How to utilize row scanning in moving display.

[swapan]

Hi Friends,

With the help of this forum, some online tutorial and specially Mike, one esteemed member I have completed a scrolling display consisting 38 columns and 7 rows based on PIC. I adopted column scanning system.

Now I am in thirst to get adept in Row Scanning system. In spite of vigorous surfing I could not get any hint in this regard.

In case of column scanning, data of each column is moved to a ghost location and the data from ghost location is moved to output port. After certain time (viewing delay) the data of ghost locations are shifted one step and data of next column is moved to the ghost location where data was moved first. As the display has 7 rows, data of each column accommodates in a register (8 bit). I am in a sense that in case of row scanning, data of one entire row consisting of parts of many characters, requires to be moved to a ghost location from where it will be serially moved to shift registers. After that, the shift registers will be latched. Likewise data of second row will be moved to shift registers through another ghost location.

If the system is like that, how a large number of data ( say- for a display of 100 columns) could be managed in a ghost location. Is it moved to multiple registers of 8 bit each?

Please give some hints or any link where I could get any idea. I know only assembly language.


Regards

swapan

 

[Ian Rogers]

Use this as a base

Its only 8x8 but changing it wouldn't be a problem.

 

[swapan]

Thanks Ian Rogers. Going through the tutorial I have got a clear conception about the technique you have adopted to scan the rows. Really it has proved to be very useful for me. But, being a newbie, it took some time to get the idea. And that's why I am a bit late to convey thanks and put forth some curiosity. Since your design uses 8 columns, you have taken 8 registers (zero through seven) for buffering row data. In case of big display consisting of many columns (say 64 columns) how it will be managed? Would it require 8 GP registers to buffer data of each row? If the display uses 10 rows, 80 registers will be required to hold the row data. I have just thought like this. I may be wrong.

Would you please through some light on it?

regards


swapan

 

[Ian Rogers]

Something I've seen before.... A guy on the GHI forums created a brilliant animation... It took me by total surprise... He created a story, full 128x64 screen using line buffers (very similar to what you are doing ) each 8 byte line buffer was read in from an external eeprom ( or raw SD data ). The animation was as if someone was drawing on the screen with a pencil.. the original was done with an Arduino.. I have never been able to find it since......

The point being... If the animation was in the order of 25fps with 128 8 byte buffers its really no different driving 100 columns of a single byte...

 

[swapan]

I have not yet done even don't know if it is the system. Following your method of scanning rows, I have thought like this. I earnestly request any hint from experts of this forum.

Leave my thinking. If you use 16 or more columns instead of 8, how would it be done? Would you take required number of registers for ghost locations for each row or adopt other method? Please extend help to a novice.

regards,

swapan

 

[Ian Rogers]

100 bytes isn't that long... The trouble is to write fast enough to keep a decent duty cycle.....

I will be making a cricket score board very soon.. I will consist of 22 alphanumeric characters.. I will be employing external latches to maintain the illumination ( the digits are 15" high ), writing to 22 bytes becomes very easy if you use external ic's...

Take a look as the font on a KS0108.... The font is stored the way YOU need it... You wont need ghost registers.. just a simple font engine to output the right information, at the right time... I have simple 3 x 8 fonts and 5 x 8 fonts, for this module.... The code I use to print each column onto the screen, one after another will probably do for this application. All that you need to do is to "print" the string to the "font engine" and let it write out the message...

 

[swapan]

Thanks Ian Rogers. Awaiting eagerly for your project. Actually I am interested to know the technique.


regards

swapan