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Tiny Code Reader: a $7 QR code sensor

excamera.substack.com

11–20 of 44 posts

Re: Tiny Code Reader: a $7 QR code sensor

#11
positioning limit may be a focus issue.

typically on these cameras the lens is mounted and focused by a screw thread. there is not usually an 'infinity stop' because the mount is very simple, so i would expect the lens may be mechanically positioned outside the useful focus range. a 110 degree FoV is a very wide lens, so the useful screw range may be quite mechanically narrow, but when positioned properly it will have a very deep in-focus field, capturing near objects and far objects clearly.

the datasheet doesn't say much about focus, but it looks like the rim of the lens is knurled for grip, so try rotating the lens. 'screw out' will bring focus nearer, 'screw in' will push focus farther. i would suggest indexing your start position with a paint pen for easy return, and then index the correct position if you find it.

if all else fails, you could place a small aperture in front of the lens. this will reduce light transmission but also improve the focus field, like squinting your eyes.

Re: Tiny Code Reader: a $7 QR code sensor

#12
post #6

My experience with small QR code readers like this on ESP32 boards is that without a viewfinder, they lose a lot of utility. The feedback loop that a viewfinder gives with positioning and knowing when the QR code is detected is invaluable.

All of the cheap camera based two-dimensional barcode modules that I see on AliExpress tend to ship with a white LED as well as a red LED. The white LED is for general flood illumination and the red LED has some sort of pattern and lens array that keeps it centered in the cameras field of view and appears sharp and focused when the barcode is at the optimal distance.

Camera detects motion, turns white LED and red LED on. Paper or screen with the QR code is now illuminated and humans can move up and down until the red Target appears in the center and in focus. Approximately a quarter of a second after that happens, you hear the beep noise indicating a successful read and decode

Re: Tiny Code Reader: a $7 QR code sensor

#15
Somewhat incidentally, is there an actual description of how a low-tech QR code reader would work? I’ve looked for this a few years ago and all solutions I could find were of two flavours: (1) use ZXing (“Zebra Crossing”, a now-unmaintained library[1] for every 1D and 2D barcode under the sun); (2) use OpenCV. Nowhere could I find any discussion of how one would actually deal with the image-processing part by hand. And yet QR codes are 1994 tech, so they should hardly require fancy computer-vision stuff to process.

[1] https://github.com/zxing/zxing

Re: Tiny Code Reader: a $7 QR code sensor

#17

Somewhat incidentally, is there an actual description of how a low-tech QR code reader would work? I’ve looked for this a few years ago and all solutions I could find were of two flavours: (1) use ZXing (“Zebra Crossing”, a now-unmaintained library[1] for every 1D and 2D barcode under the sun); (2) use OpenCV. Nowhere could I find any discussion of how one would actually deal with the image-processing part by hand. A…

You could have a look at the ISO spec on QR Codes to get the authoritative source on what kind of processing required.

Alternatively (and what I would recommend), is grab a library that is dedicated to QR Code reading (I‘ve used Quirc, for example) and just read the code.

Typically you threshold an image to get a binary representation (1: black, 0: white). Then you detect the finder patterns by looking for 1-1-3-1-1 runs of black/white. Once you have a bunch of finder patterns localized, you form triplets and decode the binary matrix that they span.

Re: Tiny Code Reader: a $7 QR code sensor

#18

Somewhat incidentally, is there an actual description of how a low-tech QR code reader would work? I’ve looked for this a few years ago and all solutions I could find were of two flavours: (1) use ZXing (“Zebra Crossing”, a now-unmaintained library[1] for every 1D and 2D barcode under the sun); (2) use OpenCV. Nowhere could I find any discussion of how one would actually deal with the image-processing part by hand. A…

I think many places roll their own. QR codes have a finder pattern of alternating black and white with relative spacing of 1-1-3-1-1 for any line that goes through the center of it. This has a low false positive rate so this step is the most important for performance. Since orientation doesn’t change the pattern horizontal scans are sufficient, once the center, scale, and rotation has been found the rest is fairly straight forward. There isn’t really a good reason why this set up couldn’t be rotation invariant, the processing power required is pretty low.

Re: Tiny Code Reader: a $7 QR code sensor

#19

Can also do this with an esp-32 camera module which are cheap and all-in-one https://github.com/alvarowolfx/ESP32QRCodeReader

I even found them on Amazon with Prime shipping for ~$8/each. Curious how challenging parsing a QR code would be with that?

Re: Tiny Code Reader: a $7 QR code sensor

#20

Can also do this with an esp-32 camera module which are cheap and all-in-one https://github.com/alvarowolfx/ESP32QRCodeReader

Just checked and the cost for a (non aliexpress) seller ESP32-CAM dev board is around £5-£6 or less than £1 from aliexpress

Aliexpress listings can have multiple different items, and the price displayed in the search results will be that of the first of those (in your case, probably just an antenna) rather than the actual item you searched for or even the item image shown on the results page.
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