Question

How can Rpi GPSD python talk to the QueCte L80-R GPS Module?

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Answer

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Short Answer

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Long Answer

Contents

1. Part A – Setting up the module and trying a get a fix
2. Part B – Checking out serial hardware /dev/ttyS0 and /dev/ttyUSB0
3. Part C – Installing GPSD and testing utilities gpsmon, cgps, and xgps
4. Part D – Installing GPS Python library and testing programs
5. Part E – Discussion and recommendation

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Part A – Setting up the GPS module and trying to get a fix

First thing first is to set up the GPS module and try to get a fix (Figures 1 ~ 3).

I placed the antenna about 15cm outside the window and powered up. As usual, the first fix takes about 1 to 2 minutes. The subsequent power off power on fixes takes from 15 sec to 45 sec, with an average of 30 seconds. This fixing timing is similar to last time of 2019may. So I quickly concluded that setup and fixing is reliable.

This is the imgur fixing video.

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And the photo.

Notes:

1. When power is on, blue LED is turned on and steady. When there is a fix, blue LED blinks as shown in the above Imgur video.
2. The serial cable is not connected in this fixing test. Serial cable test is the next step.

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Part B – Checking out the serial cable

I used my serial loopback program v0.99 (Ref 12) to verify that Rpi’s on board Tx/Rx wiring and software are more or less OK.

Next step is to install GPSD.

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Part C – Installing GPSD

I quickly read the Quectel L80RE GPS Module User Guide and follow the instructions there to install the following:

gpsd, gpsd-clients, and python-gps,

and starting running it. Everything was smooth, except a couple of errors during installation. I could enable, start, status without any problem but cgps does not seem to run properly, such as indicating no fix, though there are actually a fix.

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The above installations using CLI terminal commands $sudo apt-get install were not smooth, with a couple of error messages. So I used buster Desktop GUI and installed the similar gpsd and client packages v3.17-7 as shown below:

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References

(1) Quectel L80-R GPS Module User Guide

(2) Quectel L80-R Hardware Design GPS Module Series Rev. L80-R_Hardware_Design_V1.2 Date: 2016-04-22

(3) Quectel L80-R Compact GPS Module Integrated with Patch Antenna

(4) Quectel L80-R Compact GPS module integrated with Patch antenna for Acquisition and tracking – DIYMall US$14

(5) SkyTraq ATK1218-BD (ATK-S1216) GPS/BD dual mode GPS module – Risym ¥98

(6) SkyTraq GPS + Beidou Two-mode positioning module – US$24

(7) SkyTraq Products – SkyTraq

(8) SkyTraq S1216 [renamed S1218-BD] Family GNSS Module Data Sheet – SkyTraq

(9) Serial Port Loopback Test Program V0.60 – tlfong01 2019apr15 Ask Question

(10) Serial LoopBack Program v0.98 -tlfong01 2020jan08

(11) Serial Port Multiple Problem

(12) Serial UART LoopBack Program v0.99 tlfong01 2020jun03hkt1510

(13) Quectel GPS Module User Guide Reading Summary V0.1

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(100) Rpi UART GPSD to GPS Module Connection Problem – Rpi.SE.Q&A tlfong01 2019may22

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Appendices

Appendix A – GPS Module Pinout and Block Diagram

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Program Listings

(A) Serial Lookback Test v0.6 – 2019apr08 tlfong01

# uart_test06 tlfong01 2019apr08hkt1603 ***
# https://raspberrypi.stackexchange.com/questions/96534/rpi-python-serial-test-program/96535#96535

# uart_test06 tlfong01 2019apr08hkt1603 ***

# Computer = Rpi3B+
# Linux    = $ hostnamectl = raspberrypi Raspbian GNU/Linux 9 (stretch) Linux 4.14.34-v7+ arm 
# Python   = >>> sys.version = 3.5.3 Jan 19 2017

# Test 1   - repeatWriteBytes() - UART port repeatedly send out bytes.  
# Function - Repeat many times sending bytes, pause after each bytes.

# Test 2   - loopBackTest() - UART port send and receive bytes.
# Function - Send one bytes to TX, wait some time (Note 1), then read bytes back from RX. 
# Setup    - Connet Tx pin to Rx pin to form a loop.

# Note 1
# Bolutek BlueTooth BC04 needs at least 10mS to respond

from   time import sleep
import serial

serialPort0 = serial.Serial(port = '/dev/serial0',
        baudrate = 9600,
        parity = serial.PARITY_NONE,
        stopbits = serial.STOPBITS_ONE,
        bytesize = serial.EIGHTBITS,
        timeout= 1)

def setSerialPortBaudRate(serialPort, baudrate):
    serialPort.baudrate = baudrate
    return

def serialPortWriteBytes(serialPort, writeBytes):
    serialPort.write(writeBytes)
    return

def serialPortReadBytes(serialPort, maxBytesLength):
    readBytes = serialPort.read(maxBytesLength)
    return readBytes

def serialPortWriteWaitReadBytes(serialPort, writeBytes, maxBytesLength, waitTime):
    serialPort.flushInput()
    serialPort.flushOutput()
    serialPort.write(writeBytes)
    sleep(waitTime) 
    readBytes = serialPortReadBytes(serialPort, maxBytesLength)
    print('        bytes written = ', writeBytes) 
    print('        bytes read    = ', readBytes)
    return readBytes

def repeatWriteBytes(serialPort, writeBytes, pauseTimeBetweenBytes, repeatCount):
    print('       Begin repeatWriteOneByte(), ...')   
    for i in range(repeatCount):
        serialPortWriteBytes(serialPort, writeBytes)                
        sleep(pauseTimeBetweenBytes)
    print('       End   repeatWriteOneByte().')
    return

def serialPortLoopBack(serialPort, writeBytes, maxBytesLength, waitTime): 
    print('        Begin serialPortLoopBack() [Remember to connect Tx to Rx!] , ...')
    serialPortWriteWaitReadBytes(serialPort, writeBytes, maxBytesLength, waitTime)     
    print('        End   serialPortLoopBack(), ...')
    return

setSerialPortBaudRate(serialPort0, 9600)
#repeatWriteBytes(serialPort0, b'AT\r\n', 0.01, 200000000)
serialPortLoopBack(serialPort0, b'AT\r\n', 32, 0.030)

''' Sample output  tlfong01 2019apr0801
>>> 
=== RESTART: /home/pi/Python_Programs/test1193/uart_test02_2019apr0801.py ===
        Begin serialPortLoopBack() [Remember to connect Tx to Rx!] , ...
        bytes written =  b'AT\r\n'
        bytes read    =  b'AT\r\n'
        End   serialPortLoopBack(), ...
>>>
'''

# End

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Figures

Fig 1 – GPS Module Setup 1

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Fig 2 – GPS Module Setup 2

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Fig 3 – GPS Module Setup 3

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Fig 4 – GPS Testing Site

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