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BOB-II FAQ - Decade Engineering

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1. s input pin How can I make the overlay transparent amp What are all those video outputs for CVO2 pin 23 is an auxiliary unbuffered video output with no character overlay It s possible to connect a 2 5K pot across CVO1 and CVO2 with its wiper returned to EF IN and achieve a text overlay effect with fully adjustable transparency Be aware that video crosstalk can appear if you implement this feature and command local video mode while supplying an external video source to BOB II This feature was not operational in early shipments of BOB II Contact Decade Engineering if you need an update BOB II offers a number of video output options CVO1 pin 24 is the basic unbuffered video output CVO1 is DC coupled and offset positive by 2 3V This pin cannot drive coaxial cable so a power buffer circuit with source termination was provided at pin 26 input and pin 28 output The buffer is an emitter follower with no output DC blocking capacitor When correctly terminated downstream in 75Q it biases the video signal to about 1 VDC An external capacitor may be wired in series with pin 28 to block DC bias but it s very rarely needed If you don t want to use the buffer you can eliminate its power consumption gt 10mA by tying pin 26 to ground Composite SYNC available at pin 20 may be used to derive a clamp pulse for DC restoration in external video processing circuits How can I use external video level brightness control CLVL
2. pin 21 and SLVL pin 22 are provided for applications where it s desirable to make character or background brightness variable Because HX and HN see command protocol switch CLVL and SLVL simultaneously you must manage DC levels at both pins if you need to use either of them We suggest 2KQ pots each with a 2K resistor at the CW clockwise end connected to V 5 and 1K at the CCW end to ground Bypass each pot wiper terminal with 0 1uF to ground at BOB II pins 21and 22 More restricted voltage ranges are appropriate if non experts will be operating the end equipment How can I display the arrow symbols or any of the graphics characters Invoke no translate mode by sending T then send the literal codes listed in the character set documentation Send 7A 7D hex 122 125 decimal or ASCII z or to display the arrow symbols Always terminate your T command string with an lt ESC gt character Examples Tz lt ESC gt displays the right arrow T lt ESC gt displays three up arrows Tz lt ESC gt would display all four arrow symbols in a row lt ESC gt is a single character coded as 1B hex 27 decimal which can be sent from a PC keyboard with the Escape key or the Control plus key combination Note that upper case P in no translate mode is coded as 1B hex which is identical to the ASCII lt ESC gt code Since lt ESC gt is the command termination character for no translate mode BOB II switches back to normal ASCII t
3. the result is entirely acceptable in many applications You could use external fast analog switches controlled by BOB II to perform character insertion in S Video s Y and C channels There are a few chips on the market that have been optimized for jobs like this Linear Technology s LT1203 is one of our favorites Here are a couple of ideas to flesh out this concept We haven t tried them 1 Trick BOB II into providing an external switch control signal without modifying it This could be done by feeding a clipped or attenuated version of the Y channel into BOB IL then using a fast comparator at the video output to extract character white level transitions they would stick up above the video level at all times Disadvantage Only character foregrounds would appear in S Video Black character outlines would not be present 2 Geta switch control signal directly from internal BOB II signals The OSD chip has a number of unused outputs that should do the trick but extra logic gates may be required Only one external analog switch would be needed for the C channel and there s a possible hack using a single cheap transistor for this function Disadvantage Decade Engineering doesn t enforce the warranty on modified boards Note that video input and or output buffers may be required in addition to the analog switches The clipping circuit mentioned in 1 may require upstream DC restoration as well I get strange results with JD and other col
4. turn off time a micro manager or low voltage brownout detector IC must control BOB II s reset pin Examples of acceptable LV detector ICs Motorola MC34164P 5 no delay Dallas DS 1233 10 delayed An off board pullup resistor is not required EMI electrical noise could cause unwanted CPU resets if picked up by the reset pin The recommended bypass capacitor prevents this antenna action and permits external CPU reset control as described in the note above What are pins 17 19 used for Along with RES pin 10 these pins are used to configure and test BOB II at the factory Hackers and engineering professionals will deduce other possibilities that are beyond the scope of this document Let it suffice to say that Decade Engineering will assist qualified organizations with specialized applications under the terms of a legal non disclosure agreement What is Genlock Genlock is the capability of synchronizing to an external video signal source generator To overlay text on video BOB II has to extract scan timing information sync from incoming video and use it to synthesize all required internal video timing These internal timing signals control the exact placement of visible dots that form character shapes in the display Can you suggest part numbers for compatible SIMM sockets Molex part numbers are 15 46 3053 Tin and 15 46 3043 Gold Amp numbers are 822056 2 Tin and 822061 2 Gold Adam Technologies numbers
