Using USB with internal Oscillator possible?

gommel · ‎2008-06-02

Posted on June 02, 2008 at 17:01

gommel · ‎2011-05-17

Posted on May 17, 2011 at 12:35

Hello,

we develop a very small and cost sensitive circuitry that is a USB device. Looking for affordable and small resonators/crystals we considered to use the internal oscillator of the STM32F203T8 instead. Is this possible and reliable enough?

lanchon · ‎2011-05-17

Posted on May 17, 2011 at 12:35

USB full speed requires crystal. (I think the stm32 can't do low speed.)

maybe you could run at 48MHz from HSI+PLL, while continually calibrating in software from LSE running a 32KHz crystal (these are cheaper, aren't they?), but you may have too much jitter.

jj · ‎2011-05-17

Posted on May 17, 2011 at 12:35

Years past we had similar issue while attaching 2 micros

via Uart. Equation uncovered acceptable variance between

the ''fastest'' sender versus the ''slowest'' receiver.

However - the issues of temperature and aging also arose.

Crystal & resonator solved this in the past - I especially

like lanchon's 32Khz xtal ''reference'' suggestion. It's

unfortunate that ''normal'' xtals for STM32 are BIGGER than the micro...