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Problems with i2c (and an LCD display)

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By Nicola

July 29, 2008
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So, i just wasted an evening trying to make an LCD with i2c work with my picaxe.

I connected the SCL and SDA of the board to the other end on the LCD. (of course not crossing them :P)  BTW on the picaxe the pins are: Digital input 3 = SCL; Digital input 4 = SDA, am i right ?

If so, other question is: do i need the two pullup resistors ? i've read somewhere that they're already there on the board. But if so, the pin should be high most of the time, shouldn't it ? testing with my voltmeter reads 0V. 

PS i have the picaxe 28x1. 

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By Chris the Carpenter
@ Mon, 2009-06-29 18:29
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Yes, yes, yes you need to add the pull-up resistors, they are not on the LCD modual. Second, as said above, you need the jumper. Third, you must also add/remove the jumper dealing with the voltage level going to the lcd -this one is very important. Also be sure to add some pauses between data sends pause 10 should do it.
By iamdenteddisk
@ Mon, 2009-06-29 17:38
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did you ever get this project to work?, I am interested in the idea is the LCD controled by I2C or does it output I2c? I am using the pcf8574 to expand my bs2 project and would love to add LCD if possible..

 

 

 

By jka
@ Tue, 2008-07-29 23:03
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I haven't done anything with i2c yet, but take a look at http://www.rev-ed.co.uk/docs/axe110_i2c.pdf. It seems like you need the resistors.
By Nicola
@ Wed, 2008-07-30 08:57
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Yes, i've read it.. But i'm using a board AXE033 which connect to the LCD, and should have the resistor. This one:

http://www.rev-ed.co.uk/docs/axe033.pdf

When i start it, the first line gets completely black and the second line stays clear.. no text :(

By robologist
@ Wed, 2008-07-30 17:25
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There are always little things that I've missed with a new device. Have you checked jumper J1 for I2C use? How about the contrast adjustment, turning it a bit with the device powered? Think it said something about displaaying a time message when the 2 CLK contacts are shorted.

Sort of sounds like a contrast adjustment is needed.