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From:	karl AT aspodata DOT se
To:	geda-user AT delorie DOT com
Subject:	Re: [geda-user] Education board
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Comments:	In-reply-to "John Griessen (john AT ecosensory DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
	message dated "Sat, 12 Aug 2017 12:48:14 -0500."
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Date:	Sat, 12 Aug 2017 20:53:08 +0200 (CEST)
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John Griessen:
> On 08/12/2017 12:16 PM, karl AT aspodata DOT se wrote:
> > pt100-inputs
> 
> by this do you mean a Pt thermocouple?

No, platinum 100 Ohm temperature sensor, but a thermocouple input
would nice to have also.

> >   chip reader (as in credit card with chip)?
> How about RFID cards -- they can be bought for about 0.50 USD each in qty 50.
> the programming chips are not bad either... but the antenna loops take up as much board space as
> a credit card...

For rfid I usually have a module on a separate card with a rs232
(ttl-levels) connection, I thought of it as too specific and complex
for this.

I don't think the antenna is a problem, just let it loop around the
whole pcb or just enlarge the pcb a few cm's, for an education card
one don't need high signal levels, it would suffice if you must have
the tag closer than 5mm from the pcb. I have an antenna design and some
docs in http://aspodata.se/git/openhw/rfid/. According to 
http://ww1.microchip.com/downloads/en/AppNotes/00710c.pdf p.5, eq 12,
the optimum radius of antenna is r = sqrt(2) * s (antenna to tag 
distance). If s = 5mm, the optimum radius would be about 7mm, which
isn't difficult to fit on a board, especially since there is no size
constraint.

Since this probably is "research use" I don't think one need a
"Declaration of Conformity" for it so one could have it on board.
Do you have a simple solution for rfid or suggestion of ic's ?

///

Speaking about rf functionality, would bluetooth be diffucult to
program on a bare metal board ?

Regards,
/Karl Hammar

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