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Let's say I have a smart pen. It has a microcontroller that can communicate with my server. I want to have a really small and flat gadget (let's call it The Receiver) that when you touch it with that pen, you save a 16 character string on it. The pen also has a GET mode in when I touch The Receiver, it sends the string stored on that Receiver to the server.
My question is, what is the best way to make that Receiver and the tip of the pen? Bluetooth isn't preferred, because there will be multiple Receivers in a small area. My thinking was also some sort of a scanner at the tip of the pen, but I don't want the receivers to be ugly looking with some codes printed on them (that is still a possibility). I think the best solution would just be some sort of identification for each receiver so that the pen can identify it just by touching it.

Davide Andrea
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Marin Dedic
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  • BT is the preferred interface https://www.wired.com/gallery/best-smart-pens/ – Tony Stewart EE75 Jan 12 '22 at 00:56
  • The pen isn’t writing anything. I just called it that because it resembles that shape. The tip doesn’t write, it’s purpose is to connect and identify the receiver. – Marin Dedic Jan 12 '22 at 01:01
  • Doesn't sound like a "smart" pen. Define potential interfaces of all devices – Tony Stewart EE75 Jan 12 '22 at 06:36
  • Define all interface specs. Are you just wanting to copycat a solution or understand why and how to make it work – Tony Stewart EE75 Jan 12 '22 at 06:57
  • I just want a solution for the tip of the pen and the Receiver. The pen has a microcontroller, microphone and speaker if that means anything to you. – Marin Dedic Jan 12 '22 at 08:40
  • Anything 2.4GHz will have problems with multiple radio sources in the same band, but the band is huge and they use methods to avoid collisions. You can have multiple phones, mics and so in a limited area. The key is to reduce the output power so that each device has a limited range and therefore also a limited area where it causes interference with other devices. – Lundin Jan 12 '22 at 10:53
  • Anyway this is much too broad and the "best" criteria is fuzzy, so you end up asking for opinions. – Lundin Jan 12 '22 at 10:54
  • Yeah, I am asking for opinions basically. – Marin Dedic Jan 12 '22 at 11:29
  • Without any pen specs and interface options, you are expecting a mind-reader – Tony Stewart EE75 Jan 12 '22 at 13:25

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RFID does something like what you want, but building a receiver into a little pen shaped object may be difficult. The reader might have to be larger than a pen.

https://www.sparkfun.com/products/11827

bob_monsen
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You're talking about "Optical ID"

This is like a 2D bar code.

You print a microscopic pattern with black (carbon based) ink. The rest of your picture is done in colors that don't contain carbon (i.e. "black" is just really really dark brown)

Requires some high end printing to keep the dots to an invisible size.

The pen tip has a lens and a CMOS imager.

This is used in many learning toys, especially in Japan

https://github-wiki-see.page/m/entropia/tip-toi-reveng/wiki/PEN-Optical-ID-and-codes

Kyle B
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