Published May 6, 2016 © GPL3+

GPS on the Ci20

Integrate GPS functionality on your next robotic project.

IntermediateProtip5 hours778

Things used in this project

Hardware components

u-blox GPS module

Creator Ci20

Software apps and online services

Debian 8

Story

Hardware Setup

This project will show how to interface a GPS module with a serial interface on the Ci20 development board. A U-blox NEO6MV is used. This module has a male header that exposes the VDD, RX, TX and GND pins.

On the Ci20 this will be connected to connector J4P. This is the 4-pin white Molex connector near the HDMi port.

1 / 2 • Schematic of UART header on the Ci20.

As seen from the above schematic, pin 1 is VDD. This is the pin adjacent to the white triangle indicator sign. Remember to criss-cross the TX and RX pins from the GPS to the connector.

Enabling the Serial Port

The serial port brought out on the Molex connector is /dev/ttyS4. This port is used by the getty program. In order for the user to leverage the port capabilities in his/her programs , the user has to disable the serial port.

Issue:

sudo nano /etc/inittab

Now comment the line that references the /dev/ttyS4 port.

#Spawn a getty on the Ci20 serial line

#T0:23:respawn:/sbin/getty -L ttyS4 115200 vt100

The serial port should be usable from userspace right now without intervention from the getty program.

Serial Terminal

The easiest way to observe the GPS output is to install a serial terminal.

The following commands install minicom , give appropriate permissions to the serial port and open the terminal with a baud rate of 9600 which is the same as the GPS baud rate.

sudo apt-get install minicom

sudo chmod a+rw /dev/ttyS4

sudo chmod g+s /usr/bin/minicom
sudo minicom -b 9600 -o -D /dev/ttyS4

To configure the serial port after opening minicom, press CTRL-A and then Z to get a list of options. Press Z then once the menu opens press O.

Set UART port ttys4 so that it does not have hardware flow control since only the TX and RX pins are exposed.

Select serial port setup from the Menu. Enter the letter of the option you want to change.

Normally this is either the baud rate in which case you should select option E.

Or the hardware flow control which is option F. The serial port is selected via option A.

GPS data streaming on the minicom terminal.

Python code

The python code below can be used to parse the GPS data. The code depends on the pyserial library. Open a console terminal and issue:

sudo apt-get install python-pip  
sudo pip install pyserial

Then use the python code attached below to interpret the data from the GPS.

Graphical Display

There is also a GPS client on Linux. Install this by issuing:

sudo apt-get install gpsd gpsd-clients

If you want to see a graphical representation of the GPS data issue xgps.

Alternatively issue cgps by passing it the correct port number to see the data on the console.

Epilogue

This tutorial showed how to quickly interface a GPS module with the serial port on the Ci20 MIPS development board. Hopefully, your robot can now pinpoint its location anywhere in the globe.

Code

GPS with python

#! /usr/bin/python
# Written by Dan Mandle http://dan.mandle.me September 2012
# License: GPL 2.0
 
import os
from gps import *
from time import *
import time
import threading
 
gpsd = None #seting the global variable
 
os.system('clear') #clear the terminal (optional)
 
class GpsPoller(threading.Thread):
  def __init__(self):
    threading.Thread.__init__(self)
    global gpsd #bring it in scope
    gpsd = gps(mode=WATCH_ENABLE) #starting the stream of info
    self.current_value = None
    self.running = True #setting the thread running to true
 
  def run(self):
    global gpsd
    while gpsp.running:
      gpsd.next() #this will continue to loop and grab EACH set of gpsd info to clear the buffer
 
if __name__ == '__main__':
  gpsp = GpsPoller() # create the thread
  try:
    gpsp.start() # start it up
    while True:
      #It may take a second or two to get good data
      #print gpsd.fix.latitude,', ',gpsd.fix.longitude,'  Time: ',gpsd.utc
 
      os.system('clear')
 
      print
      print ' GPS reading'
      print '----------------------------------------'
      print 'latitude    ' , gpsd.fix.latitude
      print 'longitude   ' , gpsd.fix.longitude
      print 'time utc    ' , gpsd.utc,' + ', gpsd.fix.time
      print 'altitude (m)' , gpsd.fix.altitude
      print 'eps         ' , gpsd.fix.eps
      print 'epx         ' , gpsd.fix.epx
      print 'epv         ' , gpsd.fix.epv
      print 'ept         ' , gpsd.fix.ept
      print 'speed (m/s) ' , gpsd.fix.speed
      print 'climb       ' , gpsd.fix.climb
      print 'track       ' , gpsd.fix.track
      print 'mode        ' , gpsd.fix.mode
      print
      print 'sats        ' , gpsd.satellites
 
      time.sleep(5) #set to whatever
 
  except (KeyboardInterrupt, SystemExit): #when you press ctrl+c
    print "\nKilling Thread..."
    gpsp.running = False
    gpsp.join() # wait for the thread to finish what it's doing
  print "Done.\nExiting."

Credits

Dimiter Kendri

23 projects • 159 followers

Robotics and AI

Thanks to Dan Mandle.

GPS on the Ci20

Things used in this project

Hardware components

Software apps and online services

Story

Hardware Setup

Enabling the Serial Port

Serial Terminal

Python code

Graphical Display

Epilogue

Schematics

Serial port pinout

Code

GPS with python

Credits

Dimiter Kendri

Comments

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GPS on the Ci20

GPS on the Ci20

Things used in this project

Hardware components

Software apps and online services

Story

Hardware Setup

Enabling the Serial Port

Serial Terminal

Python code

Graphical Display

Epilogue

Schematics

Serial port pinout

Code

GPS with python

Credits

Dimiter Kendri

Comments

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