Tuesday, November 4, 2008

How-to: wiring MIDISpeak for both play modes

Welcome to the first 'How-to' entry of the re-launched 'Magic Bullet'. As promised, I'm going to detail (in excruciating detail) how I wired up my Speak and Spell to function in ROM Modes A and B, as well as Keypad mode with the MidiSpeak kit from HighlyLiquid.


For an (admittedly shotty) diagram of what I did above, and what I will be describing, click on the preview picture below.

Here are the parts that I used (or would have used) in addition to the MidiSpeak kit.


  • (1) male-to-male DB25 cable.
    Make sure that it has all 25 pins active.



    I'd advise using a multimeter to double-check this (I ended up buying what appeared to be a functional DB25 cable and found out it only used eight pins, after the fact).

  • (2) panel-mount DB25 jacks.
  • (3) single-pole, single-throw switches.
  • (1) double-pole, single-throw switch.
  • (?) drill bit(s) matching in size to the shafts of your chosen switches.
  • (2) feet of five-conductor ribbon cable.
  • (1) half-meter of twenty-conductor ribbon cable (it's cheap to buy from HighlyLiquid).
  • (3) feet of wire (doesn't matter, just keep it small - we're working in tiny spaces)
  • (1) dremel tool with cutting discs.
  • (1) socket that fits the DIP switch provided with the 'kit.

    I ended up using an eighteen (if I recall) pin socket that fit the switch, and cut off the unused legs and spaces on the socket. Just find a socket that fits the DIP switch, and test for continuity across the legs to make sure it functions properly.
Now, I'm going to assume that if you're interested in this project, you've either done your research on modifying a Speak and Spell and are familiar with the tools for the job, or that you've already modified a Speak and Spell. If you have not done either, I'd suggest at looking around for any guide on circuit bending a Speak and Spell for a good explanation on how to open the case, what not to do and so-forth. If you're still interested in making your 'Spell be a Swiss-Army Knife of play methods, read on.

The DIP Switch Explained

How the DIP switch functions with the 'kit is that, on completion of a power-circuit, the position of the switches determines how the 'kit is going to be configured to operate. Because the switch is located on the board, and we'll be placing our board inside the case when we're done, changing play methods after installation would traditionally be off-limits. However, we're going to set it to default to run 'on all cylinders', and use in-line switches as convenient methods to play Gatekeeper.



In this way, we can power-down the 'kit, flip a few switches, power-on the kit and have it boot into another play mode.

How-to: re-locating the DIP Switch

First, cut around two eight-inch sections of the five conductor ribbon cable, remove one of the conductors and strip both ends. What you're going to be doing is soldering the cable between each of the four contact points for both rows of the DIP switch on the 'board, to corresponding pins on the socket you purchased. Once the cable is cut and stripped, tin the ends and solder wire between the contacts for DIP Switch pins 1 thru 4 on the circuit board of the 'kit and the socket legs for pins 1 thru 4. Do this for both sides of the switch pins and socket legs.

Now, we're going to wire up two of our single-pole, single-throw switches in-line between the contacts for DIP Switch pins 5 and 6 on the 'board, and the socket legs for pins 5 and 6. Cut and strip the ends off of (roughly) two foot-long lengths of wire, and solder a length between the contacts for DIP Switch pin 5 and a leg on one of the switches. Do the same for the pin 6. Now, cut and strip another two foot-long lengths of wire, and solder the other leg of each switch to their corresponding leg on the socket. To complete this love affair, we're going to (again) cut and stirp another two foot-long sections and solder them betwen the remaining DIP Switch pin contacts on the 'board, and their corresponding legs on the socket.



If you test continuity on the 'board between matching DIP switch contact points, you should get no continuity between pins one and four, and your in-line switches should determine if you do or do not have continuity for pins five and six.



If that is the case, you rock. Continue.

The Keypad Connections, ROM and Keypad and us.

If you've poked around the HighlyLiquid website and taken a gander at the connection notes for ROM and Keypad mode, you would notice that they're drastically different. What we're going to be doing, using the design of Cedric Bodereau as inspiration, is use a DB25 cable and two DB25 jacks to switch between the connection points. How this works it that we wire all of the output points of the 'kit (Keypad 1-13 and Glitch 1-6) to a DB25 cable and wire each of the proper points on the board to corresponding DB25 jacks.

How-to: wiring the DB25 cable and jacks.

