Port expansion, 100s of ports?

Tdk408:
Wow, brilliant idea. Won't work for me, though. because the cables are custom each time.

One (or very few) offs?

Maybe you could use a jig to build cables on more than a post-build tester? Something with leds to show each step so none are missed that checks connects as they're made?

allanhurst:
Some commercial cable testers deal with cross-connections by having a 'learn' mode - you connect a known good cable, record it's connections, and check cables to be tested against that.

It'd be handy for checking out Enigma rotors.....

Allan.

That's how they do PCB continuity testing too. It can go horribly wrong if there is a systematic fault
with all the devices!

I don't see 74hc596 as a purchaseable part at Digikey or Mouser. Maybe a different logic family?

"4051/4052/4053 - The CDx4HCx4051 devices are a single 8-channel multiplexer having three binary control inputs, S0, S1, and S2 and an ENABLE input. The three binary signals select 1 of 8 channels to be turned on, and connect one of the 8 inputs to the output.
The CDx4HCx4052 devices are a differential 4-channel multiplexer having two binary control inputs, S0 and S1, and an ENABLE input. The two binary input signals select 1 of 4 pairs of channels to be turned on and connect the analog inputs to the outputs.
The CDx4HCx4053 devices are a triple 2-channel multiplexer having three separate digital control inputs, S0, S1, and S2 and an ENABLE input. Each control input selects one of a pair of channels that are connected in a singlepole, double-throw configuration."

Not I2C interfaced at all, so not sure how that helps.

Here's a diagram I did up while ago. Very straightforward to connect clock & latch signals to all chips in parallel, and daisy chain the data out and data in signals from chip to chip.

I've had 45 TPIC6B595s daisy chained like that to make 360 outputs.
Haven't tried that many shift-in registers, but they work in similar manner.

CrossRoads:
I’ve had 45 TPIC6B595s daisy chained like that to make 360 outputs.
Haven’t tried that many shift-in registers, but they work in similar manner.

I smell a new product.
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