In order to connect two small electrical circuits, I needed 17 pins. Because of its availability and compact form, I chose the HDMI connector.
The two circuits are connected using an HDMI cable that was provided with a computer screen and everything worked as expected.
I tried with another cheap HDMI cable but it doesn't work and I see some missing connections. However, this cable works for its intended purpose: connecting a screen to a computer.
If I take a multimeter and test the ends of each cable, the results vary.
For the "good" cable, I get the "beep" for all 19 wires whereas, for the "bad" one, more than a few show no connection.
From this SE link, I understood that there are no unused pins in the HDMI standard. Is there any kind of redundancy function or something that could explain why a functional cable seems to have pin conductors between some pins?
Connections are as follow (bold is connected):
19 17 15 13 11 9 7 5 3 1
18 16 14 12 10 8 6 4 2