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Author Topic: Unused I/O pins when LCD shield is used  (Read 1190 times)
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Hi,

I guess not all I/O ports are used with an LCD shield in place, but all of them are covered. Are the unused pins the open spots on the LCD shield on (for example) the top right, see picture?

cheers,

Arthur



* Picture 2.jpg (16.21 KB, 320x240 - viewed 47 times.)
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Yep.  Since it is a human interface of sorts, should it have exposed pins?  This type of shield is usually the last device placed on an Arduino "stack".
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Ah, that makes sense indeed! In my case I am trying as my first Arduino project to interface with a DCF77 atomic clock receiver for which I only need a single I/O pin. I could do without an intermediate shield in my case, only one wire in the way then...
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You might have to break out that soldering iron and tack in a lead.  If you can get the schematics or look really carefully, you should be able to determine the unused pins.  From here it looks like pins D0-D7 look free.
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If it was not the last shield in the stack you would not be able to see the LCD!
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If it was not the last shield in the stack you would not be able to see the LCD!

right, it does not make sense to be able to stack another shield on top, but that does not mean you should not be able to use the unused pins anymore. I believe the lcd shield has through holes to solder a female header so you can use jumper wires to use the pins not used by the lcd shield.
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Be careful with that receiver as it operates at 77? KHz (in the US it is 60 KHZ, WWVB) and it is an AM receiver and although the antenna is more magnetic that electrostatic ( A Ferrite loop antenna) the receiver is still subject to radiated noise from the Arduino's clock. I personally would shield everything but the antenna in a metal container and make certain that my power supply to the receiver was very clean. I live in Southern California and it is about 1000 miles to the antenna for the DCS 60 service here because of that there is almost no reliable coverage here during the daytime just at dawn and dusk. For 10 12 dollars more you can buy a GPS receiver and it is much easier to interface than the DCF77 service is. They aren't the best indoors but both of mine work well enough to receive the time data. I might not always (30% of the time) get position data that is accurate but the time always works as you only need one or two sat's for time data to be valid. you are fairly close to the DCS77 service and it should be no problem, If you do have issues make sure that you have the bigger of the two antenna's that CMS sells for that receiver as it is more sensitive and use a small co-axial cable to connect the antenna (RG-174) so you can "remote" the antenna by a meter or so to remove it from the immediate radiated noise from the Arduino.

Doc
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Thanks for the WWVB information.  I was wondering why there were not very many projects for WWVB RTCs.
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My preferred method is to use a set of screw terminal boards like this http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&pa=2144534&productId=2144534&keyCode=WSF&CID=GMC&gclid=CPek5IDNsbICFahAMgodwmYAOw between the screen and main board. 
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Pretty sharp sandwich!  Better than mine with a nipped header pin and insert some 22AWG.
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Soldered headers on the LCD shield and connected my DCF77 receiver successfully to show the time, see picture.



* Picture 3.jpg (37.58 KB, 320x240 - viewed 48 times.)
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