Date: Wed, 19 Jan 94 17:12:45 EST
Message-Id: <9401192205.AA07002@ipf690a.erim.org>
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Reply-To: beyer@erim.org
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From: beyer@erim.org (James Beyer)
To: Multiple recipients of list <robot-board@oberon.com>
Subject: faq on building boards, finally.

At long last, I finally got something together.  It needs to be expanded
(and updated) to reflect more software issues (i.e. the right files, using GCC,
etc.)  Here's what I got so far:


PROBLEMS:

        BUILDING BOARDS

        Q1.     Where are my L293D chips?
        Q2.     Which RED LEDs are the low power ones?
        Q3.     Which side is which on the IR LEDs?
        Q4.     Resistance test fails on expansion board
        Q5.     How do I attach the LCD to the expansion board?
        Q6.     Why doesn't the resistor pack fit on the IR trans. board?
        Q7.     How do I solder the resistor pack to the board?
	Q8.	How do I fit C10 onto this board?

        DOWNLOADING IC

        Q9.     The yellow light won't go off for download

        RUNNING IC

        Q10.    These port addresses don't seem to work.

        RUNNING APPLICATIONS

        Q100.   My Robot can't pass the Turing Test....


	ANSWERS

        Q1.     Where are my L293D chips?

	A1.	Many of the kits had TI SN754410 chips substituted for the
L293Ds.  These are compatible upgrades to the L293Ds.  Here's a chart which
shows how the different chips relate:

								  MAX Standby
Chip Model	Current Sourced/Channel		Clamping Diodes?  current drain

L293D		600  mA				Yes		  60 mA
L293B		1000 mA				No		  ???
SN754410	1000 mA				Yes		  70 mA

For more info, see the Texas Instruments Data Book "Interface Circuits".  
The SN754410 is on page 4-103 of my 1991 edition.  

        Q2.     Which RED LEDs are the low power ones?

	A2.	The low power LEDs (the red, green, and yellow) all look
very similar, except for their color.  The RED lo-power LEDs are thus the
ones which most resemble the green and yellow LEDs (small tops, long leads).
The remaining LEDs (larger tops, shorter leads) are the normal power LEDs.
The IR LEDs have little square silvery tops.

        Q3.     Which side is which on the IR LEDs?

	A3.	Some of the IR leads have absolutely nothing on one face. For
those, its obvious that the transmitting side is the other side with the little
triangle and central dot visible.  Some of them have a larger circle on the 
back, which could resemble a transmitting region.  If you look at several of 
them, however, it becomes clear what the transmitting side looks like. 

        Q4.     Resistance test fails on expansion board

	A4.
	paraphrased from Fred Martin:	The documentation is a bit too strict.
Anything other than a dead short is probably OK at this stage.  Dave Goodwin
stated his board stabilized at 93K ohms
	
        Q5.     How do I attach the LCD to the expansion board?

	A5.

   |~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|
   | /~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\ |
   | |                                             | |
   | |                                             | |
   | |                                             | |
   | |_____________________________________________| |
   |                  o o o o o o o o o o o o o o o  |
   |_________________________________________________|
                     (1)                         (14)

        Q6.     Why doesn't the resistor pack fit on the IR trans. board?

	A6.	Because it has too many pins!  A pin needs to be cut off the
47 ohm resistor packs in order for it to fit on the board.  Be sure that you
don't cut off the common leg.  Verify with an ohmeter if you are unsure which
leg to cut.

        Q7.     How do I solder the resistor pack to the board?
Dave Goodwin wrote:

Well, a few questions have come up during assembly of the main 6270 board.
The revised 2.21 docs say that RP1 and RP2 are not to be soldered on the
solder side of the board.  Say what??!  Am I correct in assuming that this
is simply a typo?  I see no advantage in mounting them on the solder side
and then soldering on the component side; I did pre-read the whole assembly
guide and didn't notice any other steps that are likely to cause a problem
around those resistor packs.

	A7.

	Fred Martin replied:

This is an error in the documentation.  Mount them normally.