5. IM DECADE ENGINEERING 5504 ValView Dr SE Turner OR 97392 9517 USA tel 503 743 3194 fax 503 743 2095 email info decadenet com web site www decadenet com BOB II FAQ amp Discussion June 6 2001 Please discard earlier versions How can I get BOB II working quickly Refer to the basic hookup diagrams below Also build the simple RS 232 receive interface described in another FAQ topic Why does the data have to be inverted further below and connect it to the COM port of a PC Launch HyperTerminal or equivalent and configure it for 9600 8N1 no handshake plain ASCII terminal emulation Power up BOB II and type Characters appear at the upper left corner of your TV monitor screen BOB II 30 pin SIMM Socket VIDEO IN a OPTIONAL GND O DATA IN Ce VIDEO OUT Figure 1 Basic BOB II Hookup P SUFFIX PLASTIC PACKAGE oa CASE 29 Pin t Reset TO 226AA 2 Input 3 Ground 1 23 Figure 2 MC34164P 5 Brownout Detector IC Pinout It s important to use a brownout detector circuit at the reset pin 10 There s more information on this topic in the discussion about BOB II start up problems and reset pin management The BOB II Control Protocol spec is too terse Where can I get an application program example BOB II application program examples are available for download at Decade s web site www decadenet com Go to the Products page then click on BOB IL Scroll down the BOB II p
6. In addition to the crystal difference for NTSC vs PAL chroma subcarrier frequencies in Local mode firmware differences affect OSD control registers and vertical line spacing Due the greater number of scan lines in PAL systems it was necessary to add some padding between text rows in order to fill the available screen space The only negative consequence is that character bitmaps cannot be vertically contiguous in the PAL version which means that high resolution vertical bar graph displays should not be attempted What the heck does BOB mean anyway Basic Overlay Board Too simple eh Decade Engineering BOB II FAQ Page 6
7. OB II and the BASIC Stamps both use ceramic resonators to control baud rate Accuracy limitations of these timing devices are such that baud rate mismatch can occur when they re used at both ends of a serial com link Try small baud rate changes in your Stamp program if nothing else works Do I have to provide a video signal to pin 30 You don t have to supply video to this input pin BOB II generates background video internally if you don t When a video signal is supplied BOB II genlocks to it and superimposes characters A command has been provided to force local video generation while video is supplied to the input pin but it shouldn t be used if a transparency control is installed Decade Engineering BOB II FAQ Page 2 If you re using the video input supply it with clean composite baseband not RF video from a source that delivers 1 Vpp into a 75Q termination That s the most common type BOB II provides a correct input termination Many video device outputs contain some incidental DC bias voltage because it s awkward to design video circuits to operate on a single supply voltage any other way It s unlikely but if you measure DC bias greater than 2 5V at pin 30 you must find a way to reduce or eliminate it because BOB II may suffer damage due to reverse bias on the input coupling capacitor A typical solution would be to insert a large electrolytic blocking capacitor 470uF or greater in series with the video line to BOB II
8. age to find the download links Here s a simple BOB II test program for a PC running MS QuickBASIC Decade Engineering BOB II FAQ Page 1 OPEN coml 9600 n 8 1 cs0 ds0 cd0 op1000 rs FOR OUTPUT AS 1 PRINT 1 A Clear the display pause required FOR x 1 TO 425 NEXT About 5mS time delay on a 486DX2 66 interpreting PRINT 1 BOB II Test Program 12345678 PRINT 1 Tzz CHRS 27 Do you see arrows PRINT 1 CO505Row 5 Column 5 CO506 T CHR 27 CO504 T CHRS 27 CLOSE 1 How much current can I really get from the 5V output pin 3 BOB II uses a 78M05 type regulator IC to derive its internal operating voltage from the raw power supply at pin 1 Its heat dissipation capabilities are modest but far in excess of 78L05 types BOB II consumes about 65mA internally The spec sheet gives 50mA as a maximum load on pin 3 but this may be doubled if ambient temperature isn t excessive If you need to press the limit refer to the 78M05 spec sheet published elsewhere Also be aware that the power supply input filter capacitor carries a 25V maximum rating which must be derated if operating temperature is elevated Why does the data have to be inverted BOB II expects inverted serial data at pin 7 with 5V logic levels This allows a direct connection to the UART transmit output pin of any standard microcontroller but you need an inverting receive interface if you re going to connect to th
9. are SIMM 130 VTL Tin and SIMM 130 VGL Gold Adam Tech gold sockets are currently available from Decade Engineering for 1 00 each in any quantity Note The reliability of tin plated contacts can be dramatically improved by application of widely available Caig Laboratories Nye Lubricants etc contact treatments Why does the text overlay jitter This trouble symptom is universally caused by weak and or noisy video applied to pin 30 Typically the video signal has been attenuated by passage through a long cable or double termination The best cure for long cable woes is a robust cable drive amplifier with pre equalization for cable loss characteristics Decade Engineering offers a Camera Adapter Board CAB with broad adjustment ranges and high drive capability for this purpose A Cable Compensator or Video Processor at the receiving end may also be acceptable Bear in mind that long cables are subject to noise injection from a variety of sources including ground loops so cable receiver circuits may have to deal with several kinds of signal defect simultaneously Why does BOB II miss or mangle incoming characters after a video mode change or at power up time BOB II is effectively off line for an indeterminate period of time during video mode changes This interval can be up to a few 3 4 seconds when entering Genlock Overlay mode but it s normally insignificant when switching to Local mode If your application relies on automatic mode
10. e COM port of a PC or any true RS 232 circuit MAX232 style interface chips are the industry standard solution You probably should go ahead and use one if you re running a long data cable because it conveniently provides features that maximize noise immunity If your hookup is short and direct you can abbreviate this requirement to a simple transistor inverter stage as shown below The RS 232 Receive Input line connects to pin 3 of a 9 pin PC COM port TX Out Pin 5 of the PC COM port connects to Ground Use BOB II pin 3 for the V 5 power source TO BOB II DATA RS 232 RECEIVE N3904 INPUT PIN INPUT D1 1N4148 Figure 3 Simple RS 232 Receive interface Be aware that some PC serial cables are not wired straight through modem style but instead swap the TX RX and control signal pins These are sometimes sold as serial printer or null modem cables BOB II works correctly with my PC but displays gibberish with my BASIC Stamp Why The Parallax PBASIC documentation for SEROUT views data polarity in a sense opposite to that which Decade Engineering adopted in the BOB II documentation This is true for both BS1 and BS2 as of February 2000 Therefore use Baudmode expression T2400 in your BS1 program 2400bps is the only compatible rate for BS1 The BS2 argument for SEROUT at 9600bps for example would have Baudmode set to 84 or 85 This discussion assumes a straight wire data connection Be aware that B
11. nate in a simple subcarrier delay line rather than a real chroma modulator circuit in the chip so it s impossible to be precise about the colors you get and it varies somewhat from sample to sample Wish the news was better Why did you leave out the comma character We had to accept the standard character set that was offered by the character generator IC vendor because we re not rich enough to order a custom mask for the character ROM Perhaps the character set was determined by a high volume customer with specific priorities that didn t include a comma but demanded enough other stuff to fill up ROM space You might try the tic mark for large number formatting How can BOB II be used in S Video systems S Video is a method of transmitting video on two wires labeled Y and C The Y signal is video brightness information Luma mixed with sync The C wire carries color Chroma information with hue and saturation encoded like the color component of composite video S Video represents a qualitative middle ground between one wire composite video as used in TV broadcasting and three wire component video signal transmission schemes The simplest method to handle S Video with BOB II is to route the Y channel only through it Just bypass your C channel around BOB II We ve done this with good results There s a little color from the underlying video in superimposed characters but if color saturation in your source image isn t extreme
