Saturday, October 6, 2012

Raspberry Pi - GPIO buffer and Webserver Questions

Doug emailed me with some questions:

> These days, embedded control generally means a web page for monitoring and controlling the device.

Well, IMHO the rPI makes this VERY easy, see

http://ve3epp.blogspot.ca/2012/08/raspberry-pi-display-time-on-rpi-web.html


> Need a small board that has a header that plugs directly into the rPi header

Check out this:

http://adafruit.com/products/914

This was mentioned in 

http://ve3epp.blogspot.ca/2012/08/raspberry-pi-home-brew-breadboard.html



> ... buffers for the GPIO lines -- not sure how to address direction.

IMHO Easiest to dedicate lines for out and in. Take a look at this:

http://ve3epp.blogspot.ca/2012/08/raspberry-pi-safely-interfacing-to-gpio.html (first part)

http://ve3epp.blogspot.ca/2012/08/raspberry-pi-why-74hc14n.html

I bought 10 74HC14N off eBay from a cdn supplier for $0.50 each. Looks like he still has some:

http://www.ebay.ca/itm/Lot-2-74HC14N-Hex-Inverter-Schmitt-Trigger-Inputs-7414-QTY-2-/110787294662?pt=LH_DefaultDomain_2&hash=item19cb6ff5c6



> I am thinking seriously of included a dedicated Rs232 interface -- I am a
> big fan of using RS232 for automation interfaciing ( it is reasonable
> robust, and you can always go debugging without a lot of special equipment

Yes, I like good old RS232. If you don't need the full +/-12 volt swing, you can just do a 3.3 to 5 v ttl conversion. See above. Also see:

http://ve3epp.blogspot.ca/2012/08/raspberry-pi-more-about-serial-33v-ttl.html


> I am also interested in 1-wire interface.

Have not done much with this yet, but a lot of people have, see here



You may get the idea that reading some of my old blog posts MAY be useful :-)


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