You can buy LED arrays (eg Rapid 57-0655) set up so that you drive them by setting a row high and a column low to illuminate a single LED. This LED is a pixel in the 7x5 picture. If you set all the rows high and just one column low, you get a line of LEDs illuminated. Using a 4017 decade counter, as in the top pcb, you can strobe all the columns in sequence using only one output of the Picaxe, leaving the other seven outputs for the rows. This principle can be used to display a letter or a simple picture like a smiley. You could also use a 4028 and strobe the rows using 3 outputs from the Picaxe leaving the other 5 for the columns as in the second pcb. Here is a scrolling message using the 4017:
'outputs 76543210 are used for
' row 0123456 and bit 0 to clock the 4017
'each 4017 clock pulse moves to the next column
symbol frame=b0 'each frame is a
symbol loop=b1 'column in a character
symbol data=b2 'read from eeprom
symbol finish=b3
symbol speed=b4
'put values for frames in eeprom - must be on one line
'each value includes the bit0 clock pulse
eeprom(%00000001,%00000001,%00000001,%00000001,%10000011,
%11111111,%10000011,%00000001,%01110001,%10001001,%00100101,
%10001001,%01110001,%00000001,%11111101,%00000011,%00000011,
%00000101,%11111111,%00000001,%00000001,%00000001,%00000001,
%00000001)
init: pause 500 'need to reset the 4017
for b0=1 to 4 'so it starts at column 1
high 0 'clock 4017 4 times
low 0 'so that we start in the
next b0 'right place
main: for frame=0 to 19 'no of characters multiple of 5
for speed=0 to 20 'sets speed of scrolling
finish=frame+4
for loop= frame to finish
read loop,data
pins=data
low 0 'clock 4017
pause 2
next loop
next speed
next frame
goto main
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