I have used 4028 IC's as in the Robolympic circuit and using a PDB with a SX28 and 0.1 caps. I have them going to a custom built LED array going through ULN2003 drivers (20 using 16) and PN200 transistor circuit (7).

I am trying to build the Robolympic circuit to learn how it works and build from it. What I am getting is all 16 x 7 LEDs display "rows" of patterns up and down. Do I have to do something to the SXB code first?

See this picture showing what the LED display looks like.

I have rechecked all the connections 3 times and see nothing wrong with the wiring.

Ideas on where to go with this?

The Robolympic badge drives the rows high (from RC) while pulling the selected column (output on RA through a multiplexer) low -- does your modified circuit work like this too?

Jon,
That explains it. I have the opposite with the 7 Rows LOW (black wires) and the collumns HIGH (red wires).

Is it possible to modify the code to invert the lines?

Well, I figured out what the problem was..Kind of embarrasing too but...

On the PDB, I had the 4028 Vcc pins connected to GND and the 4028 GND pins connected to Vcc. (also had 1 7404 inverter wrong too). All those wires...

When I fixed this messages starting going across with inverse lettering (cool all the same). In the SX/B code I changed 1 line of code to get it to work correctly with LOW rows and HIGH columns.

I changed this:

RC = Display( RA )     'LOAD NEW ROW DATA TO RC to this (begining of the SX/B code)...

RC = NOT Display( RA )     'LOAD NEW ROW DATA TO RC



Now I get it to work beautifully.

What I will do next is modify the code (and add another 4028) to add another 5 columns of LEDs (20 x 7 display) and the original Robolympic uses 15 x 7.

Thanks Jon!!

I added another 4028 and moved the inverter to the last 4028 pin 11 (D). However, when changing this line:

Display VAR Byte (15)
to
Display VAR Byte (20)
I get the error message:

...VARIABLE EXCEED AVAILABLE RAM
All of the other variables used, I don't see a way to reuse them either.

How about adding another SX28 to fix this RAM issue? or is there another way?

Please help...I really like it but can't expand it past "Display VAR Byte (16)"
Ideas???

(Just back from Thanksgiving with friends) -- The SX28 only supports 16-byte arrays, so what you can do is split the buffer into two chunks (16 + 4).  If you look at the Serial Inkjet Printer code I wrote it has a 64-byte character array that uses four banks this way.

The problem I am seeing is the interupt code with RA:

---------------------------
INTERRUPT
' ---------------------------
ISR_Start:

RC = 0       'CLEAR DISPLAY OUT TO PREVENT GHOSTING
Inc RA       'INCREMENT COLUM ADDRESS (RA I/O PINS)
RC = NOT Display( RA )     'LOAD NEW ROW DATA TO RC
ISR_Exit:
RETURNINT 63

RA can only go from 0 (%0000) to 15 (%1111) (actually it goes from 0 to 14 (%1110) for 15 lines out).

I need to go to 20 lines out but RA always is reset back to %0000 after it reaches 15 (%1111). How do I create another array such as:

RC = NOT DisplayExt( RA )
to push data to the remaining 5 lines when RA gets reset back to 0 (%0000) after it reaches 15 ($1111).

I tried modifying the code to use RB as a counter but it did not work correctly.

Please Help if you can.

You don't have enough bits on the RA port for more than 16 lines (or 15 with blanking) without a whole lot of complicated trickery.  Best to move your column select to RB.

I really beleive that this can not be easily solved unless an array can be used greater than 16. I am becoming clueless of what else to try.

I have moved the RA lines over to RB and have the following Interupt code:

' ---------------------------
INTERRUPT
' ---------------------------
ISR_Start:

RC = 0       'CLEAR DISPLAY OUT TO PREVENT GHOSTING
' Inc RA       'INCREMENT COLUM ADDRESS (RA I/O PINS)
Inc RB
' RC = NOT Display( RA )     'LOAD NEW ROW DATA TO RC
RC = NOT Display( RB )
IF RB > 15 then
RB = 0
EndIf
ISR_Exit:
RETURNINT 63
SEE ATTACHED MODIFICATION FILE...

Here's what I would do to create a 20-byte column buffer:

colBufLo   VAR    Byte (16)        ' define 20-byte array
colBufHi   VAR    Byte (4)
I would also define a separate column and buffer index pointers:

colPntr    VAR    Byte
bufIdx     VAR    Byte
Now the ISR is a can handle the code pretty cleanly:

' ---------------------------
 INTERRUPT
' ---------------------------
ISR_Start:
 LEDs = %00000000                 ' blank outputs to prevent ghosting
 INC colPntr                      ' update column pointer
 IF colPntr = 20 THEN             ' roll-over if at end
   colPntr = 0
 ENDIF
 IF colPntr.4 = 0 THEN            ' in low portion of buffer?
   idx = colPntr & %00001111      ' calculate buffer index
   LEDs = colBufLo(bufIdx)        ' output current column
 ELSE
   idx = colPntr & %00000011
   LEDs = colBufHi(bufIdx)
 ENDIF
ISR_Exit:
 RETURNINT 63
Note that if you use a 32-byte buffer then you can simplify the buffer pointer manipulation (with roll-over) like this:

Jon,
I don't know how it affects (RA or RB) and RC especially with...

INC RB
RC = NOT Display ( RB ) ??

or
INC RA
RC = NOT Display ( RA ) ??

In my example code "colPntr" is an alias for RB.  I don't think it's a good idea to embed the port name into the code like you're doing because it makes reassignment more work later.  That's just a style choice.  And, of course, I forget that your outputs a inverted so I've edited my example code accordingly.