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esp32: add support for 8MD256 and external 32k as slow clock options

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This commit is contained in:
Ivan Grokhotkov 2018-08-13 01:12:01 +03:00
parent 5bf3654637
commit 96971e3e9f
2 changed files with 57 additions and 10 deletions
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23
components/esp32/Kconfig
View file

@ -683,18 +683,39 @@ choice ESP32_RTC_CLOCK_SOURCE
default ESP32_RTC_CLOCK_SOURCE_INTERNAL_RC
help
Choose which clock is used as RTC clock source.
- "Internal 150kHz oscillator" option provides lowest deep sleep current
consumption, and does not require extra external components. However
frequency stability with respect to temperature is poor, so time may
drift in deep/light sleep modes.
- "External 32kHz crystal" provides better frequency stability, at the
expense of slightly higher (1uA) deep sleep current consumption.
- "External 32kHz oscillator" allows using 32kHz clock generated by an
external circuit. In this case, external clock signal must be connected
to 32K_XP pin. Amplitude should be <1.2V in case of sine wave signal,
and <1V in case of square wave signal. Common mode voltage should be
0.1 < Vcm < 0.5Vamp, where Vamp is the signal amplitude.
Additionally, 1nF capacitor must be connected between 32K_XN pin and
ground. 32K_XN pin can not be used as a GPIO in this case.
- "Internal 8.5MHz oscillator divided by 256" option results in higher
deep sleep current (by 5uA) but has better frequency stability than
the internal 150kHz oscillator. It does not require external components.
config ESP32_RTC_CLOCK_SOURCE_INTERNAL_RC
bool "Internal 150kHz RC oscillator"
config ESP32_RTC_CLOCK_SOURCE_EXTERNAL_CRYSTAL
bool "External 32kHz crystal"
config ESP32_RTC_CLOCK_SOURCE_EXTERNAL_OSC
bool "External 32kHz oscillator at 32K_XP pin"
config ESP32_RTC_CLOCK_SOURCE_INTERNAL_8MD256
bool "Internal 8.5MHz oscillator, divided by 256 (~33kHz)"
endchoice
config ESP32_RTC_CLK_CAL_CYCLES
int "Number of cycles for RTC_SLOW_CLK calibration"
default 3000 if ESP32_RTC_CLOCK_SOURCE_EXTERNAL_CRYSTAL
default 1024 if ESP32_RTC_CLOCK_SOURCE_INTERNAL_RC
range 0 27000 if ESP32_RTC_CLOCK_SOURCE_EXTERNAL_CRYSTAL
range 0 27000 if ESP32_RTC_CLOCK_SOURCE_EXTERNAL_CRYSTAL || ESP32_RTC_CLOCK_SOURCE_EXTERNAL_OSC || ESP32_RTC_CLOCK_SOURCE_INTERNAL_8MD256
range 0 32766 if ESP32_RTC_CLOCK_SOURCE_INTERNAL_RC
help
When the startup code initializes RTC_SLOW_CLK, it can perform

