Feather M0 Wifi and LED Display

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EBCrp
 
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Feather M0 Wifi and LED Display

Post by EBCrp »

I am using the Feather M0 Wifi and trying to attach (via breadboard) the LED Display (Adafruit 1.2" 4-Digit 7-Segment Display w/I2C Backpack - Red, Product ID: 1270). I am using the sevenseg example program to troubleshoot and I am getting no display (it displayed once and that was it). I have tried it using the standard Metro using 5V and then 3.3V and it worked fine. I am attaching "+" to USB and "IO" to 3V on the M0. I am also attaching a picture of the simple circuit. Thoughts?
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circuit file
circuit file
IMG_0875.jpg (175.71 KiB) Viewed 79 times

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bidrohini
 
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Re: Feather M0 Wifi and LED Display

Post by bidrohini »

I recommend that you check your 7-segment display first separately. With a direct power supply to all the respective pins.

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EBCrp
 
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Re: Feather M0 Wifi and LED Display

Post by EBCrp »

It is working fine with the Metro board so I am confident there is no issue with the LED. I have also set up the circuit so that I can take out the M0 and put in the Metro without moving any of the wires on the circuit. I also tried moving the M0 to another place on the breadboard just in case that was the problem. I also tried connecting the wires directly to the pins on the M0 as a doublecheck...nothing.

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adafruit_support_carter
 
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Re: Feather M0 Wifi and LED Display

Post by adafruit_support_carter »

You can remove the pull up resistors on SCL and SDA. Those are included on the LED board. Try removing those and just wire SCL/SDA directly to the Feather. Then see if the board shows up in an I2C scan:
https://learn.adafruit.com/scanning-i2c ... es/arduino

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EBCrp
 
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Re: Feather M0 Wifi and LED Display

Post by EBCrp »

I removed the pull up resistors as you suggested and ran the program you attached. "no I2C device found". The red power light is on.

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adafruit_support_carter
 
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Re: Feather M0 Wifi and LED Display

Post by adafruit_support_carter »

Bummer. It may be a marginal issue when the power and logic levels are split between 5V and 3.3V. It may require level shifting. See here for a similar case:
viewtopic.php?p=862908#p862908

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EBCrp
 
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Re: Feather M0 Wifi and LED Display

Post by EBCrp »

I will read through this but this is not making too much sense to me - this came right out of the Exploring Arduino book by Jeremy Blum and everything else worked fine, and he uses your products throughout the entire book. Are you sure this is not a product issue?

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adafruit_support_carter
 
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Re: Feather M0 Wifi and LED Display

Post by adafruit_support_carter »

The issue is the HT16K33 (the chip that drives the LEDs) is 5V. Using it with 3.3V boards can be marginal when it's powered at 5V. To get around that, a level shifter is used. Something like this:
https://www.adafruit.com/product/1875

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EBCrp
 
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Re: Feather M0 Wifi and LED Display

Post by EBCrp »

Thank you.

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