All posts by Mark Williams

Double tap detection with BerryIMUv3

November 6, 2020 Mark Williams Leave a comment

The accelerometer(LSM6DSL) on the BerryIMUv3 has built in double tap detection, which makes it very easy to detect double taps without the need for any fancy code.

When the LSM6DSL detects a double tap, it can fire an interrupt pin on the BerryIMUv3. We will use a Raspberry Pi to monitor the interrupt pin and turn a LED off and on when a double-tap is detected.

Double-Tap event recognition has special registers which control tap recognition functionality, these are the tap threshold and the Shock, Quiet and Duration time windows

The Raspberry Pi will configure the BerryIMUv3 for double tap recognition. It will also monitor for double taps, which will be used to turn a LED on and off.

INT1 On the BerryIMUv3 will go high when a double tap is detected.

GPIO18 (physical pin 12) on the Raspberry Pi will be used to monitor INT1 , using an interrupt.

GPIO20 (physical pin 28) will be used to drive the LED.

The resister below is 330 Ohms

Here is the hock up diagrams

import signal
from LSM6DSL import *
import sys
import RPi.GPIO as GPIO 
import smbus

bus = smbus.SMBus(1)

LED_ON = 0                                                           #Used to track of the current state of the LED
INTERRUPT_PIN = 12                                                   #The interrupt pin which will be connected to the IMU
LED_PIN = 38                                                         #The pin which will be driving the LED

#Used to clean up when Ctrl-c is pressed
def signal_handler(sig, frame):
    GPIO.cleanup()
    sys.exit(0)
    

#Used to write to the IMU
def writeByte(device_address,register,value):
    bus.write_byte_data(device_address, register, value)




def LEDnotification(channel):
	global LED_ON
	if LED_ON:
		GPIO.output(LED_PIN,0)
		LED_ON = 0
	else:
		GPIO.output(LED_PIN,1)
		LED_ON = 1


writeByte(LSM6DSL_ADDRESS,LSM6DSL_CTRL1_XL,0b01100000)                 #ODR_XL = 416 Hz, FS_XL = +/- 2 g
writeByte(LSM6DSL_ADDRESS,LSM6DSL_TAP_CFG,0b10001110)                  #Enable interrupts and tap detection on X, Y, Z-axis
writeByte(LSM6DSL_ADDRESS,LSM6DSL_TAP_THS_6D,0b10001100)               #Set tap threshold
writeByte(LSM6DSL_ADDRESS,LSM6DSL_INT_DUR2,0b01111111)                 #Set Duration, Quiet and Shock time windows
writeByte(LSM6DSL_ADDRESS,LSM6DSL_WAKE_UP_THS,0b10000000)              #Double-tap enabled 
writeByte(LSM6DSL_ADDRESS,LSM6DSL_MD1_CFG,0b00001000)                  #Double-tap interrupt driven to INT1 pin

        

GPIO.setmode(GPIO.BOARD) # Use physical pin numbering
GPIO.setup(INTERRUPT_PIN, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)
GPIO.setup(LED_PIN, GPIO.OUT)
GPIO.output(LED_PIN, 0)
GPIO.add_event_detect(INTERRUPT_PIN, GPIO.RISING, callback=LEDnotification, bouncetime=300)


while True:
    signal.signal(signal.SIGINT, signal_handler)
    signal.pause()

We will cover specific code which relates to double-tap recognition.

Line 37 , LSM6DSL_TAP_CFG is used to enable tap recognition on the X, Y, Z directions. It is also used to enable the interrupt function for double-tap recognition.

Line 38 , LSM6DSL_TAP_THS_6D is used to set the tap thresholds. a lower value will result in softer taps being detected.

Line 39 , LSM6DS_INT_DUR2 is used to set the duration, quiet and shock time window. A larger duration will result in a longer time between 1st and 2nd tap.

Line 40, LSM6DSL_WAKE_UP_THS. Set the left most bit to enable double tap recognition.

Line 41, LSM6DSL_MD1_CFG is used to set which interrupt pin ont he BerryIMUv3 is used. In this instance, it is set to INT1.

BerryIMU

New BerryIMU version

October 23, 2020 Mark Williams Leave a comment

We are now selling version 3 of the BerryIMU.

BerryIMUv3 has been updated with the latest sensors, resulting in lower noise and a faster output rate (up to 6,664 times a second!).

We have also included level shifters for 5V MCUs. Which means you can safely connect the BerryIMUv3 directly to an Arduino.

BerryIMUv3 is compatible with the SparkFun QWIIC echo system.

We sell a QWIIC connector and cable for the Raspberry here. This does away with the need to solder headers onto the BerryIMUv3 when connecting to a Raspberry Pi.

Some of the features.

Gyroscope and accelerometer output rates of 6.7KHz (6,664 times a second!)
Detect tilt, tap and double tap
Pedometer, step detector and step counter
Interrupt pins
Read temperature
supports both 3.3V and 5V
I2C and SPI
“Always-on” experience with low power
consumption for both accelerometer and gyroscope

BerryGPS

GPS Position accuracy and how to tell if you have a good fix?

February 8, 2020 Mark Williams Leave a comment

One of the main contributing factors to GPS position accuracy is the geometric configuration (the position in the sky) of the satellites used to obtain a position.
The best position fix is given when a satellite is directly overhead and another three are equally spaced around the horizon.

This aspect is called the 'geometry' of the system and is measured as DOP (Dilution of Precision).

