Rick's b.log - entry 2024/08/08

Netum NT-2012 laser barcode reader

The barcode reader aimed at the screen.

While the name might give the impression that it's a 2012 model, you can see in through the red window that the circuit board says NT-BLM-A1 and 2021.03.04.

Using this barcode scanner is an exercise in simplicity. When you plug it in, it pretends to be a human interface device (HID) which is a nerdy way of saying "keyboards and stuff". What you scan is decoded and entered at the current caret position as if typed out by hand.

Here, let me scan a tin of Fray Bentos "Just Chicken": 5012427049703

By default the "Enter" key is given at the end of the code. You can define a number of things, like what characters you want before or after the code, and what sort of termination (if any) you would like. So I could have "#5012427049703#<LF>" if I wanted. I can also clip numbers from the front and/or end of the code if I want. Additionally, I can set it up to scan continuously, or to scan only when triggered, to bleep (or not) upon decoding a barcode, and what sort of keyboard layout it should use for (it defaults to US, UK and France (etc) are options).
There is a mode where it can be configured as a sort of serial port so information can be read from the device without interfering with the keyboard, but in this case it would require some sort of driver.
Finally, there is a code that reports the firmware version number. Mine says "bn0_NT_LASERD43hc_CC07". Neither Google nor Bing have any information on this.

The barcode reader scanning a tin of Fray Bentos.

There are various sorts of barcodes that the device is capable of reading. I don't have a big selection of barcodes here, but it was happy with the three on the Amazon envelope, various EAN13 codes on things, plus the interleaved 2 of 5 on a Tassimo disc. It wasn't able to read the other barcode on the Tassimo disc because while it is known to be UPC-E, it is a broken UPC-E (missing the start and end markers). It can also read the little secondary barcode next to EAN13 (these tend to turn up on books). By default it ignores them, but it can be turned on and off at will.
More specifically, the sales blurb says: Code11, Code39, Code93, Code32, Code128, Codabar, UPC-A, UPC-E, ISBN, EAN-8, EAN-13, JAN, EAN/UPC Add-on 2/5, MSI/Plessey, Telepen, China Postal Code, Interleaved 2 of 5, Industrial 2 of 5, and Matrix 2 of 5.
It cannot, however, read 2D barcodes (like QR or whatever). That would require a much more sophisticated device. Still, for less than €10/£10 it's pretty impressive.

Inside is a powerful laser and a mirror that wobbles side to side to make the laser dot 'sweep'. What is illuminated by this gets reflected back and is picked up by some sort of optical sensor that translates the code (along with the mirror position) into a series of pulses to represent the barcode that is being 'seen', which then gets decoded (if recognised) into a set of alphanumerics.

The scanning in slow motion.
(this doesn't animate in mobile view)

Now, of course, for the part you've been waiting for. ☺

The laser path.

The metal can to the lower left is the laser. It is bloody bright, there should probably be some sort of warning label, given that CD players (that don't normally engage the laser until the lid/door is closed) have to have warnings but this thing that can be aimed at people's eyes don't have one? Doesn't make sense...
Anyway, the laser shoots up from that can towards that odd little mirror just above it, and then bounces leftwards to the wobbling mirror. As you can see, there is no actual mechanical connection to the wobbling mirror. How it works is similar to the heads in a harddisc, there is a magnet embedded at the back of the mirror using (in clear plastic) and this is next to a big coil. The coil creates a magnetic field that may attract/repel the magnet in the mirror unit, thus altering its position. Change the magnetic field in the coil rapidly, the mirror unit can be made to wobble, to scan the laser beam from left to right and back again.

Here's another view.

The laser path from a different angle.

The laser, mostly hidden, fires towards the little mirror (the sort of orangey-yellow thing) which bounces the laser beam to the wobbling mirror. The only new thing visible here is the green square inside a red square that is the thing between the laser and the wobbling mirror. This is some sort of sensor, probably a very very low resolution CCD imager (might even be a single pixel?).
If you do a quick calculation in your head, you might realise that the fixed mirror (the orangey-yellow one) is actually pointing at the sensor. This is correct. There's a tiny mirror embedded in the mirror at a different angle for bouncing the laser. Otherwise, what comes back is sent to the sensor.

The flip side of the board is where the brains are.

The brains of the barcode reader.

The metal covered thing on the right is the circuitry that deals with the laser/mirror/sensor. It's probably shielded to prevent interference.
To the left of that, an LM324 (quad op-amp).
To the upper left of the op-amp, the button that is pressed when the trigger button is squeezed.

Which leaves, finally, the big chip at a 45 degree angle. This is a Nation N32G435 which is a little system-on-chip comprising of an ARM Cortex-M4F running at up to 108MHz. It has an FP unit, DSP instructions, 128K Flash, 32K SRAM, and the usual DACs, ADCs, USB, UART, SPI, RTC, timers, etc etc.

Your comments:

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A tree-dwelling mammal, 8th August 2024, 20:44

So did it still work after you'd put it back together?

Rick, 8th August 2024, 21:20

Of course it did...

David Pilling, 9th August 2024, 12:37

Very interesting tear-down. One thought about the laser power is that it is moving so spread out. The scanners in shops look bright but hard to get your eye in direct line with the laser.  Vague idea they are now selling laser power meters so you can check what it says on the tin.  Then one moves to are the laser safety glasses they sell on AliEtc, the real thing.  Feel I should be inspired to think of something it could be used for (other than bar codes). Are there cheap QR code readers - and what would they have inside.

Zerosquare, 9th August 2024, 16:03

There are cheap 2D barcode readers, yeah. But there's nothing really peculiar about the insides. It's just a camera, LEDs for illumination and a CPU running a barcode detecting/decoding algorithm.

SteveP, 9th August 2024, 21:59

"Of course it did..."    It's a natural talent. Like, I took my bedroom clock apart when I was 7, and it worked when I put it back together.      When I was thirteen. :) I was busy on other stuff, OK?

Clive Semmens, 27th August 2024, 19:10

I took a light switch apart when I was about eight. Since the light went out when I did it, I couldn't put it back together again until after the sun came up the next morning. Putting it back together, I was VERY careful - not wishing to repeat the shocking experionce of the previous evening.

Clive Semmens, 29th August 2024, 14:53

Does this wrok? Why did I think I couldn't do this? https://clive.semmens.org.uk/Recounts/ThreeLessons.html [linkified for you - Rick]

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