- PBASIC
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PBASIC is a microcontroller based version of BASIC created by Parallax, Inc. The language was created to bring ease of use to the microcontroller and embedded processor world. PBASIC is used for writing code for the BASIC Stamp microcontrollers. After the code is written it is tokenized and loaded into an EEPROM on the microcontroller. These tokens are fetched by the microcontroller and used to generate instructions for the processor.
Contents
Syntax
When starting a PBASIC file, the programmer defines the version of the BASIC Stamp and the version of PBASIC that will be used. Variables and constants are usually declared first thing in a program. The DO LOOP, FOR NEXT loop, IF and ENDIF, and some standard BASIC commands are part of the language, but many commands like PULSOUT, HIGH, LOW, DEBUG, and FREQOUT are native to PBASIC and used for special purposes that are not available in traditional BASIC (such as having the Basic Stamp ring a piezo-speaker, for example).
Programming
In PBASIC you have to select 1 of 7 different basic stamps, BS1, BS2, BS2E, BS2SX, BS2P, BS2PE, and BS2PX, and to that you have to select one of these commands:
' {$STAMP BS1}
you also have to select a PBASIC version. To do that you have to select one of these commands:
' {$STAMP BS2}
' {$STAMP BS2e}
' {$STAMP BS2sx}
' {$STAMP BS2p}
' {$STAMP BS2pe}
' {$STAMP BS2px}
' {$PBASIC 1.0} ' use version 1.0 syntax (BS1 only)
' {$PBASIC 2.0} ' use version 2.0 syntax
' {$PBASIC 2.5} ' use version 2.5 syntaxAn example of a program using HIGH and LOW along with the DO...LOOP Would Be:
DO HIGH 1 'turn LED in pin 1 on PAUSE 1000 'keep it on for 1 second LOW 1 'turn it off PAUSE 500 'keep it off for ½ second LOOP 'repeat forever
An example of a program using HIGH and LOW along with the FOR NEXT loop would be:
counter VAR Byte 'sets variable "counter FOR counter = 1 to 5 HIGH 1 'turn LED in pin 1 on PAUSE 1000 'keep it on for 1 second LOW 1 'turn it off PAUSE 500 'keep it off for ½ second NEXT 'redirects to beginning four more times END 'end program
Comments in the code are preceded by an apostrophe ('). The microcontroller ignores the rest of the line and continues to the next each time it encounters a comment. PBASIC codes can be simply a list of statements:
HIGH 1 'turn on LED on pin 1 PAUSE 1000 'pause for one second LOW 1 'turn off LED on pin 1 END 'end program
Other Chips
The PICAXE microcontroller uses a version of Basic similar to the version used to program the Basic Stamp I.
External links
- "Comparing PBASIC 2.5 control structures to the old PBASIC" – By Tracy Allen, EME Systems, 2003
- Parallax, Inc. – Corporate website
Categories:- Embedded systems
- Parallax products
- BASIC programming language
- Programming language topic stubs
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