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soc/rtc: add support for external 32k oscillator 

Compared to external 32k XTAL, when active oscillator is used as input,
some parameters need to be set differently.
pull/2261/merge
Ivan Grokhotkov 2018-08-13 01:10:29 +03:00
rodzic 9efc06be0f
commit 8365f0f5d2
2 zmienionych plików z 17 dodań i 3 usunięć
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5
components/soc/esp32/include/soc/rtc.h
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@ -193,6 +193,11 @@ void rtc_clk_xtal_freq_update(rtc_xtal_freq_t xtal_freq);
*/
void rtc_clk_32k_enable(bool en);
/**
* @brief Configure 32 kHz XTAL oscillator to accept external clock signal
*/
void rtc_clk_32k_enable_external();
/**
* @brief Get the state of 32k XTAL oscillator
* @return true if 32k XTAL oscillator has been enabled

15
components/soc/esp32/rtc_clk.c
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@ -62,6 +62,10 @@
#define XTAL_32K_BOOTSTRAP_DBIAS_VAL 0
#define XTAL_32K_BOOTSTRAP_TIME_US 7
#define XTAL_32K_EXT_DAC_VAL 2
#define XTAL_32K_EXT_DRES_VAL 3
#define XTAL_32K_EXT_DBIAS_VAL 1
/* Delays for various clock sources to be enabled/switched.
* All values are in microseconds.
* TODO: some of these are excessive, and should be reduced.
@ -98,7 +102,7 @@ static bool rtc_clk_cpu_freq_from_mhz_internal(int mhz, rtc_cpu_freq_t* out_val)
// Current PLL frequency, in MHZ (320 or 480). Zero if PLL is not enabled.
static int s_cur_pll_freq;
static void rtc_clk_32k_enable_internal(int dac, int dres, int dbias)
static void rtc_clk_32k_enable_common(int dac, int dres, int dbias)
{
SET_PERI_REG_MASK(RTC_IO_XTAL_32K_PAD_REG, RTC_IO_X32N_MUX_SEL | RTC_IO_X32P_MUX_SEL);
CLEAR_PERI_REG_MASK(RTC_IO_XTAL_32K_PAD_REG,
@ -113,12 +117,17 @@ static void rtc_clk_32k_enable_internal(int dac, int dres, int dbias)
void rtc_clk_32k_enable(bool enable)
{
if (enable) {
rtc_clk_32k_enable_internal(XTAL_32K_DAC_VAL, XTAL_32K_DRES_VAL, XTAL_32K_DBIAS_VAL);
rtc_clk_32k_enable_common(XTAL_32K_DAC_VAL, XTAL_32K_DRES_VAL, XTAL_32K_DBIAS_VAL);
} else {
CLEAR_PERI_REG_MASK(RTC_IO_XTAL_32K_PAD_REG, RTC_IO_XPD_XTAL_32K);
}
}
void rtc_clk_32k_enable_external()
{
rtc_clk_32k_enable_common(XTAL_32K_EXT_DAC_VAL, XTAL_32K_EXT_DRES_VAL, XTAL_32K_EXT_DBIAS_VAL);
}
/* Helping external 32kHz crystal to start up.
* External crystal connected to outputs GPIO32 GPIO33.
* Forms N pulses with a frequency of about 32KHz on the outputs of the crystal.
@ -150,7 +159,7 @@ void rtc_clk_32k_bootstrap(uint32_t cycle)
SET_PERI_REG_MASK(RTC_IO_XTAL_32K_PAD_REG, RTC_IO_X32P_RUE | RTC_IO_X32N_RDE);
ets_delay_us(XTAL_32K_BOOTSTRAP_TIME_US);
rtc_clk_32k_enable_internal(XTAL_32K_BOOTSTRAP_DAC_VAL,
rtc_clk_32k_enable_common(XTAL_32K_BOOTSTRAP_DAC_VAL,
XTAL_32K_BOOTSTRAP_DRES_VAL, XTAL_32K_BOOTSTRAP_DBIAS_VAL);
}