I will try to briefly comment my project and my issue. Then I will post the code and the errors. This is my first post.
My project is a PCB with an STM32 blue pill, a BME280 sensor and a 128x32 SSD1306 display connected at B6/B7 I2C bus. I got also a W5500 DEVMO USR-ES1 ethernet module to connect to a MQTT server. This project aims to publish temperature and humidity to an IoT platform and to detect fire.
Sensor, display and W5500 are powered from the 3.3V pin, and the blue pill is powered with 5V from the PC. Both voltages have two caps in order to stabilize them. The project gets an IP and posts to the MQTT server without any problem, but I do have a problem with the sensor. Sensor gives correct values only before the Ethernet.begin(mac) call. After ethernet begin both the sensor and the display go wrong. The display doesnt follow instructions and the bme gives values such as -140ºC or so.