X-Git-Url: https://defiant.homedns.org/gitweb/?a=blobdiff_plain;f=bus_pirate.py;h=cdd259fa7581ee42dba23da879fbf10b3aa4d287;hb=c9dbcc66879f0e1d8beb05b49179fcb200ef8cf0;hp=4ef9c61d4eacf79612be535156477e553b4d770b;hpb=6af0c706c1dd1b0ae4cbc38adf1f056a8686aae4;p=pyshared.git

diff --git a/bus_pirate.py b/bus_pirate.py
index 4ef9c61..cdd259f 100644
--- a/bus_pirate.py
+++ b/bus_pirate.py
@@ -64,6 +64,29 @@ class BP:
 		v = struct.unpack(">h", s)
 		return v[0]/1024.0*6.6
 
+	# http://codepad.org/qtYpZmIF
+	def pwm(self, freq, duty_cycle_percent):
+		lPrescaler = {0:1, 1:8 , 2:64, 3:256}
+		Fosc = 32e6
+		Tcy = 2.0 / Fosc
+		period = 1.0 / freq
+		prescaler = 1
+
+		# find needed prescaler
+		for i in range(4):
+			prescaler = lPrescaler[i]
+			PRy = period * 1.0 / (Tcy * prescaler)
+			PRy = int(PRy - 1)
+			OCR = int(PRy * duty_cycle_percent)
+
+			if PRy < (2 ** 16 - 1):
+				break # valid value for PRy, keep values
+
+		cmd = struct.pack(">BBHH", 0b00010010, i, OCR, PRy)
+		ret = self.command(cmd, 1)
+		if ord(ret) != 0x1:
+			raise Exception()
+
 	def spi_command(self, cmd):
 		ret = self.command(cmd, 1)
 		if ord(ret) != 0x1: