[Index] [Project Info] [Overview] [Tracking Algorithm] ([Hardware]) [Acknowledgements] [Download]
[Hardware]
The Eagle in a Rack is actually composed of two hardware versions - both are very close to each other electrically. The following
section will highlight these two designs.
Rack Hardware
Hardware Overview
Main Board
Video Digitizer
Input/Output Board and On-Screen Display Generator
Video Signal Stabilizer
Eagle in a Board Hardware
[Rack Hardware]
This front panel was machined by Front Panel Express to my specifications.
[Hardware Overview]
The system is in a 3U size rack enclosure currently. It uses a D2E Board from Digilent Inc, a CSA/UL approved switch-mode power supply, and two custom boards. All the components are shown below:
The main parts are the D2E Development board with XC2S200E FPGA from Xilinx, the analog video digitizer board, the switch-mode power supply, the video overlay generator and amplifier, and the video stabilizer.
The D2E Development board (will be referred to from now on as the main board, since it has the FPGA on it) holds the most important part of the project, the Field Programmable Gate Array (FPGA) itself. Its function is to provide a stable regulated power supply for the FPGA of 2.5 volts for the core logic in the FPGA and 3.3 volts for the input/output (I/O) pins.
The analog video digitizer board is based on the TVP5145 from Texas Instruments, and can accept any sort of analog video (component, composite, S-Video) in any format (NTSC, PAL). In this project it is configured to use the National Television Standards committee (NTSC) video signal, which is the type used in Canada (and all of North America).
The video overlay generator's job is to generate white pixels on the screen at specific places. This is used to provide feedback to the user in an easy-to-use way. As well, the video signal is amplified to help give the signal more strength.
The video stabilizer is only used when needed. Some video signals will be corrupted, as extra pulses are inserted in the vertical blanking interval. This corrupted video signal may be actually a patented and purposely generated signal, and may be called the MacrovisionŽ system. The video signal stabilizer will remove these extra pulses, which would normally trigger a protection circuit in the video digitizer, thus allowing the device to continue to operate normally.
Finally the switch-mode power supply provides power to the boards, as well as providing power to three power connectors mounted on the front panel.
[Main Board]
At the beginning of this project, the idea of using a pure analog solution was tested. Although it seemed possible, it was clear that the complexity would be far too great with no clear advantage over a digital solution. It was decided though that the system would run in true real-time, using the idea of running almost at the same speed as the input signal.
Next it was decided to use programmable logic, specifically a FPGA. Eventually a low-cost development board was found; the D2E from Digilent Inc is shown below with some slight modifications performed.
It contains a XC2S200E FPGA from Xilinx Inc. This includes two linear voltage regulators mounted on the board, which take the 5 volt input and convert it to 2.5 volts (for the FPGA's core logic) and 3.3 volts (for the input/output connections). There are four distinct 40-pin female connectors (six total, but two of them are repeats), two of which are used in this project.
Physically the board is a four-layer Printed Circuit Board (PCB) with two full power planes.
The FPGA only has RAM-based configuration storage, which means that after the configuration data is loaded onto it a power-down will result in loss of configuration data. The board does have an 8-pin socket for a configuration Programmable Read Only Memory (PROM), but these memories are only programmable once. Since this is a development project a reprogrammable memory was needed. An XCF04S chip from Xilinx was used. This chip can configure a FPGA using the same lines as the configuration Programmable Read Only Memory (PROM), which means that little modifications would need to be done to the circuit board. As well it can be programmed via JTAG, which is the same method used to program the FPGA and the board already had a JTAG interface on it. By adding the device into the JTAG chain it could be easily programmed. A SchmartBoard was used to do all this, a SchmartBoard being a Surface Mount Device (SMD) development platform. The 8-pin socket was removed, and the SchmartBoard was soldered in its place. As well four additional lines were taken from the JTAG programmer and added onto the SchmartBoard as shown below.
[Video Digitizer]
Digitizing the video signal is one of the most important parts of the project, and also went through a number of revisions. Originally it was considered to only use the luminance information from the video signal. This would only allow the tracker to tell how bright or dim an area of the picture was though, which makes the tracking algorithm almost entirely reliant on some sort of shape detection.
It was then decided that at least some sort of colour (chroma) information was needed. Several quick circuits were tested that attempted to separate the chroma information from the luminance information on the video signal. On the video signal the luminance information and chroma information can be roughly separated using two filters - the luminance information extracted from a low-pass filter, the chroma from a high-pass filter. This does not provide very good results though, and would still require more post-processing!
A number of chips designed to separate chroma from luminance information were researched. However, almost every chip researched was obsolete as most were used in older TVs that there was no longer a demand for. At that point this would not even be digitizing the video signal, so a considerable amount more circuitry would be needed!
