hardware_clocks

Typedefs
typedef void(*	resus_callback_t) (void)
	Resus callback function type. More...

Enumerations
enum	clock_index {   clk_gpout0 = 0 , clk_gpout1 , clk_gpout2 , clk_gpout3 ,   clk_ref , clk_sys , clk_peri , clk_usb ,   clk_adc , clk_rtc , CLK_COUNT }
	Enumeration identifying a hardware clock. More...

Functions
void	clocks_init (void)
	Initialise the clock hardware. More...
bool	clock_configure (enum clock_index clk_index, uint32_t src, uint32_t auxsrc, uint32_t src_freq, uint32_t freq)
	Configure the specified clock. More...
void	clock_stop (enum clock_index clk_index)
	Stop the specified clock. More...
uint32_t	clock_get_hz (enum clock_index clk_index)
	Get the current frequency of the specified clock. More...
uint32_t	frequency_count_khz (uint src)
	Measure a clocks frequency using the Frequency counter. More...
void	clock_set_reported_hz (enum clock_index clk_index, uint hz)
	Set the "current frequency" of the clock as reported by clock_get_hz without actually changing the clock. More...
void	clocks_enable_resus (resus_callback_t resus_callback)
	Enable the resus function. Restarts clk_sys if it is accidentally stopped. More...
void	clock_gpio_init_int_frac (uint gpio, uint src, uint32_t div_int, uint8_t div_frac)
	Output an optionally divided clock to the specified gpio pin. More...
static void	clock_gpio_init (uint gpio, uint src, float div)
	Output an optionally divided clock to the specified gpio pin. More...
bool	clock_configure_gpin (enum clock_index clk_index, uint gpio, uint32_t src_freq, uint32_t freq)
	Configure a clock to come from a gpio input. More...

Detailed Description

Clock Management API

This API provides a high level interface to the clock functions.

The clocks block provides independent clocks to on-chip and external components. It takes inputs from a variety of clock sources allowing the user to trade off performance against cost, board area and power consumption. From these sources it uses multiple clock generators to provide the required clocks. This architecture allows the user flexibility to start and stop clocks independently and to vary some clock frequencies whilst maintaining others at their optimum frequencies

Please refer to the datasheet for more details on the RP2040 clocks.

The clock source depends on which clock you are attempting to configure. The first table below shows main clock sources. If you are not setting the Reference clock or the System clock, or you are specifying that one of those two will be using an auxiliary clock source, then you will need to use one of the entries from the subsequent tables.

Main Clock Sources

Source	Reference Clock	System Clock
ROSC	CLOCKS_CLK_REF_CTRL_SRC_VALUE_ROSC_CLKSRC_PH
Auxiliary	CLOCKS_CLK_REF_CTRL_SRC_VALUE_CLKSRC_CLK_REF_AUX	CLOCKS_CLK_SYS_CTRL_SRC_VALUE_CLKSRC_CLK_SYS_AUX
XOSC	CLOCKS_CLK_REF_CTRL_SRC_VALUE_XOSC_CLKSRC
Reference		CLOCKS_CLK_SYS_CTRL_SRC_VALUE_CLK_REF

Auxiliary Clock Sources

The auxiliary clock sources available for use in the configure function depend on which clock is being configured. The following table describes the available values that can be used. Note that for clk_gpout[x], x can be 0-3.

