Subject:
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Musings regarding Handyboard Expansion & Interfacing
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Wed, 14 Aug 1996 01:13:18 GMT
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Original-From:
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Brian Lavery <[blavery@acslink.aone.net]stopspam[.au]>
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Viewed:
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1475 times
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Just got Aug issue of Circuit Cellar.
Full of robotics goodies & interface circuits .
In the meantime, following are some more of my thoughts on interfacing.
********************************************************
* MUSINGS ON THE SUBJECT OF HANDYBOARD INTERFACING *
********************************************************
* Special interfaces *
********************************************************
Vector 2X compass unit:
=======================
Refer http://www.newtonlabs.com/datasheets/vector-2x-compass/
Needs 2 inputs, 3 latched outputs, and the SPI input
(& reset? probably get away without it).
|------|
8255 -->|SS* | Select Vector 2X device as slave
8255 -->|P*/C | Poll control continuous or not
8255 -->|CAL | Calibrate request
8255 <--|CI | Calibrate indicator
8255 <--|EOC | End of A/D conversion
??? -->|RESET | (maybe?)
| |
(SPI) SCLK -->|SCLK |
MISO <--|SDO | Data to Handyboard
|------|
5 I/O lines: Use 8255 I/O or
other I/O as desired.
ULTRASONIC SONAR:
=================
(Without the polaroid module)
The text "SENSORS FOR MOBILE ROBOTS" (Everett) gives a useable
amount of help data on timings of ultrasonic pulsing & echo timing.
Eg say 40 kHz carrier, about 16 pulses (0.4 mSec) of ping output,
a couple of mSec of dead time after the transmission to let the
TX ringing die out, then listen for the echo coming back.
Speed of sound about 13 cm per mSec. Can using two transducers
instead of a common tx/rx one, allow shorter dead time (& shorter
minimum range)?
Use a very simple 40 kHz osc circuit like the H/B one (pity, the
handyboard does not pass its IR 40 kHz carrier on to the expansion
bus!), and an OP AMP and 567 as ultrasonic receiver (looking at
"Robot Builders Bonanza" for some help). The 567 takes several cycles
of the 40 kHz carrier to yield an output. Since the ultrasonic
transducers themselves are cheap, putting a whole array of
multiplexed sonar devices aboard should cost quite little.
Another thought - why not feed the received & amplified 40 kHz
signal thru an IR led & IR receiver module tied together --
saves the 567 decoder!
Or is all this a waste of time? - Is a Polaroid unit the way to go?
Telemetry to PC:
================
The SCI async system is normally dedicated on H/B to the boot load process
from PC. But by adding an RJ11 flying lead out from expansion board,
and putting a fresh RJ11 socket on the expansion, the expansion board
could be given an option of multiplexing the async signals. Pipe it
thru to the Charger/RS232 board for talking with the PC, or divert it
thru to say the Mini-SSC servo board after loading. Or maybe even send
it to a new Infrared Tx/Rx or even fancier communications channels for
live run-time telemetry link to PC. My mind is turning itself
into spread-spectrum!
Real Time Clock Chip:
=====================
Wake up your 'bot at 6 am, so it can wake YOU up!
I'm out of obvious circuit ideas on this one. (Read "lazy"?)
Anyone?
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