BASIC Stamp Programming

Introduction

PBASIC:
- developed by Parallax
- similar to BASIC (goto, for...next, if...next)
- specialized instructions (serout, pwm, count)
- variable and constant names, labels, and instructions are case insensitive

Programming Connection:

BASIC Stamp Editor:

"Hello World":

'{ $STAMP BS2 }

DEBUG "Hello World!" 'Test message

END                  'End program and put stamp in low-power mode

BASIC Stamp Architecture

Memory Organization:

All varieties of BS2 have 32 bytes of RAM.
The first 6 bytes are reserved for input (INS), output (OUTS), and direction (DIRS) control of the I/O pins.
INS is read-only and reflects the state of I/O pins P0 to P15.
DIRS controls the direction of each I/O pin. A 0 in a particular DIRS bit makes the corresponding pin an input and a 1 makes the pin an output.
A pin that is an output (DIRS value = 1) is set to the state indicated by the corresponding bit of the OUTS register.

Variables and Arrays:

'{ $STAMP BS2 }

mybit    VAR  BIT      'Value can be 0 or 1
mynib    VAR  NIB      'Value can be 0 to 15
mybyte   VAR  BYTE     'Value can be 0 to 255
myword   VAR  WORD     'Value can be 0 to 65535
myarray  VAR  BYTE(2)  'An array of two bytes

Aliases and Modifiers:

'{ $STAMP BS2 }

cat    VAR  BYTE            'cat is byte-sized variable
tabby  VAR  cat             'tabby is an alias to cat

rhino  VAR  WORD            'A 16-bit variable
head   VAR  rhino.HIGHBYTE  'Alias to upper byte of rhino using modifier HIGHBYTE
tail   VAR  rhino.LOWBYTE   'Alias to lower byte of rhino using modifier LOWBYTE

Scratch Pad RAM (BS2e, BS2sx, and BS2p only):

Shared memory between programs which can only be accessed with the GET and PUT commands.
BS2e and BS2sx: 64 bytes; BS2p: 128 bytes.
The highest byte (location 63 or 127) of Scratch Pad RAM is read-only and contains the number of the currently running program.

Constants (like #defines):

'{ $STAMP BS2 }

midinoteon    CON  144    'MIDI note on status byte (for channel = 0)
midinoteoff   CON  128
midicontchng  CON  176
midiprogchng  CON  midicontchng+16

Number Representations:

'{ $STAMP BS2 }

LetterA  CON  "A"    'ASCII code for A (65)
Cheers   CON  3      'Decimal
Hex128   CON  $80    'Hexadecimal
FewBits  CON  %1101  'Binary

Order of Operations:

BASIC stamp solves math problems in the order they are written, left to right.
Parenthesis can be used to override the default behavior.
Constant expressions are evaluated at "compile time".

One-argument Operators:

ABS	absolute value
COS	cosine in two's compliment binary radians
DCD	2ⁿ-power decoder
~	inverse
-	negative
NCD	priority encoder of a 16-bit value
SIN	sine in two's compliment binary radians
SQR	square root

Two-argument Operators:

+	addition
-	subtraction
*	multiplication
**	multiplication (returns upper 16-bits)
*/	multiply by 8-bit integer, 8-bit fraction
/	division
//	modulus (remainder of division
MIN	limits a value to a specified low
MAX	limits a value to a specified high
DIG	returns specified digit of number
<<	left shift
>>	right shift
REV	reverse specified number of bits
&	bitwise AND
\|	bitwise OR
^	bitwise XOR
&/	logical AND NOT
\|/	logical OR NOT
^/	logical XOR NOT

A Short Example:

'{ $STAMP BS2 }

MyBytes VAR  BYTE(10)       ' Define 10-byte array.
Index   VAR  NIB            ' Define normal nibble variable.

FOR Index = 0 TO 9          ' Repeat with Index= 0,1,2...9
MyBytes(Index) = Index * 13 ' Write index*13 to each cell of array.
NEXT

FOR Index = 0 TO 9          ' Repeat with Index= 0,1,2...9
DEBUG ? MyBytes(Index)      ' Show contents of each cell.
NEXT
STOP

WWW Resources:

Downloads: Basic Stamp Editor and Manuals