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pwm.c
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pwm.c
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/*
* This file is part of the MicroPython project, http://micropython.org/
*
* The MIT License (MIT)
*
* Copyright (c) 2016 Mark Shannon
* Copyright (c) 2017 Damien P. George
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "stddef.h"
#include "lib/ticker.h"
#include "nrf_gpio.h"
#include "py/runtime.h"
#include "py/gc.h"
#define PWM_TICKER_INDEX 2
// The maximum number of pins that can have PWM at once, plus 1 for OFF_EVENT
#define PWM_MAX_PINS (20)
// Default period of 20ms
#define DEFAULT_PERIOD ((20*1000)/MICROSECONDS_PER_TICK)
typedef struct _pwm_event {
uint16_t time : 11;
uint16_t pin : 5;
} pwm_event;
typedef struct _pwm_events {
uint8_t count;
uint16_t period;
uint32_t all_pins;
pwm_event events[PWM_MAX_PINS];
} pwm_events;
static const pwm_events OFF_EVENTS = {
.count = 1,
.period = DEFAULT_PERIOD,
.all_pins = 0,
.events = {
{
.time = 1024,
.pin = 31,
}
}
};
// Data in RAM to hold the PWM events, double buffered
static pwm_events pwm_events_buf0;
static pwm_events pwm_events_buf1;
// Pointers to active and pending event buffers
static const pwm_events *active_events;
static const pwm_events *pending_events;
// Index inte the events array of the active_events buffer
static uint8_t next_event;
void pwm_init(void) {
active_events = &OFF_EVENTS;
pending_events = NULL;
next_event = 0;
}
static inline int32_t pwm_get_period_ticks(void) {
const pwm_events *tmp = pending_events;
if (tmp == NULL)
tmp = active_events;
return tmp->period;
}
#if 0
void pwm_dump_events(const pwm_events *events) {
printf("Count %d, period %d, all pins %d\r\n", events->count, events->period, events->all_pins);
for (uint32_t i = 0; i < events->count; i++) {
const pwm_event *event = &events->events[i];
printf("Event. pin: %d, duty cycle: %d\r\n", event->pin, event->time);
}
}
void pwm_dump_state(void) {
while(pending_events);
pwm_dump_events(active_events);
}
#endif
static pwm_events *get_pending_for_update(void) {
// Atomically take the pending events
__disable_irq();
const pwm_events *orig = pending_events;
pending_events = NULL;
__enable_irq();
// If the pending events were not NULL then they can be now used for update
if (orig != NULL) {
return (pwm_events*)orig; // Will be one of buf0 or buf1, in RAM
}
// Pending events were NULL so make a copy of active ones and return them
orig = active_events;
pwm_events *events;
if (orig == &pwm_events_buf0) {
events = &pwm_events_buf1;
} else {
events = &pwm_events_buf0;
}
events->count = orig->count;
events->period = orig->period;
events->all_pins = orig->all_pins;
for (uint32_t i = 0; i < orig->count; i++) {
events->events[i] = orig->events[i];
}
return events;
}
static int find_pin_in_events(const pwm_events *events, uint32_t pin) {
for (int i = 0; i < events->count; i++) {
if (events->events[i].pin == pin)
return i;
}
return -1;
}
static void sort_events(pwm_events *events) {
// Insertion sort
for (int32_t i = 1; i < events->count; i++) {
pwm_event x = events->events[i];
int32_t j;
for (j = i - 1; j >= 0 && events->events[j].time > x.time; j--) {
events->events[j+1] = events->events[j];
}
events->events[j+1] = x;
}
}
int32_t pwm_callback(void) {
int32_t tdiff;
const pwm_events *events = active_events;
const pwm_event *event = &events->events[next_event];
int32_t tnow = (event->time*events->period)>>10;
do {
if (event->pin < 31) {
// Event is to turn on a specific pin
nrf_gpio_pin_set(event->pin);
next_event++;
} else {
// Event is to turn off all pins and start period again
nrf_gpio_pins_clear(events->all_pins);
next_event = 0;
tnow = 0;
if (pending_events) {
events = pending_events;
active_events = events;
pending_events = NULL;
}
}
event = &events->events[next_event];
tdiff = ((event->time*events->period)>>10) - tnow;
} while (tdiff == 0);
return tdiff;
}
void pwm_start(void) {
set_ticker_callback(PWM_TICKER_INDEX, pwm_callback, 120);
}
void pwm_stop(void) {
clear_ticker_callback(PWM_TICKER_INDEX);
}
static void pwm_set_period_ticks(int32_t ticks) {
pwm_events *events = get_pending_for_update();
events->period = ticks;
pending_events = events;
}
int pwm_set_period_us(int32_t us) {
if ((us < 256) ||
(us > 1000000)) {
return -1;
}
pwm_set_period_ticks(us/MICROSECONDS_PER_TICK);
return 0;
}
int32_t pwm_get_period_us(void) {
return pwm_get_period_ticks()*MICROSECONDS_PER_TICK;
}
void pwm_set_duty_cycle(int32_t pin, uint32_t value) {
if (value >= (1<<10)) {
value = (1<<10)-1;
}
uint32_t turn_on_time = 1024-value;
pwm_events *events = get_pending_for_update();
// If pin is not already in PWM list then set its GPIO as output
if (((1 << pin) & events->all_pins) == 0) {
nrf_gpio_cfg_output(pin);
}
int ev = find_pin_in_events(events, pin);
if (ev < 0 && value == 0) {
// Pin not in PWM mode and set to 0 duty, so nothing to do
pending_events = events;
return;
} else if (ev < 0) {
// Pin not in PWM mode, so add it to the list
if (events->count >= PWM_MAX_PINS) {
// No more room left for another PWM, so must ignore this pin!
pending_events = events;
return;
}
events->all_pins |= 1 << pin;
events->events[events->count].time = turn_on_time;
events->events[events->count].pin = pin;
events->count += 1;
} else if (value == 0) {
// Pin in PWM mode and set to 0 duty, so remove it from the list
events->count -= 1;
events->all_pins &= ~(1 << pin);
if (ev < events->count) {
events->events[ev] = events->events[events->count];
}
} else {
// Pin in PWM mode, change duty cycle
events->events[ev].time = turn_on_time;
}
sort_events(events);
pending_events = events;
}
void pwm_release(int32_t pin) {
pwm_set_duty_cycle(pin, 0);
const pwm_events *ev = active_events;
int i = find_pin_in_events(ev, pin);
if (i < 0)
return;
// If i >= 0 it means that `ev` is in RAM, so it safe to discard the const qualifier
((pwm_events *)ev)->events[i].pin = 31;
nrf_gpio_pin_clear(pin);
}