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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, 2013 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, 2013 at 3:47
  • Have you been able to get your display running?
    – Norbert
    Dec 29, 2013 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, 2013 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, 2014 at 23:12

2 Answers 2

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2

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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7
  • Hi Recantha, I have the same results on i2cdetect -y 1 :( Any other idea?
    – lolouk44
    Jun 15, 2013 at 16:01
  • Hmmm. That is weird. What pins have you got connected to what? Pin by pin
    – recantha
    Jun 15, 2013 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, 2013 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, 2013 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, 2013 at 9:01

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