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.