topic LPC43xx Chip_Clock_EnableCrystal Hard fault advisory in LPC Microcontrollers

LPC43xx Chip_Clock_EnableCrystal Hard fault advisory

Eli_H — Mon, 16 Dec 2019 14:06:27 GMT

I am posting this as I ran into this issue after starting some new development with the LPC4357.

The function void Chip_Clock_EnableCrystal(void) in the chip support library has a while loop delay to pause for the crystal osc. to stablize before engaging the PLL. The "stock" value of 1000 is not quite enough for many crystals and/or layouts.

I am using the embedded artists 4357 developer kit and found that I can get a hardfault during the PLL init phase about 50% of the time. Simply making this larger fixes the issue. In my case I make it very large (100000) and the PLL starts 100%.

No to need to respond, I am just posting this as an advisory. I ran into this back in 2013 with the LPCOpen libraries and completely forgot I had versions of the libraries with this patched.

Re: LPC43xx Chip_Clock_EnableCrystal Hard fault advisory

xiangjun_rong — Tue, 17 Dec 2019 09:12:11 GMT

Hi, Eli,

Regarding the snippet of code, I think it is okay if you increase the delay as 100 000, it just waits for the stabilization of the crystal.

Hope it can help you

XiangJun rong

/* Enables the crystal oscillator */
void Chip_Clock_EnableCrystal(void)
{
volatile uint32_t delay = 1000;

uint32_t OldCrystalConfig = LPC_CGU->XTAL_OSC_CTRL;

   /* Clear bypass mode */
   OldCrystalConfig &= (~2);
   if (OldCrystalConfig != LPC_CGU->XTAL_OSC_CTRL) {
       LPC_CGU->XTAL_OSC_CTRL = OldCrystalConfig;
   }

   /* Enable crystal oscillator */
   OldCrystalConfig &= (~1);
   if (OscRateIn >= 20000000) {
       OldCrystalConfig |= 4;   /* Set high frequency mode */

}
LPC_CGU->XTAL_OSC_CTRL = OldCrystalConfig;

/* Delay for 250uSec */
while(delay--) {}
}