LPC2378 USB not Recognized by using 16MHz crystal oscillator,PLL setting

[nanjooh]

Hi Friends,

I am using LPC2378 processor with 16 MHz crystal oscillator.I am trying to connect the USB CDC but the USB device not recognized by PC.

The same code using the 12 MHz oscillator is working.

Fcco value = 288 MHz
Crystal oscillator value = 12MHz
PLL 'M' value = 12
PLL 'N' value = 1
USBCLKCFG,USBSEL value = 6

Result : The USB CDC is detecting in PC

Fcco value = 288 MHz
Crystal oscillator value = 16MHz
PLL 'M' value = 9
PLL 'N' value = 1
USBCLKCFG,USBSEL value = 6

Result : The USB CDC is Not Recognized

I am using the Formula to calculate the M value is
M = Fcco/2xcrystal oscillator vale

Please help me to solve this problem.

With Regards,
Murthy.R

[Andy Ayre]

I'm not sure you'll get much response, because people come here to find and help with ISP related problems. You might be better off posting on 8052.com or on NXP's own forums. Also you can try contacting your local NXP FAE, and I would recommend investing in a USB protocol analyser.

Andy