In some examples, a device includes at least two light sources, buffer circuitry configured to receive a bit stream, and driver circuitry configured to receive the bit stream from the buffer circuitry and to drive the at least two light sources based on the bit stream. In some examples, the device further includes monitor circuitry configured to determine a voltage drop across each light source of the at least two light sources and snooping circuitry configured to read an inactive bit of the bit stream. In some examples, the snooping circuitry is further configured to read an active bit of the bit stream after reading the inactive bit and based on a value of the inactive bit and to cause the monitor circuitry to determine a voltage drop across a light source of the at least two light sources based on a value of the active bit.