From fca8f5db4d521d8805777a782f9d2b0285f61a28 Mon Sep 17 00:00:00 2001
From: Aleksei <t79217777329@yandex.ru>
Date: Sat, 19 Feb 2022 20:44:43 +0300
Subject: [PATCH] duty_cycle bug fixed

fixed duty-cycle bug: you cant set frequency, if old duty-cycle value is not valid for new frequency

changed duty-cycle logic: now duty cycle in range in float 0.0 .. 1.0 and recalculates, depending of the frequency

class attributes are private now

the sysPWM class has constructor with  frequency argument. I could not find a case, when I need an instance without frequency.
---
 syspwm.py | 118 +++++++++++++++++++++++++++++-------------------------
 1 file changed, 63 insertions(+), 55 deletions(-)

diff --git a/syspwm.py b/syspwm.py
index 2272681..8ce49d5 100644
--- a/syspwm.py
+++ b/syspwm.py
@@ -22,61 +22,69 @@ class SysPWMException(Exception):
 # /sys/ pwm interface described here: http://www.jumpnowtek.com/rpi/Using-the-Raspberry-Pi-Hardware-PWM-timers.html
 class SysPWM(object):
 
-	chippath = "/sys/class/pwm/pwmchip0"
-
-	def __init__(self,pwm):
-		self.pwm=pwm
-		self.pwmdir="{chippath}/pwm{pwm}".format(chippath=self.chippath,pwm=self.pwm)
-		if not self.overlay_loaded():
-			raise SysPWMException("Need to add 'dtoverlay=pwm-2chan' to /boot/config.txt and reboot")
-		if not self.export_writable():
-			raise SysPWMException("Need write access to files in '{chippath}'".format(chippath=self.chippath))
-		if not self.pwmX_exists():
-			self.create_pwmX()
-		return
-
-	def overlay_loaded(self):
-		return os.path.isdir(self.chippath)
-
-	def export_writable(self):
-		return os.access("{chippath}/export".format(chippath=self.chippath), os.W_OK)
-
-	def pwmX_exists(self):
-		return os.path.isdir(self.pwmdir)
-
-	def echo(self,m,fil):
-		#print "echo {m} > {fil}".format(m=m,fil=fil)
-		with open(fil,'w') as f:
-			f.write("{m}\n".format(m=m))
-
-	def create_pwmX(self):
-		pwmexport = "{chippath}/export".format(chippath=self.chippath)
-		self.echo(self.pwm,pwmexport)
-
-	def enable(self,disable=False):
-		enable = "{pwmdir}/enable".format(pwmdir=self.pwmdir)
-		num = 1
-		if disable:
-			num = 0
-		self.echo(num,enable)
-
-	def disable(self):
-		return self.enable(disable=True)
-
-	def set_duty_cycle(self,milliseconds):
-		# /sys/ iface, 2ms is 2000000
-		# gpio cmd,    2ms is 200
-		dc = int(milliseconds * 1000000)
-		duty_cycle = "{pwmdir}/duty_cycle".format(pwmdir=self.pwmdir)
-		self.echo(dc,duty_cycle)
-
-	def set_frequency(self,hz):
-		per = (1 / float(hz))
-		per *= 1000    # now in milliseconds
-		per *= 1000000 # now in.. whatever
-		per = int(per)
-		period = "{pwmdir}/period".format(pwmdir=self.pwmdir)
-		self.echo(per,period)
+        __chippath = "/sys/class/pwm/pwmchip0"
+        __pwm = None
+        __pwmdir = None
+        __period_ns = 0
+        __frequency_hz = 0
+        __duty_cycle = 0
+
+        def __init__(self,pwm,frequency):
+                self.__pwm=pwm
+                self.__pwmdir="{chippath}/pwm{pwm}".format(chippath=self.__chippath,pwm=self.__pwm)
+                if not self.overlay_loaded():
+                        raise SysPWMException("Need to add 'dtoverlay=pwm-2chan' to /boot/config.txt and reboot")
+                if not self.export_writable():
+                        raise SysPWMException("Need write access to files in '{chippath}'".format(chippath=self.__chippath))
+                if not self.pwmX_exists():
+                        self.create_pwmX()
+                self.set_frequency(frequency)
+                return
+
+        def overlay_loaded(self):
+                return os.path.isdir(self.__chippath)
+
+        def export_writable(self):
+                return os.access("{chippath}/export".format(chippath=self.__chippath), os.W_OK)
+
+        def pwmX_exists(self):
+                return os.path.isdir(self.__pwmdir)
+
+        def echo(self,m,fil):
+                #print "echo {m} > {fil}".format(m=m,fil=fil)
+                with open(fil,'w') as f:
+                        f.write("{m}\n".format(m=m))
+
+        def create_pwmX(self):
+                pwmexport = "{chippath}/export".format(chippath=self.__chippath)
+                self.echo(self.__pwm,pwmexport)
+
+        def enable(self,disable=False):
+                enable = "{pwmdir}/enable".format(pwmdir=self.__pwmdir)
+                num = 1
+                if disable:
+                        num = 0
+                self.echo(num,enable)
+
+        def disable(self):
+                return self.enable(disable=True)
+
+        def set_duty_cycle(self,duty_cycle):
+                self.__duty_cycle = max(0, min(1, duty_cycle))
+                duty_cycle_ns = int(self.__duty_cycle*self.__period_ns)
+                path = "{pwmdir}/duty_cycle".format(pwmdir=self.__pwmdir)
+                self.echo(duty_cycle_ns, path)
+
+        def set_frequency(self,frequency):
+                old_dc = self.__duty_cycle
+                self.set_duty_cycle(0)
+
+                self.__frequency = int(frequency)
+                self.__period_ns = int((1.0/self.__frequency)*1e9)
+
+                self.set_duty_cycle(old_dc)
+                path = "{pwmdir}/period".format(pwmdir=self.__pwmdir)
+                self.echo(self.__period_ns,path)
 
 if __name__ == "__main__":
 	from time import sleep