1.2" 4-Digit 7-Segment Display w/I2C Backpack
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1.2" 4-Digit 7-Segment Display w/I2C Backpack

by scotts on Mon Mar 18, 2013 8:35 pm

Hi,

After following the RPi tutorial for this device, I only get the following error:

Error accessing 0x70: Check your I2C address

I have a rev 2 Raspberry Pi with an up-to-date Wheezy distro and get the following output:

$ sudo i2cdetect -y 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: 70 -- -- -- -- -- -- --

$ uname -a
Linux pi2 3.6.11+ #371 PREEMPT Thu Feb 7 16:31:35 GMT 2013 armv6l GNU/Linux

Forcing it to use bus 1 (or 0) makes no difference.

My soldering looks good to this amateur eye and I can read 3.28v from the + SDA & SCL on the backpack.

Where to go from here?

Thanks,
Scott
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Re: 1.2" 4-Digit 7-Segment Display w/I2C Backpack

by scotts on Mon Mar 18, 2013 8:55 pm

Image:

Image
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Re: 1.2" 4-Digit 7-Segment Display w/I2C Backpack

by redwire on Mon Mar 18, 2013 11:54 pm

What's the fifth pin (V_IC) for? A schematic for this product would help :(
The (LED chip) HT16K33 is a 5V part and the Raspberry Pi is 3.3V logic, so I'd suggest using a level-translator on the I2C bus. The Adafruit tutorial mentions the display will run dimly on 3.3V but I'm skeptical.
http://www.adafruit.com/datasheets/ht16K33v110.pdf
http://learn.adafruit.com/downloads/pdf/matrix-7-segment-led-backpack-with-the-raspberry-pi.pdf
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Re: 1.2" 4-Digit 7-Segment Display w/I2C Backpack

by adafruit_support_bill on Tue Mar 19, 2013 6:03 am

The 5th pin is for the I/O voltage level. Connect to 5v for 5v communication. 3.3v for 3.3v communication. A separate level shifter is not required.
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Re: 1.2" 4-Digit 7-Segment Display w/I2C Backpack

by scotts on Tue Mar 19, 2013 7:03 am

As for my problem, how can I troubleshoot what is going on? Is the display/backpack dead?
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Re: 1.2" 4-Digit 7-Segment Display w/I2C Backpack

by adafruit_support_bill on Tue Mar 19, 2013 7:07 am

You need the fifth pin connected. Connect the V_IO line to 3.3v.
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Re: 1.2" 4-Digit 7-Segment Display w/I2C Backpack

by scotts on Tue Mar 19, 2013 7:18 am

So both the V_IO and the "+" pin should connect to 3.3v?

That still doesn't work.
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Re: 1.2" 4-Digit 7-Segment Display w/I2C Backpack

by adafruit_support_bill on Tue Mar 19, 2013 7:50 am

Still getting the same error "Error accessing 0x70: Check your I2C address" ?
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Re: 1.2" 4-Digit 7-Segment Display w/I2C Backpack

by scotts on Tue Mar 19, 2013 8:01 am

Yes, same error message.

For what it's worth, even without the V_IC pin connected to 3.3v, my multimeter shows that the V_IC pin is getting 3.3v anyway. And there is no visible short anywhere...
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Re: 1.2" 4-Digit 7-Segment Display w/I2C Backpack

by adafruit_support_bill on Tue Mar 19, 2013 8:50 am

the V_IC pin is getting 3.3v anyway.

That makes sense since the Pi has its own pullups on the I2C lines.

It seems to be communicating well enough to respond to the i2cdetect. The only other thing I can think of would be a software problem. These drivers were all developed and tested with Raspbian. Do you have a Raspbian image to try it with?
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Re: 1.2" 4-Digit 7-Segment Display w/I2C Backpack

by scotts on Tue Mar 19, 2013 3:03 pm

I've been using Raspbian Wheezy. Is there another version of Raspbian you want me to try? If so, do you have a URL, as the Raspbian page just points back to raspberrypi.org/downloads and only offers Wheezy.

Thanks
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Re: 1.2" 4-Digit 7-Segment Display w/I2C Backpack

by adafruit_support_bill on Tue Mar 19, 2013 3:08 pm

Sorry, I meant to say Occidentalis. Occidentalis is derived from Raspbian, but has added kernel support.
http://learn.adafruit.com/adafruit-rasp ... s-v0-dot-2
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Re: 1.2" 4-Digit 7-Segment Display w/I2C Backpack

by scotts on Tue Mar 19, 2013 6:27 pm

While I was waiting for the Occidentalis download to finish, I reinstalled Wheezy and followed the tutorial and this time I got the colons to appear with no error messages. I swapped the 3.3v source for the 5v and the rest of it appeared. Not sure what was wrong with the state of my Pi before, but now it works. That fifth connection to V_IC doesn't appear to be necessary.

I will mention one fix to the code -- the setColon() method in Adafruit_7Segment.py turns both colons and the decimal point on (on this 1.2" display), however, writeDigitRaw(2, 0x2) turns on just the middle colon.

Thanks for the help.
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Re: 1.2" 4-Digit 7-Segment Display w/I2C Backpack

by adafruit_support_bill on Tue Mar 19, 2013 7:04 pm

Glad you got it working. And thanks for the feedback. :)
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