I2C Problem with RPi 16x2 LCD + Keypad

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sprombo
 
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Joined: Mon Feb 24, 2014 2:27 am

I2C Problem with RPi 16x2 LCD + Keypad

Post by sprombo »

Hey guys, I'm pretty new to this whole hacking scene, so I've got a [hopefully] basic question. I put my RPi 16x2 LCD + Keypadhttp://www.adafruit.com/products/1110 kit together, followed all the steps http://learn.adafruit.com/adafruit-16x2 ... y-pi/usage, and got nothing on the display. I checked all the solders for shorts, and a few of them displayed inter-connectedness, but I'm assuming that's normal as they're connected by the board. I started backtracking and tried the I2C Detect command, and got this:

>>pi@raspberrypi ~/Adafruit-Raspberry-Pi-Python-Code/Adafruit_CharLCDPlate $ sudo i2cdetect -y 1

0 1 2 3 4 5 6 7 8 9 a b c d e f
00: 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
10: 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
20: 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f
30: 30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f
40: 40 41 42 43 44 45 46 47 48 49 4a 4b 4c 4d 4e 4f
50: 50 51 52 53 54 55 56 57 58 59 5a 5b 5c 5d 5e 5f
60: 60 61 62 63 64 65 66 67 68 69 6a 6b 6c 6d 6e 6f
70: 70 71 72 73 74 75 76 77

Now on the tutorial it says you're just supposed to get one response, in 0x20, but I got a response from literally every position. Is this the problem, or is there something else I'm probably doing wrong? I followed all the other directions, and investigated more deeply, but this is the only thing that struck me as odd.

Thanks,
sprombo

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adafruit_support_bill
 
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Re: I2C Problem with RPi 16x2 LCD + Keypad

Post by adafruit_support_bill »

That does look pretty strange. If you disconnect the LCD/Keypad, do you still get the same response from i2cdetect?

If you post photos of the front and back of your board, we'll check it over too.

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adafruit_support_mike
 
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Re: I2C Problem with RPi 16x2 LCD + Keypad

Post by adafruit_support_mike »

FWIW, you'd get those results from an SDA line that's shorted LOW.

An I2C bus master detects other devices by sending a control byte that contains the device address during the first 8 ticks of SCK, then looking for an ACK. Slave devices generate an ACK by pulling SDA LOW on SCK's 9th tick.

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