
How to cable to the PR-650

The CMETER routine is written to send signals out the Modem port on the
Macintosh to the PhotoResearch P5-650 spectral radiometer.

The modem port takes an 8 pin male plug.  Orient the plug sothat you see
three horizontal rows of pins with two pins in the top row, three in the
middle row, and three in the bottom row.  The pins are then numbered 1-8
going across each rows and then down through the rows.  (So pin 1 is the
upper left, pin 2 the upper right, pin 3 the middle left, etc.)  See
Guide to the Macintosh Family Hardware , p. 360 for a picture of the
pin-out.

The PR-650 comes with an interface cable that ends in a standard female
DB-25 connector.  If you look into the male connector that will plug
into the 650 with the long row of pins on top, then the top row is
numbered 1-13 from left to right and the bottom row is numbered 14-25.

To get CMETER to work, you need to connect as follows

Mac Pin				DB-25 Pin

1									20
2									4
3									3
4									7
5									2
6									7				(I'm not sure this is necessary)
7									open
8									open

You can buy cables that plug into the modem port on one end and has a
DB-25 connector on the other.  What pin is connected to what varies
depending on who made the cable.  I suggest you get one, measure its
connectivity, and then build a cross-over cable to get the desired
overall effect.  (That is what we did.)

The PR-650 cable has a little switch on it with two positions, xfer and
ctrll.  The switch should be set to ctrlr.

David Brainard
March 13, 1997

%%%%%%%%%

Although I still use a cable like that for connecting to an old Mac G3, 
I find it a little hard to believe that anyone new will still find the
above information useful.  I think that by now the most common method 
for talking to even an old spectroradiometer like the PR-650 is through
a USB cable.  PhotoResearch sells a USB to RS-232 adapter.  I asked them
what it cost, but I found one for only $6, so it didn't bother me when 
PhotoResearch didn't answer my question.

I had a lot of trouble trying to use the adapter when calling PR650init 
directly, but apparently calling it many times in rapid succession (as 
CMCheckInit will do) solves most of those problems.  The other major 
problem I had to face was that the device driver that came with my adapter
would not work with my system.  The company that made my adapter apparently
isn't proud of their handiwork.  I could not find any hint of a company name
(other than PnP) anywhere on the package.  I was able to determine that the 
chip that forms the heart of the device is PLP-2303XH.  If you can find any 
adapter based on the PLP-2303 chip (made by Prolific: 
http://www.prolific.com.tw/eng/Products.asp?ID=59), you should be alright,
but you may have to download (or otherwise obtain) the latest driver
from the Prolific website.

Mickey Rowe
November 26, 2007




