Hi all,
I am working on a project that utilizes LPC1788 MCU. I am using LPCOpen library.
I want to run it at 120 MHz clock speed. Function Chip_SetupIrcClocking(); is called code to set 120 MHz freq.
void Chip_SetupIrcClocking(void)
{
/* Clock the CPU from SYSCLK, in case if it is clocked by PLL0 */
Chip_Clock_SetCPUClockSource(SYSCTL_CCLKSRC_SYSCLK);
/* Disable the PLL if it is enabled */
if (Chip_Clock_IsMainPLLEnabled()) {
Chip_Clock_DisablePLL(SYSCTL_MAIN_PLL, SYSCTL_PLL_ENABLE);
}
/* It is safe to switch the PLL Source to IRC */
Chip_Clock_SetMainPLLSource(SYSCTL_PLLCLKSRC_IRC);
/* FCCO = 12MHz * (9+1) * 2 * (0+1) = 240MHz */
/* Fout = FCCO / ((0+1) * 2) = 120MHz */
Chip_Clock_SetupPLL(SYSCTL_MAIN_PLL, 9, 0);
Chip_Clock_EnablePLL(SYSCTL_MAIN_PLL, SYSCTL_PLL_ENABLE);
Chip_Clock_SetCPUClockDiv(1);
while (!Chip_Clock_IsMainPLLLocked()) {} /* Wait for the PLL to Lock */
Chip_Clock_SetCPUClockSource(SYSCTL_CCLKSRC_MAINPLL);
/* Peripheral clocking will be derived from PLL0 with a divider of 2 (60MHz) */
Chip_Clock_SetPCLKDiv(1);
}
I have not changed in this function. It shows it sets multipler and per-scaler to proper values to get 120 MHz freq.
Chip_SYSCTL_EnableBoost();
Chip_SetupIrcClocking();
But MCU still runs on 12 MHz.
I have verified by checking SystemCoreClock variable. It shows 12000000 value.
I have also verified using test code as below:
dprintf(UART_DEBUG_PORT, "START\r\n");
for(int i = 0; i < 120 * 1000* 1000; i++) {
asm("nop");
}
dprintf(UART_DEBUG_PORT, "END\r\n");
If MCU is running on 120 MHz it should take around 1 second to execute the code. But it takes around 10 seconds to execute. Which shows it is running on 12 MHz clock.
I have also tried to External Crystal but no luck. Any idea or suggestions ??
