SPO256 Speech Board Components

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Component Placement

Speech Board Component-side View
(Enlarged to show detail. Actual size is 2.5" x 1.5")
(Same view without annotation.)
Please use this page for version 2.3 and older.

The latest version - 3.1 - has the component id's ON the board. Use them!
  • GREEN - chip (sockets)
  • RED LETTERS - Component identification.
  • RED LINES - Used to make it clearer which holes the component goes into.
  • RED BOXES - header blocks
  • BLACK OPEN CIRCLES - holes to solder components into
  • BLACK SOLID CIRCLES - vias [nothing gets soldered in these holes!]

  • Versions 3.0 and newer have small holes and trace errors FIXED. Ignore any other references to these problems.
  • All components soldered on "top" where text is readable. [No components on "bottom", even the nested 74HC164 which is _under_ the SPO chip.]
  • All chips aligned with pin 1 in top left corner.
  • 10K Audio Potentiometer can be mounted in various orientations. [Plan ahead as this is one of the more difficult components to place with other components so close.]
  • Many components are mounted vertically [R1 & R9 are not].
  • All header blocks are optional. You could just solder in pigtail wires with external connections.

    SPO Circuit Components:

    Be sure to use an open frame 28-pin socket so you can cut out the center brace(s) to leave room for the 74HC164 below. If you socket the '164 [I'm planning on it], you may have to use two sockets to get the SPO256 high enough. (Or perhaps use a wire-wrap socket so you can raise it up to make clearance - but this doesn't work very well.)

    On my first board I did not socket the '164. I did on my next one, but there is not quite enough clearance for the SPO chip to fully seat in the socket. Either raise the socket more or just stack two sockets. Both approaches work, but you could just not socket the '164. It would be a bit of a pain to replace it if it gets zapped, but it's up to you.

    For a limited time I also have a very few kits of components for the SPO PCB (MINUS the SPO chip).

    Speech circuitAll resistors 5% or 10%, 1/4 watt. All caps 10%, 35v or higher.
    D11N914 -or-
    R3, R433K
    C122 pF
    C222 pF -or -
    5-30 pF Trimmer
    Holes may be too small and bad orientation for trimmer.
    C30.1 uF
    C4, C50.022 uF
    C61.0 uFtantalum or electrolytic
    X13.120 MHzHC-49U expected - small holes
    Other values work: 3.07, 3.20, 3.2768, & 3.579545 MHz (colorburst) tested.
    H14x1 0.1" male Header BlockOptional: 6x1 0.1" to include power [V] and ground [G] instead of optional C12.
    Trace layout above has NOT been updated, but it should be apparent.
    H24x1 0.1" male Header BlockOptional: Can be omitted if H1 is 6x1. Only required if using the PIC.
    Optional: pigtails would work for any header.

    Audio Circuit Components:

    Audio CircuitOptionalAll resistors 5% or 10%, 1/4 watt. All caps 10%, 35v or higher.
    R510K Pot10K-50K acceptable
    Audio Taper (preferred)
    Bourns 3386H [or C,W, or X]
    R610 Ohm
    C7,C9,C100.1 uFSee detail about diagonal caps.
    C810 uFElectrolytic
    C11100 uF - 330 uFElectrolytic
    H32x1 0.1" male Header BlockOptional: For speaker connection.
    small holes
    Speaker4 Ohm, 8 Ohm, 16 Ohm, or 32 OhmSmall speaker: 2" - 3" dia
    (speaker from PC)

    Optional Circuit Components:

    U57805 T0-220on-board 5v voltage regulator. See voltage regulator instructions.
    C13,C1422 (or 33, or 47) uF electrolyticFilter caps for voltage regulator.
    R71.2KHoles for this part removed - we already have 200 gain.
    LED1(as desired)Board On-Indicator
    R81K (330 Ohm)Current-limiting resistor for LED1
    C1230uF-100uFBoard bypass - size as desired - omit if onboard voltage regulator present
    (very limited space)
    Also note that the holes have been changed and may be occupied by Header 1.
    U412C508/9PIC for controlling the board with fewer lines. You'll have to program this yourself until I get around to it.
    R95K-10KPull-up/pull-down for PIC. Please see note about trace error! [Fixed in newer versions.]
    H4,H520x1, 2x1 0.1" male Header BlocksOptional: For accessing ALL control and ROM control pins on SPO256. ( schematic) Will require cutting some traces!

    SPO Circuit:

    NOTE: The following circuit schematics originally came from Jon Williams' article "Using the SPO256-AL2 Speech Allophone Processor" in the June 1998 issue of Nuts and Volts [Volume 40]. Go to the Paralax site, Downloads, Nuts and Volts columns for more useful stuff!
    Note: I originally found the gif of this circuit at TheOneSpot - Robotics - Text 2 Speech but that link appears to be broken. :-(

    SPO Circuit

    Note that the output pins QA-QH from the shift register [74HC164] are swapped MSB for LSB going to the SPO256 chip. This greatly reduced the difficulty of the trace routing for the nested shift register [which was nested to conserve board space].

    Audio Amp circuit:

    Audio Amp

    Original audio circuit gif.

    This page made of 100% recycled bits.
    Edited (as my 12-year son brags of his web pages) with Notepad.