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Author Topic: [SOLVED] LCD Shield + USB Host Shield not working - Voltage too low?  (Read 981 times)
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Hello everybody,

I just started playing around with my brand new Arduino but now I encountered one problem I am not sure how to solve it the best way.

For my project I want to use an USB connection, a LCD and some buttons. My board is a SainSmart Arduine Mega 2560, for Buttons and LCD i use SainSmart LCDKeyPad Shield and for the USB Connection an USB Host Shield from tinyosshop.com.

When i attach only one of the shields everything works fine, but when both are stacked (LCD Shield on USB Shiel on Arduino) the display light goes on, but it doesnt  show anything at all.

I think the voltage may drop too low? Does anybody know this problem and maybe some solution?

PS: sorry if this is the from category, wasnt sure which one to use and search currently doesnt work for me.
« Last Edit: August 01, 2012, 04:36:01 am by installboy » Logged

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I think the voltage may drop too low? Does anybody know this problem and maybe some solution?
Another possibility is a conflict between the pins that each shield uses.  You will have to check the documentation for each shield and see which Arduino pins it uses.  If both shields require the use of the same Arduino pin then this is probably the source of your problem.  If you provide links to the documentation then you might even get some help with this task!

Don
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Thank you for your answer! I thought it should work together because the USB Shield has all needed connectors on top, too. Maybe I was wrong.

It would be really nice if you would help me out with checking the documentation, here are the links:
LCD KeyPad Shield: http://www.thesunrain.com/Amazon/LCDKeypad%20Shield/LCD1602.rar
USB Host Shield: http://www.circuitsathome.com/products-page/arduino-shields/usb-host-shield-2-0-for-arduino

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From LCD Readme.txt:
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Pin Allocation
Pin            Function
Analog 0    Button (select, up, right, down and left)
Digital 4    DB4
Digital 5    DB5
Digital 6    DB6
Digital 7    DB7
Digital 8    RS (Data or Signal Display Selection)
Digital 9    Enable
Digital 10    Backlit Control


From USB Host Shield hardware manual (http://www.circuitsathome.com/usb-host-shield-hardware-manual):
Quote
Digital I/O pins 8-13. In this group, the shield in its default configuration uses pins 9 and 10 for INT and SS interface signals.

So they both use pins 9 and 10.
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Ah okay. So it should work if i connect these two pins to other pins for one device and change the pin assignments in the library, right?
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Ah okay. So it should work if i connect these two pins to other pins for one device and change the pin assignments in the library, right?
Yes, in theory.  But this is not a trivial task since it generally involves modifying the traces on a PC board.

Don
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Well,I tried it anyway and it worked smiley I cut two traces with a cutter knife and connected the lanes to two unused pins. After changing the pins in the library everything works fine! Thank you guys very much!
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I'm looking at doing the same thing, (exactly the same brand components) interfacing the USB host to a radio and using the buttons to send AT commands via the USB host port.

Did you change the LCD or the USB Host. I think it will be easier to changing the LCD hardware rather than the USB.

Any chance of supplying your libary and source code. Only new too Arduino and find I learn if I have something to work from rather from scratch. (Slowly making my way through books, webpages and simple projects)

Cheers.
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