12. or control commands What s going on Operation of certain BOB II color control commands is described incorrectly or incompletely in the first edition of the printed user manual and BOB II Control Protocol documents previous to version 1 21 Please download the most current version of the BOB II Control Protocol document from our web site and observe the following Decade Engineering BOB II FAQ Page 5 e All of the color control commands have global scope except En which affects only those characters written subsequent to each command instance e Jn JE mode for character cells that have been written with background enabled the background color is controlled by Dn not In e In JD mode the background for the entire character display area character grid is black Fn still controls screen color which is the border surrounding the character display area but Dn and In have no effect En affects subsequent character foreground and background colors simultaneously Character foregrounds are high luma versions of background colors In other words foreground and background hue for each character is identical only the higher video brightness value makes character foregrounds distinct e JE is the default power up condition A final reminder These commands are useful in Local Mode only In Genlock Overlay mode BOB II superimposes only monochrome characters What are the differences between NTSC and PAL versions of BOB II
13. ou may freely restructure channel assignments in your local cable system A potential problem is that Decade Engineering BOB II FAQ Page 3 low cost modulators are often poorly filtered and may generate interference on adjacent channels Be sure to use modulators that are designed for adjacent channel operation or else leave dead channels between the ones that are in service In home automation systems it s often practical to assign just one TV channel for messages from your system controller Provide some sort of annunciator to get the user s attention when important messages are generated and leave it at that Why doesn t BOB II start up correctly or What do I need to know about BOB II reset pin management If you have to cycle the power supply multiple times to get BOB II working correctly it may be an indication that supply voltage rise takes too long or isn t sufficiently linear This problem has been reported most often in connection with cheap wall wart power supplies Possible solutions Switch the DC supply line reduce power supply filter capacitance or reduce series resistance The Atmel AVR series CPU in BOB II may also fail to reset properly if its power supply voltage is not allowed to decay all the way to zero before switching on A small dummy load resistor at pin 3 should help if this becomes problematic in your system Important Note In all applications particularly when power supply voltage decays slowly at
14. ranslate mode instead of printing a P Your application program should use the normal ASCII translation mode of BOB II for displaying text Also be aware that the current v1 2 BOB II firmware suppresses automatic video mode switching while a T command is executing The T command was intended to be used with short strings of special characters which would otherwise be unavailable Can I insert BOB II in a cable TV system and display the same text on all channels at once This isn t possible for a number of reasons In a cable system video signals are modulated onto RF carriers at numerous different frequencies that s why the TV tuner is able to pick out just one The signals often originate at widely separated locations with no regard for scan synchronization and individual signal strengths may be poorly controlled BOB II s input and output are both baseband video This means that incoming TV channels must be demodulated from RF to baseband if you wish to place a text overlay on the image To display the output from BOB II on a standard TV receiver you must use an RF modulator to re create a TV broadcast channel which may then be fed into your cable system for distribution to as many TV sets as required Each TV set must be tuned to the modulator s output channel in order to view the text Of course you need a demodulator a BOB II and a modulator for each TV channel requiring a text overlay A side benefit of this arrangement is that y
15. switching to maintain constant video output then your host controller should monitor pin 15 and take appropriate action In general this means refreshing the display if any data was sent during a mode change event Display data already in BOB II RAM will not be corrupted Decade Engineering BOB IIFAQ Page 4 In a few applications automatic video mode switching has been found undesirable because of the stabilization time required by BOB II when re entering Genlock Overlay mode Please contact Decade Engineering for a special firmware version in this case What is the Reset Flag output pin 14 for This pin may be used to inform the host processor that a local CPU reset was forced by watchdog time out In applications where the video display contains fixed label fields along with dynamically updated data fields a spurious reset in BOB II effectively erases the labels The host processor can refresh these fields but only if it s aware that BOB II got into trouble Use an external latch or timer circuit to extend the pulse if your host cannot guarantee polling this pin at 10mS or smaller intervals What colors correspond to the color number fields in the BOB II command protocol Black is color numbers 0 and 7 Blue is 1 and 5 Red is 4 What color is 3 Is it olive Is 6 brown The manufacturer of the character generator chip we use in BOB II is vague about this issue in their product literature The truth is probably that the colors origi

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