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Interface for the Canon Data Memory Back 90

In 1985, Canon released the Data Memory Back DMB90 for their
top of the line manual focus camera, the legendary T90.
The DMB90 can record a lot of useful data (time, exposure data, etc.),
but unfortunately, the only available interface to get the data from
the DMB90 into a computer was for nowadays rather hard to find
MSX computers. You will find lots of useful info about the T90,
the DMB90 and the MSX interface here.
A friend asked me to build a DMB90 interface for him that
allows to download all the stored information to a PDA, the
nowadays rather hard to find Siemens IC35... But since the
PDA side of the interface is RS232, it will work with any
PC, PDA or whatever, as long as it has a RS232 interface
capable of 9600,8N1 communication.

Because the DMB90 uses a synchronous serial protocol, and RS232
is an asynchronous interface, I used a small microcontroller to
do the interfacing.
The interface was only built once, from parts that I had lying
around (that should explain the unusual RS232 level converter).
That means it is a prototype, hopefully a good starting point
for people who want to build their own DMB90 interface.
This is the schematics:

 

The firmware for the controller is available as
source code and as binary. The source code file
also contains information regarding:
- how to make the binary from the source code,
- how to program the controller chip, and
- how to talk to the interface via RS232

The 3V power supply for the controller and the RS232
level converter comes from the Siemens PDA.
This will also work for Palm and Handspring PDAs.
For a PC, you will need a separate 3V power supply.
I suggest two AA batteries.
And don't forget the power switch...

I also made a Win32 PC program for DMB90 data download
using the interface, but this has never been tested.

If anyone happens to have a Siemens IC35 and wants to use
the interface with it, here is the download application.

Thanks to Vladimir Pantelic for decoding the DMB90 serial
protocol and the format of the stored data, and thanks
to Pawel Nabe for working out all the details about the
format of the stored data, and making the program that
converts raw DMB90 data into a human readable form.

About the connector
As far as I know, the 6 Pin connector used by Canon for the
TBE and the DMB90 can not be obtained separately.
It comes only attached to an Interface Unit TB, the DMB90
MSX interface or the Keyboard Unit E. The best way to equip
your self built interface with such a connector is to cut
one off of one of these devices. Insert a common connector
pair (such as MiniDIN or Binder type 712) and you can use
it on both devices.
 

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