Arduino library for MCP3021 & MCP3221 I2C ADC Example #include <Wire.h> #include "MCP3X21.h" const uint8_t address = 0x4D; const uint16_t ref_voltage = 3300; // in mV MCP3021 mcp3021(address); void setup() { Serial.begin(115200); #if defined(ESP8266) Wire.begin(SDA, SCL); mcp3021.init(&Wire); #else mcp3021.init(); #endif } void loop() { uint16_t result = mcp3021.read(); Serial.print(F("ADC: ")); Serial.print(result); Serial.print(F(", mV: ")); Serial.println(mcp3021.toVoltage(result, ref_voltage)); delay(1000); }