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@@ -1,7 +1,7 @@
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/*
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* softPwm.c:
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* Provide 2 channels of software driven PWM.
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- * Copyright (c) 2012 Gordon Henderson
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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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@@ -28,17 +28,22 @@
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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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+
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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 uS, so a pulse time
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-// of 100 and a range of 100 gives a period of 100 * 100 = 10,000 uS
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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 100uS - this is because the Linux timer calls are just
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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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@@ -46,8 +51,9 @@
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#define PULSE_TIME 100
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-static int marks [MAX_PINS] ;
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-static int range [MAX_PINS] ;
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+static int marks [MAX_PINS] ;
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+static int range [MAX_PINS] ;
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+static pthread_t threads [MAX_PINS] ;
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int newPin = -1 ;
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@@ -106,13 +112,20 @@ void softPwmWrite (int pin, int value)
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/*
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* softPwmCreate:
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- * Create a new PWM thread.
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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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+
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+ if (range [pin] != 0) // Already running on this pin
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+ return -1 ;
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+
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+ if (range <= 0)
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+ return -1 ;
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pinMode (pin, OUTPUT) ;
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digitalWrite (pin, LOW) ;
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@@ -121,10 +134,30 @@ int softPwmCreate (int pin, int initialValue, int pwmRange)
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range [pin] = pwmRange ;
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newPin = pin ;
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- res = piThreadCreate (softPwmThread) ;
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+ res = pthread_create (&myThread, NULL, softPwmThread, NULL) ;
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while (newPin != -1)
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delay (1) ;
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+ threads [pin] = myThread ;
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+
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return res ;
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}
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+
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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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+
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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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