relayout in progress.

there are several component changes to make, they are:-

• longer ethernet connector - there is a 5mm pcb overhang requirement to allow connector access through the chassis wall
• contact connectors - when originally specified, there was insuffiucient bill of materials data and they are fairly tall

i will also need some series resistors as the traces are a bit long...

the next device that will be supported by skipper is the siglent SDM3055-SC. i have not yet decided whether to support the front panel or scan card first; there is a forced exclusivity between the two as when the scanner card is active, the chosen input is routed to the front panel

this will lead to a new DMM and scanningDMM? interface. the interface name for when a DMM with a scan card is used is currently undecided as this may fit better under a DAQ label but this is uncertain as i have not looked at DAQ that deeply

after many hours of work, the layout was complete. then the enclosure was drawn and does not fit. the layout(which was provisional) is now undergoing major rework

the mezzanine structure has been scrapped as it would impose too many cutouts, the two levels of PCB will be retained but their stacking will be directly above with wire to board connectors allowing the position offset

this has also triggered a rethink on the internal contact connectors as the existing vertical molex KK are fairly tall and the new layout allows more vertical freedom, the current connectors under review are molex microfit 3.0

front panel connectors are not under review as they still meet all requirements. i did think about instead fitting some D-sub instead but the lower cost connectors dont have the same current rating and this is a non-negotiable feature

layout work is going well. there have been several changes to the initial plan:

• the connectors on the PCB(other than power) are going to be exposed through the chassis wall
• there is a large cutout section to allow stacked PCB to fit against the chassis wall

the USB interface will now need a PCB mount common mode choke as the original plan to wrap a toroid over the interior chassis cable is no longer feasible

it might be worth adding better ESD protection now

right now, there are only 32 unrouted nets so changes are probably not going to be major...

XP power ITR0324S05 is a reasonable looking power module
will need to look into how it performs as it is an unregulated supply. this may be fine, the datasheet says 10% regulation from 0-100% load...