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How to implement a real working USB 2.0 CDC without crystal in MK64FN1M0VLL12?

Question asked by Marco Antonio de Oliveira on Dec 20, 2018
Latest reply on Feb 20, 2019 by Marco Antonio de Oliveira

Dear sr.


I am a hardware/software designer here in Brazil working for the Post (ECT). We are developing a protocol translator (Siemens/USS over RS485) using MK64FN1M0VLL12 (I got some free samples from NXP. Thank you very much). The UART part has been accomplished, but there is this demand to send some data to a USB host. In my hand-made board everything works like a charm through debug console (I put a 16 MHz crystal to pins 50-51 LQFP 100 pins package) but I got a “unknown device” in Windows when I try IRC48 MHz configuration.

I´ve searched the forum and I´ve read these posts so far:


IRC48M Clock Synchronisation with USB Mark Butcher  18 de Fevereiro de 2016 05:55:22


Crystal-less USB operation on Kinetis FRDM64F platform with IRC48M. qingjun wang 24 de Setembro de 2014 04:15:28


And AN4905.


Unfortunately, I cannot help myself till now.

So the question, this specific micro-controller really works USB crystal-less?

We are in the proceedings of manufacturing some boards for testing in site. It works fine for the job it is required. And I know I can put an FTDI converting or so on the USB/UART side, but it will be nice to use on-chip USB feature that I brag about to my boss. Of course I can put a 16 MHz crystal into the board too, but a company has already been contracted to build it and I have not time to redesign the PCB.


Thanks in advance.