For our new hybrid laboratory, we created new revisions for the Quaduino PCB.
This Version 2 had a few bugs:
- RGB LED was wrongly connected (GND is the right-most pin)
- Test points for the oscilloscopes were to small
Those were adressed in V2.1:
We encountered an issue that may or may not occur – depending on the component quality:
- Ethernet-Module does not restart
Thanks to the work of my colleague, we found, that the issue sits with the cross-lane-connection via RS485 chips. Those have pull-up resistors for the 5V Arduino circuit. This results in the active lanes introducing a voltage in the offline lane.
This in turn results in powering the Ethernet module slightly (about 1,4V), which means: the module cannot reset properly (RST pin must be pulled LOW and then HIGH).
Our mitigation for this: connect W5500 RST pin to Arduino IO and perform the reset manually during bootup or reboot.
This issue presents only for some W5500 Ethernet modules. Our other option would be to decouple the RS485 communication using diodes or to decouple the Ethernet module using Z-diodes.
For our current layout, we need to patch-wire: