topic Re: Low-speed USB operation in host mode on the K22? in Kinetis Microcontrollers

Low-speed USB operation in host mode on the K22?

scottm — Fri, 04 Aug 2017 05:17:30 GMT

I'm pretty sure the answer to this ought to be 'yes', but I don't see it clearly documented and I want to check before I waste too much time on a dead end. Does the K22 series support low speed USB (not full speed) in host mode? I'm thinking about interfacing a specialty device that only supports low speed mode.

The second half of my question is what USB stack should I be using for a new project? One in KSDK 2, I assume? I'm still on the now-obsolete 4.x bare metal stack for my current projects.

Thanks,

Scott

Re: Low-speed USB operation in host mode on the K22?

miduo — Wed, 09 Aug 2017 06:08:35 GMT

Hi,

Yes, you are correct. The USB module of K22 operates at Full Speed.
The Low Speed support is for when it operates as Host and LS devices are connected to it.
Low speed devices use pull-up resistor on D- line. So you will need to disable the D+ resistor and add externally a pull-up resistor on D-.
(Because OTG controller does not have a field to enable pull-up resistor on D-)
For software change, remember that maximum packet size must be set according low speed specifications.

Re: Low-speed USB operation in host mode on the K22?

scottm — Wed, 09 Aug 2017 16:17:13 GMT

That's exactly what I was looking for, thank you very much! Now to see if anyone has written any MIDI code for this thing...

Scott