10 years, 4 months ago.

How to restart PLL0 after wakeup from power-down?

In the LPC176x User Manual, its stated:

PLL0 and Power-down mode: Power-down mode automatically turns off and disconnects PLL0. Wake-up from Power-down mode does not automatically restore PLL0 settings, this must be done in software. Typically, a routine to activate PLL0, wait for lock, and then connect PLL0 can be called at the beginning of any interrupt service routine that might be called due to the wake-up. It is important not to attempt to restart PLL0 by simply feeding it when execution resumes after a wake-up from Power-down mode. This would enable and connect PLL0 at the same time, before PLL lock is established.

I tried SystemInit() after wakeup and PLL0FEED, without success. The System clock/PLL Settings stay unrecovered.

Here is my code:

<<code title=power-down and wakeup>>

1. include "mbed.h"
2. include "adc.h"
3. include "qweeky.h"
4. include "VLSIcodec.h"
5. include "SDFileSystem.h"

1. define PinWakeup P2_12

InterruptIn wakeup(PinWakeup); DigitalOut led(LED1); DigitalOut led2(LED2); Serial pc(P0_10,P0_11); TXD, RXD

static void wakeUpHandler(void) { led2 = 1; wait(1); led2 = 0; return; }

void PowerDown(void) { from NXP LPC1765 Erratasheet okt. 10 / 2009 LPC_SC->PLL0CON &= (1<<1); /* Disconnect the main PLL (PLL0) */ LPC_SC->PLL0FEED = 0xAA; /* Feed */ LPC_SC->PLL0FEED = 0x55; /* Feed */ while ((LPC_SC->PLL0STAT & (1<<25)) != 0x00); /* Wait for main PLL (PLL0) to disconnect */ LPC_SC->PLL0CON &= (1<<0); /* Turn off the main PLL (PLL0) */ LPC_SC->PLL0FEED = 0xAA; /* Feed */ LPC_SC->PLL0FEED = 0x55; /* Feed */ while ((LPC_SC->PLL0STAT & (1<<24)) != 0x00); /* Wait for main PLL (PLL0) to shut down */

entering power-down mode: SCB->SCR |= 0x04; LPC_SC->PCON = 0x9; WFI(); }

int main () { wakeup.rise(wakeUpHandler);

led = 1; wait_ms(100); led = 0; pc.printf("going to sleep in 5s...\n"); wait(5);

while (1) { pc.printf("now going to sleep...\n"); wait(0.5); PowerDown();

LPC_SC->PLL0FEED = 0xAA; /* Feed */ LPC_SC->PLL0FEED = 0x55; /* Feed */ SystemInit();

pc.printf("Waking up and analysing Audio Signal...\r\n"); led = 1; wait_ms(100); led = 0; wait(5); pc.printf("done - ready to go back to sleep...\n"); wait_ms(0.5); } } <<code>>

Any help would be great! Thanks :-)

static void wakeUpHandler(void)
{
    SystemInit();
    Serial pc(P0_10,P0_11); //TXD, RXD
    pc.printf("in wakeupHandler... flashing LED2 now...\n");
    led2 = 1;
    wait_ms(100);    // here it freezes !!??!!
    led2 = 0;
    return;
}

void PowerDown(void)
{
    //entering power-down mode:
    SCB->SCR |= 0x04;
    LPC_SC->PCON=0x1; // PM1=0, PM0=1, enter power down mode if the SLEEPDEEP bit in SCR is 1
   __WFI();
}
 
int main ()
{
    wakeup.rise(wakeUpHandler);  // Setup rising edge interrupt
    
    led = 1;
    wait_ms(100);
    led = 0;
    pc.printf("going to sleep in 5s...\n");
    wait(5);  // for debug purposes. Wait 5 Seconds to allow JTAG access in case System doesn't wake up. 
 
    while (1)
    {
        pc.printf("now going to sleep...\n");
        wait(0.5);
        PowerDown();
        pc.printf("Waking up and analysing Audio Signal...\r\n");
        led = 1;
        wait_ms(100);
        led = 0;
        wait(5);
        pc.printf("preparing to go back to sleep...\n");
    }
}