Finally a chip was found that did it all - the TVP5145 from Texas Instruments. Not only did it perform the chroma and luminance separation, but it even digitized the signal. Most importantly though - the chip was available. There were a number of other chips found that were either vapourware (don't exist in real life), obsolete, or only available in quantities of thousands - however the TVP5145 was available in quantities of one from Digikey at a reasonable cost.
In the video digitizer board the main chip (the TVP5145) is in a Thin Quad Flat Pack (TQFP) with 80 pins, so it was necessary to make a circuit board for it since prototyping would be difficult. As well the chip has fairly high requirements for frequencies (internal clocks running at least 30 MHz) which makes careful layout of the circuit board a must.
This board gives a number of output signals to the FPGA. These signals are the pixel clock (one clock pulse for every pixel), the vertical synchronization pulse (for every new frame), the horizontal synchronization pulse (for every new line), the chroma (or colour) information, and the luminance information.
An overview of the PCB is shown above - the bottom layer is blue, the top layer is red, and the silkscreen layer is white. The analog portion of the circuit includes a ground plane to help reduce noise. This revision of the circuit board includes three errors. The first being that the connector needs the power lines moved to the other side of the connector (ie: pin 39 and 40 instead of pin 1 and 2), the second being that the ground and 3.3 volt rail are shorted together, and the final error is that there is no pull-up resistors on the I2C lines. All these errors were easily fixed with an Xacto knife, some solder, and wire.
The final board is shown below.
[Input/Output Board and On-Screen Display Generator]
There is one general purpose board that has a number of functions, including the connector for the PS/2 mouse, the connections to the LEDs on the front panel, and the on-screen display generator.
The original plan was to use a touch-screen that is put over the output LCD. By doing this the interface would be a touch based interface, which would be the easiest and most practical to use. However touch-screens were found to be prohibitively expensive, so this option was turned down. Instead a mouse was used - and eventually the mouse could be replaced with a touch-screen.
The on-screen display generator uses a 4066 CMOS analog switch to generate white pixels. Normally the switch will select the video in as the video output. Whenever a white pixel must be generated, the switch selects a voltage divider that is set to a white-level. Then after the location of the white pixel is passed, it is switched back to the video in source.
A video amplifier is added before the signal is passed to the video out connector, since otherwise the system's performance will be affected by what sort of device is connected to the video out jack. The amplifier helps to buffer the video out jack, and the amplifier chip is shown mounted below.
[Video Signal Stabilizer]
The video signal stabilizer is a simple commercial device intended to clean up a video signal if it has been degraded. When the front-panel switch selects the device, the video input signal is first routed through it. Otherwise the video bypasses this device and goes directly to the video digitizer. It can be seen the unit is simply bolted to the chassis below.
[Power Supply]
The power supply is a commercial UL approved device. It was deemed far too dangerous and complex to design a specialized power supply, especially when a good power supply can be bought for $15 (surplus) from Sayal Electronics (located in Burlington, Ontario).
This power supply is specifically a SRW-45-4001 from Integrated Power Designs. This is a switchmode power supply that can deliver 45 watts of output power in four voltages, +5 volts, -5 volts, +12 volts, and -12 volts. It will automatically shut down at 110% overload, and cycle power until the fault is removed. It is mounted in a translucent plastic case from Hammond Mfg.
The UL file number is E137708, and is recognized in Canada as well (CAN/CSA-C22.2 No. 950-M95).
[Eagle in a Board Hardware]
The idea of the Eagle in a Board is to put all the power of the Eagle in a Rack in a 10cm by 10cm circuit board. Originally I
claimed that I could reduce the Eagle in a Rack to a 10cm board that could be powered by batteries fairly easily. This
board is proof that this is possible.
However the board is not yet finished - in fact at the time of writing this the blank Printed Circuit Board (PCB) has
been shipped out via FedEx and should arrive on the 10th of May.
See the download page on this site for more information on this board, including a complete
schematic and gerber files.
The following images show what the Gerber files look like. This board was design with AutoTRAX EDA, and is a four-layer PCB with
the two inner layers being ground planes. The software I used at this time (Release 2.24) still has a number of problems
that make it different to generate a 4-layer PCB. So the gerber files will have a few errors in them, or routing that appears
to be sub-optimal. In fact as far as I know this will be the first
four-layer PCB created using this software (based on mailing list discussion).
Overview of all layers superimposed:
Top Layer:
Inner 1 Layer (Connected to VCC_O):
Inner 2 Layer (Connceted to GND):
Bottom Layer:
[Index] [Project Info] [Overview] [Tracking Algorithm] ([Hardware]) [Acknowledgements] [Download]