0.91" OLED doesn't show in I2C Scan, but green power LED comes on

EL Wire/Tape/Panels, LEDs, pixels and strips, LCDs and TFTs, etc products from Adafruit

Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.
Locked
User avatar
ChrisElectron
 
Posts: 8
Joined: Sun Jun 28, 2020 5:43 pm

0.91" OLED doesn't show in I2C Scan, but green power LED comes on

Post by ChrisElectron »

Issue:
When trying to run the OLED sample code, nothing shows on the display, but the green power LED comes on.

Trying to run the I2C_Scan.ino sketch doesn't find a connected device.

Hardware:
0.91" OLED
ESP32-S2 QTPY
STEMMA Cable

Software:
Arduino IDE v2
Adafruit Testbed library
The problem showed up when trying to run the sample code for the OLED.

Output from I2C_Scan.ino

Code: Select all

Default port (Wire) I2C scan: 
Secondary port (Wire1) I2C scan: 0x3C, 


Default port (Wire) I2C scan: 
Secondary port (Wire1) I2C scan: 0x3C, 
Thanks!
Attachments
Green power LED lights up
Green power LED lights up
IMG_3865 (Medium).jpeg (341.27 KiB) Viewed 72 times
Nothing on display even though sample script is outputting to serial
Nothing on display even though sample script is outputting to serial
IMG_3864 (Medium).jpeg (335.75 KiB) Viewed 72 times

User avatar
dastels
 
Posts: 15659
Joined: Tue Oct 20, 2015 3:22 pm

Re: 0.91" OLED doesn't show in I2C Scan, but green power LED comes on

Post by dastels »

It is showing up as I2C_Scan shows: the display is at 0x3C. It's on the STEMMA-QT I2C port, which is Wire1 not Wire. See https://learn.adafruit.com/adafruit-qt- ... or-3107922.

In the code you will need to pass a pointer to Wire1 to the Adafruit_SSD1306 constructor instead of a pointer to Wire.

Dave

User avatar
ChrisElectron
 
Posts: 8
Joined: Sun Jun 28, 2020 5:43 pm

Re: 0.91" OLED doesn't show in I2C Scan, but green power LED comes on

Post by ChrisElectron »

dastels wrote: Sun Sep 25, 2022 10:11 pm It is showing up as I2C_Scan shows: the display is at 0x3C.
Lesson 1: I need to learn to read what the output actually means. I saw the 0x3C and thought that was the address of Wire1, not a device on Wire1.

dastels wrote: Sun Sep 25, 2022 10:11 pm In the code you will need to pass a pointer to Wire1 to the Adafruit_SSD1306 constructor instead of a pointer to Wire.
Lesson 2: Reading the docs doesn't just mean skimming and looking at the sample code.

I saw the I2C section and the idea that the STEMMA port would be on anything other than the first I2C bus never crossed by mind.

Thanks for the notes! The demo is running nicely. Now to see what I mess I can make of this! :)

User avatar
dastels
 
Posts: 15659
Joined: Tue Oct 20, 2015 3:22 pm

Re: 0.91" OLED doesn't show in I2C Scan, but green power LED comes on

Post by dastels »

Awesome! On some boards with a STEMMA-QT as well as 2C pins on the headers they're differend, but not all of them. It really does pay to read the guides associated with any new boards you get ;)

Dave

Locked
Please be positive and constructive with your questions and comments.

Return to “Glowy things (LCD, LED, TFT, EL) purchased at Adafruit”