Aux Source	clk_gpout[x]	clk_ref	clk_sys
System PLL	CLOCKS_CLK_GPOUTx_CTRL_AUXSRC_VALUE_CLKSRC_PLL_SYS		CLOCKS_CLK_SYS_CTRL_AUXSRC_VALUE_CLKSRC_PLL_SYS
GPIO in 0	CLOCKS_CLK_GPOUTx_CTRL_AUXSRC_VALUE_CLKSRC_GPIN0	CLOCKS_CLK_REF_CTRL_AUXSRC_VALUE_CLKSRC_GPIN0	CLOCKS_CLK_SYS_CTRL_AUXSRC_VALUE_CLKSRC_GPIN0
GPIO in 1	CLOCKS_CLK_GPOUTx_CTRL_AUXSRC_VALUE_CLKSRC_GPIN1	CLOCKS_CLK_REF_CTRL_AUXSRC_VALUE_CLKSRC_GPIN1	CLOCKS_CLK_SYS_CTRL_AUXSRC_VALUE_CLKSRC_GPIN1
USB PLL	CLOCKS_CLK_GPOUTx_CTRL_AUXSRC_VALUE_CLKSRC_PLL_USB	CLOCKS_CLK_REF_CTRL_AUXSRC_VALUE_CLKSRC_PLL_USB	CLOCKS_CLK_SYS_CTRL_AUXSRC_VALUE_CLKSRC_PLL_USB
ROSC	CLOCKS_CLK_GPOUTx_CTRL_AUXSRC_VALUE_ROSC_CLKSRC		CLOCKS_CLK_SYS_CTRL_AUXSRC_VALUE_ROSC_CLKSRC
XOSC	CLOCKS_CLK_GPOUTx_CTRL_AUXSRC_VALUE_XOSC_CLKSRC		CLOCKS_CLK_SYS_CTRL_AUXSRC_VALUE_ROSC_CLKSRC
System clock	CLOCKS_CLK_GPOUTx_CTRL_AUXSRC_VALUE_CLK_SYS
USB Clock	CLOCKS_CLK_GPOUTx_CTRL_AUXSRC_VALUE_CLK_USB
ADC clock	CLOCKS_CLK_GPOUTx_CTRL_AUXSRC_VALUE_CLK_ADC
RTC Clock	CLOCKS_CLK_GPOUTx_CTRL_AUXSRC_VALUE_CLK_RTC
Ref clock	CLOCKS_CLK_GPOUTx_CTRL_AUXSRC_VALUE_CLK_REF

Aux Source	clk_peri	clk_usb	clk_adc
System PLL	CLOCKS_CLK_PERI_CTRL_AUXSRC_VALUE_CLKSRC_PLL_SYS	CLOCKS_CLK_USB_CTRL_AUXSRC_VALUE_CLKSRC_PLL_SYS	CLOCKS_CLK_ADC_CTRL_AUXSRC_VALUE_CLKSRC_PLL_SYS
GPIO in 0	CLOCKS_CLK_PERI_CTRL_AUXSRC_VALUE_CLKSRC_GPIN0	CLOCKS_CLK_USB_CTRL_AUXSRC_VALUE_CLKSRC_GPIN0	CLOCKS_CLK_ADC_CTRL_AUXSRC_VALUE_CLKSRC_GPIN0
GPIO in 1	CLOCKS_CLK_PERI_CTRL_AUXSRC_VALUE_CLKSRC_GPIN1	CLOCKS_CLK_USB_CTRL_AUXSRC_VALUE_CLKSRC_GPIN1	CLOCKS_CLK_ADC_CTRL_AUXSRC_VALUE_CLKSRC_GPIN1
USB PLL	CLOCKS_CLK_PERI_CTRL_AUXSRC_VALUE_CLKSRC_PLL_USB	CLOCKS_CLK_USB_CTRL_AUXSRC_VALUE_CLKSRC_PLL_USB	CLOCKS_CLK_ADC_CTRL_AUXSRC_VALUE_CLKSRC_PLL_USB
ROSC	CLOCKS_CLK_PERI_CTRL_AUXSRC_VALUE_ROSC_CLKSRC_PH	CLOCKS_CLK_USB_CTRL_AUXSRC_VALUE_ROSC_CLKSRC_PH	CLOCKS_CLK_ADC_CTRL_AUXSRC_VALUE_ROSC_CLKSRC_PH
XOSC	CLOCKS_CLK_PERI_CTRL_AUXSRC_VALUE_XOSC_CLKSRC	CLOCKS_CLK_USB_CTRL_AUXSRC_VALUE_XOSC_CLKSRC	CLOCKS_CLK_ADC_CTRL_AUXSRC_VALUE_XOSC_CLKSRC
System clock	CLOCKS_CLK_PERI_CTRL_AUXSRC_VALUE_CLK_SYS

