LPCXpresso IDE中的主题 Re: USB Bootloader only works with external crystal?

USB Bootloader only works with external crystal?

lpcware — Thu, 16 Jun 2016 00:47:34 GMT

Content originally posted in LPCWare by ktownsend on Fri Jan 08 06:24:45 MST 2010
I'm just putting some prototypes together for the LPC1343 and I have the impression that the USB bootloader will only work if an external crystal is present? Given the following remark in the user manual ("[FONT=Arial][SIZE=2][FONT=Arial][SIZE=2]Always select the system oscillator to produce a stable 48 MHz clock for the USB block"[/SIZE][/FONT][/SIZE][/FONT]) perhaps ISP simply won't work with the IRC, but I definately wasn't expecting that. Is someone able to confirm this or correct me if I'm wrong?

Re: USB Bootloader only works with external crystal?

lpcware — Thu, 16 Jun 2016 00:47:35 GMT

Content originally posted in LPCWare by NXP_USA on Fri Jan 08 15:33:24 MST 2010

Quote: KTownsend
I'm just putting some prototypes together for the LPC1343 and I have the impression that the USB bootloader will only work if an external crystal is present? Given the following remark in the user manual ("[FONT=Arial][SIZE=2][FONT=Arial][SIZE=2]Always select the system oscillator to produce a stable 48 MHz clock for the USB block"[/SIZE][/FONT][/SIZE][/FONT]) perhaps ISP simply won't work with the IRC, but I definately wasn't expecting that. Is someone able to confirm this or correct me if I'm wrong?

An accurate external clock, crystal or high-accuracy ceramic resonator is required by the USB bootloader to produce a stable 48 MHz for USB. The clock frequency must be 12 MHz. The clock accuracy must better than +/- 0.25% to meet USB specs for a full speed device.

UART ISP runs from the internal oscillator.

-NXP

Re: USB Bootloader only works with external crystal?

lpcware — Thu, 16 Jun 2016 00:47:35 GMT

Content originally posted in LPCWare by annodomini2 on Tue Jan 19 14:34:01 MST 2010
The USB PLL is driven only from the external clock, this is typical of most devices.

Re: USB Bootloader only works with external crystal?

lpcware — Thu, 16 Jun 2016 00:47:36 GMT

Content originally posted in LPCWare by bobi-one on Wed Apr 27 14:37:15 MST 2011

Quote: NXP_USA
An accurate external clock, crystal or high-accuracy ceramic resonator is required by the USB bootloader to produce a stable 48 MHz for USB. The clock frequency must be 12 MHz. The clock accuracy must better than +/- 0.25% to meet USB specs for a full speed device.

UART ISP runs from the internal oscillator.

-NXP

So does this mean that I cant use 16MHz crystal? because I was wondering why my device doesn't enumerate?

Re: USB Bootloader only works with external crystal?

lpcware — Thu, 16 Jun 2016 00:47:36 GMT

Content originally posted in LPCWare by NXP_Europe on Wed Apr 27 15:30:15 MST 2011
Hello bobi-one

see http://support.code-red-tech.com/CodeRedWiki/LPC1xxxChangeClock

USB speed is 48 MHz.

Re: USB Bootloader only works with external crystal?

lpcware — Thu, 16 Jun 2016 00:47:37 GMT

Content originally posted in LPCWare by domen on Wed Apr 27 23:50:09 MST 2011
Jup, for usb bootloader you need a 12MHz crystal. Found that out by disassembling the bootloader.

Re: USB Bootloader only works with external crystal?

lpcware — Thu, 16 Jun 2016 00:47:37 GMT

Content originally posted in LPCWare by bobi-one on Thu Apr 28 00:42:04 MST 2011
So modification without giving much of a thought what to change is pointless?