[Oberon] PO2013 - Real time measurement

Paul Reed paulreed at paddedcell.com
Sun Dec 16 19:24:49 CET 2018

> How about extending board's SPI socket, into a sort of cable bus,
> devices put on a ribbon cable. Then question remains, how to address the
> nodes using distinct CS signal for each, also not sure what length of
> ribbon cable could SPI handle. It is meant just for sensor logic in
> immediate vicinity of FPGA board. The analog signals will be carried by
> longer cables to actual sensors / probes.

It's wise not to be too general about this but just design for some
specific examples.  I2C attempts to solve the multiple-select-line problem
by having devices respond to a (sometimes-configurable) address instead,
but I2C is much more complicated than SPI (in implementation more than in

Long analogue lines are usually avoided, because of the possibility of
interference and attenuation.  Hence I suggested radio as being much
easier nowadays; but you could use e.g. RS485.  Tradeoffs for distance vs
baudrate are usually made; in the case of sensors this is not usually a


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