Page 57 - The Definitive Guide to Building Java Robots

Preston_5564C02.fm Page 38 Wednesday, September 14, 2005 5:42 AM

38 CHAPTER 2 ■ SERIAL COMMUNICATION

■Note If you’re just starting out with robotics, it’s great to have this bread board for adding sensors or
creating circuits.

Once your board is hooked up and you can see the microcontroller you’ve connected,
you’re ready to program. Your first goal will be to just send some data to the microcontroller
and get some data in return.

Code Objective

The objectives for this example are to:
• Send 2 bytes of data to a microcontroller.
• Receive a specific byte back that confirms the byte sent to it.

Code Discussion
The Stamp program has a byte array of size 3 called serialIn. This byte array will be populated
from the SERIN command when it’s either full or when it receives a termination command of
“!”. Then, based on the first byte received from the PC, the program will branch to SEROUT
with an “a” or “b”. (See Example 2-9.)

■Note Adjust the serial port timeout or the time between the write and the delay. Then adjust the pause
time in the Stamp code and see how the results vary.

Example 2-9. SerialEcho.bs2
'{$STAMP BS2}
'{$PORT COM1}

serialIn VAR Byte(3)
foo VAR Byte

main:
foo = 255
serialIn(0) = 0
serialIn(1) = 0
serialIn(2) = 0
SERIN 16,16468,1000,main,[STR serialIn\3\"!"]
PAUSE 100
LOOKDOWN serialIn(0),[100,101,102],foo
BRANCH foo,[test1, test2, getCompass]
PAUSE 5
GOTO main

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