[Coco] BIGGEST PROBLEM

[Mathieu Bouchard]

Le 2017-03-06 à 15:23:00, David Ladd a écrit :

> On Mon, Mar 6, 2017 at 2:03 PM, John Guin <johnguin at hotmail.com> wrote:
>
>> Can USB slow down to 9600 baud?  I know on the Arduino for the serial
>> monitor (and serial connections in general) you set the speed to 9600 to
>> 115K or so.
>
> ​I believe the USB speeds are, (USB 1.1)12Mbit, (USB 2.0)480Mbit, (USB
> 3.0)5Gbit, & (USB 3.1)10Gbit.​

USB 1.1 has two speeds : normal speed at 12 Mbps, and low speed at 1.5 Mbps, 
which is one eighth of the normal speed, but is still as much as 13 times the 
115200 bps speed. To process the max throughput of low speed, the CPU would 
still need to be able to process a whopping 183 kilobytes per second. I don't 
know about the abilities to further reduce the speed by other means (flow 
control, bitrate negociation). However, very low throughput devices (keyboards 
and mice) wouldn't need those tricks, as they would use much less than that (the 
USB clock would still run at 666 ns, it's just that the data queue wouldn't be 
very busy).

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| Mathieu BOUCHARD --- tél: 514.623.3801, 514.383.3801 --- Montréal, QC