Make CPU speed configurable when running program

sipsi-8.py

@@ -705,7 +705,7 @@ def initialize_keyboard():
 	waiting_for_keypress = False
 	keypress_arrived = False
 
-def initialize_cpu():
+def initialize_cpu(clockspeed):
 	global cpu_clock, data_registers, ip, stack, i_register
 	data_registers = [0] * 16
 
@@ -718,10 +718,7 @@ def initialize_cpu():
 
 	i_register = 0
 
-	# TODO: Don't hardcode the update speed
-	# Run the interpreter at 500Hz
-	# This was picked from https://github.com/AfBu/haxe-CHIP-8-emulator/wiki/(Super)CHIP-8-Secrets
-	cpu_clock = 500
+	cpu_clock = clockspeed
 
 def load_program(f):
 	global ram
@@ -733,6 +730,19 @@ def load_program(f):
 def main():
 	global window
 	global cpu_cycles_to_go, frames_to_go
+
+	if len(sys.argv) == 2:
+		program_path = sys.argv[1]
+		# Run the interpreter at 500Hz by default
+		# This was picked from https://github.com/AfBu/haxe-CHIP-8-emulator/wiki/(Super)CHIP-8-Secrets
+		cpu_clock = 500
+	elif len(sys.argv) == 3:
+		program_path = sys.argv[1]
+		cpu_clock = int(sys.argv[2])
+	else:
+		print(f'Usage: {sys.argv[0]} program [cpu-speed]', file=sys.stderr)
+		sys.exit(1)
+
 	# TODO: Don't hardcode the size
 	window = pyglet.window.Window(640, 320, resizable = True)
 
@@ -760,10 +770,10 @@ def main():
 	initialize_screen()
 	initialize_timers()
 	initialize_keyboard()
-	initialize_cpu()
+	initialize_cpu(cpu_clock)
 
 	# TODO: Deal with missing file gracefully
-	with open(sys.argv[1], 'rb') as f:
+	with open(program_path, 'rb') as f:
 		load_program(f)
 
 	cpu_cycles_to_go = 0