Comments on: ESP32 Built-in OLED Board (Wemos Lolin32): Pinout, Libraries and OLED Control

By: Sara Santos

Sara Santos — Mon, 10 Mar 2025 05:49:38 +0000

Hi.
It may be useful to take a look at this tutorial: https://randomnerdtutorials.com/esp32-spi-communication-arduino/
Regards,
Sara

By: Konstantin

Konstantin — Thu, 06 Mar 2025 19:00:26 +0000

Hello Sara,
as I understand, your board, unlike normal ESP32, does not use VSPI bus (pins 5,18,19,23).
Can you provide any instructions about how to activate and use HSPI bus?
Can you confirm your board uses standard HSPI pins GPIO12,13,14,15?

By: Bruno Morra

Bruno Morra — Sat, 23 Sep 2023 14:46:29 +0000

Hi Sara,
just to let you know that, thanks to your tutorial on uPy I was able to use this undocumented board as a datalogger of data from a BME280and with an OLED 1306ssd. I found on a forum discussion in French a hint on the SPI pins that have to be used
sck=machine.Pin(25),
mosi=machine.Pin(14),
miso=machine.Pin(13))
whilecs is Pin 15.
Hope this could save time to other people
Best

By: Bruno

Bruno — Mon, 18 Sep 2023 13:31:06 +0000

Hia Sara,
please could you give me the help I need ? Thanks for your patience
Best
Bruno

By: Bruno

Bruno — Wed, 06 Sep 2023 19:31:47 +0000

Hi Sara,
sorry for bothering you again for the same problem but it’s still unsolved. In fact, if I use your suggestion to define for I2C the pins 4 & 5 and the line of code to override the default pins of the Adafruit library I’m able to show your image on the oled but I was not able to show any other info
The problem is that I need to show on the screen the data from a BME280 and from a SHT3X but for the BME280 if I follow the suggestion of your I2C tutorial I’m able to get data on the serial monitor BUT nothing on the display ( and I was not able to get any data even in the serial monitor from the SHT3X)
Probably I’m very dumb but you have to forgive me since I’m old (73) and I have probably not understood your suggestion.
Could you explain me with a practical example how to wire a BME280 to this board and which code to use to show data from the sensors on the OLED ?
By the way, after an extensive googling and asking Arduino forum I didn’t find any useful answer and at the present I’m still stuck as I was one month ago.
Thanks for your help
Best regards

By: Sara Santos

Sara Santos — Sun, 06 Aug 2023 09:59:48 +0000

In reply to Bruno Morra.

Hi.

To use multiple I2C buses, you can follow our I2C tutorial: https://randomnerdtutorials.com/esp32-i2c-communication-arduino-ide/
To connect other devices, I think you can use any pins, except the ones marked in green: 6, 7, 11, and 7.

Regards,
Sara

By: Bruno Morra

Bruno Morra — Fri, 04 Aug 2023 20:15:46 +0000

Hi Sara,
following your suggestion I carefully read the tutorial
https://randomnerdtutorials.com/esp32-i2c-communication-arduino-ide/
However, I was not able to solve my problem (I’m old for age but a newbie for ESP)
I understand that the Wemos Lolin32 uses by default the pins 5 and 4 for SDA and SCL to connect the OLED and, if I use the Adafruit library, I have to insert the code line you indicated to override the pins 21 and 22. However when I did this I still have the problem of connect two other I2C devices ( a BME280 and a RTC clock). If I try to use the same pins (5 and 4) nothing happens and I2C scanner says no I2C device found. If I define, following your suggestion, other pins for SDA and SCL for BME 280 modifying the Adafruit library, on the serial monitor < see the correct values from. the sensor but I am not able to see them on the display. I’ve also tried the library “SSD1306Wire.h” but the negative result was the same.
In conclusion, after having defined pins for OLED display as 5 and 4, how can I define other SDA and SCL pins to connect I2C sensors and RTC clock ? I’ve also tried to use Wire and Wire1 ( even if the devices have different addresses) but with no success.
I was not able to find a single example of this on the web and in an Arduino forum discussion a forumer with High Karma says that according to Espressif port B cannot be used in ESP32 for I2C.
I’m just asking for a solution to this very usual problem that in my poor hands is still unsolved and in this case I2C scanner seems not properly working.
Thx, as usual, for your help
Bruno
PS If I use a “usual”ESP32 or ESP8266 with a separated OLED I2C screen I have no problem.
One more question: which are the pins that can be used for this variant of ESP32(WemosLolin32 with OLED) if I have to connect a SPI SD card module ? I was not able to find any info on this important issue

By: Sara Santos

Sara Santos — Tue, 25 Jul 2023 10:08:45 +0000

In reply to Bruno.

Hi.
To better understand how to use multiple I2C peripherals, take a look at the following tutorial:
https://randomnerdtutorials.com/esp32-i2c-communication-arduino-ide/
Regards,
Sara

By: Bruno

Bruno — Mon, 24 Jul 2023 20:46:44 +0000

Hi Sara,
thanks to your tutorial I was able to have an image displayed on the OLED screen but if I try to display a timestamp from a RTC or temp and humidity data from BME280 and SHT3X sensors ( all connected to the same pins 4 and 5 of the OLED screen ) I have no response and I2C scanner test says that no I2C device are found.
So which are the pins to be used for I2C ?
Thanks for yor help
Bruno

By: Anonymousaga

Anonymousaga — Sun, 07 May 2023 20:17:47 +0000

In reply to Sara Santos. I checked all the ADC pins on the board. I found only 2 actually had ADC - GPIO 36 & 39. These are the pins labeled SVN and SVP. Please correct the diagram to correct this. Thanks.