1. Programming the BASIC Stamp
Computers do exactly what you tell them, no more, no less
BASIC Stamp uses the PBASIC programming language
You can go a long ways with just a few instructions
See the BASIC Stamp Guide (2011 web site)
- Programs are the list of instructions (recipe) for telling the computer what to do.
- Programming language defines a particular vocabulary set and syntax. You must follow without deviations. Mistakes often hard to find.
- PBASIC is (a little) like BASIC, but greatly simplified, and tailored to running I/O ports on the Stamp chip. - Pentium III runing Visual Basic: $600
- Microchip running Stamp Basic: $1

2. On the Stamp Programming cable Power pins EEPROM Brain I/O pins
Breadboard area
9V battery
Reset

3. Schematic icons 1K
TIP120

4. Dealing with the outside world
SENSOR
COMPUTER
ACTUATOR
Switch
Light beam
Potentiometer
Encoder
Temperature …
Lamp
Relay
Motor
Solenoid …

5. Driving actuators High 4 Program sets ports high/low (1/0) Low 4 +5V
Stamp board pins set to +5V/0V
TIP120 1K
PIN 4
+12 V
Interface electronics use signal voltages and power supply to switch motors on/off

6. Reading sensors Program reads value of ports (1/0) IF in4 = 1 THEN ….
Stamp board pins set to +5V/0V
10K
PIN 4
+5 V
Interface electronics change sensor signals into +5V/0V

7. Format Labels, comments loop: toggle 0 ‘ toggle motor
pause 250 ‘ pause for 250
goto loop
Labels
- colon to define, no colon to use
- letters, numbers, _ start with letter
Symbol Definition
- text substitution
- can make it simpler to read
- don’t used reserved words
- define at the top
- use capitals (convention)
- symbols are not variables
Comments
- ‘ or REM
Misc:
- case insensitive.
Symbols
LED con 1
MOTOR con 0
start:
toggle LED
toggle MOTOR
pause 250
goto start

8. Data sizes A bit is one binary digit: 0/1 A byte is 8 bits b0 b7
(binary) = 3 (decimal)
= 255
Generic, for any computer
Most modern programming languages deal in 32-bit words (4 billion or 4 Gigs)
- Stamp is positive integers only
- byte: 0-255
- word: 0-65,535
Type #bits Number range
bit
byte
word ,535

9. Variables Pins 15 i/o pins 0-15 for outputs in0-in15 for inputs
Data variables
26 bytes of variable space
byte (0-255)or word(0-65,535)
Allocate like this:
length var byte
width var byte
area var word
Then in program:
length = 20
width = 20
area = length * width
Positive numbers only!!
For HIGH, LOW, TOGGLE, use 0-7 rather than Pin0-Pin7

10. Math +,- add, subtract * multiply / division (truncates) x var byte
x = x+2 result?
Positive integers only
Will overflow at 255 (demo with debug dec x)
watch multiply overflow
If x defined as a byte
x = 50*50 = error (will return 196)
division truncates
y = 5/2 will return 2
Can use variables and constants
x var byte
x = 254
x = x+2 result?
y var word
y = 50*50 = 2500
x var byte
x = 5/2

11. A FIRST PROGRAM ‘Turns on LED for a brief time LED con 0 high LED
pause 200
low LED
end
Logical conditionals: = <> > < >=
Most common use is to check state of a switch

12. LOOP LED con 0 doit: toggle LED pause 200 goto doit
Logical conditionals: = <> > < >=
Most common use is to check state of a switch

13. FOR…NEXT LOOP LED con 0 i var byte for i = 1 to 20 toggle LED
pause 200
next
end
Logical conditionals: = <> > < >=
Most common use is to check state of a switch

14. IF....THEN x var byte y var byte x = 5 y = 7 start:
if x < y then motor
high 1 ‘ led on
goto continue
motor:
high 0 ‘ motor on
continue:
Conditionals:
= <> > < >= <=
Logical conditionals: = <> > < >=
Most common use is to check state of a switch

15. IF....THEN, CHECKING AN INPUT
motor con 1
start:
if in4 = 1 THEN start
gomotor:
high motor ‘ motor on
pause 2000
low motor
end
Logical conditionals: = <> > < >=
Most common use is to check state of a switch