#!/usr/bin/python
import sys
import tty
import serial
import time

ser = serial.Serial("/dev/ttyUSB0", 38400)

power = 0
incdec = 0

while 1:
	tdata = ser.read()

	if tdata == 'a':
		print power
		ser.write(str(power) + '\x0d')
		#ser.write('100\n')
		ser.flush()

		if incdec == 0:
			power = power + 10
		else:
			power = power - 10
		
		if power > 400:
			power = 400
			incdec = 1
		
		if power < 0:
			power = 0
			incdec = 0
	#else:
		#data_left = ser.inWaiting()
		#tdata += ser.read(data_left)
		#print tdata