Trying to connect to the sonar with the Nano switch is very difficult – it rarely connects, but we have no problem with the Small Gigabit switch.
We are now looking to use the Gigablox SFP unit and want to know if it uses the same hardware as the Nano switch. If it does we need to understand why there is a difference between the two systems (small and nano) and how we overcome this problem of unreliable connectivity.
The difference between GigaBlox and GigaBlox Nano is that GigaBlox Nano uses transformerless ethernet. Transformerless ethernet is a great way to reduce spacing but it does reduce compatibility with some other devices. Most crucially, transformerless ethernet requires that any link partner contains transformers. It’s likely that sonar does not contain transformers, so the two devices aren’t playing nice together.
GigaBlox Nano and SPEBlox are the only devices we sell that are transformerless. GigaBlox SFP has transformers and so the same issue shouldn’t occur.
I have connected two gigablox-nano using a one-to-one differential pair connection on port 3 (each). Does the above information mean I need to add a transformer between the two gigablox-nanos? Reading the data sheet it says it is ok to make “A GigaBlox Nano transformerless ethernet connection to any other transformerless, capacitively isolated PHY”.
My upstream gigablox-nano perfectly communicates with a network (over a transformer which I have added) and with CPU1 (which also uses a transformer). The downstream gigablox-nano which is directly connected without transformer to the upstream gigablox-nano does not seem to make communication and there is also no communication to CPU2, CPU3 and CPU4 which are connected to the downstream device. What can be wrong?
Connecting two GigaBlox Nano together using a port on each works fine without a transformer. However you do need to make sure that you don’t use the same port number on each GigaBlox Nano. There is a known hardware bug that causes same numbered ports between two GigaBlox boards to not come up when powered on at the same time. See the datasheet page 20 (snippet below).
The solution is to just use different numbered ports. Connect port 1 on GigaBlox Nano A to port 2 on GigaBlox Nano B, for example.
That would explain why your two GigaBlox Nanos are unable to communicate. However you should still see connections between your CPU2, CPU3 and CPU4 to the downstream GigaBlox Nano. Do you see the LEDs flash on the associated ports for those CPU connections?
Thanks a lot. My datasheet is of May 2024. Removing one of the modules with power on and re-connecting it makes a perfect communication. I will need to do some additional testing and - unfortunately - make a redesign of the circuit with different port numbers connected to each other.
Ok, the fact that removing the GigaBlox Nano and reseating it will mean the power-on between each GigaBlox Nano is staggered, which confirms this is indeed the issue.
Shame that you’ve already designed the circuit. You could try adding a large capacitance locally to the power rail of one of the GigaBlox Nanos to try and delay the power on of that module. We haven’t tested to see if that could be a workaround.
