Newsgroups: comp.robotics
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From: fredm@media.mit.edu (Fred G Martin)
Subject: Re: MON/DMON Mini Board problem
Message-ID: <1994Feb13.020812.12221@news.media.mit.edu>
Sender: news@news.media.mit.edu (USENET News System)
Organization: MIT Media Laboratory
References: <1994Feb12.212949.197863@zeus.aix.calpoly.edu>
Distribution: usa
Date: Sun, 13 Feb 1994 02:08:12 GMT
Lines: 31


Has your board ever worked (i.e., "it was working but now it suddenly
died") or you're just trying to get it going?

Common failure modes:

*  TxD and RxD swapped.  This is the problem 95% of the time.  What is
the status of the Red/Green LEDs before, during, and after download?
These can provide important clues; see the manual.

*  Wrong serial port.  Give command line flag to MON.

*  Substituted regular (instead of low-current) LED for green serial
line receive LED.  Causes serial transmit to fail.  Quick hack
solution:  pull green LED (you lose serial status info, but circuit
will work if that's your only problem).

*  Forgot to wire loopback circuit on RS-232 adapter (pins 5, 6, 20 on
DB25; pins 4, 6, 8 on DB9).  Only relevant for MS-DOS host computers. 

*  Serial transistor (2N3906) fried.  It happens.  (In fact, it's
fairly easy to short the transistor so it's driving power to ground
when it gets turned on.)

If none of these helps, post back with more detailed info about what
you've tried.

	-Fred

Fred Martin | fredm@media.mit.edu | (617) 253-5108 | 20 Ames St. Rm. E15-320
Epistemology and Learning Group, MIT Media Lab     | Cambridge, MA 02139 USA
