Page 190 - Amphibionics : Build Your Own Biologically Inspired Robot

Amphibionics 05 3/24/03 8:44 AM Page 169
Chapter 5 / Serpentronic: Build Your Own Robotic Snake
:1001A000A8009630A9009630AA009630AB00963091
:1001B000AC00F020CD2824088C0025088D005520A7
snake-test.hex file
listing (continued)
:1001C0000C08A4000D08A5005F302405A60005302A PROGRAM 5.2
:1001D000A2001030A00026088E0004301420080071
:1001E0000130AE00640015302E02031825292708BF
:1001F0008C008D01063084000430012028088C001A
:100200008D01063084000830012029088C008D0102
:1002100006308400803001202A088C008D010630D1
:100220008400403001202B088C008D0106308400B2
:10023000203001202C088C008D0106308400103005
:0C02400001200C306420AE0FF2280800F2
:02400E00F53F7C
:00000001FF

The next program will be used to calibrate the infrared sensor so
that the robot can safely avoid obstacles. The modulation frequen-
cy of the sensor was set using a multimeter when the circuit board
was initially built. The software calibration routine will be used to
fine-tune the frequency to improve the sensor’s response. The rou-
tine works by taking the input from the sensor and then outputting
the opposite state to the LEDs. The sensor input value is inverted
before being output to the LEDs because the sensor’s output is nor-
mally logic 1 (high) when it is not receiving a signal, and switches
to a state of logic 0 (low) when a signal is received. This will allow
us to visually see how the sensor is responding to the modulated
infrared radiation, and then adjust the modulation frequency
accordingly. The program is called ircal-serpent.bas, and is listed
in Program 5.3. Program the PIC 16F84 with the corresponding
ircal-serpent.hex file listed in Program 5.4 and insert it into the 18-
pin socket on the controller board. When the power is turned on
and nothing is in front of the sensor, the LEDs should be off. To cal-
ibrate the circuit, use a small screwdriver to turn potentiometer R3
counterclockwise until the LEDs are on solid. Figure 5.58 shows
resistor R3 on the infrared circuit board being adjusted. Once the
LEDs are on solid, slowly rotate potentiometer R3 clockwise until

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