Arduino Uno-I think I hurt something... I2C related
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Arduino Uno-I think I hurt something... I2C related

by 01txdmax on Sun Mar 03, 2013 1:18 pm

I recently picked up an Uno, an I2C 8x8 LED matrix, and the 16x2 LCD shield kit to begin doing things with.

The first time I put the shield on the Uno it worked fine. I was able to upload the "hello world" example and made some little changes to see how similar the program was to my C++ class that I'm taking. No issues.

I then turned my attention to the 8x8 matrix, but was less than successful with it. It would only blink a couple of LEDs regardless of which program I tried to upload to it. I went back to the LCD shield with no issues.

I picked up a power supply that was center pin negative, realized it after I plugged it in, and swapped the polarity on it. I haven't used it since I swapped the leads.

This morning I plugged the Arduino with LCD shield into the computer, and uploaded the hello world program to start playing again. There were no errors in the compiler, nor in the uploading process. The top, left two digits on the LCD were cycling between numbers and question marks. The buttons would change the backlight color, but would not display any words and the reset seemed to do nothing. I realized that when reset was pressed the hello world would flash for just a brief moment, then go back to the numbers and question marks.

Everything seems to be soldered on the shield that should be, and I replaced the standard height headers for extra long ones after initial testing so I could use the other analog or digital pins in the future.

To me it seems as if maybe I got the IC on the shield to hot during the soldering process, and that explains the issue after swapping the headers. It doesn't explain the LED matrix issue though.

Has anyone seen something like this? Any suggested remedies?
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Re: Arduino Uno-I think I hurt something... I2C related

by 01txdmax on Sun Mar 03, 2013 1:48 pm

I'll post the trouble shooting steps that I come across and their results in case they help to isolate what I did wrong, or in the case someone else comes across the same issue! If you didn't know by now, I'm a noob at this... :mrgreen:

I have a Mac, and figured out that I was using the wrong COM port. I picked up a starter book, "Getting Started with Arduino" by Prof. Banzi, and it says I should have been using the /def/cu/.usbmodemfa/141.

With the Uno only, I uploaded the "Blink" example to verify proper communication with the board. works as advertised.

I was concerned that the Uno output voltage was low: the output of the 5V pin was 4.75VDC.
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Re: Arduino Uno-I think I hurt something... I2C related

by adafruit_support_bill on Sun Mar 03, 2013 2:09 pm

I was concerned that the Uno output voltage was low: the output of the 5V pin was 4.75VDC.

How are you powering this? If it is from USB only, you should get a steady 5v from your Mac. If not, check the calibration of your meter. A fresh battery often helps.

If you post photos of the front & back of the shield & the soldering on the matrix, we can check your assembly.
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Re: Arduino Uno-I think I hurt something... I2C related

by 01txdmax on Sun Mar 03, 2013 2:38 pm

I have a new meter, and put my own batteries in it when I got it. It's not an expensive meter, but it was steady when I checked the polarity of my power supply.

I'll check the output of the Mac shortly, I am connected through a USB hub that is not powered. I didn't think about that being an issue, but I'll try that.
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Re: Arduino Uno-I think I hurt something... I2C related

by 01txdmax on Sun Mar 03, 2013 8:10 pm

I checked the voltage of the 5V output pin on the board sans USB hub, and I got 4.98V. Good enough.

I tried to upload the 'Hello World' program again, and go the same results. The backlight colors change as the program dictates, but still not text output. I noticed their was only one line of characters changing, and they changed in much the same way that the clock would count in the original program. Never numbers, but still cycling.

I took pictures of the soldering I did, it's not the best, but with a magnifying glass I can't see where I may have shorted out terminals.

solder.jpg
solder.jpg (390.99 KiB) Viewed 488 times
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Re: Arduino Uno-I think I hurt something... I2C related

by 01txdmax on Sun Mar 03, 2013 8:35 pm

I suspect I found my problem with the 8x8 LED matrix...

I went through the assembly instructions again, and it seems as if I didn't align the text on the board to the side of the PCB with the filled in dot. I'll have to wait to take it to work to use better tools, but I'll swap that around and see if it fixes that problem.
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Re: Arduino Uno-I think I hurt something... I2C related

by adafruit_support_bill on Mon Mar 04, 2013 7:22 am

The orientation of the matrix is critical. That would explain the problems there. On the LCD, it sounds like possibly an intermittent connection. Your photos are too small & dark to really see much detail, but some of the joints on the top near the reset pin look like they might be cold joints. If you could post some larger images that would be good. In the mean-time, take a look at our soldering guide and touch up any joints that are not smooth and shiny or do not flow well onto both the pin and the solder pad.
http://learn.adafruit.com/adafruit-guid ... n-problems
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Re: Arduino Uno-I think I hurt something... I2C related

by 01txdmax on Mon Mar 04, 2013 9:11 pm

The LED Matrix works as advertised not that it's put together properly. Amazing isn't it? It is really….


I took the LCD shield to work, and there were solder that had not flown through the holes to the other side of the board. I reworked all of the headers, and touched up a couple of pins on the IC.

The operational check yields similar results, but now the backlighting changes as advertised in the 'Hello World' program, but the screen still doesn't display characters properly. The 'hello world' is on for a fraction of a second after pushing reset, but then disappears and the intelligible counting of random characters starts again.

I'm going to have a closer look at it under the scope again tomorrow, maybe even remove the shield to board headers in lieu of connecting wires to rule out header solder bridges.
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