Xtal on BasicBoard

[Pompey2]

I'm adding a 12Mhz Xtal to my BB.
Reading the 1114 user guide it looks as if some registers (SYSOSCCTRL, SYSPLLCLKSEL, MAINCLKSEL, others?) may have to be updated to effect the switch from the RC osc to the Xtal - but it's really not very clear, to me anyway!
Can Coridium add details to the BB User Guide please?

Chris

[Pompey2]

Here's my code to enable the BasicChip to use an external 12Mhz crystal.

Code: Select all

 '******************************************************************
 ' Derived from the Clock Start Up code in:
 '
 '* @file     system_LPC11xx.c
 '* @brief    CMSIS Cortex-M0 Device Peripheral Access Layer Source File
 '*           for the NXP LPC11xx Device Series
 '* @version  V1.00
 '* @date     17. November 2009
 '
 ' This version uses ~470 bytes of code space, no data space.
 ' I suspect there are a number of lines here that are unnecessary!
 '
 ' Chris Parker 11/28/12
 '******************************************************************

#define SYSPLLCTRL      *&H40048008    ' System PLL control (R/W)
#define SYSPLLSTAT      *&H4004800C    ' System PLL status (R/ )
#define SYSOSCCTRL      *&H40048020    ' System oscillator control (R/W)
#define SYSPLLCLKSEL    *&H40048040    ' System PLL clock source select (R/W)
#define SYSPLLCLKUEN    *&H40048044    ' System PLL clock source update enable (R/W)
#define MAINCLKSEL      *&H40048070    ' Main clock source select (R/W)
#define MAINCLKUEN      *&H40048074    ' Main clock source update enable (R/W)
#define PDRUNCFG        *&H40048238    ' Power-down configuration Register (R/W)

  PDRUNCFG = PDRUNCFG AND NOT(1 << 5)  ' Power-up System Osc  - Clear bit5
  SYSOSCCTRL    = 0                    ' Should not be needed, this is the default
  TIMER=0
  WHILE (TIMER < 10000)                ' Give it 10 mS to stabilise
  LOOP

  MAINCLKSEL    = 0                    ' Select IRC as MainClk
  MAINCLKUEN    = 1                    ' Update MCLK Clock Source
  MAINCLKUEN    = 0                    ' Toggle Update Register
  MAINCLKUEN    = 1
  WHILE (MAINCLKUEN = 0)               ' Wait Until Updated
  LOOP

  SYSPLLCLKSEL  = 1                    ' Select SYSOSC as PLL Input
  SYSPLLCLKUEN  = 1                    ' Update Clock Source
  SYSPLLCLKUEN  = 0                    ' Toggle Update Register
  SYSPLLCLKUEN  = 1
  WHILE (SYSPLLCLKUEN = 0)             ' Wait Until Updated
  LOOP

  PDRUNCFG = PDRUNCFG OR (1 << 7)      ' Power-down SYSPLL   Set bit 7
  SYSPLLCTRL = &H23                    ' *** The BasicChip has this set incorrectly ***
  PDRUNCFG = PDRUNCFG AND NOT (1 << 7) ' Power-up SYSPLL     Clear bit7
  WHILE (SYSPLLSTAT = 0)               ' Wait Until PLL Locked
  LOOP

  MAINCLKSEL    = 3                    ' Select PLL Clock Output
  MAINCLKUEN    = 1                    ' Update MCLK Clock Source
  MAINCLKUEN    = 0                    ' Toggle Update Register
  MAINCLKUEN    = 1
  WHILE (MAINCLKUEN = 0)               ' Wait Until Updated
  LOOP

' User program starts here

The code is derived from the NXP startup code, and has several lines that are probably not required - but I've left them in anyway.

[hyte]

Thanks for the code. Do you have to add 39 pF caps as in http://www.coridium.us/ARMhelp/index.ht ... rPins.html ?

[Pompey2]

Thanks for the code. Do you have to add 39 pF caps as in http://www.coridium.us/ARMhelp/index.ht ... rPins.html ?

I added 22pF caps as spec'd 'somewhere' for the BasicChip/LPC1114.

[hyte]

Ordered some parts after reading this (pdf) http://www.eetkorea.com/ARTICLES/2001SE ... AMD_AN.PDF and explained the things I was missing. Will report back if they work.

[hyte]

Works a treat, cheers