VGA Driver Advice

lanternfish

Hi all

I have a little project that requires a 3 digit number (0 - 255 received via DMX) to be displayed on a VGA monitor. Ideally the characters will be take up most of the display. A screen resolution of 800 x 600 resolution is acceptable.

Can anyone suggest a suitable driver from the OBEX. This is my first (ad)venture into the world of Prop VGA and just need a little nudge in the right direction.

And then I will probably let loose a barrage of questions when all else fails.

I will be building the project using a Proto Board.

Thanks in advance
Lindsay G

JBWolf

I'm no expert in this area... but I I believe the backback may be the solution you are looking for.
It allows you to overlay text and other ansii chars on your vga display.


Item code

28327


http://www.parallax.com/StoreSearchResults/tabid/768/txtSearch/28327/List/0/SortField/4/ProductID/602/Default.aspx


Also, I am interested in doing some work with DMX on the propeller... can I ask for some details as to how you are generating/receiving the DMX signals?
I would like to be able to decode DMX signals from lighting equipment. Later I would like to make my own DMX controller.
Do you have a part number or schematic of what you are running off the propeller for your DMX work?
Thanks

Mike Green

The Propeller Backpack is not what you need. It only supports TV video. The ProtoBoard's accessory VGA connector should work fine in terms of hardware needed. I suggest using the VGA Text driver which provides for 32 characters x 15 rows. If you really want this to appear larger, you can use a 5 x 7 number font with each pixel represented by a space in one color (for black) or a space in another color (for white).

lanternfish

Hi JBWolf

Thanks for the comment on the backpack. I am not overlaying though. Rather I want to simulate 3-digit LCD type display full screen on a VGA monitor.

Re DMX:

I usually use jm_dmxin and jm_dmxout. Both of which can be found in the OBEX. Jon "JonnyMac" McPhalen (aka Jon Williams) is the creator of these objects and is one of the forum experts on DMX. Another is hippy.
I have also used DMX-512A Receive Driver.

All very easy to use.

I usually use a MAX488 RS485 IC as this allows independent rx and tx unlike some other IC's of the same type There are cheaper IC's that allow you to select either tx or rx at anytime e.g. the SN75176.

When receiving the serial data from any 5V RS485 receiver it is important to either use a 5V to 3V level converter or a potential divider to ensure you don't damage your Prop.

It is important to provide adequate isolation of your home-brewed DMX controlled equipment if using in a professional/commercial environment. There are a variety of circuits available (you can use Google (Image) search) to locate one like this. The optoisolator (6N137)and the DC-DC converter provide the required isolation.

I am currently (longer term project) attempting to redesign an AVR project that emulates a DMX Pro interface using the Prop. Slow progress as it is a bit of a side project.

Cheers
Lindsay G

lanternfish

Mike Green wrote: »

The Propeller Backpack is not what you need. It only supports TV video. The ProtoBoard's accessory VGA connector should work fine in terms of hardware needed. I suggest using the VGA Text driver which provides for 32 characters x 15 rows. If you really want this to appear larger, you can use a 5 x 7 number font with each pixel represented by a space in one color (for black) or a space in another color (for white).

Hi Mike

Thanks for the reply. I will look into it and see how I go. I have a couple of weeks before it is needed so plenty of time for me to explore this.

Cheers
Lindsay G

Peter Jakacki

I have used a graphics driver with font scaling so you can fill the entire screen with a single digit even if you wanted too. There are a couple of different threads but here's one where I demonstrate a capacitance meter with large digits.

Plus this one from a tachometer demo.

Mike Green

You'll probably get a nicer looking display with what Peter used. The graphics display objects work very well except that the display buffer uses a lot of memory. My suggestion would use just a small display buffer. It depends on how complex the rest of your program has to be and how much space the DMX objects need.

lanternfish

@Peter:This looks very promising. I look forward to having an in depth look at it.

@Mike:thankfully the rest of the program is minimal in that it only needs to read one DMX channel and pass that on to the display object(s).

Probably a lot of questions later.

Thanks for your assistance.