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Topic: Unable to get a 7 segment LED display working with an I2C backpack (Read 2264 times) previous topic - next topic

tckd

Hi there,

I am struggling to get a 7 segment LED display + HT16K33 backpack to work correctly (this one to be exact: https://makersify.com/products/adafruit-0-56-4-digit-7-segment-display-w-i2c-backpack-green).

I've soldered on the backpack, and ensured that the correct pins are connected to the I2C pins (A4 to SDA  and A5 to SCL in my case for my Arduino Uno). VCC is connected to 5V and GND to ground.

I installed the Adafruit LED backpack and GFX libraries and tried running their test sketch (https://github.com/adafruit/Adafruit_LED_Backpack/blob/master/examples/sevenseg/sevenseg.ino) but only 4 segments and one dot (all on the second digit) ever light up. I've also tried my own sketch and I can't get any other segments to light up. I've tried re-soldering and I'm fairly happy that I don't have any bad joints.

Does anyone have any idea what might cause this? I'm not sure if it's a software thing, or whether the display/backpack could be faulty (or I damaged it somehow during soldering). I've also tried with a different Arduino and got the exact same result.

Any advice greatly appreciated!

Grumpy_Mike

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Does anyone have any idea what might cause this?
Yes, you are doing something wrong.

However all you have told us is that you have done everything right so there is not much to go on.
A clear photograph of your wiring and posting the exact code would at least give us something to go on.

tckd

Photos attached of my wiring, and also the resulting segments that light up when running the test sketch here (unmodified):

https://github.com/adafruit/Adafruit_LED_Backpack/blob/master/examples/sevenseg/sevenseg.ino

Grumpy_Mike

Thanks, something to work on.
I notice that you have no pull up resistors on the I2C lines. I would put a 4K7 resistor from A4 to 5V and another between A5 and 5V.

Next try a 0.1uF ceramic capacitor between the 5V and ground, up close to the module.

If that does not fix it then maybe your seven segment module is broken or the wiring is intermittent.

tckd

Thanks for the advice, unfortunately I still get the same result. I've also tried replacing all the wires just in case, but no joy.

Looks like the 7 seg might be faulty then. I'll try another one and if that's fine with the same setup then I'll know for sure!

tckd

OK, not sure why I'm admitting this. But in case this helps future newbies such as myself...
I have just realised that the backpack was soldered on back-to-front.

Grumpy_Mike

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OK, not sure why I'm admitting this.
You nailed it.
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But in case this helps future newbies such as myself
It takes a bit of courage to do that, thanks. Have some karma +1

damain

Don't know if this would help, but, the Arduino UNO R3 comes with pins for SCL & SDA, next to AREF. You do not have to use A4 and A5.

Wawa

Don't know if this would help, but, the Arduino UNO R3 comes with pins for SCL & SDA, next to AREF. You do not have to use A4 and A5.
I think you're trying to say that if you use the ones next to Aref, you still have A4/A5 left for analogue in.
Not true though.
The two sets are connected to the same MCU pins.
Leo..

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