Subject:
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Polaroid 6500 Ranging System
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Sat, 16 Jan 1999 21:28:55 GMT
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Original-From:
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Ted Mylenbusch <amylen@worldnet.attANTISPAM.net>
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Viewed:
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944 times
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I recently purchased a 6500 ranging system and have connected it to the
HandyBoard (HB) 1.2 Expansion Board. I am using IC ver 3.1 from Newton
Research Labs and loaded the sonar.c code module provided through the MIT
website. The HB passed all testing as described in the manual and I have
successfully run servos from the expansion board plug-ins and used the IR
detector to decode my Sony TV remote and hence control the movement of the
HB rudimentary robot. The servos have been hacked using the resistor
divider method in place of the internal position feedback pot and serve as
drive motors for the two wheel tail dragging configuration.
My next goal was installation of this ranging system and then development of
the code for object recognition and avoidance. I have also purchased the 2X
compass module and plan to install that after this process.
My problem is that I can only get the ranging system to return a 540 to 548
value from either the sonar_sample() or sonar_closeup() routines. One out
of five reading is say ~1200 or ~900 but the majority are right on 545 and
can range as above. I am aware of the 1.33 foot ranging limit but this is
supposed to be compensated for when using the sonar_closeup by manipulating
the BINH signal. Even so, 540 is well below even the initial blanking
interval as programmed into the 6500 module. There are no obstructions and
I have placed the module facing a wall at 2, 3, 4, and 5 feet with the same
result. I have repeatedly tested the digital input 7 pin and it tests
normal using the testdigitals() function. The board does not reset during
the ping event and I can hear an audible clicking when the transducer fires.
The software is waiting for the PD0 high ECHO event because when I
disconnect the jumper from J12 the routines time out and return a -1. It
appears that the only way this can be happening is if the PD0 input is high
all the time. But, then it would return even lower numbers, right?
I've checked all connections multiple times. I've traced the circuits
through the 9 pin ribbon cable for continuity. Do I still need to install
the .1 (F cap in position C7 on the 6500 board as mentioned in the earlier
pre-expansion board documentation? Do I need to install the pull-up
resistor? It looks like the HB has this installed. After some research I
found other users mentioning a 470 (F cap between two jumpers on the 6500
board. Based on their notes, this was to protect the 6.270 board from
resetting due to the 2A surge current during the ping event. I don't see
the reset happening. Everything works fine after each event, indeed after
several repeated ping events as I am testing using the IC interactive mode.
Anyway, that's the extent of my understanding and the end of my ability to
diagnose and make this system work. Any help would be greatly appreciated.
Thanks
Ted Mylenbusch
Amylen@worldnet.att.net
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