BerryGPS-IMU v2 Plate has been designed to fit perfectly with the Raspberry Pi Zero. It is also compatible with all other versions Raspberry Pi, including the Pi 3B+.
BerryGPS-IMU v2 uses the M20048 from Antenova, which is a high quality GPS module which is able to track 22 satellites. The BerryGPS-IMU v2 is a GPS module which also includes the sensors that can be found on the BerryIMU v2 Plate.
BerryGPS-IMU v2 is also fitted with a barometric sensor (BMP280) which can be used to calculate altitude. A temperature sensor is also included.
Sensors included are;
- Magnetometer (Compass)
GPS Module M20048
- Low current consumption, <200uA when using Periodic mode.
- Antenova M20048 ( MT3337-E chip) GPS module
- 3.3v supply
- NMEA 0183
- UART 4800/9600/38400/115200 bps
- Channels – 210 PRN / 66 Acquisition / 22 Tracking
- Max update rate 5 Hz
- Horizontal position accuracy <2.5m CEP
- Acquisition sensitivity -148dBm
- Tracking sensitivity -165dBm
- Hot start <1s
- Warm start <25s
- Cold start <35s
- Orbit prediction
- 1PPS Sync
- Fix LED
- PPS LED
- Internal antenna
- Connector for external antenna
- SuperCap to help store ephemeris data.
An inertial measurement unit, or IMU, measures and reports on velocity, orientation and gravitational forces, using a combination of an accelerometer, gyroscope and a magnetometer.
Global Positioning System (GPS) satellites broadcast microwave signals to enable GPS receivers on or near the Earth’s surface to determine location and time and derive velocity. The GPS system itself is operated by the U.S. Department of Defense (DoD) for use by both the military and the general public.
The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Air Force. It is a global navigation satellite system that provides geolocation and time information to a GPS receiver anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. Obstacles such as mountains and buildings block the relatively weak GPS signals.
BerryGPS-IMU uses the serial port on the Raspberry Pi. By default, the serial port is already assigned to the console. This can be confirmed by using;
pi@raspberrypi ~ $ dmesg | grep tty [ 0.001609] console [tty1] enabled [ 0.092061] 3f201000.uart: ttyAMA0 at MMIO 0x3f201000 (irq = 87, base_baud = 0) is a PL011 rev2 [ 0.594855] console [ttyAMA0] enabled
The last line above shows that the console is enabled for the serial port.
ttyS0 = Serial for Raspberry Pi 3
ttyAMA0 = Serial for all other Raspberry Pi
On new versions of Raspbian, ‘serial0’ is assigned as an alias to either of the above devices. This makes the device a lot easier to remember.
pi@raspberrypi ~ $ ls -l /dev/serial0 lrwxrwxrwx 1 root root 5 Aug 28 12:49 /dev/serial0 -> ttyS0
We now need to disable the console so we can use the serial device for BerryGPS.
Setup Serial for BerryGPS
1. Update software and OS
pi@raspberrypi ~ $ sudo apt-get update pi@raspberrypi ~ $ sudo apt-get upgrade pi@raspberrypi ~ $ sudo reboot
2. Open raspi-config and disable serial console
The serial console needs to be disabled and then the serial port enabled.
interfacing options -> Serial -> No -> Yes
Yes to reboot
Test and View GPS data
We can now test to see if we can see the raw GPS data, which would be outputted in NMEA sentences .
NMEA sentences contain all the requered GPS data needed to get and acruate location reading. E.g longatute, latitude, number of statilites, etc..
There are a number of ways to do this, using cat, Minicom or Screen and specifying the serial device.
pi@raspberrypi ~ $ cat /dev/serial0
pi@raspberrypi ~ $ sudo apt-get install minicom -y pi@raspberrypi ~ $ minicom -b 9600 -o -D /dev/serial0
-b = baurdrate. BerryGPS’s default baurdrate is 9600
-d = Serial device
Here are some useful commands while using Minicom
Exit – Ctrl+A and then q
Help, – Ctrl+A and then z
Settings, – Ctrl+A and then o
pi@raspberrypi ~ $ sudo apt-get install screen pi@raspberrypi ~ $ screen /dev/serial0 9600
Below is two examples of what you would see.
The first image is when you GPS has been up and running for awhile and has a fix. If your GPS has a fix, you would also see the green fix LED flash.
The second image is when your GPS is trying to obtain a fix. As you can see, most of the NMEA data is empty. On first power up, it can take your GPS module awhile to get a fix. It could be longer than 10 minutes in some situations, it all depends on interference and if your GPS has clear access to the sky.
|$GPVTG||Vector track and Speed over the Ground|
|$GPGGA||GGA – essential fix data which provide 3D location and accuracy data.|
|$GPGLL||GLL – Geographic Latitude and Longitude|
|$GPGSA||GSA – details on the nature of the fix. It includes the numbers of the satellites|
|$GPGSV||Detailed satelite data|
|$GPRMC||RMC – The recommended minimum|
This link has some great information on how to read NMEA sentences.
Viewing Meaningful GPS Data
There are number of freely available tools which we can used to view meaningful information from BerryGPS, like longitude, latitude and ground speed.
First, we will install GPSD. gpsd is a daemon that receives data from a GPS receiver, and provides the data back to multiple applications such gpsmon and cgps.
Install, gpsd, gpsmon and cgps;
pi@raspberrypi ~ $ sudo apt-get install gpsd-clients gpsd -y
If you need to stop gpsd, you can use
pi@raspberrypi ~ $ sudo killall gpsd
Be default, gpsd is configured to stat at boot and run in the background. If you are fine with this, you will need to edit the config file so that gpsd uses the correct serial device.
pi@raspberrypi ~ $ sudo nano /etc/default/gpsd Look for DEVICES=”” and change it to DEVICES=”/dev/serial0″ Reboot once you have updated the above file.
If you want to manually run gpsd, you will need to disable it from starting at boot;
pi@raspberrypi ~ $ sudo systemctl stop gpsd.socket pi@raspberrypi ~ $ sudo systemctl disable gpsd.socket
To force it to autostart again at boot;
pi@raspberrypi ~ $ sudo systemctl enable gpsd.socket pi@raspberrypi ~ $ sudo systemctl start gpsd.socket
If you have disabled gpsd from automatically started at boot, you will need to start if before running gpsmon or cgps
pi@raspberrypi ~ $ sudo gpsd /dev/serial0 -F /var/run/gpsd.sock
You can now use gpsmon or cgps to view GPS data.
pi@raspberrypi ~ $ gpsmon
pi@raspberrypi ~ $ cgps
When gpsd is running, you will not be able to see the raw NMEA data on /dev/serial0 as the serial device will show as busy.
You can use gpspipe to view this data while gpsd is running.
pi@raspberrypi ~ $ gpspipe -r
gpsprof performs accuracy, latency, and time drift profiling on a GPS. It emits to standard output a GNUPLOT scatter graph.
The command below will take 100 samples from BerryGPS and display them in a graph.
pi@raspberrypi ~ $ gpsprof | gnuplot -persist