LEGO MINDSTORMS Robots Manual page 111

pbFORTH from your RCX, you'll need to remove the batteries to clear the memory. Then you can use nqc or firmdl to download a different set of firmware. If you want to reinstall the default
firmware, you can use the RIS software.
Talking to pbFORTH
To interact with pbFORTH, you need to use a terminal emulator to exchange data with the RCX over the IR link.
Windows users can use the HyperTerminal application that comes with Windows. Linux users can use minicom or something similar. You'll need to point your emulator at whatever serial port
has the IR tower attached. The other relevant settings are 2400 Baud, 8 data bits, 1 stop bit, and no parity.
Once you've got your emulator running, press Enter on your keyboard a couple of times. pbFORTH should respond with ''ok" messages:
ok
ok
To get a quick start with pbFORTH, let's turn on one of the outputs. First, you'll need to initialize the RCX like this (the stuff you should type is shown in bold):
RCX_INIT
ok
To turn on an output, use the MOTOR_SET command, which will be covered later. Type the following:
7 2 0 MOTOR_SET
ok
Remember to press Return after you enter the whole line. Depending on your terminal settings, you will see the letters you type two or three times in a row, like this:
77 22 00 MMOOTTOORR__SSEETT
I have removed the extra letters in the examples in this chapter, for clarity. To minimize the repeated characters as you type in the examples, make sure "local echo" is disabled in your terminal
emulator.
The MOTOR_SET line turns on output A (represented in the code by 0) in reverse (represented by 2) with full power (represented by 7). If your RCX is about to drive off your desk, you can turn
off the output like this:
7 3 0 MOTOR_SET
ok
This is the same as the previous example, except the 2 is now a 3. The 3 tells pbFORTH to turn the output off. I'll get to the details of MOTOR_SET later, after I've introduced you to the Forth
language itself.
Make sure you separate everything with spaces. pbFORTH reads different words by assuming that they're all separated by whitespace, either spaces or returns. If you miss a space, pbFORTH will
get confused and complain that it can't find a word definition.
pbFORTH is also case sensitive. While MOTOR_SET is a defined word, Motor_Set is not, nor is motor_set or MOTOR_SEt.
Sending Files
For serious development, you'll want to create your source code in a text file and send the whole file to pbFORTH when you're ready to test. You can do this with many terminal emulators,
although you have to set it up correctly.
Page 119
Page 120