the hot and cold pair in the XLR connector. You could also do signal/ground. This probably (definitely?) isn't the most efficient protocol on the planet, but would be trivial to whip up in the Prop and since all you're sending is text, you'll be fine.

If you want to get all fancy, you could add a real-time clock so the messages could be timestamped so your mic tech knows how long ago you sent the message.

I'm actually kinda thinking about building a few of these myself now [noparse]:)[/noparse]

lcyepiz

The propeller is a excellent choice,

You can download and test object of keyboard, VGA text out and serial comunication

http://obex.parallax.com/objects/

For the comunication link you can use RS485 (32 nodes over link, new chip allow 256), 9000ft a 9600 baud, in short distance like a theatre 1Mbaud

and the propeller can send data a this speed.



for each station use a address·and you master station cand send a private message a each, or make

a global message if you make·simple protocol in ascii

for example send the next string

··· "S99M hello stations"

or

·· "S01M hello station1"

You have the RS485 in receiving mode get the characters from the link

if you·receive S99M show the message in all station, the address 99·is broadcasting

and if you receive S01M only show the station have the adress 01



If you need power, and you have time to make a diference use propeller



Luis C. Yepiz

XE2NBW

RS_Jim

Jonny Mac wrote an article in Spin Zone available from Parallax as a download that sets the Prop up as both a DMX transmitter and receiver. You can lookinto that article and gets some Ideas for 2 wire coms.
RS_Jim

Timothy D. Swieter

I would recommend RS485 or wireless. The thing to note though is that RS485 really isn't a two wire communication network - it is three. The ground/shield line is very important.

SparkFun has some RS485 breakout boards you could use to plug into a Prop Proto Board or Prop Demo board for testing.

Your application of the Propeller is great. I think you have a cool project to work on. You are essentially creating a hardware instant messaging system for your theater and shouldn't be too much trouble. Nail down the communication medium (wired or wireless), then create your protocol (how the devices share information), then start diagramming your software. You can probably use objects posted in the exchange already - finally glue the pieces together in software and see the system come alive - you will be addicted.

I also recommend going through the Propeller Labs as Mike said.

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Timothy D. Swieter, E.I.
www.brilldea.com - Prop Blade, LED Painter, RGB LEDs, 3.0" LCD Composite video display, eProto for SunSPOT
www.tdswieter.com