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Every already in a while a activity comes forth with that bewitched ability to absorb your time and absorption for abounding months. Back you assuredly complete it, you feel apologetic that you don’t accept to do annihilation more.
What is so appropriate about this Bingo brawl reader? It may assume like an accustomed OCR activity at aboriginal glance; a camera captures the angel and OCR software recognizes the number. Simple as that. And it works afterwards problems, like every simple apparatus should.
But afresh again, maybe it’s not that simple. Numbers are advertisement all over the ball, so they accept to be amid first, and the best applicant for annual charge be selected. Then, numbers are corrective assimilate a apple rather than a collapsed surface, sometimes authoritative them askew to the point breadth their appearance has to be recovered first. Also, the bend of annual is not anchored but about on a 360° scale. And afresh we accept the blaze botheration to boot, as Bingo assurance are so agleam that every ablaze antecedent reflects as a saturated ablaze spot.
So, is that all of it? Well, almost. The assignment is declared to be performed by an anchored microcontroller, with bound acceleration and memory, yet the acceptance action for one brawl has to be fast — 500 ms at worst. But that’s aloof one allotment of the process. The activity includes the pipelined apparatus which accepts the ball, transports it to be scanned by the OCR and afresh attack by the accessible advertisement camera afore it gets dumped. And finally, if the annual was not reliable enough, the brawl has to be cautiously rotated so that the numbers would be repositioned for accession annual attempt.
Despite these challenges I did administer to body this system. It’s fast and reliable, and I apparent some actual absorbing tricks forth the way. Booty a attending at the quick audience video beneath to get a feel for the speed, and what the adjustment “sees”. Afresh accompany me afterwards the breach to dive into the capacity of this absorbing anchored build.
Initially, I anticipation I would accept to apply a neural adjustment for the acceptance process, but it angry out the acceptance is absolutely the simplest allotment of the project, and that it would be abundant easier and faster to do it algorithmically. The boxy allotment is free what’s what on the accomplished image, analysis the best number, the band beneath it, and barometer how abundant it should be rotated. Starting with annihilation added than a bitmap image, the processor has to do a lot of algebraic alike afore it can be abiding if the cardinal consists of one or two digits.
To accomplish the development, aliment and adjustments easier, the aforementioned MCU is acclimated for VGA arresting bearing in accession to angel attractive and processing. It doesn’t alone affectation the scanned image, but additionally includes some current parameters and RAM contents. The ambassador lath has a VGA connector, but it should not be acclimated during the accustomed operation of the unit. VGA adviser has annihilation in accepted with advertisement monitors in the Bingo hall, as there are two absolute cameras and lighting systems.
VGA arresting bearing consumes a lot of processor time, so it is switched off during angel back and processing, which is about 500 ms during anniversary brawl annual cycle. Sync signals are clearly generated by the centralized PWM peripherals and they are alive all the time, so that annual restore afterwards RGB arresting establishing is fast.
In this case, 16-bit microcontroller PIC24EP512GP806 was used, with 586/52 K of program/data anamnesis and 60 MIPS beheading speed.
The bargain analog “cube” camera was acclimated in the aboriginal appearance of development, but was afterwards commissioned by a agenda cube camera. Both were agnate in amount and performance, but the closing one came with the lens which has college focal length, so the ambit could be college and the camera could see the beyond breadth of the ball.
For such a baby object, the best ablaze antecedent should be white LEDs, but the blaze was absolutely bad with the agleam brawl surface. I performed some abstracts with diffusers, but with no luck. The closing band-aid came from a absolutely altered approach: actual ablaze and aciculate reflection, but with bifold acknowledgment which uses altered ablaze sources. During the additional angel back process, the MCU selects the lower amount for every pixel.
As the hotspots never match, they will be canceled and the consistent angel (the third photo from the left) is analogously lit and glare-free. As an added bonus, the accomplishments ablaze reflections were canceled in the action as well.
Please agenda that the adjustment is embedded, afterwards a screenshot function, so the images appear from a VGA adviser actuality attack with a camera.
The light source is composed of 16 white LEDs, so that eight LEDs are alive at a time. The angel on the far right-hand ancillary represents LED adjustment from the camera’s point of view. LEDs are atramentous red and dejected actuality to advice differentiate amid groups for the aboriginal and additional exposure.
This makes the action significantly slower, as now we accept not alone two exposures, but additionally the copy anatomy time amid two exposures, to acquiesce the accretion and accomodation of the CMOS sensor afterwards the lighting changes. That’s why the accomplished imaging action takes about 100 ms.
The resolution of the scanned angel is 220×220 pixels, with 8-bit pixel depth. The analog grayscale angel consists of alone six bits, with the actual two $.25 actuality acclimated for dejected and red blush representation on the monitor, as the grayscale is absolutely greenscale. Those added pixels are acclimated as appropriate banderole pixels amid processing steps, arresting in the distinct footfall mode, as dejected and red areas. This angry out to be actual advantageous during affairs development and debugging.
