USB min frequency

[martindusek]

Hello,

what's the min CPU frequency Freesscale bare metal USB stack (namely generic HID device) can reliably run on KL26?

I clock USB module 48 MHz.

When I compile my C code without optimization and CPU runs on 12 MHz I mainly get "USB device not recognized" error in Windows when I connect my device to PC (90% probability I will get the error)

No optimization and 24 Mhz CPU leads to "USB device cannot start, Code 10" in Windows (10 % probabality I will get the error)

Optimization and 12 MHz CPU leads to "USB device cannot start, Code 10" in Windows (10 % probabality I will get the error)

Optimization and 24 Mhz leads to no error.

[mjbcswitzerland · Accepted solution]

Hi

When I run the uTasker USB-HID mouse on the FRDM-KL26Z I can set the system clock to 24MHz and the Flash/Bus clocks to 3MHz and build with GCC with no optimisation and it operates normally (connected >20 times without any errors). Generally there shouldn't be much time critical with the enumeration process.

Regards

Mark