This was a fun exercise: How many Raspberry Pi can be operated in a standard Shipping Container
What if... we connect the raspis over SPI? .... I would think we would lose some switches 🤔 😊
@Ollivdb How many devices can you connect, and which additional hardware and power does that need?
If I'm right SPI has no hard limit of devices that can be connected like the i²C has ( 128 or so ). It's more about speed which is nothing compared to a switch when it comes to multiple devices. And at least I have never tried to control a raspi over SPI but used it as controler.
But the question was how many raspis can you operate at maximum in a container, right?
So maybe 1 Rpi as controller with LAN and 100 as slaves over SPI? Would be an interesting question too 🙂
Would be hard to use SPI like that, whilst its a multidrop bus, you need peripheral select lines to manage bus access.
Plus gate capacitance, trace length and slew rate come into play to limit things in practice.
Would be much better off going with CAN or RS485, except none of that would get close to the bandwidth of Ethernet, especially for the cost point.
@intrbiz @ascherbaum
Yesterday I read a little bit about the SPI controller of the Pi5. At least it should be able to use a slave mode. But unfortunately I haven't found anyone who ran a Pi in slave mode except SoftSPI. So atm I'm not really sure if it could be done at all over SPI.
But nevertheless the challange is now "run as many unchanged Pi5 in a container as possible". And therefore I have to get rid of the ethernet and switches. But yeah, a lot of exploring new land here 😊
"What's that black sculpture in front of the container?"
"Oh. That's Hans. He accidentically switched on the wifis. All of them." 😅
@intrbiz @ascherbaum 100000 wifis in a metal box? That would be more some sort of microwave 😁