Page 148 - The Unofficial Guide to Lego Mindstorms Robots

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To dive into this a little more, check out the whole tortask.txt example at the pbFORTH web site.

An Expensive Thermometer

This section contains an example that will help you get your feet wet with pbFORTH. We'll build a simple Celsius
thermometer using a temperature s ensor. Hook the sensor up to input 2 and enter the following (I've omitted pbFORTH's ''ok"
responses for clarity):

HEX
: buttonState RCX_BUTTON DUP BUTTO N_GET @ ;

: i sRunButtonPressed buttonState 1 AND ;

: showTempera ture
3003 SWAP 3001 LCD_NUMB ER
LCD_REFRESH
;

: clear LCD_CLEAR LCD_ REFRESH ;

: thermometer
RCX_INIT
S ENSOR_INIT
BUTTON_INIT
2 1 SENSOR_TYPE
A0 1 SENSOR_MODE
BEGIN
BEGIN
1 SENSOR_READ 0=
UNTIL
1 SENSOR_VALUE
showTemperature
isRunBu ttonPressed
UNTIL
clear
;

To run this program, use the thermometer word. The LCD display will show the temperature read by the sensor until you
press the Run button.

The isRunButtonPre ssed word simply tests to see if Run has been pressed, using the buttonState word. This is
how thermometer knows to stop running. ShowTe mperature takes the top item on the stack and shows it on the
display with the de cimal point placed to show tenth s. The clear word simply erases the entire display using the
LCD_CLEAR word.