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Decade BOB-3 Application Manual

Videotext overlay module
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E
E C A D E
N G I N E E R I N G
5504 ValView Dr. SE, Turner, OR 97392-9517 (USA) ~ tel: 503.743.3194 ~ fax: 503.743.2095
website: www.decadenet.com
BOB-3 Application Guide ~ Firmware V3.4 ~ December 21, 2004
(Please check our website for the latest version of this document.)
Introduction
BOB-3 is Decade's third-generation low-cost videotext overlay module. BOB-3 lets your microcontroller or PC
display up to 680 characters on standard video monitors and TV sets. With 63 user-definable characters, BOB-3
supports pseudo-graphics and multiple languages. BOB-3 generates video on-board, or automatically genlocks to
your video source and superimposes characters over the image. Printable characters and commands control BOB-
3 through a fast RS-232 style data link, much like a simple serial printer. BOB-3 works with most microcontroller
tm
chips and modules, including the BASIC Stamp
. PAL video compatibility is optional at ordering time.
Cautions & Revision History
ESD (electro-static discharge) safety precautions must be followed at all times when handling BOB-3 modules. Use
a grounded wrist strap and grounded work surface. BOB-3 modules must be stored and shipped in static-shield
(metallic, not pink poly) packaging. Use a SIMM socket! Soldering directly to BOB-3 voids the warranty.
[V3.40] Fixed bugs: BE command repetition eventually trashes display, video status ignored during vertical scroll.
Allowed printing outside active vertical scroll block. Revised vertical scroll behavior to print incoming characters
immediately instead of waiting for line buffer full or <CR>. Added simple 'networking' support on pin 6. Added 2C
and 2L commands, to support <LF> code.
[V3.30] Fixed bugs: RAM characters sometimes invisible after video mode change, JN command fails if new value
is less than current line number. Allowed arbitrary data with Y command in boot script. Disabled P command
execution in boot script. Added hardware method to clear boot script. Supported double-width characters in text
crawl. Added work-around for minor artifact of JO command.
[V3.20] Fixed minor bugs in H command processors. Added PAL range limits for H commands and corrected the
list of supported ASCII codes in this document.
[V3.10] The status report string was further extended in firmware version 3.10, to include video standards
compatibility reporting (NTSC or PAL). See S command description.
[V3.00] Several commands were added or extended. The new commands are: JR, K, MI, MN, VL, Y, ZC, ZP, 1D
and 1S. Boot script capacity (N command) was doubled, and three new communication bit rates were added. All
changes are believed to be backward compatible with version 2 application programs except increased start-up
delay time (to 500mS), a different report string generated in response to the S command, and the (simplified)
response to bad commands.
[V2.00] N command termination character was changed from <CR> to"|" (the vertical bar symbol).
BOB-3 Version 3.4 Application Guide ~ Copyright © 2004 by Decade Engineering ~ Page 1

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Summary of Contents for Decade BOB-3

  • Page 1 Printable characters and commands control BOB- 3 through a fast RS-232 style data link, much like a simple serial printer. BOB-3 works with most microcontroller chips and modules, including the BASIC Stamp .

  • Page 2: Video Modes

    “Automatic,” derives from BOB-3’s ability to switch between the basic modes by detecting video input. BOB-3 powers up in Automatic. If there’s no video input, it selects local mode. In this case, BOB-3 generates the complete video signal, and characters appear on a blue (by default) matte background. If video input is present, BOB-3 switches to genlock mode so that characters are superimposed on the externally generated video signal.

  • Page 3: System Hookup

    (to pin 3) are required at pins 12, 13, and 14 unless those three socket contacts are left floating. An RS-232 hardware interface is required for connection to a PC COM port (see next section), but not for connection to a microcontroller. Some optional BOB-3 features are not implemented here, but are discussed in other parts of this document.
  • Page 4 Note that some industry-standard RS-232 interface chips do not support the highest communication bit rate now offered by BOB-3. If you’re using one of the highest bit rates, be sure to check this specification as part of your component selection process. Also confirm that cable capacitance does not exceed the chip’s drive capability at your system’s maximum speed.
  • Page 5 3. Clockwise end: +5VDC (BOB-3 pin 3) Decade Engineering recommends the addition of 4.7K pullup (to +5V) resistors at pins 12~14 unless they are tied permanently high or low for baud rate selection. Weak internal pullups are provided, but wrong baud rate selection is possible under some conditions if pullup current is not augmented.

  • Page 6: Video Mix

    Digital Output Ports: P0~P5 may be used as general-purpose logic outputs to control circuitry external to the BOB-3 module. These are unbuffered 200uA CMOS outputs; don’t attempt to drive heavy loads such as LEDs without buffering. See {O commands for application programming details.
  • Page 7 Use the new video output at J1 instead of BOB-3 pin 28. Do not substitute Q1 with a buffer IC. The DC offset voltage across its base-emitter junction is an important feature of this application circuit. The AD8041 is a video op- amp from Analog Devices that works well on 5V power.

  • Page 8: Application Programming

    {2 commands change this behavior in ways that are useful for some applications. Commands sent to BOB-3 must be prefixed by the left curly brace character: { All commands except {N and {VW employ a fixed-length format, and do not require a command suffix. Command salvos require a { prefix to each command in the string.
  • Page 9 Blink rate. “b” = 0~1. 0: Default slow (1S), 1: Fast (0.5S) {HN & {HX Not valid in BOB-3. External video levels are always active if the controls are installed. {HHphh Horizontal display position offset with single-pixel resolution. “p” is a polarity sign (+ or -). “hh” is a two-digit hex value in the range of 00~FF.
  • Page 10 {ODh Selects alternate functions of 6 logic output pins on the BOB-3 module. “h” is a single byte in the range of 00~3F which selects alternate video control output functions of P0~P5 if bits are set true.
  • Page 11 Starting with firmware version 3.0, command exceptions cause the command processor to abort. BOB-3 emits {?<CR> as in previous firmware versions, but does nothing else in response to the faulty command. BOB-3 Version 3.4 Application Guide ~ Copyright © 2004 by Decade Engineering ~ Page 11...
  • Page 12 ROM Character Set: Default RAM Character Set: BOB-3 Version 3.4 Application Guide ~ Copyright © 2004 by Decade Engineering ~ Page 12...

  • Page 13: Troubleshooting

    {P command, etc. Mistakes like this can be especially confusing if they occur in a boot script! Rogue boot scripts can be cleared by holding pin 15 low as power is applied, even if BOB-3 is unable to communicate properly with the host computer.
  • Page 14 ), from Caig Laboratories. Apply the contact treatment to a cotton swab and polish all of the contact pads on your BOB-3 module, then reinstall it in the SIMM socket. This procedure should result in a permanent cure for intermittent operation due to poor contact, where Tin or Tin/Lead plating is present on the BOB-3 module or SIMM socket contacts.

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