Measure about three feet from the end of your DB25 cable and cut it open. Now, get to strippign (and you better strip good). If your DB25 cable is anything like mine, you'll have a web of annoying shielding to get through before you even get to the conductor ends. Once you have the ends free and stripped, test continuity between each of the pins on the end of the cable and the stripped ends. I'd suggest marking each end with table designating what number pin it is, for the time being.

Now, solder conductors 1 thru 13 to the board connections for Keypad 1 thru 13. Then solder the connections for Glitch 1 thru 6 to the DB25 conductors for pins 14 thru 19. Now cut about two foot-long sections of the 20 conductor cable. One one of them, strip it down to having 13 arranged conductors, so you have created a 7 conductor ribbon cable. Strip both of the ends on both cables.

How-to: the Keypad DB25 jack

Now solder between the designated places on the 'board for the Keypad connections, and the corresponding pins of the DB25 jack (with the first pin for the DB25 jack going to the Speak and Spell circuit board point for the Keypad 1 conneciton, and so-forth). This will take up an entire row of pin connections on the DB25, as well as the 13 conductor cable you created. Save the 7 conductor cable that you created for the ROM DB25 jack, and strip three conductors off of the complete foot-long length of 20 conductor cable you have. Strip both ends of the 3 conductor cable you created and make connections between the 'Suggested Glitch Points' (see the Keypad installation guide) and pins 14 thru 16 of the DB25 jack.


How-to: the ROM DB25 jack

The ROM jack is much easier to deal with, because we're only using eight of the pins on the DB25 jack. Strip 2 of the conductors off of the aforementioned (and now mangled, 17 conductor) ribbon cable, you'll need that for the ROM trigger points. Strip both ends and make connections between pins 1 and 3 of the DB25 jack, and their corresponding points on the Speak and Spell circuit board (see the ROM installation guide). Seperate one more conductor off the 7 conductor cable you created (to create a 6 conductor ribbon cable), and strip it's ends. Now make connections between the listed Glitch points on the 'board and pins 14 thru 19 on the DB25 jack.

Power cycling the 'Kit

Now, the MIDISpeak kit requires a power-cycle for it to notice any changes in the DIP switches, so we're going to have to put an in-line switch between the battery and the power contacts for the 'kit.

How-to: Power Control for the 'Kit

All you need to do is strip 4 conductors off of what remains of your ribbon cable. Strip all of the ends. Now, make a connection between the negative (-) terminal of the battery case for the Speak and Spell and one of the legs of your double-pole, single-throw switch. Likewise, make a connection between the positive (+) terminal of the battery case for the Speak and Spell and the other leg of your double-pole, single-throw switch. Now make connections between the negative (-) leg of the double-pole, single-throw switch and the negative (-) power point on the cirucit board for the MIDISpeak. Again, make another connection between the positive (+) leg of the double-pole, single-throw switch and the postive (+) point on the circuit board for the MIDISpeak.

(Please ignore the switch to the right of the speaker, that is an in-line switch for the speaker and it is not discussed in this guide)

How-to: Jumper 4 to Keypad 10

One of the funky differences between Keypad and ROM mode is that, in ROM mode, there is a connection made between the contact point for Jumper 4 and the contact point for Keypad 10, on the MIDISpeak board. Just seperate two conductors from the mangled remains of your 20 conductor cable, strip the ends and connect the contact point for Jumper 4 to one leg of your single-pole, single-throw switches... and the other leg of the switch to Keypad 10.


Summary: What we Did

Here is how you work what you have now. Let's say you want the Speak and Spell to be set to act for Keypad mode. Just connect the DB25 tail that you soldered to the Keypad and Glitch points on the MIDISpeak kit's board to the corresponding DB25 jack. Then, you flip the proper switches. For instance, in Keypad mode you do not want DIP Switch pins 5 and 6 to be sending power, so you flip the corresponding in-line switches to their 'off' position. You also flip the switch for Jumper 4 - Keypad 10 to be in it's 'off' position. Then you flip the in-line power switch for the MIDISpeak kit to be 'on', and then you turn the Speak and Spell on.

For going to ROM mode, you'd then turn the Speak and Spell off, turn the MIDISpeak off, flip the switches again and then turn the MIDISpeak on, and the 'Spell on.

3 comments:

misoft said...

Hi there!

I was looking for "How-to: wiring MIDISpeak for both play modes" but can't see any pictures. ???

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