Embodiments of the invention are generally directed to detection of cable connections for electronic devices. An embodiment of an apparatus includes a port for the connection of a cable, the port being compatible with a first protocol and a second protocol, the port including multiple pins including a first pin for a first line and a second pin for a second line. The apparatus further includes a processor to determine a type of source device connected to the cable, where determination of the type of source device includes the apparatus detecting a low signal on the first line and a high signal on the second line, and, upon detecting the low signal on first line and the high signal on the second line, the apparatus initiates a discovery sequence, the discovery sequence including transmitting a signal sequence on the second line and attempting to receive the signal sequence on the second line. If the signal sequence is successfully received on the second line, the apparatus determines that a source device compatible with the first protocol is connected to the cable.