stm_timers.h File Reference

To be used with the timer peripherals on STM32 microcontrollers. More...

#include <libopencm3/stm32/gpio.h>
#include <libopencm3/stm32/timer.h>
#include <stdint.h>

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Macros
#define	setup_timer_periodic_output_pulse(timer, prescale, period, pulse_length, output, gpio_port, gpio_pin, gpio_af)
	Initialize a timer to output a periodic pulse on an output pin.
#define	setup_timer_capture_pwm_input(timer, prescale, max_timer_counts, input, gpio_port, gpio_pin, gpio_af)
	Initialize a timer to capture periodic pulses on an input pin.

Detailed Description

To be used with the timer peripherals on STM32 microcontrollers.

Definition in file stm_timers.h.

Macro Definition Documentation

setup_timer_capture_pwm_input

#define setup_timer_capture_pwm_input	(		timer,
			prescale,
			max_timer_counts,
			input,
			gpio_port,
			gpio_pin,
			gpio_af )

Value:

  gpio_mode_setup(gpio_port, GPIO_MODE_AF, GPIO_PUPD_NONE, gpio_pin);          \
  gpio_set_af(gpio_port, gpio_af, gpio_pin);                                   \
  timer_set_mode(timer, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP); \
  timer_ic_set_input(timer, TIM_IC1, input);                                   \
  timer_ic_set_polarity(timer, TIM_IC1, TIM_IC_RISING);                        \
  timer_ic_set_input(timer, TIM_IC2, input);                                   \
  timer_ic_set_polarity(timer, TIM_IC2, TIM_IC_FALLING);                       \
  timer_slave_set_trigger(timer, TIM_SMCR_TS_TI1FP1);                          \
  timer_slave_set_mode(timer, TIM_SMCR_SMS_RM);                                \
  timer_ic_enable(timer, TIM_IC1);                                             \
  timer_ic_enable(timer, TIM_IC2);                                             \
  TIM_PSC(timer) = prescale;                                                   \
  TIM_ARR(timer) = max_timer_counts

Initialize a timer to capture periodic pulses on an input pin.

This really just sets up a timer for PWM input capture

Usage

The pulse period should be available in TIM_CCR1(<timer>) in timer ticks

The pulse length should be available in TIM_CCR2(<timer>) in timer ticks

So duty cycle is TIM_CCR2(<timer>) / TIM_CCR1(<timer>)

Polling: bool flag = timer_get_flag(<timer>,TIM_SR_CC1IF);, if true read out TIM_CCR2(<timer>) and TIM_CCR1(<timer>), then check the overcapture bits: timer_get_flag(<timer>,TIM_SR_CC1OF) && timer_get_flag(<timer>,TIM_SR_CC2OF).

Interrupt: Setup the interrupt on CC1: timer_enable_irq(<timer>,TIM_DIER_CC1IE), then in the handler read out both CCRs and then check the overcapture bits: timer_get_flag(<timer>,TIM_SR_CC1OF) && timer_get_flag(<timer>,TIM_SR_CC2OF)

DMA: ?

If overcapture happens, you have to clear the flag with timer_clear_flag(<timer>,TIM_SR_CC1OF) or timer_clear_flag(<timer>,TIM_SR_CC2OF).

Notes

The user must setup the peripheral clocks for both this timer and the input port.

The user must enable the counter when ready with: timer_enable_counter(<timer>);

Uses input compare channels 1 and 2, so timer must have 2 IC units!

This macro takes care of setting up the GPIO pin.

Sets timer in: upcount, edge-aligned, not one-pulse mode, using the un-divided peripheral clock as input to the prescaler. This should be available on all general-purpose timers.

Registers Relevant to Ascii-Serial-Com

TIM_PSC(<timer>): which should be set to the prescaler value in peripheral clock ticks

TIM_CCR1(<timer>): read the pulse period in timer ticks

TIM_CCR2(<timer>): read the pulse length in timer ticks

Parameters

timer: the timer you want to use like TIM2

prescale: the number of peripher clock ticks between timer ticks, uint32_t (but only ever 16 bit)

max_timer_counts: you probably want 0xFFFF for 16 bit counters and 0xFFFFFFFF for 32 bit ones.

input: which input compare input: TIM_IC_IN_TI1, TIM_IC_IN_TI2, TIM_IC_IN_TI3 or TIM_IC_IN_TI4 (don't quote; some not avaiable on all timers)

gpio_port: GPIOA, GPIOB, ... (must match input)

gpio_pin: GPIO0, GPIO1, ... (must match input)

gpio_af: alternate function for the given pin/port and input, e.g. GPIO_AF0, GPIO_AF1, ...

Definition at line 156 of file stm_timers.h.

setup_timer_periodic_output_pulse

#define setup_timer_periodic_output_pulse	(		timer,
			prescale,
			period,
			pulse_length,
			output,
			gpio_port,
			gpio_pin,
			gpio_af )

Value:

  gpio_mode_setup(gpio_port, GPIO_MODE_AF, GPIO_PUPD_NONE, gpio_pin);          \
  gpio_set_output_options(gpio_port, GPIO_OTYPE_PP, GPIO_OSPEED_HIGH,          \
                          gpio_pin);                                           \
  gpio_set_af(gpio_port, gpio_af, gpio_pin);                                   \
  timer_set_mode(timer, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP); \
  timer_set_oc_mode(timer, output, TIM_OCM_PWM1);                              \
  timer_enable_oc_output(timer, output);                                       \
  TIM_PSC(timer) = prescale;                                                   \
  TIM_ARR(timer) = period;                                                     \
  TIM_CCR1(timer) = pulse_length

Initialize a timer to output a periodic pulse on an output pin.

This really just sets up a timer in edge-aligned PWM mode.

Notes

The user must setup the peripheral clocks for both this timer and the output port.

The user must enable the counter when ready with: timer_enable_counter(<timer>);

This macro takes care of setting up the GPIO pin.

Uses output compare unit 1 on the timer. Make sure this is available on the timer.

Sets timer in: upcount, edge-aligned, not one-pulse mode, using the un-divided peripheral clock as input to the prescaler. This should be available on all general-purpose timers.

Registers Relevant to Ascii-Serial-Com

TIM_ARR(<timer>): which should be set to period in timer ticks

TIM_CCR1(<timer>): which should be set to pulse_length in timer ticks

TIM_PSC(<timer>): which should be set to the prescaler value in peripheral clock ticks

Parameters

timer: the timer you want to use like TIM2

prescale: the number of peripher clock ticks between timer ticks, uint32_t (but only ever 16 bit)

period: The number of timer ticks between pulse rising edges, uint32_t

pulse_length: length of pulse in timer ticks, uint32_t

output: the output compare output to use: TIM_OC1, TIM_OC2, TIM_OC3, TIM_OC4 (availability depends on timer)

gpio_port: GPIOA, GPIOB, ... (must match output)

gpio_pin: GPIO0, GPIO1, ... (must match output)

gpio_af: alternate function for the given pin/port and output, e.g. GPIO_AF0, GPIO_AF1, ...

Definition at line 66 of file stm_timers.h.