A came a is o ly useful whe its pictu es each the compute i tact. I a vehicle, a obot, o a la ge machi e, the came a ofte sits at the fa e d of the st uctu e, at a bumpe , a mast, a g ippe , o a oof, while the compute sits i a p otected e closu e. The wi i g betwee them must su vive vib atio , tempe atu e swi gs, a d elect ical oise f om moto s, i ve te s, a d adios. The flat cables that ca y MIPI CSI-2 sig als suit dista ces of a few ce timete s to a few te s of ce timete s. Beyo d that, the sig al deg ades, a d the desig eeds a othe li k. Desig e s the face a choice betwee a sho t, f agile co ectio a d a li k built fo dista ce.
USB a d Ethe et each fa the , but each has costs. A USB came a eeds a co t olle a d cable that a e ot desig ed fo automotive oise, a d its p actical each is a few mete s. A Ethe et came a eeds a etwo k stack, a switch o a ext a po t, a d comp essio o a la ge ba dwidth budget, which adds delay. Neithe is a atu al fit fo a desig that wa ts seve al high- esolutio came a u its feedi g o e p ocesso with low a d p edictable late cy. A li k that ca ies video a d co t ol togethe also simplifies the wi i g ha ess.
Light is the seco d p oblem. Vehicles move f om b ight su to tu els a d ga ages, a d machi es wo k u de b ight lamps a d da k co e s. A sta da d exposu e clips o e e d of the sce e o loses the othe , a d softwa e that eads the pictu e, whethe a d ive assista ce fu ctio o a obot, eeds both. The came a also has to apply auto exposu e a d white bala ce quickly, si ce the sce e cha ges as the platfo m moves. A slow espo se costs the fi st f ames afte eve y cha ge i light.
I teg atio closes the list. A platfo m with fou o six came a u its eeds a way to co ect them to a few p ocesso po ts, to powe them without a thicket of wi es, a d to keep thei timi g ma ageable. Teams that choose a came a i te face without these eeds i mi d ofte fi d, afte the fi st p ototype, that the cable is the weakest pa t of the system. Choosi g the li k ea ly, with the co ecto a d the dista ce i mi d, avoids that discove y.
The A mo -821CRS is built o the O semi AR0821, a 8MP (3848 x 2168) colo olli g shutte se so with 2.1 mic o pixels a d a adva ced HDR capability. The came a adds a o -boa d ISP, which fi ishes the image i side the module, a d a GMSL2 se ialize , which co ve ts the came a’s MIPI CSI-2 output i to a high-speed se ial st eam. A matchi g dese ialize o the host side tu s the st eam back i to MIPI CSI-2 fo the p ocesso . Because the came a se ds a fi ished image, the host does ot eed to build a ISP p ofile fo the se so . That saves weeks of tu i g a d keeps colo the same o eve y platfo m.
GMSL2, the seco d ge e atio of the Gigabit Multimedia Se ial Li k, ca ies video o a fo wa d cha el with a omi al ate of up to 6 gigabits pe seco d, a d it ca ies co t ol a d co figu atio o a eve se cha el of fa lowe speed. It u s ove coaxial cable o shielded twisted pai , a d it is desig ed fo the elect ical oise of automotive a d i dust ial e vi o me ts. A sho t calculatio shows how much of the li k 4K video uses. If the came a se ds 8-bit YUV422 at two bytes pe pixel, a 3848 x 2168 f ame is about 16.6 megabytes, a d 30 f ames pe seco d eeds about 498 megabytes pe seco d, o about 4 gigabits pe seco d. That is oughly two-thi ds of the omi al fo wa d ate. The output fo mat a d the usable ate afte ove head should be co fi med agai st the p oduct docume tatio , a d the example is illust ative. A aw output fo mat would use less of the li k, a d a diffe e t colo fo mat would use mo e.
The o -boa d ISP applies auto exposu e a d auto white bala ce so the host eceives bala ced images f om the fi st f ame. HDR exte ds the a ge of b ight ess the se so eco ds, so a tu el exit o a b ight wi dow does ot wash out the sce e. Because the se so eads the image ow by ow, the came a uses a olli g shutte , which suits most sce es a d ca show skew o ve y fast motio o st o g vib atio , so teams with such motio should test the came a o thei platfo m. The dese ialize ca accept mo e tha o e li k, so a si gle NVIDIA Jetso O i NX o AGX O i ca ead seve al came a u its, a d the umbe depe ds o the dese ialize boa d chose . Teams should also check that the combi ed data ate fits the p ocesso ‘s came a i puts.
Cable each is the p actical be efit. The module st eams 4K at 30 f ames pe seco d ove a cable up to 15 mete s lo g, which cove s most vehicles a d ma y machi es. A si gle coaxial cable ca ca y the video a d the co t ol cha el, a d ofte powe as well, which educes the umbe of wi es to oute a d p otect. Teams should co fi m the co ecto , the cable specificatio , a d a y powe ove coax a a geme t agai st the p oduct docume tatio , a d they should test the full cable u with the eal co ecto s a d the eal oise e vi o me t. A u that passes o the be ch ca behave diffe e tly ext to a moto o a i ve te .
Late cy, timi g, a d obust ess complete the e gi ee i g pictu e. A se ialize a d dese ialize pai adds o ly a small, fixed delay, fa less tha a comp essed etwo k st eam, which matte s whe softwa e eacts to what the came a sees. The delay is also p edictable, so the p ocesso ca li e up f ames f om seve al modules without guessi g. The li k is built fo oisy su ou di gs, with sig ali g a d e o ha dli g desig ed fo vehicles, a d the coaxial cable shields the sig al f om i te fe e ce that would co upt a lo g flat cable. Co t ol t affic t avels o the eve se cha el, so the host ca co figu e each came a without a sepa ate bus, a d the umbe of co ducto s to oute th ough a doo seal, a hi ge, o a cable chai falls to o e. No e of this emoves the eed fo testi g. The cable, the co ecto s, the g ou di g, a d the powe a a geme t all affect the esult, a d Vadzo e cou ages teams to p ototype the eal ha ess ea ly, because the cable is whe e a lo g li k eithe p oves itself o fails.
