MAVLink Peripherals - Companion Computer

QGroundControl v4.1.4, PX4 Pro v1.12

I simply want to read vehicle GPS values on a Raspberry Pi Python program. Currently have a serial connection from CUAV Telem 2 to RPi UART pins.

I set the following parameters on QGC:

MAV_1_CONFIG: TELEM2
MAV_1_MODE: Onboard
MAV_1_RATE: 80000 B/s
MAV_1_FORWARD: 1
SER_TEL2_BAUD: 921600 8N1

Is there anything else to do on the QGroundControl side?

Then I run a program making a serial connection to mavlink:
mav = mavutil.mavlink_connection(’/dev/ttyS0’)
msg = mav.recv_match(blocking=True)

It doesn’t receive a message. Am I missing anything?