Aux Source	clk_rtc
System PLL	CLOCKS_CLK_RTC_CTRL_AUXSRC_VALUE_CLKSRC_PLL_SYS
GPIO in 0	CLOCKS_CLK_RTC_CTRL_AUXSRC_VALUE_CLKSRC_GPIN0
GPIO in 1	CLOCKS_CLK_RTC_CTRL_AUXSRC_VALUE_CLKSRC_GPIN1
USB PLL	CLOCKS_CLK_RTC_CTRL_AUXSRC_VALUE_CLKSRC_PLL_USB
ROSC	CLOCKS_CLK_RTC_CTRL_AUXSRC_VALUE_ROSC_CLKSRC_PH
XOSC	CLOCKS_CLK_RTC_CTRL_AUXSRC_VALUE_XOSC_CLKSRC

Example

 
#include <stdio.h>
#include "pico/stdlib.h"
#include "hardware/pll.h"
#include "hardware/clocks.h"
#include "hardware/structs/pll.h"
#include "hardware/structs/clocks.h"
 
void measure_freqs(void) {
    uint f_pll_sys = frequency_count_khz(CLOCKS_FC0_SRC_VALUE_PLL_SYS_CLKSRC_PRIMARY);
    uint f_pll_usb = frequency_count_khz(CLOCKS_FC0_SRC_VALUE_PLL_USB_CLKSRC_PRIMARY);
    uint f_rosc = frequency_count_khz(CLOCKS_FC0_SRC_VALUE_ROSC_CLKSRC);
    uint f_clk_sys = frequency_count_khz(CLOCKS_FC0_SRC_VALUE_CLK_SYS);
    uint f_clk_peri = frequency_count_khz(CLOCKS_FC0_SRC_VALUE_CLK_PERI);
    uint f_clk_usb = frequency_count_khz(CLOCKS_FC0_SRC_VALUE_CLK_USB);
    uint f_clk_adc = frequency_count_khz(CLOCKS_FC0_SRC_VALUE_CLK_ADC);
    uint f_clk_rtc = frequency_count_khz(CLOCKS_FC0_SRC_VALUE_CLK_RTC);
 
    printf("pll_sys  = %dkHz\n", f_pll_sys);
    printf("pll_usb  = %dkHz\n", f_pll_usb);
    printf("rosc     = %dkHz\n", f_rosc);
    printf("clk_sys  = %dkHz\n", f_clk_sys);
    printf("clk_peri = %dkHz\n", f_clk_peri);
    printf("clk_usb  = %dkHz\n", f_clk_usb);
    printf("clk_adc  = %dkHz\n", f_clk_adc);
    printf("clk_rtc  = %dkHz\n", f_clk_rtc);
 
    // Can't measure clk_ref / xosc as it is the ref
}
 
int main() {
    stdio_init_all();
 
    printf("Hello, world!\n");
 
    measure_freqs();
 
    // Change clk_sys to be 48MHz. The simplest way is to take this from PLL_USB
    // which has a source frequency of 48MHz
    clock_configure(clk_sys,
                    CLOCKS_CLK_SYS_CTRL_SRC_VALUE_CLKSRC_CLK_SYS_AUX,
                    CLOCKS_CLK_SYS_CTRL_AUXSRC_VALUE_CLKSRC_PLL_USB,
                    48 * MHZ,
                    48 * MHZ);
 
    // Turn off PLL sys for good measure
    pll_deinit(pll_sys);
 
    // CLK peri is clocked from clk_sys so need to change clk_peri's freq
    clock_configure(clk_peri,
                    0,
                    CLOCKS_CLK_PERI_CTRL_AUXSRC_VALUE_CLK_SYS,
                    48 * MHZ,
                    48 * MHZ);
 
    // Re init uart now that clk_peri has changed
    stdio_init_all();
 
    measure_freqs();
    printf("Hello, 48MHz");
 
    return 0;
}

Typedef Documentation

resus_callback_t

typedef void(* resus_callback_t) (void)

Resus callback function type.

User provided callback for a resus event (when clk_sys is stopped by the programmer and is restarted for them).

Enumeration Type Documentation

clock_index

enum clock_index

Enumeration identifying a hardware clock.

