Thys may give you a direction //Programa: Medidor de corrente com sensor ACS712 //Autor: Arduino e Cia #include <Wire.h> #include <U8glib.h> //Definicoes do display Oled U8GLIB_SSD1306_128X64 u8g(U8G_I2C_OPT_NONE); //int valor = 0; String str; int tamanho; const int analogIn = A0; int mVperAmp = 66;...

Try change Arduino IDE tool flash frequency to 40 Mhz

I noted that have several variants for pins_arduino.h

What is the correct way of code, to set Arduino IDE to use a specific variant?