Barcode scanner unable to read specific barcode from phone screen - Page 1
Forum section: electronics / projects

author: miketan3904
author_rank: Contributor
timestamp: December 28, 2020, 12:21:24 pm
content: Hi guys. I am using the AS-8120 barcode scanner from Argox. The barcode scanner is able to read barcode from my mobile phone screen when I use it to read barcode that I randomly downloaded from Google. Then, I have tried to generate some code 39 barcode using barcode font in Microsoft Word. The barcode scanner is able to read the barcode that I generated when I printed it on paper, but it is unable to read it from my phone screen. It seems like the barcode scanner only unable to read the barcode scanner that I generated. As the barcode scanner is able to read the barcode that I generated from paper, this should indicate that the barcode that I generated is a valid barcode and is readable. Does anyone know the reason why the barcode scanner unable to read the barcode that I generated from my phone screen?Thanks

author: ledtester
author_rank: Super Contributor
timestamp: December 29, 2020, 09:55:07 am
content: This article might explain your problem:https://www.asp.com.au/can-barcode-scanner-read-barcode-off-lcd-screen/or this one:https://www.quora.com/Can-barcode-scanners-read-barcodes-displayed-on-an-iPhone-or-other-smartphones-Why-or-why-not?share=1

author: tooki
author_rank: Super Contributor
timestamp: December 29, 2020, 02:50:07 pm
content: Quote from: ledtester on December 29, 2020, 09:55:07 amI don't think you read the original post carefully enough. It's not about scanning off a screen in general. It's about why some barcodes will, and some won't, scan off thesamescreen with thesamescanner.

author: m k
author_rank: Super Contributor
timestamp: December 29, 2020, 05:55:19 pm
content: Quote from: miketan3904 on December 28, 2020, 12:21:24 pmDo you mean that it can't scan the picture of your printed stuff?

author: tooki
author_rank: Super Contributor
timestamp: December 29, 2020, 06:22:14 pm
content: Quote from: m k on December 29, 2020, 05:55:19 pmHow could that even distantly be a possible interpretation of "the barcode scanner is able to read the barcode … when … printed … on paper"?!?What the OP is saying is this:Randomly downloaded barcode on screen: scansCustom-generated Code 39 barcode on screen: doesn't scanCustom-generated Code 39 barcode on paper: scans

author: Domagoj T
author_rank: Frequent Contributor
timestamp: December 29, 2020, 06:29:03 pm
content: Are you trying to put too much data into the barcode to the point where the display is reaching the limits of resolution?I had similar issues with printing on thermal paper. Inkjet printer would be print readable code, but the reader would struggle with ones printed on thermal paper. I narrowed it down to fuzziness of lines and general clarity of print.Try generating code with less data (thicker lines and wider spaces).

author: m k
author_rank: Super Contributor
timestamp: December 30, 2020, 01:27:23 pm
content: Quote from: tooki on December 29, 2020, 06:22:14 pmOn paper is clear but from Microsoft Word to phone screen is not.On paper and in cloud are not the same.

author: Jeroen3
author_rank: Super Contributor
timestamp: December 30, 2020, 01:36:19 pm
content: What happens when you make the background on your barcode red?If you must scan from screens, get this one:http://www.argox.com/product/as-9300/Those use white illuminators and don't filter only for red.

author: tooki
author_rank: Super Contributor
timestamp: December 30, 2020, 04:19:46 pm
content: Quote from: m k on December 30, 2020, 01:27:23 pmWhat the heck are you talking about?!?Nobody said anything about the cloud, but that’s irrelevant anyway.Again, what the OP is saying is this:Randomly downloaded barcode on screen: scansCustom-generated Code 39 barcode on screen: doesn't scanCustom-generated Code 39 barcode on paper: scansWhat part of that is not crystal clear to you?!?

author: jmelson
author_rank: Super Contributor
timestamp: December 30, 2020, 04:59:05 pm
content: Quote from: tooki on December 30, 2020, 04:19:46 pmOK, knowing nothing about any of this, the thing that comes to mind is that the downloaded bar code may have some html that forces the phone to display it at a resolution where the code pixels map onto screen pixels with some integral ratio. The custom-generated code doesn't do this, and so the phone displays it at a convenient resolution where the code pixels are arbitrarily mapped to the screen, leading to distortion.Jon

author: wizard69
author_rank: Super Contributor
timestamp: December 30, 2020, 05:09:48 pm
content: there are many potential issues here, some already covered by other posts. One thing I haven't seen mentioned is the need for quiet areas on both ends of the barcode. Since you have no pictures I can only suggest this as a possibility.Quote from: miketan3904 on December 28, 2020, 12:21:24 pm

author: m k
author_rank: Super Contributor
timestamp: December 30, 2020, 08:32:12 pm
content: Quote from: tooki on December 30, 2020, 04:19:46 pmHow it came there, on screen.

author: jiarui
author_rank: Contributor
timestamp: March 17, 2023, 01:46:29 pm
content: For Code39, you need to put "*" at the beginning and the end to make it a valid barcode. If you are using apps that generate the barcode, the app knows to wrap the text with the "*". If you are using the barcode font, you have to put the "*" at the front and the end yourself.

author: Haenk
author_rank: Super Contributor
timestamp: March 17, 2023, 03:50:24 pm
content: Please note the pretty precise sizing of the bars and spaces (and/or the ratio) which might be on the edge of "good enough on paper" and "not good enough on screen".

author: MathWizard
author_rank: Super Contributor
timestamp: March 17, 2023, 04:29:35 pm
content: I've seen people ,ake images with sensor in an optical mouse. Some day I'd like to try doing something with one, like read a barcode, to track speed or position.