Enumerator
clk_gpout0	GPIO Muxing 0.
clk_gpout1	GPIO Muxing 1.
clk_gpout2	GPIO Muxing 2.
clk_gpout3	GPIO Muxing 3.
clk_ref	Watchdog and timers reference clock.
clk_sys	Processors, bus fabric, memory, memory mapped registers.
clk_peri	Peripheral clock for UART and SPI.
clk_usb	USB clock.
clk_adc	ADC clock.
clk_rtc	Real time clock.

Function Documentation

clock_configure()

bool clock_configure	(	enum clock_index	clk_index,
		uint32_t	src,
		uint32_t	auxsrc,
		uint32_t	src_freq,
		uint32_t	freq
	)

Configure the specified clock.

See the tables in the description for details on the possible values for clock sources.

Parameters

clk_index	The clock to configure
src	The main clock source, can be 0.
auxsrc	The auxiliary clock source, which depends on which clock is being set. Can be 0
src_freq	Frequency of the input clock source
freq	Requested frequency

clock_configure_gpin()

bool clock_configure_gpin	(	enum clock_index	clk_index,
		uint	gpio,
		uint32_t	src_freq,
		uint32_t	freq
	)

Configure a clock to come from a gpio input.

Parameters

clk_index	The clock to configure
gpio	The GPIO pin to run the clock from. Valid GPIOs are: 20 and 22.
src_freq	Frequency of the input clock source
freq	Requested frequency

clock_get_hz()

uint32_t clock_get_hz

(

enum clock_index

clk_index

)

Get the current frequency of the specified clock.

Parameters

clk_index

Clock

Returns

Clock frequency in Hz

clock_gpio_init()

static void clock_gpio_init ( uint  gpio, uint  src, float  div  )

inlinestatic

Output an optionally divided clock to the specified gpio pin.

Parameters

gpio	The GPIO pin to output the clock to. Valid GPIOs are: 21, 23, 24, 25. These GPIOs are connected to the GPOUT0-3 clock generators.
src	The source clock. See the register field CLOCKS_CLK_GPOUT0_CTRL_AUXSRC for a full list. The list is the same for each GPOUT clock generator.
div	The float amount to divide the source clock by. This is useful to not overwhelm the GPIO pin with a fast clock.

clock_gpio_init_int_frac()

void clock_gpio_init_int_frac	(	uint	gpio,
		uint	src,
		uint32_t	div_int,
		uint8_t	div_frac
	)

Output an optionally divided clock to the specified gpio pin.

Parameters

gpio	The GPIO pin to output the clock to. Valid GPIOs are: 21, 23, 24, 25. These GPIOs are connected to the GPOUT0-3 clock generators.
src	The source clock. See the register field CLOCKS_CLK_GPOUT0_CTRL_AUXSRC for a full list. The list is the same for each GPOUT clock generator.
div_int	The integer part of the value to divide the source clock by. This is useful to not overwhelm the GPIO pin with a fast clock. this is in range of 1..2^24-1.
div_frac	The fractional part of the value to divide the source clock by. This is in range of 0..255 (/256).

clock_set_reported_hz()

void clock_set_reported_hz	(	enum clock_index	clk_index,
		uint	hz
	)

Set the "current frequency" of the clock as reported by clock_get_hz without actually changing the clock.

See also

clock_get_hz()

clock_stop()

void clock_stop

(

enum clock_index

clk_index

)

Stop the specified clock.

Parameters

clk_index

The clock to stop

clocks_enable_resus()

void clocks_enable_resus

(

resus_callback_t

resus_callback

)

Enable the resus function. Restarts clk_sys if it is accidentally stopped.

The resuscitate function will restart the system clock if it falls below a certain speed (or stops). This could happen if the clock source the system clock is running from stops. For example if a PLL is stopped.

Parameters

resus_callback

a function pointer provided by the user to call if a resus event happens.

clocks_init()

void clocks_init

(

void

)

Initialise the clock hardware.

Must be called before any other clock function.

frequency_count_khz()

uint32_t frequency_count_khz

(

uint

src

)

Measure a clocks frequency using the Frequency counter.

Uses the inbuilt frequency counter to measure the specified clocks frequency. Currently, this function is accurate to +-1KHz. See the datasheet for more details.