[SOLVED] Raspberry Pi transmits corrupted data

Raspberry Pi transmits corrupted data

I have a Raspberry Pi Zero trying to read GPS data.

With this command:

sudo cat /dev/ttyAMA0

I get the following correct data:

$GPGSV,1,1,0*49
$GPRMC,,V,,,,,,,,,,N*53
$GPVTG,,,,,,,,,N*30
$GPGGA,,,,,,0,00,99.99,,,,,,*48
$GPGLL,,,,,,V,N*64
$GPGSA,A,1,,,,,,,,,,,,,99.99,99.99,99.99*30

But in the Python script:

import serial
import time
import string

while True:
    port="/dev/ttyAMA0"
    ser=serial.Serial(port, baudrate=9600, timeout=0.5)
    newdata=ser.readline().strip().decode('UTF-8')
    print(newdata)

the data is corrupted:

GPGSA,A,1,,,,,,,,,,,,,99.99,99.99,99.99*30
SV,1,1,0*49
RMC,,V,,,,,,,,,,N*53
PVTG,,,,,,,,,N*30
,,,,,,0,00,99.99,,,,,,*48
L,,,,,,V,N*64

I've spent two days trying to figure out what went wrong with no success. Any tip is much appreciated.

(RaspberryPi OS Lite didn't have serial preinstalled, so I installed it like this:)

sudo apt-get install python-serial

Solution

You are recreating and reinitialising your serial port in every iteration through the loop. You should do that outside the loop as that is loop-invariant:

# Set up serial interface
port="/dev/ttyAMA0"
ser=serial.Serial(port, baudrate=9600, timeout=0.5)

while True:
    # read next line
    newdata = ser.readline().strip().decode('UTF-8')