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Topic: How many mass storage devices simultaneously connected via USB hub? (Read 727 times) previous topic - next topic

robertborkow

Hey,

Did anyone try to connect a large number of mass storage devices (each with own power) via USB hub to Yun? I want to connect 12 slave devices simultaneously. I won't write to any of them, and will read from one at a time only. Did anyone make a test regarding this or has a good guess?

I am not sure if idle mass storage devices will consume bandwidth? And how about power issue (each slave theoretically has its own power supply)?

I would like to know what number that might be before I buy hubs. If 12 won't work, I was thinking of creating a small circuit with a USB multiplexer (e.g. FSUSB74 or MAX4999) to reduce the number of devices that are connected to Yun at any given time to 3 at most (via USB hub). Do you think it makes sense?

Thanks,
Robert

sonnyyu

USB 1.1 allowed Low Speed (1.5 Mbit/s) and Full Speed (12 Mbit/s). The now-aging USB 2.0 standard can theoretically transfer data at a very high 480 Mbit/s. That's impressive, but not as much as the newer USB 3.0, which can handle up to 5 Gbit/s.  Uart will be suffer with even  Low Speed (1.5 Mbit/s).

USB at AR9331 is 2.0, but since CPU power limit never reach theoretically transfer speed.
...
The slow... speed of AR9331 (32 bits/400 Mhz/single core)  and USB 2.0 port might be bottleneck  of your application.




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