28108 Parallax Inc, 28108 Datasheet - Page 5

• Manufacturer Part Number: 28108
• Description: KIT QTI BOE-BOT LINE FOLLOWER
• Manufacturer: Parallax Inc

Specifications of 28108

• Accessory Type: QTI Infrared
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: Boe-Bot®
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

' {$STAMP BS2}
' {$PBASIC 2.5}
' CheckQtiSubroutine.bs2
' Displays QTI sensor states. 0 means white surface, 1 means
' black.
qtis VAR Nib
OUTB = %1111
DEBUG CRSRX, 8, "FMMF", CR,
DO
LOOP
Check_Qtis:
The BASIC Stamp has a variety of parallel I/O control features that make it possible to perform
operations on groups of I/O pins. CheckQtiSubroutine.bs2 uses the BASIC Stamp's DIRB and OUTB
variables to control the directions and output states of the I/O pins P7, P6, P5, and P4. When these I/O
pins are set to input with DIRB = %0000, the program also takes a snapshot of the binary states these
I/O pins sense as a result of the four QTIs' R pin voltages with the command qtis = INB.
Simple Line-Following
LineFollowWithCheckQtis.bs2 is designed to start following a line as soon as you place a QTI over the
electrical tape. It will stop line following as soon as it runs out of electrical tape. Start with an easy
course, like a large S shape as shown below. If the QTIs passed the "Testing for Line Detection" tests, it
should navigate the course with ease.
If your QTIs’ cables are reversed, the Boe-Bot will appear to try to jump off the line at the first
opportunity. Otherwise, it should faithfully follow the line until it reaches the end of the tape.
Copyright © Parallax Inc.
GOSUB Check_Qtis
DEBUG BIN4 ? qtis, CRSRUP
PAUSE 100
' Result -> qtis variable. 0 means white surface, 1 means
' black surface.
DIRB = %1111
PAUSE 0
DIRB = %0000
PAUSE 0
qtis = INB ' Store QTI outputs in INB
RETURN
√
√
CRSRX, 8, "LLRR", CR
Enter and run LineFollowWithCheckQtis.bs2.
Place the Boe-Bot on the course so that in straddles the line with the mid left and mid right QTIs
over the electrical tape.
' qti black/white states
' Set OUTB bits to 1
' Display bit positions
' Main DO...LOOP
' Get QTI states
' Display QTI states
' 1/10 s delay
QTI LIne Follower AppKit (#28108)
' P7..P4 -> output
' Delay = 230 us
' P7..P4 -> input
' Delay = 230 us
v2.0 3/23/2009 Page 5 of 6