This topic was migrated from the BotBlox ticketing system after being summarized and anonymized.
Q: I want to make sure I understand the concept of “ethernet magnetics” so that I don’t run into any issues in my application. I recently purchased the GigaBlox Nano and the PicoConn board. I just ran the following test with that hardware. I plugged one of the PicoConn ports into a camera (presumably the RJ45 on this camera has integrated magnetics but I don’t know for sure). I plugged another port of the PicoConn into a commercial ethernet switch (Switch B) with 8 RJ45 ports (presumably the ports of this switch also have integrated magnetics).
I was able to communicate with the camera just fine, from a laptop attached to Switch B. Is this how the PicoConn connections are intended to work? I was afraid that the lack of magnetics in the PicoConn board would prohibit a test setup like this from working. Are there any situations where a test setup like the one I described is not valid? Is it such that as long as the device plugging into the PicoConn has magnetics on its end, that everything will just work?
A:
Yes, the test setup you described is a valid and intended way to use the GigaBlox Nano with the PicoConn board.
The PicoConn board does not contain Ethernet transformers. However, a GigaBlox Nano transformerless port can connect to a conventional Ethernet port that has transformers on the other end of the link. The transformer at the camera or commercial switch provides the electrical isolation between the two PHYs.
In your setup, there are two separate Ethernet links:
- GigaBlox Nano to the camera
- GigaBlox Nano to Switch B
Assuming the camera and Switch B use conventional magnetics-isolated Ethernet ports, which is overwhelmingly typical for equipment with standard RJ45 ports, both connections are valid. The magnetics may be integrated into the RJ45 connector or implemented as a separate component elsewhere on the device’s PCB.
The fact that the links established and you were able to communicate reliably with the camera confirms that the devices are electrically compatible in this setup.
However, “the other device has magnetics” should not be treated as an unconditional guarantee that every possible installation will work. There are several important limitations:
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Keep PicoConn cable runs short. We recommend transformerless PicoConn connections of approximately 1 metre or less. Longer cables may work in a controlled environment, but signal integrity, common-mode noise, ESD susceptibility and EMC performance become less predictable. For longer cables, use the RJConn daughterboard or a custom carrier containing Ethernet magnetics.
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Do not use PoE through the PicoConn Ethernet connections. PicoConn does not provide the magnetics, centre taps or isolation normally associated with a PoE interface.
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Be careful when connecting to another transformerless port. Transformerless-to-transformerless connections can work, but the PHY types must be electrically compatible, the devices should share a clean common ground, and the connection should be short. Some current-mode PHYs require a transformer and will not operate correctly when connected directly to the GigaBlox Nano.
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A working bench test does not by itself verify EMC, ESD or surge robustness. PicoConn exposes the GigaBlox Nano PHY more directly to disturbances coupled onto the cable. For cables leaving an enclosure, connections between separately powered systems, or electrically noisy environments, we recommend adding magnetics by using RJConn or an appropriately designed custom carrier.
Therefore, your current camera-to-PicoConn and commercial-switch-to-PicoConn arrangement is correct. For short connections to conventional RJ45 Ethernet devices, it should work as you observed. For longer or externally routed connections, we recommend using the RJConn version so that each GigaBlox Nano port has its own local Ethernet magnetics.