ColdFire/68K Microcontrollers and ProcessorsのトピックRe: Intermittent USB Recognition Issue

Intermittent USB Recognition Issue

grt951 — Thu, 07 Mar 2013 16:26:28 GMT

I am using the freescale USB CDC stack and virtual com port driver for the MCF51JE256 as a device only and have a intermittent issue where windows will not recognize the device. The hardware is to the USB app note (33ohm series resistors and 1.5k pull-up on D+) and the device will recognize roughly 50% of the time. It seems to also be PC dependent which is why I am looking at the hardware...any ideas?

Thanks,

Gary

Re: Intermittent USB Recognition Issue

Pepe_Ruiz — Tue, 12 Mar 2013 05:16:41 GMT

Hi Gary,

Are you using an external 1.5K ohm resistor or the internal one?

If you use an external one you are not giving enough time to the MCU to enable properly the internal PLL and all the USB stack. remove the external pull-up resistor. the MCU already has an internal resistor that will be activated in SW.

try it and let us know if worked.

regards

Re: Intermittent USB Recognition Issue

grt951 — Tue, 12 Mar 2013 21:05:47 GMT

Hi Pepe,

Thanks for the info...we have resolved the issue the internal VREG was not being supplied with the correct voltage via VBUS causing a inconsistent signal.

Thanks...