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Project: HomeAutomation

Routing the USB/Dual-CAN interface rev 2

The board that connects the control PC to the HomeAutomation CAN bus via a USB serial interface was the first one I designed for this project, and it was the first larger PCB where I did most of the signal routing on the board manually. In the end, when there were three or four signals left to lay down, I had them auto-routed, and called it done. The board worked and is currently in use in my prototyping and test setup, so it probably was okay.

However, by now I have stopped using the autorouter at all (actually, I did not even license it in the EDA software I use), and I do not think the layout I did back then is really good.

Because I now wanted to include circuitry to sense the current consumed by the two CAN buses managed and powered by the interface board, and it proved quite hard to somehow mix them into the existing board design, I started the PCB layout from scratch, and am now burning the midnight oil routing the new board:

Intermediate state of the HA-B02.02 PCB layout

All components are placed, power supplies are routed, the "critical" signals are routed as well (though I am not really happy with the clock line for the two CAN controllers snaking around unguarded as it is), and I have begun laying down the remaining signals.

With the redesign, I have also included a 5V regulator on the board, so it can be powered from a single 12V supply, the extra 5V logic supply is not required any more. This should make wiring the case easier in which this interface board will go together with the Raspberry Pi acting as control computer.
The regulator is a linear one (a 7805), to help keeping the analog reference voltage free from a switching regulator's noise (though it is low-pass filtered as well).