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cpu/sam3: add opt to use external 32khz oscillator

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This commit is contained in:
Hauke Petersen 2020-03-10 15:03:04 +01:00
parent 008faef16a
commit e5d940fce8
1 changed files with 12 additions and 0 deletions
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12
cpu/sam3/cpu.c
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@ -30,6 +30,11 @@
#define MORKEY (0x37) #define MORKEY (0x37)
/** @} */ /** @} */
/**
* @brief Key for writing the SUPC control register
*/
#define SUPCKEY (0xa5)
/** /**
* @brief Start-up time for external crystal (will be multiplied by 8) * @brief Start-up time for external crystal (will be multiplied by 8)
*/ */
@ -91,6 +96,13 @@ void cpu_init(void)
/* wait for master clock to be ready */ /* wait for master clock to be ready */
while (!(PMC->PMC_SR & PMC_SR_MCKRDY)); while (!(PMC->PMC_SR & PMC_SR_MCKRDY));
/* setup the SCLK: switch to external oscillator if applicable */
#if CLOCK_SCLK_XTAL
/* enable external oscillator */
SUPC->SUPC_CR = (SUPC_CR_KEY(SUPCKEY) | SUPC_CR_XTALSEL);
while (!(SUPC->SUPC_SR & SUPC_SR_OSCSEL_CRYST)) {}
#endif
/* initialize stdio prior to periph_init() to allow use of DEBUG() there */ /* initialize stdio prior to periph_init() to allow use of DEBUG() there */
stdio_init(); stdio_init();