import os.path from os import listdir MAX_PWM_LEVEL = 255 def analog_write(pin, value): """Write to one of the pwm pins. value can be an number between 0 and 255. """ path = '/sys/class/misc/pwmtimer/' ending = 'pwm' + str(pin) pins = listdir(os.path.join(path, 'enable')) if not ending in pins: raise ValueError("Pin not found, PWM only possible on " + " ".join(str(p) for p in pins) + ".") with open(os.path.join(path, 'max_level',ending)) as f: max_value = int(f.read()) if value < 0 or value > MAX_PWM_LEVEL: raise ValueError("value must be between 0 and %s" % MAX_PWM_LEVEL) map_level = ((max_value-1) * value) // MAX_PWM_LEVEL #-1 because if it puts max_value the duty cycle somehow becomes 0 (overflow) #disable -> change level -> enable , as requested by documentation with open(os.path.join(path, 'enable', ending), 'w+') as f: f.write("0\n") with open(os.path.join(path, 'level', ending), 'w+') as f: f.write("%d\n" % map_level) with open(os.path.join(path, 'enable', ending), 'w+') as f: f.write("1\n")