44
components/esp32/clk.c
View file

@ -40,7 +40,23 @@
#define MHZ (1000000)
static void select_rtc_slow_clk(rtc_slow_freq_t slow_clk);
/* Indicates that this 32k oscillator gets input from external oscillator, rather
* than a crystal.
*/
#define EXT_OSC_FLAG BIT(3)
/* This is almost the same as rtc_slow_freq_t, except that we define
* an extra enum member for the external 32k oscillator.
* For convenience, lower 2 bits should correspond to rtc_slow_freq_t values.
*/
typedef enum {
SLOW_CLK_150K = RTC_SLOW_FREQ_RTC, //!< Internal 150 kHz RC oscillator
SLOW_CLK_32K_XTAL = RTC_SLOW_FREQ_32K_XTAL, //!< External 32 kHz XTAL
SLOW_CLK_8MD256 = RTC_SLOW_FREQ_8MD256, //!< Internal 8 MHz RC oscillator, divided by 256
SLOW_CLK_32K_EXT_OSC = RTC_SLOW_FREQ_32K_XTAL | EXT_OSC_FLAG //!< External 32k oscillator connected to 32K_XP pin
} slow_clk_sel_t;
static void select_rtc_slow_clk(slow_clk_sel_t slow_clk);
// g_ticks_us defined in ROMs for PRO and APP CPU
extern uint32_t g_ticks_per_us_pro;
@ -71,8 +87,12 @@ void esp_clk_init(void)
rtc_clk_fast_freq_set(RTC_FAST_FREQ_8M);
#ifdef CONFIG_ESP32_RTC_CLOCK_SOURCE_EXTERNAL_CRYSTAL
select_rtc_slow_clk(RTC_SLOW_FREQ_32K_XTAL);
#if defined(CONFIG_ESP32_RTC_CLOCK_SOURCE_EXTERNAL_CRYSTAL)
select_rtc_slow_clk(SLOW_CLK_32K_XTAL);
#elif defined(CONFIG_ESP32_RTC_CLOCK_SOURCE_EXTERNAL_OSC)
select_rtc_slow_clk(SLOW_CLK_32K_EXT_OSC);
#elif defined(CONFIG_ESP32_RTC_CLOCK_SOURCE_INTERNAL_8MD256)
select_rtc_slow_clk(SLOW_CLK_8MD256);
#else
select_rtc_slow_clk(RTC_SLOW_FREQ_RTC);
#endif
@ -117,12 +137,12 @@ void IRAM_ATTR ets_update_cpu_frequency(uint32_t ticks_per_us)
g_ticks_per_us_app = ticks_per_us;
}
static void select_rtc_slow_clk(rtc_slow_freq_t slow_clk)
static void select_rtc_slow_clk(slow_clk_sel_t slow_clk)
{
rtc_slow_freq_t rtc_slow_freq = slow_clk & RTC_CNTL_ANA_CLK_RTC_SEL_V;
uint32_t cal_val = 0;
uint32_t freq_hz = ((slow_clk == RTC_SLOW_FREQ_32K_XTAL) ? 32768 : 150000);
do {
if (slow_clk == RTC_SLOW_FREQ_32K_XTAL) {
if (rtc_slow_freq == RTC_SLOW_FREQ_32K_XTAL) {
/* 32k XTAL oscillator needs to be enabled and running before it can
* be used. Hardware doesn't have a direct way of checking if the
* oscillator is running. Here we use rtc_clk_cal function to count
@ -131,17 +151,23 @@ static void select_rtc_slow_clk(rtc_slow_freq_t slow_clk)
* will time out, returning 0.
*/
ESP_EARLY_LOGD(TAG, "waiting for 32k oscillator to start up");
rtc_clk_32k_enable(true);
if (slow_clk == SLOW_CLK_32K_XTAL) {
rtc_clk_32k_enable(true);
} else if (slow_clk == SLOW_CLK_32K_EXT_OSC) {
rtc_clk_32k_enable_external();
}
// When SLOW_CLK_CAL_CYCLES is set to 0, clock calibration will not be performed at startup.
if (SLOW_CLK_CAL_CYCLES > 0) {
cal_val = rtc_clk_cal(RTC_CAL_32K_XTAL, SLOW_CLK_CAL_CYCLES);
if (cal_val == 0 || cal_val < 15000000L) {
slow_clk = RTC_SLOW_FREQ_RTC;
ESP_EARLY_LOGW(TAG, "32 kHz XTAL not found, switching to internal 150 kHz oscillator");
rtc_slow_freq = RTC_SLOW_FREQ_RTC;
}
}
} else if (rtc_slow_freq == RTC_SLOW_FREQ_8MD256) {
rtc_clk_8m_enable(true, true);
}
rtc_clk_slow_freq_set(slow_clk);
rtc_clk_slow_freq_set(rtc_slow_freq);
if (SLOW_CLK_CAL_CYCLES > 0) {
/* TODO: 32k XTAL oscillator has some frequency drift at startup.