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CMUcam

CMUcam. Tom Kneeland. CMUcam – What is it?. Digital Camera with an onboard microcontroller Track a blob based on programmable color thresholds Calculate centroid Calculate mean color and variance RS-232 or TTL ~17fps. Components – CMOS Camera. Omnivision OV6620 Color Camera

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CMUcam

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  1. CMUcam Tom Kneeland

  2. CMUcam – What is it? • Digital Camera with an onboard microcontroller • Track a blob based on programmable color thresholds • Calculate centroid • Calculate mean color and variance • RS-232 or TTL • ~17fps

  3. Components – CMOS Camera • Omnivision OV6620 Color Camera • 17 MHz clock • 8 bit RGB or YCrCb* • 8 or 16 bit bus • Max Resolution: 356 x 292 • 60 fps

  4. Components - Microcontroller • Ubicom SX28 • RISC Architecture • 28 pin DIP • 75 MIPS @ 75 MHz • 2048 words of ROM • 136 bytes of SRAM

  5. How Does It Work – Firmware • Written in C • 2035 of the 2048 words of ROM • 135 of the 136 bytes of SRAM • Color Blob Tracking • Frame Dump • Line Mode • Color Statistics • Two serial IO protocols

  6. How Does It Work - Configuration • Camera Resolution: 176 x 144 • 8-bit bus • RAM Allocation • 80 bytes for a pixel buffer (one row) • 56 bytes for processing • Effective Resolution: 80 x 144

  7. How Does It Work – Pixel Format • 8 bit RGB or YCrCb • 4:2:2 RGBG • 8-bits per component • Macropixel = 2 image pixels • Red and Blue are shared • 16 bpp

  8. How It Works – Pixel Format • 16 bpp x 80 pixels = 160 bytes! • Convert to a 2:1:1 format • Skip every other pixel • Share Red and Blue Values • Sacrifices resolution and color accuracy

  9. Color Blob Tracking • Compare each pixel to min and max values • Determine if they fall within bounding box • Confidence Measure: • #pixels/box_area * 256 • Centroid • Sum x,y of matched pixels • Divide by num detected pixels

  10. Frame Dump and Line Mode • Frame Dump • Limited by serial I/O • One or Two Columns at a time • Line Mode • Line by Line binary image of detected pixels • Available during blob tracking

  11. ASCII Protocol • cr – program camera registers • sw – set window (bounding box) coords • gm – get mean value • S Rmean Gmean Bmean Rdeviation Gdeviation Bdeviation • tc – track color function • M xcen ycen x1 y1 x2 y2 #pixels confidence

  12. ASCII Protocol Example CMUcam v1.2 :cr 18 44 17 2 19 32 ACK :sw 30 60 50 80 ACK :pm 1 ACK :gm ACK S 150 20 30 5 2 6 :pm 0 ACK :sw 0 0 80 143 ACK :tc 145 18 24 155 22 36 ACK M 50 80 38 82 53 128 35 98 M 52 81 38 82 53 128 35 98 M 51 80 38 84 53 128 35 98

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