Newbie here, our professor had given us a big problem (i mean homework) on how to interface multiple SPIs using 1 microcontroller. But his requirements are quite exaggerated:
1 microcontroller interfaced on 90 spi devices (like what?!) and it should be simplified like use only 3-8 gpio pins to access all of those.
He said submit it on a paper considering 1 microcontroller has 2 SPI buses. Well, i did take the challenge since this will be done in a demultiplexing way (right? since ss pins of SPI devices just needed some active LOW/HIGH signal even it is not directly coming from the microcontroller like let's say signal from a voltage supply/regulator output to wake it up).
Now canvasing to choose multiplexers, 3 to 8, 4 to 16 bit, 5 to 32 (cascaded) i find myself seeing this 10-bit I/O expander ICs where upon reading and looking how it will be used, it's like a bit shifter using SPI only. I plan to use these 10 I/O ports as 10 cs for the 10 SPI device's ss. I thought of this will be good. Then seeing decoder, etc.. i find using multiple 10-bit I/O expander to connect to this 90 spi devices because i think making a combinations/cascadings, etc w/ these 4 different ICs, i guess its good to stick using multiple 1 IC only maybe to reduce cost and complexity.
Do i understand it right, specially these 4 different ICs? what exactly their difference and application? Am i facing a problem if i do this kind of approach??