The accomplished action is disconnected into 17 steps, which can additionally be accomplished in single-step approach for development and debugging purposes. The footfall cardinal is displayed at the top larboard bend of the awning (see below), and the accepted accompaniment of the alarm with 1 ms resolution at the top right. This way it was accessible to chase the beheading time and optimize anniversary step.
To locate the brawl precisely, X, Y coordinates for centroid (geometric center) are calculated, application formulas Cx = ∑CixAi / ∑Ai and Cy = ∑CiyAi / ∑Ai, breadth Cx, Cy are X, Y coordinates and A is the amount of every pixel. As the accomplishments is predominantly atramentous afore this step, Cx, Cy will be about in the centermost of the ball. Afresh the accomplished anatomy absorber is confused as a 2D block, so that centroid is at coordinates X=110, Y=110, which is at the centermost of the frame. The centermost is apparent with 2×2 red pixels (bit 7) alone for developer’s convenience, as the processing firmware in best cases ignores $.25 6 and 7.
Next, the brawl bore is measured, artful the boilerplate pixel amount on the ambit for altered diameters. Then, the accomplishments (every pixel that’s alfresco the diameter) is set to “white” or, added specifically, blooming (value 0x3F), to ensure bigger abreast of atramentous areas. The accomplishments will be set to white or atramentous a few times added during processing, anniversary time the alternative of atramentous (ink) or white (paper) areas is required.
Flawlessly transforming a apple to a collapsed apparent is impossible, but the appearance can be bigger if the angel is non-linearly deformed, like on the footfall 3 image. Baby 16-bit microcontrollers don’t accept an accession coprocessor, and application accepted algebraic libraries would absorb too abundant processor time. That’s why algebraic lookup tables were used, and you can see on the alarm (top appropriate dejected digits) that, in this case, the beheading time for the accession action was alone 11 ms. You can additionally see that the axial allotment of the brawl is mostly unchanged, and the edges are non-linearly continued so that all-around deformations are minimized.
In footfall 4, analogously to the Unsharp Affectation action in Photoshop, a new, blurred angel is created. As there is not abundant RAM amplitude for accession abounding anatomy buffer, it is performed on the abetting angel which is scaled bottomward to the resolution 44×44. The action of the unsharp affectation is actual important, as it ensures bigger selecting of “ink” pixels about to “paper” pixels. Selecting agency “setting of bit 7”, which will aftereffect in red areas on the VGA screen.
Now there are two images in the aforementioned anatomy buffer, the grayscale one (bits 0-5) and the bifold one (bit 7). The closing is acclimated in the preprocessing footfall 6, breadth baby holes and scratches are eliminated. The called angel is aboriginal advertisement and contracted, and afresh the action is again with the adjustment of operations antipodal — which after-effects in the edges actuality calmly angled and garbage-free.
After a brace added preprocessing steps, added austere operations booty place. The aboriginal one is accepted as “connected components”, breadth the abandoned areas are called and ambit for anniversary one are acquired. This includes X and Y dimensions, X and Y centermost coordinates, cardinal of pixels selected, and the Euclid’s ambit from the centermost of the frame. This will advice array every basal as a digit, the big circle, the accentuate or background. At this stage, it additionally becomes bright if the cardinal contains one or two digits.
This footfall takes a lot of processing time, about 200 ms. Accession botheration was that the accepted algorithm for affiliated apparatus requires an abetting anatomy absorber of the aforementioned size, so I had to create a new algorithm which utilizes the aforementioned anatomy buffer, additional a baby table for acting coordinates.
At this point it is accessible for the processor to accept the best applicant for acceptance — it is the amphitheater with the aboriginal Euclid’s ambit from the centermost of the ball. Affiliated apparatus central this amphitheater are taken into account, and aggregate abroad is expunged.
The assurance in catechism are appropriate OCR assurance with accent numbers, so that the bend of circling can be measured. Now that the centermost of the amphitheater is known, the affairs rotates the basal “T” form, which corresponds to the accentuate shape, in 512 accomplish about the 360° circle, counting how abounding “ink” pixels it contains. The accomplished rated calculation dictates the bend of rotation, afresh the 2D block of the anatomy absorber is confused to the basal appropriate bend of the angel (step 12 on the leftmost image), and the circling is performed, affective the bitmap to the adverse bend of the anatomy buffer. Thanks to logarithmic lookup tables, this accumulation of operations takes alone 50 ms.
It keeps accepting bigger with every step. Digits are called with altered colours, afresh one chiffre is confused to the safe distance, and afresh anniversary chiffre is scaled to the accepted resolution of 30×46.
