mirror of
https://github.com/clockworkpi/WiringPi.git
synced 2025-12-12 16:08:49 +01:00
b1dfc186ef
for kernels 4.8 onwards. Some very old stuff might break. Additional fixes for the ISR code and some tweaks here and there. I've removed the checks for some operations that might fail when using the gpiomem interface - which is now the default way of doing things - if your program segfaults, then you may need to use sudo on it.
177 lines
4.4 KiB
C
177 lines
4.4 KiB
C
/*
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* softPwm.c:
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* Provide 2 channels of software driven PWM.
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* Copyright (c) 2012-2014 Gordon Henderson
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***********************************************************************
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* This file is part of wiringPi:
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* https://projects.drogon.net/raspberry-pi/wiringpi/
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*
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* wiringPi is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as
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* published by the Free Software Foundation, either version 3 of the
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* License, or (at your option) any later version.
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*
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* wiringPi is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with wiringPi.
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* If not, see <http://www.gnu.org/licenses/>.
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***********************************************************************
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*/
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#include <stdio.h>
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#include <malloc.h>
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#include <pthread.h>
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#include "wiringPi.h"
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#include "softPwm.h"
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// MAX_PINS:
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// This is more than the number of Pi pins because we can actually softPwm
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// pins that are on GPIO expanders. It's not that efficient and more than 1 or
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// 2 pins on e.g. (SPI) mcp23s17 won't really be that effective, however...
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#define MAX_PINS 1024
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// The PWM Frequency is derived from the "pulse time" below. Essentially,
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// the frequency is a function of the range and this pulse time.
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// The total period will be range * pulse time in µS, so a pulse time
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// of 100 and a range of 100 gives a period of 100 * 100 = 10,000 µS
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// which is a frequency of 100Hz.
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//
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// It's possible to get a higher frequency by lowering the pulse time,
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// however CPU uage will skyrocket as wiringPi uses a hard-loop to time
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// periods under 100µS - this is because the Linux timer calls are just
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// accurate at all, and have an overhead.
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//
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// Another way to increase the frequency is to reduce the range - however
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// that reduces the overall output accuracy...
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#define PULSE_TIME 100
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static volatile int marks [MAX_PINS] ;
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static volatile int range [MAX_PINS] ;
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static volatile pthread_t threads [MAX_PINS] ;
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static volatile int newPin = -1 ;
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/*
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* softPwmThread:
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* Thread to do the actual PWM output
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*********************************************************************************
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*/
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static void *softPwmThread (void *arg)
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{
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int pin, mark, space ;
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struct sched_param param ;
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param.sched_priority = sched_get_priority_max (SCHED_RR) ;
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pthread_setschedparam (pthread_self (), SCHED_RR, ¶m) ;
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pin = *((int *)arg) ;
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free (arg) ;
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pin = newPin ;
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newPin = -1 ;
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piHiPri (90) ;
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for (;;)
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{
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mark = marks [pin] ;
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space = range [pin] - mark ;
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if (mark != 0)
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digitalWrite (pin, HIGH) ;
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delayMicroseconds (mark * 100) ;
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if (space != 0)
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digitalWrite (pin, LOW) ;
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delayMicroseconds (space * 100) ;
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}
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return NULL ;
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}
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/*
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* softPwmWrite:
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* Write a PWM value to the given pin
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*********************************************************************************
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*/
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void softPwmWrite (int pin, int value)
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{
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pin &= (MAX_PINS - 1) ;
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/**/ if (value < 0)
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value = 0 ;
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else if (value > range [pin])
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value = range [pin] ;
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marks [pin] = value ;
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}
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/*
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* softPwmCreate:
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* Create a new softPWM thread.
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*********************************************************************************
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*/
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int softPwmCreate (int pin, int initialValue, int pwmRange)
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{
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int res ;
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pthread_t myThread ;
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int *passPin ;
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if (range [pin] != 0) // Already running on this pin
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return -1 ;
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if (pwmRange <= 0)
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return -1 ;
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passPin = malloc (sizeof (*passPin)) ;
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if (passPin == NULL)
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return -1 ;
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pinMode (pin, OUTPUT) ;
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digitalWrite (pin, LOW) ;
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marks [pin] = initialValue ;
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range [pin] = pwmRange ;
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*passPin = pin ;
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newPin = pin ;
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res = pthread_create (&myThread, NULL, softPwmThread, (void *)passPin) ;
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while (newPin != -1)
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delay (1) ;
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threads [pin] = myThread ;
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return res ;
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}
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/*
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* softPwmStop:
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* Stop an existing softPWM thread
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*********************************************************************************
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*/
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void softPwmStop (int pin)
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{
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if (range [pin] != 0)
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{
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pthread_cancel (threads [pin]) ;
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pthread_join (threads [pin], NULL) ;
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range [pin] = 0 ;
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digitalWrite (pin, LOW) ;
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}
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}
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