import serial,time

s = serial.Serial('/dev/ttyS0')

bm = '01000101'
bitzeit = 0.2

s.setRTS(0)
time.sleep(0.005)
# Startbit
s.setRTS(1)
time.sleep(bitzeit)
# Datenbits
for i in range(8):
    s.setRTS(int(bm[i]))
    time.sleep(bitzeit)
# Stoppbit
s.setRTS(0)
time.sleep(bitzeit)

s.close()