» Iosoft Ltd
- ChipVid Video
- Software Updates
- Embedded Web
» Embedded TCP/IP
- License FAQ
- 802.11 kit
- Wireless FAQ
- Frame Grabber
» Real-time data
- Air Quality
- First Edition
- Second Edition
- Application notes
» Online Sales
The Iosoft ChipVid project is a demonstration of high-speed low-cost networking; video images are captured using a 'frame grabber' added to the Microchip PICDEM.net board, as shown above. The raw image data is transmitted in UDP format over Ethernet at approx. 2 images/sec, the net data throughput being approx. 2 Mbit/s.
The frame grabber is compatible with both European (625-line) and US (525-line) composite video signals, and produces good-quality monochrome images from low-cost monochrome or colour cameras.
The UDP network data is received and displayed by a Windows utility written in Visual C v6. The above picture is an unretouched screen-grab from that Windows utility, and shows the frame grabber capturing a picture of itself.
The frame grabber hardware was designed by Iosoft Ltd. The PCB artwork was produced by Microchip Technology Inc., and has been released for general non-profit use.
Important note. It is feasible for an experienced hobbyist or student constructor to undertake this project, though it does demand a significant level of electronics knowledge, skill and equipment. Although the design has been kept as simple as possible, it does include a mix of high-speed analog and digital circuitry, and both through-hole and surface-mount components. A faulty ChipVid board could damage the PICDEM.net board as well, so take great care when constructing and testing the board. Always use a current-limited supply, and remove power immediately if there is any sign of overcurrent.
Iosoft offers this design 'as-is', with no warranties of any kind, and regrettably can not provide assistance in the event of problems.Click here for a PDF of the circuit diagram.
Click here for a PDF of the PCB.
Click here for a zipfile with the PCB artwork (Gerber files) and parts list (CSV file).
ChipVid assemblyAssemble all the components on the PCB; U4, U5 and Y1 may be socketed. Omit C10 if using 625-composite (PAL) video. JP1 enables 75-ohm termination of the video input, and should normally be made. U2 and U6 may be HC or HCT devices. All the PCB interconnect sockets (to the PICDEM.net board) are mounted on the underside of the PCB.
ChipVid testingBefore attaching the ChipVid board to the PICDEM.net, apply a 9 volt DC supply to it and check that the idle current is about 90 mA. Connect a video source to the board (ideally a video pattern generator with a grayscale or colour bar output) and check with an oscilloscope
PICDEM.net modificationsFour 0.1"" pitch sockets are mounted on the underside of the ChipVid frame grabber board, so 0.1" pins (Berg pins or equivalent) have to be soldered to the PICDEM.net PCB at the corresponding locations.
With the ChipVid board fitted to the PICDEM.net, the total current consumption should be approx. 150 mA.
If the same supply is used to power the video source and the PICDEM.net assembly, then there is the possibility that the return current for the PICDEM.net will flow through the video cable screen, rather than the negative supply connection. This is due to the bridge rectifier on the PICDEM.net, which effectively introduces a single diode drop between the supply -ve terminal and the PICDEM.net ground. To cure this problem, the PICDEM.net bridge rectifier should be replaced with a single series diode in the +ve supply connection.
Modifying the designIf you are considering any changes to the circuit diagram or PCB layout, please bear in mind the following points:
The PICmicro software is described in chapter 14 of TCP/IP Lean 2nd edition, which also includes the source code on CD-ROM (see file P16CAP.C)
There is a Win32 network client which receives and displays the images, and a Linux network client which creates an uncompressed GIF file. Click here for a zipfile containing the source code. The client software may only be used in non-commercial applications, and the Iosoft copyright notices must be retained. Contact Iosoft for commercial licensing information.
© Iosoft Ltd. 2002 All rights reserved.
|© Iosoft Ltd 2005|