LogoChip
Bus Communications
Group
members: Adrien Grise and Thomas Kneeland
Document
Author: Adrien Grise
Date:
February 26, 2003
Synopsis: Using current project code and circuitry work, utilize the LogoChip’s bus to either transmit and/or receive data from another device such as a HandyCricket. See lab assignment #5’s documentation for more information.
Description of Project
Our
current project revolves around the use of the 5x7 LED display chip. Previous experimentation allowed us to build
a simple circuit connecting the LogoChip to the
5x7 LED’s inputs and having the LogoChip display an alphanumeric character
utilizing a subset of the 35 LEDs in the 5x7 LED chip. For this assignment, we now utilize the B0
port as a bus between the LogoChip (the slave) and the HandyCricket (the
master). The HandyCricket will send a command message followed by a data
message that will instruct the LogoChip to display
a character on the 5x7 LED. The
LogoChip displays the character by outputting lines 1 through 7 that will make
up the character, quickly flashing each one once on the 5x7 LED. If flashed quickly enough and successively,
the character will look steady as if all 7 lines were being displayed at one
time.
Goal
We
must attempt to build as simple a circuit as possible without damaging any of
the circuitry involved. The 5x7
LED requires less than 5 volts, the power output by the LogoChip, so care
must be taken to ensure the individual LEDs of the 5x7 LED are not blown
out. A bus cable
must be built and plugged in to both the LogoChip’s B0 pin and the XMIT pin
of the HandyCricket. Finally, a series
of character maps must be developed that will instruct what LEDs should be lit
for a particular character.
Issues
§
Initially
we powered the 5x7 LED with just +5 volts and, in turn, blew out one of the 35
LEDs on the 5x7 LED chip. We originally
tried a voltage divider circuit, but found that this was too costly in terms of
breadboard space, resistors, wiring, and time.
We next attempted to use a resistor between each LED pin and its
corresponding LogoChip pin. While this
worked, we found that the voltage either too high or too low when all 35 LEDs
in the display we attempted to be lit up.
Next we tried utilize transistors, but again found the voltages were
incorrect to properly power the LEDs as we had wired it. We finally resolved the situation by quickly
flashing a single row of the LEDs one at a time for a short duration with no
transistors, resistors, or voltage dividers between the LED and LogoChip
pins. This seems to successfully
provide enough power to the LED but in short enough duration so as to not burn
it out either.
§
We
then found that when displaying each of the seven lines of a character map in
quick succession, the LED was incapable of clearly displaying the character –
the lines “bled” into each other. We
staggered the lines being displayed by the LogoChip so successive rows were not
display immediately after each other allowing the signals to dissipate from the
pins before sending a new signal.
§
However,
even after staggering the line displays, we still found the lines to
“bleed”. We next determined that we
needed a small unit of time between when one line was displayed until when the
next line was displayed. While 1 second
was too long a time, if no delay was inserted, we found the lines continued to
“bleed” into each other. To solve this
we inserted a dummy repeat loop and experimented with the number of times to
loop to have a properly displayed character on the 5x7 LED display.
§
We
had hoped to utilize an array data structure to store the character maps, but
were disappointed to find that LogoChip Logo does not currently support
arrays. A work-around was provided by
after we had developed another work-around to display the character maps. We did not re-visit the array work-around
provided due to time constraints.
Possible Extensions
Instead of simple character maps flashing to the LED
display, simple animations could be done to either morph 1 character into
another or just to provide interesting, yet simplistic graphical
animations. Due to time constraints,
neither of these ideas was developed, but it would simply be a case of having a
series of character maps available, flashing each to the LED display briefly,
and then displaying the next character map in quick succession.
Circuit Diagram
The
following is a circuit diagram that illustrates how the HandyCricket, LogoChip,
and UML Development Board are wired together for this project.
LogoChip Code
;
; * * * 14 0E
; * * 17 21
; * * 17 21
; * * * * * 31 2f
; * * 17 21
; * * 17 21
; * * 17 21
;
;to
init
; Character A
; aset characters 0 14
; aset characters 1 17
; aset characters 2 17
; aset characters 3 31
; aset characters 4 17
; aset characters 5 17
; aset characters 6 17
; Character B
; aset characters 7 30
; aset characters 8 17
; aset characters 9 18
; aset characters 10 31
; aset characters 11 18
; aset characters 12 17
; aset characters 13 30
; Character C
; aset characters 14 15
; aset characters 15 16
; aset characters 16 16
; aset characters 17 16
; aset characters 18 16
; aset characters 19 16
; aset characters 20 15
;end
global
[cat curr_char command_chk]
constants [[portb 6][portb-ddr $86][porta 5][porta-ddr $85]]
to
display_generic :b1 :b2 :b3 :b4 :b5 :b6 :b7
; 1st Row
write portb $FE
clearbit 1 portb
write porta :b1
repeat 32 [ setcat 1 ]
;wait 1
; 4th Row
write portb $FE
clearbit 4 portb
write porta :b4
repeat 32 [ setcat 1 ]
;wait 1
; 2nd Row
write portb $FE
clearbit 2 portb
write porta :b2
repeat 32 [ setcat 1 ]
;wait 1
; 5th Row
write portb $FE
clearbit 5 portb
write porta :b5
repeat 32 [ setcat 1 ]
;wait 1
; 3rd Row
write portb $FE
clearbit 3 portb
write porta :b3
repeat 32 [ setcat 1 ]
;wait 1
; 6th Row
write portb $FE
clearbit 6 portb
write porta :b6
repeat 32 [ setcat 1 ]
;wait 1
; 7th Row
write portb $FE
clearbit 7 portb
write porta :b7
repeat 32 [ setcat 1 ]
;wait 1
end
to
display :character
if :character = 65
[display_generic $0E $21 $21 $2f $21 $21 $21]
if :character = 0
[display_generic $00 $00 $00 $00 $00 $00 $00]
; more if statements
end
to
main
write
portb-ddr $01
write porta-ddr $00
write portb $FE
write porta $00
setcommand_chk 1
loop
[
if newbus?
[
ifelse command_chk = 1
[
if brcv = $180
[
setcommand_chk 0
]
]
[
setcurr_char brcv
setcommand_chk 1
]
]
display curr_char
]
end
to
test
loop [
write
portb-ddr $00
write porta-ddr $00
write portb $FE
write porta $2F
]
end
HandyCricket Code
to
main
bsend $180
wait 5
bsend 65
wait 20
bsend $180
wait 5
bsend 0
wait 20
main
end
Contributions
As a
partner of Thomas Kneeland, I assisted in the writing of the LogoChip and HandyCricket code. I also assisted in the experimentation to
find a suitable circuit layout that would properly connect and power the 5x7
LED chip from the LogoChip (see Issues).