4 EMI

Electromagnetic interference, also known as EMI, is another potential source for false edges or data corruption to occur. The concept behind this is that the SDA/SCL PCB traces and even the leaded legs of I2C device’s packages can pick up EMI because the devices are made of electrically conductive material, metals, which can act as antennas to pick up this electrical noise. Generally, this kind of concern is present in electrical noisy environments such as a power stations with high switching currents which is emitted through the air. Other potential EMI sources can also pose a problem. High current loads firing off like in a laser printer or a motor in fan can emit large amounts of EMI. I2C traces near these EMI sources can see signal integrity issues and, in some cases, cause errors with the hardware peripherals within the I2C controller or I2C target since these devices weren’t designed to see this kind of electrical stress. If the magnitude of the EMI is large enough and frequency is slow enough a stuck bus event can trigger on the I2C bus.