Recently I am considering to design a macro USB dongle for Android (as HID/CDC device). Due to its limited space, I am trying to find a USB micro which can operate without external crystal. I know Microchip/Cypress can do, but STM claims that USB has to work with external crystal.
Can I use IRC(4MHz) of KL24/25Z as clock source for USB OTG?
Allan
Solved! Go to Solution.
It is impossible to use IRC for USB module because the internal reference clock does not have required accuracy which is strictly needed for peripheral USB.
Regard
Pavel
For just CDC, the CP2105 is a tiny self-contained UBS-to-serial device. Smaller & cheaper than an osc.
It is impossible to use IRC for USB module because the internal reference clock does not have required accuracy which is strictly needed for peripheral USB.
Regard
Pavel
It's not recommended to use internal clock for USB applications.