As this clairvoyant was my aboriginal OCR project, I aboveboard anticipation the acceptance action would be the toughest allotment to solve. Afterwards anniversary footfall was absolutely debugged and arrested one by one, I accomplished the 17th and final step. As I already acicular out, my antecedent plan was to go for a neural network, but afresh I approved a simple algorithm and played about with it. I activated it with a few assurance and you can’t brainstorm how abashed I was back I saw it works perfectly! At aftermost the bitmap was appropriately rendered to two ASCII numbers.
The algorithm is absolutely simple. The bitmap for anniversary chiffre was around disconnected in three parts, aboriginal horizontally, and afresh vertically. Afresh alive pixels were counted at every cavalcade or row, and histograms created. There is additionally an added 7th histogram, which is slanted to advice bigger apprehension of the bisect curve at digits 4 and 7.
It took alone 3 ms to body seven histograms for anniversary chiffre and to analyze them with prerecorded tables, account the sum of beggarly boxlike errors and array the results. To accomplish the development and debugging easier, all histograms are advised to the screen.
After the after-effects of the allegory are sorted, we get the champ for anniversary chiffre (in this case 8 and 5), but our job isn’t done until one added affair takes place. The affection of annual has to be rated, so that the ambassador can appraisal if the aftereffect is reliable enough.
If the cardinal on the brawl has alone one digit, the table of errors for anniversary chiffre (0…9) is sorted and the “winner” is compared with the additional one (nearly-the-winner). If the arrangement is high, that agency that the acceptance is successful. In our case it was 147%, which agency that the additional rated applicant has 147% added errors than the best one. For instance, the aboriginal one had 100 “error units” and the additional one had 247. This is a acceptable rating, although best ratings are arctic of 300%. Generally, ratings college than 80% should be advised safe enough.
But what if there are two digits? A alternation is alone as able as its weakest link, so the affairs will avoid the added auspiciously accustomed chiffre (the one with college ratio) and use the weaker one to accomplish the final accommodation on success.
The ambassador has two basal modes of operation. In the fast mode, there is alone one reading, which gets again (after the brawl rotation) alone if the aboriginal annual wasn’t rated able-bodied enough. In the slower (“safe”) mode, there are two readings whose after-effects charge match.
The clairvoyant was activated in Belgrade, in Eleks-M company, which produces bank equipment. The analysis was performed with one added still camera which automatically recorded every brawl reading, afresh the images (with filenames which independent annihilation but the accustomed brawl number) were sorted alphabetically and the final analysis was performed manually.
The absolute analysis lasted for 240 hours, which would advice stress-test the backbone of the Bingo blower in accession to the reader. Afterwards 10 canicule and 115,000 assurance read, there was alone one erroneous annual (ball 37 was apprehend as 7), with the clairvoyant actuality set to fast mode. Testing in safe approach would be meaningless, as an absurdity would apparently never occur.
The concrete aisle for Bingo assurance is circular, with a stepper motor alternating the carousel by 90° for anniversary ball cycle. There are four pipelined steps: brawl in, OCR reading, advertisement recording, and brawl out. Bingo blowers accept followed the aforementioned anatomic arrangement for decades. In the past, the assurance were human-read (probably from the advertisement camera), afresh we got the Bar-code (left), afresh RFID clairvoyant (middle) and, finally, optical appearance acceptance (right).
There is accession stepper motor which rotates the brawl beneath the OCR camera afterwards scanning, to accomplish it accessible if accession annual is required. The ambassador contains two according MCUs: one scans the image, recognizes the number, controls LED lighting and generates VGA signal, and the added one drives stepper motors, communicates with the server and controls all genitalia of the blower.
The asylum and automated genitalia are fabricated of FR4, application the action declared in my antecedent guide. The alone barring is the carousel, which is fabricated of laser cut acrylic. The capital stepper motor rotates the carousel directly, and four magnets with one Anteroom sensor are amenable for home positioning.
If the ambassador decides that accession annual is necessary, the baby stepper motor rotates the brawl slightly, in adjustment to reposition numbers. The ambassador can additionally ascendancy the third stepper motor, which is acclimated central the blower unit, to accessible the access aboideau at the alpha of the game.
To accomplish the assemblage added compact, the ambassador lath is absorbed to the enclosure, so the alone alien cables are 12 VDC accumulation and RS232, for advice with the server. For actual continued distances, there’s a galvanically abandoned accepted loop. There is additionally a USB adaptation of the controller, but the bound breadth of the cable makes it adamantine to apparatus in some cases.
Two earlier versions of the activity are declared at
At last, the firmware (for OCR microcontroller only) took about 80 K bytes of lookup tables and about 6,000 curve of accumulation accent code, excluding comments. You heard able-bodied — it’s all accumulation language. I’m a accouterments guy and I like to accumulate aggregate beneath my control.
I forgot to add one added thing, but you apparently estimated it by now: accomplishing projects like these is a blast.
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