nodeLynk “in” vs. “out” ports

Is there any difference, electrically, between the “in” and “out” ports on a nodeLynk device? I was surprised to see them marked in this way, as I²C is a bus architecture, and the SCL and SDA signals should be identical on an entire bus.

My assumption is that “in” and “out” are so marked solely to ensure that cabling is done correctly, but that the ports are directly connected to one another.

Physical limitations of a prototype are such that it’s substantially easier for me to connect to the “out” ports, and I expect that as long as I take care to connect the signals properly, this won’t be a problem. But if nodeLynk is doing anything sneaky that would keep this from working, it’d be nice to know.


You are correct. It is a bus protocol. We label the in and out connections like that because if you do not flip the cable to the correct orientation it will not work. If you look at the labeling behind the I2C in/out ports you will notice that the in port has the GND connection to the left end of the connector and the out port has the GND connection to the right end of the connector. So if you just tried to plug the I2C cable we include to the out port it would not work because the polarity of the connector is not right. I suppose you could clip the spring clip off the cable connector and flip it over to use the out port if you like though. Or if you have the tool to pull the pins out of the connector you can flip them around so orientation of the wires is correct.

Thanks, Travis. The other end of the cable is my own board. I’ll just wire it up as an ordinary 5V I²C device and use the port that’s physically most convenient.

No problem. Let us know if you have any other questions.