>
>Data is received over a single pin serial line and
>transmitted over a second single pin serial line. This
>allows me to connect the "output" of one PIC driver module to the
>"input" of the next. Currently I use a portable PC to
>input the data to the first (rightmost) Pic driver module.
>
>Input data is received as 8 bit data and stored in a
>file register. Every time new data comes in, the data
>is "bumped" or moved to the file register to the "left".
>When data is bumped out of the "leftmost" register,
>I send it in serial format to the PIC module to the
>left of the current pic module. I use a single system
>clock that drives all the PIC modules.
>
>Modules can be added pretty much indefinitely as long
>as you buffer the clock occassionally.
>
>Instead of using standard serial UART routines, I used a
>self-clocking scheme that allows a large range of
>baud rates. The PC communicates in serial mode, but using
>a bit from the PCs parallel port. My reason was simply
>so that I could control the self-clocking. One bit
>of the parallel port was used as an input. This allowed
>me to send clocking and other handshake info to the PC so it
>could operate at maximum speed.
>
>The PC would output serial data in self-clocking fashion
>to the rightmost PIC. The MSB of the 8 bit data was used to
>indicate that control rather than data was being sent.
>This allowed me to send instructions such as Clear All LEDs
>to the entire string of PIC modules. Each PIC would
>simply relay these commands when they received them.
>I wrote up a program in Foxpro that allows me to create
>custom characters up to 7x8. This program then created
>a memory map that allows me to decode any ascii character
>to its visual components. To make the display capable of
>handling more characters I use the MSB to indicate when
>a character is finished. I usually include one blank
>column as a separator for characters. Thus a character
>like "i" will occupy less width than the character "W".
>In other words, the technique allows proportional fonts.
>
>I prepare the text that I want displayed in a text file.
>Then I run the PC program that loads the desired font
>set, decodes the characters, and sends the column data
>to the first PIC. Scrolling speed is software adjustable,
>and provision is made to use multiple font sets within a
>single message. Once a message is completely sent I send
>out a string of spaces and send the message out again and
>again.
>
>This all works fairly well, is easy to understand and
>implement on a 16C84, and has a reasonable parts count.
>The biggest expense is all the LEDs. If you use the newer
>super-bright LEDs you will pay more, but you can move the
>LEDs further apart and get a really large display that
>is visible for reasonable distances.
>
>Hope this helps.
>Fr. Tom McGahee
>
>----------
>> From: Pedro Barrios <
KILLspambarriosspamBeGone
NANOFAB.TAMU.EDU>
>> To:
EraseMEPICLISTEraseMEMITVMA.MIT.EDU
>> Subject: 32 bit rotate
>> Date: Tuesday, June 09, 1998 2:59 PM
>>
>> Hi everyone,
>>
>> I'm trying to find a way of displaying a message in a 5x7 LED
>> array. Basically, I don't have a good idea of how this is
>> usually done, but since I have worked a little bit with the
>> 16C84, I thought I give it a try.
>>
>> I was thinking about having a message array 32 bits long by
>> 5 bit wide containing the information I want to display. I would
>> then take each one of the 32 bit words and rotate sequentially
>> bit by bit and display the 7 most significant bits after each
>> rotation. I would do this for each of the 5 rows of the LED display.
>>
>> I will appreciate any help on how I do this 32 bit rotation with
>> the PIC, and also any suggestions or comments as of how messages
>> can be displayed in LED display arrays with the PIC.
>>
>>
>> Best Regards,
>>
>> Pedro
>
