Rapid development of reliable embedded systems

I was recently contacted by a customer asking if he could use the RTC oscillator as a clock source for the PLL on the LPC-2378.

While investigating this issue I found out that if I chose to use the RTC oscillator on the LPC-2378, uploading and debugging through JTAG was a problem. The code compiles fine on the Builder but then I had to use the generated .hex file and a flash tool (like Flash Magic) to upload the code.

In order to use the RTC Oscillator as the PLL clock source, I had to make some slight modifications to the code provided in RapidiTTy Builder. This is illustrated below:

main.h

// Oscillator / resonator frequency (in Hz) 
// e.g. use (32768UL) for  the RTC oscillator on LPC-2378
#define FOSC (32768UL)
 
// PLL multiplier value
// Use 4395 as a multiplier (with 1 as a divider )
// to get an FOSC of 288 MHz
#define PLL_MULTIPLIER (4395UL)

system_init.c

Comment out the following lines of code:

// Do not need the main oscillator
// when using the RTC oscillator
SCS |= 0x20;   
while( !(SCS & 0x40) );

Use the following clock source selection value:

CLKSRCSEL = 0x02;

— Anjali.