Scrolling Text Using MAX7219 to Drive 7 Segment LED Displays

CDP

I am very new and very apprehensive about posting on a forum. I have seen some pretty angry responses to posts. I hope I can be clear enough in what I am working on and my question to elicit a kind and helpful response.

I am an artist working to gain control of the LED and sound output of an alarm clock. I hope to generate scrolling text messages across the face of the alarm clock.

I am using the Basic Stamp and MAX7219 IC to drive 4-6 7 segment LED displays with pbasic code. I am currently hung up on finding and altering the code to scroll the text. I went through the lessons on single 7 seg displays and successfully programed the alphabet. I then graduated to 4 7 seg displays using code for a change counter (the pdf with code I am referencing is attached) and I am still working to understand how it functions so i may change the code to create scrolling text. Today I found another pdf with information about avr firmware (see attachment) but I am not sure if this is something I can use with pbasic and basic stamp, but it appears to be just what I am looking for.

If someone could point me in the right direction to find code for scrolling text on a 7 seg LED display or advice in reference to the avr firmware, I would really appreciate it.

sw29.pdf
avr_7seg1_doc.pdf

Tomato

Just a suggestion, maybe you want to use 14-seg displays. You could make much clearer letters. I guess you need some kind of muxing though, for the extra bits.

-Tomato

CDP

Thanks for the suggestion Tomato. I agree the 14 seg displays would give me clearer letters.
I am planning to graduate to 14 seg displays after I figure out coding the 7 seg displays.

CDP

PTaylor

You might want to look into using a smart display such as the HDSP series.

These are great little displays and can communicate serial so not all the lines are tied up. You get many more options as far as characters, brightness control, etc.... with them. there are also several projects on the web using them with Stamps and other controllers, or hooking them to a PC port.
An example:
http://www.f-16simulator.com/pdf/CMDS_DISP_guide.pdf

CDP

Thanks PTaylor

I will for sure look into using these smart displays. They look nice!

I guess one part of being an artist is making life difficult or making life difficult for myself rather. I feel the integrity of this art piece is using the type of led display most commonly found in alarm clocks such as the 7 seg display. The clock needs to be believable as a clock unaltered until it starts to react differently than expected. That is kind of the "magic" of the piece. I will ultimately branch out into different displays in the future, especially according to the needs of the projects.

Thanks for the suggestions, but for this project I need to make the 7 seg displays scroll or blink text.

CDP

Franklin

Does that chip select each digit to display with a pin to ground? And if so you could swap those in sequence to "scroll" the text.

vaclav_sal

Here is a first shot at the code. I cannot test it today, give me few days.
I am sure it will not work without some tweaking.
(For sure it will not scroll past the left display)
It is just a pseudocode suggestion on one way how to do it.
The key is to separate the display multiplexing loop from the scrool loop.
The indexes are probably wrong to display correct character in correct place.
In theory it should scroll left to right.



Data index 1 to 4
Scroll index 4 to 1
Output scroll index = data index

Do while scroll index

DO while output scroll index
Get data @ data index

Output data @ sctoll index
output scroll index - 1
loop

Data Index + 1
Output scrool index = data index
Scroll Index - 1
Loop

Vaclav

CDP

Thank you all!
These are very good options/suggestions.
I am going to work with them a bit and see what I can do.

CDP

CDP

I thought I had it!
I found a Nuts and Volts article which provided code (see attachment) but after wiring and trying to load the code I noticed it said it is for BS1. Does anyone know how to update this code for BS2?

BestOption!.pdf

Franklin

I believe in the bs2 manual there is an appendix that explains converting code.

arun.kalyan.sundaram

I had implemented a scrolling text on 7-segment LEDs using a shift register and 7447 IC. The code is written in C and the number of LEDs and the scroll speed is configurable. However the code runs on a PC/ laptop and uses the parallel port to interface to the LEDs. Let me know if this is something that can be of help to you.