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I'm trying to use a SainSmart 20x4 LCD connected via I2C.

  1. I can manually drive pins 0 & 1 to high and low so I know they work.
  2. I've commented the blacklist I2C-bcm2708 and blacklist SPI-bcm2708 entries from raspi-blacklist.conf
  3. I've added i2c-dev in /etc/modules underneath snd-bcm2835
  4. I've installed i2c-tools
  5. Running ls -la /dev/i2c-0 returns crw-rw---T 1 root i2c 89, 0 Jun 15 10:21 /dev/i2c-0

Yet i2cdetect -y 0 returns nothing:

    0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

Any idea about what's wrong or what I could test?

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  • 1
    Left field suggestion...I need to run "sudo modprobe i2c-dev" before my LCD shows in i2cdetect. Not really sure why or what it does, might be helpful to you? – KHibma Jun 20 '13 at 2:13
  • I would agree with the previous answer, but since it didn't work, my suggestion is one of those, "Im sure you tried it, but" have you rebooted since you changed your config files, and have you verified the changes were saved? – Butters Aug 15 '13 at 3:47
  • Have you been able to get your display running? – Norbert Dec 29 '13 at 17:39
  • Hi Norbert, Yes I have. Turns out it has to be powered with +3.3V. Direct +5V doesn't get recognised by the Pi, even if I use a Logic Level Converter (I tried this one between others: tandyonline.co.uk/…) – lolouk44 Dec 30 '13 at 23:03
  • @lolouk44 If your problem has been solved, please mark the answer that solved it as such. We're trying to get the site's Q:A ratio up. Thanks! – RPiAwesomeness Jan 11 '14 at 23:12
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Turns out it has to be powered with +3.3V. Direct +5V doesn't get recognised by the Pi, even if I use a Logic Level Converter (I tried this one between others)

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Depending on your Raspberry Pi model and revision, you will need to use the 'other' I2C channel. Try:

i2cdetect -y 1
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  • Hi Recantha, I have the same results on i2cdetect -y 1 :( Any other idea? – lolouk44 Jun 15 '13 at 16:01
  • Hmmm. That is weird. What pins have you got connected to what? Pin by pin – recantha Jun 15 '13 at 19:54
  • Hi @recantha. same wiring as link. Wires go straight to the same named pins on the LCD screen. I also tested the wiring to ensure continuity. – lolouk44 Jun 16 '13 at 15:45
  • Sounds like you might have a faulty board... I've just ordered one of these and should have it this week. Will try to remember to post my results here! – recantha Jun 25 '13 at 5:45
  • Hi @recantha. I though the LCD might be faulty too so I had it exchanged. Same issue with the new one. I'm a bit lost now :( – lolouk44 Jun 26 '13 at 9:01

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