: The Packet Sniffers Projects :

VMU Hacking
by: dosman


    A few years back when the Sony Dreamcast was still new and cool, people started playing with a device called the Visual Memory Unit (VMU). This is a memory card for the Dreamcast, but with a twist. It has a small LCD screen and basic NES style controls. It connects into your controller and gives you additional animations for the game you are playing as well as being able to store game saves. It can also be used to play games by itself. An interesting concept to say the least... So anyway people started figuring out how to directly connect to the devices and do their own custom coding for them.

    Now let me make a statement here for the elitists reading this: I have done nothing all that original here, I have only followed directions of others to make this. The VMU hacking scene peaked back around 2000 so I am late to the party. Really all I am doing here is making an adapter cradle for my VMU, but with a bit more style than most ;). And with that warning out of the way, here we go.

    Here are my sacrificial devices, a nice translucent charcoal VMU for $3 and a Dreamcast controller for $5 from the used game store at the mall. I got the controller so I could make a nice adapter without soldering wires directly to the VMU.








Staring down the VMU sockets and a disassembled controller





I used a box cutter to slice the plastic and side cuts to do the connector pins





The connector freed and wires soldered to the socket. Note: this shot was before I added the 4.7k Ohm resistors



    Here is the pinout for the adapter. This nicely formatted layout is stolen directly from John Maushammer's terrific VMU site.

LPT Pin In/Out LPT Signal Name     VMU Pin  VMU Name             #define 
------- ------ ---------------     -------  -------------------- ----------- 
   2     I/O   Data Bit 0             12     PC2VMU clock        OUT_CLK 
   3     I/O   Data Bit 1             10     PC2VMU data         OUT_DATA 
   4     I/O   Data Bit 2              4     PC2VMU delayed data OUT_DLYDATA 
   5     I/O   Data Bit 3              6     PC2VMU handshake    OUT_HSK 
  10      I     -ACK           **      3     VMU2PC clock        IN_CLK 
  11      I     BUSY           **      5     VMU2PC data         IN_DATA 
  13      I     SLCT           **     11     VMU2PC delayed data IN_DLYDATA 
18-25    ---    Ground               7,8     Ground 
                           1-14 Make sure these are connected to each other 
                                 so that the VMU's drivers are enabled.
*** Also connect these pins through 4.7kohm resistors to ground. You need a total of 3 resistors. (note: depending on your parallel port, a different value may be needed. If you want to live dangerously, you can omit them (but I didn't and wouldn't recommend it))


    I used a standard DB25 printer cable and cut off the Centronics printer connector for my cable. Then I used an Ohm meter to make a map of which wires where connected to which pins. I think it took about 35 minutes to get this portion completed.


    Here the VMU socket housing is being worked on.


I used a soldering gun with a cutting tip to separate the two VMU holders





Once again, hot glue is the way to go. With the VMU plugged in you can CAREFULLY glue the connector in place. You will want to be sure you don't accidentally glue the VMU's connector to the grey housing, you can see I didn't just run glue all over the entire connector for this very reason. It is still sturdy even with this small amount of glue used.




The reassembled Dreamcast controller. The first VMU port is still functional, this controller will go to my friend that actually owns a Dreamcast.





Note that this is before I glued the connector the grey housing. Also notice the 4.7k Ohm resistors now in place. As I had read, connecting the VMU without them does cause the screen to black out. Fortunatly my unit was not damaged, but it would not accept files like this. The resistors corrected both problems.




The completed unit! Yea!



Tada! A little advert for a cable access show a friend and myself are putting together.



    Now that I have this completed I will start some work on some animations of my own. I may even try my hand at some assembler code if I feel really motivated. I will post some of my creations below once I get something worthy of posting.



Gutted VMU

    I decided to take the VMU apart so I could clean the screen properly. Here are some pics of that near fiasco.







Here you can see the circuitry really well along with the pin numbering stenciled onto the VMU circuit board.





If you take out the LCD screen, watch which way it goes back in as I did not. There is a small "bump" on the LCD glass that goes to the top of the VMU, you will notice on the left picture.


Additional Info

This site has a ton of good VMU info and is where I got all of my info and tools for doing this project:

Here is another site that has some good VMU animation creation tools:


Notice: This site is not in any way affiliated with Sony or any of it's subsidiaries or affiliates. 

Copyright 2004 The Packet Sniffers - http://www.packetsniffers.org
Web Template by http://www.quickness.uni.cc. All Rights Reserved.