	Q8.	How do I fit C10 onto this board?
Dave Goodwin wrote:

Also, anyone have any suggestions on mounting the C10 capacitor?  My PLCC
socket nearly blocks access to the location for that piece.  I dropped it in
place and then tried putting the socket into position but it didn't seem to
want to fit.  If I put the socket in first, I can squeeze the capacitor in
next to it.  I might have to insulate the legs of the cap from the socket
though as they're mighty close.

	A8.
	Fred Martin wrote:

Some electrolytics are bigger than others for the same value and
voltage rating.  You probably have one of the bigger types.  Do your
best.  

It's a good idea to see how everything will fit. (Don't forget the expansion
board)  <We good use further clarification for this answer>.

        DOWNLOADING IC

        Q9.     The yellow light won't go off for download

	A9.

Several people have already had problems with the 6.270 board.  The
common one seems to be the problem of the SER XMIT yellow LED not
turning off like the Docs indicate it will.

THE SOLUTION:
The docs aren't right.  Fred Martin has pointed out to several of us
that if you hold down the CHOOSE button while pressing the large red
reset button, the board will go into the proper bootstrap mode.

This solved the problem for me.


(from : James Fraser.)


        RUNNING IC

        Q10.    These port addresses don't seem to work.


	A10.	The problem is that the older code made for the older
board, has different port addresses.  People who have played with the board
note that the ports are mis-addressed. A newer library is needed to access 
these ports (i.e. DIP switches, etc.) correctly.


Fred wrote:

I've put libraries for the Rev 2.21 board onto cherupakha, in
pub/6270/interactive-c/lib_r22.tar.  These -may- fix the mis-mapping
problem everyone is having with the Expansion Board analog ports.
Consider these libraries an "alpha" release as I haven't tested them.

There is nothing terribly mysterious about how the mapping function
works.  Look at the following code for the analog() function from the
file "lib_r22.c":

int analog(int port)
{
    if (port<8) /* accessing a hardware digital port */
      if (digital(port)) return 0;
      else return 255;
    if (port<12) /* accessing direct 6811 analog port */
      return analog_header_port(port);
    if (port<36) /* accessing analog port on an analog mux */
      return(read_analog(port));
    else {/* out of range */
        printf("Analog port out of range\n");
        beep();
        return -1;}
}

You can see that depending on the value requested a call to
digital()), analog_header_port(), or read_analog() is used.
The last of these two functions is defined in analog.asm.

Hmm.  It is looking to me like no special translation is done here.

Well, anyway, you people can try it and let us know if this code works
any better.

        -Fred

(response on library R22 from Dave Goodwin)

Initial results with the R22 library failed with a syntax error around line
390.  Looking at that area, the problem was the attempted initialization of
a persistent variable.  According to the docs, that's not allowed.  As a quick
test, I simply duplicated the line, commented the original, and removed the
initializations.  It loaded successfully then.

I ran the testboard program and unfortunately breezed past the other tests to
get to the previously-bad analog port testing, so I can't comment on how the
new library or the code change affects that section of the board.  I'll do
that tomorrow unless someone else reports on it.  Within the analog tests,
however, the new library seems to do the trick.  The frob knob is now active,
the ports I tested all worked (all but those covered by the Exp. board) and
the DIP switches worked.  One question; should the DIP switches return 1
when on?  Is there a convention for this?  In either case, they now respond
and the results could be easily inverted if necessary.

What I don't know at this point is the effect of the persistent variable.
>From the context I assume it to be setting the threshhold for the digital
ports, and as such it will probably need to be somehow initialized in order
to work since persistents have an arbitrary content upon allocation.  That's
why I'm sorry I skipped over the digital port tests now :^(  Oh well...

I am now confident that the board is working correctly.  That's a big relief.

---Dave Goodwin                                   

P.S.

I forgot to mention in the last note that the R22 library file has the older
servo motor routines apparently.  It won't handle the dummy parameter that
the newer ones need to have.  Just something to look out for...

- Dave