The influence of satellite geometry on imprecision is demonstrated in the image below. When both satellites are widely separated (figure left) the position error (area in red) is smaller. If the satellites are close to one another (right figure), then the area of error is more spread out. This is valid when the uncertainty for determining the position,
known as the Range Error (R-E: yellow and blue areas), is the same for both satellites. R (R1 and R2) refers to the
measured distance of the satellites to the user (pseudorange).

HDOP overlap — Satellite precision error

There are a number of different DOP elements which can be used, we will focus on HDOP (Horizontal-DOP).

The HDOP can be seen when using gpsmon. The image below has HDOP highlighted;

The HDOP can also be found in the GSA sentence. Below it is shown as 1.3;

$GPGSA,A,3,04,05,,09,12,,,24,,,,,2.5,1.3,2.1*39

A HDOP value of 1 or below would give you an accuracy of about 2.5M.

When in mountainous areas, forests and urban canyons, you can experience high HDOP values as some of the available satellites will be obstructed. The satellites used will be closer together creating a large area of error as the signal from each satellite have a larger intersect.

Out on the open see, you should be able to see a low HDOP value as the satellites used would be spread out and has less area of a intersect.

BerryGPS, featured1, GSM, Linux, Raspberry Pi

Using u-Center to connect to the GPS on Raspberry Pi

October 17, 2019 Mark Williams 3 Comments

u-Center from u-Blox is a graphical interface which can be used to monitor and configure all aspects of the GPS module on a BerryGPS-IMU or BerryGPS-GSM.

u-Center only runs on Windows. It can connect over the network to a Raspberry Pi. This will require us to redirect the serial interface on the Raspberry Pi to a network port using ser2net.

Pi Setup

Do an upt-get update and then install ser2net;

pi@raspberrypi ~ $ sudo apt-get update
pi@raspberrypi ~ $ sudo apt-get install ser2net

Edit the ser2net config file and add the serial port redirect to a network port. We will use network port 6000

pi@raspberrypi ~ $ sudo nano /etc/ser2net.conf

And add this line at the bottom;

6000:raw:600:/dev/serial0:9600 NONE 1STOPBIT 8DATABITS XONXOFF LOCAL -RTSCTS

This is a breakdown of the syntax for the line above;
TCP port : connection type : timeout : serial port : serial port speed : serial options

you can now start ser2net using;

pi@raspberrypi ~ $ sudo ser2net

And you can use the below command to check if it is running by seeing if the port is open and assigned to the ser2net process;

pi@raspberrypi ~ $sudo netstat -ltnp | grep 6000

If it is running, you should see something similar to the output below;

Windows PC Setup and Connecting to the GPS module

You can download u-Center from here.

Once installed, open u-Center. You will get the default view as shown below. No data will be shown as we are not connected to a GPS.

The next step, is to create a new network connection and connect to the GPS which is connected to our Raspberry Pi. You can create a new connection under the Receiver and then Network connection menus.

In the new window, enter the IP address of the Raspberry Pi and specify port 6000. This is the port we configured in ser2net on the Raspberry Pi.

This is what the default view looks like when connected and the GPS has a fix.

u-Center

Below I will list of the more useful windows/tools within u-Center.
You can also click on the images below for a larger version.

Data View
This window will show you the longitude, latitude, altitude and fix mode. It will also show the HDOP, which is the Horizontal Dilution of Precision. Lower is better, anything below 1.0 means you have a good signal.

Ground Track
This window will show you where the satellites are as well as what time.

Skye View
Sky view is an excellent tool for analyzing the performance of antennas as well as the conditions of the satellite observation environment.

Deviation Map
This map shows the average of all previously measured positions.

Continue reading Using u-Center to connect to the GPS on Raspberry Pi →

BerryGPS, GSM, Raspberry Pi

Control the GPIO of a Raspberry Pi using SMS from a mobile phone

October 2, 2019 Mark Williams Leave a comment

In this guide we will show you how to control the GPIO pins of a Raspberry pi by send a SMS to the Raspberry Pi from a mobile phone.

For this guide, the GSM modem we are using to receive the SMS is the BerryGPS-GSM.

On the software side, we will be using Gammu, which is specifically designed to control phones and GSM modules. It also has a daemon which will monitor the GSM modem for incoming SMSs.

We will configure Gammu to trigger a python script when a new SMS is received. We will use the contents of the SMS to control what happens in Python

LEDs are used here as an example, but you can do anything you like Eg. Open a garage door, turn on some lights, etc..

Wiring

We will be using the three bottom right GPIO pins on the Raspberry Pi header. These are GPIO 16, 20 and 21.
Each is connected to a different color LED as shown above. The
The resistors used are 330 Ohm and the GND pin (shorter pin) of the LEDs is connected to the GND power rail.

Setup

Install Gammu and python bindings;

pi@raspberrypi ~ $ sudo apt-get update
pi@raspberrypi ~ $ sudo apt-get install gammu-smsd python-gammu

Edit the config file;

pi@raspberrypi ~ $ sudo nano /etc/gammu-smsdrc

Find the below lines and add port and speed.
For the BerryGPS-GSM, use /dev/ttyACM1 for port and at115200 for speed

port = /dev/ttyACM1
connection = at115200

At the bottom of the file, add the line below. This is the python script which will run when a new SMS is received.

RunOnReceive = sudo python /home/pi/smsReceived.py

We will do a quick test. Restart the gammu service so the new config takes effect;

pi@raspberrypi ~ $ sudo /etc/init.d/gammu-smsd restart

Send a test SMS to a mobile number. The mobile number below is an example, you will need to update this;

pi@raspberrypi ~ $ echo "This is a test from a Raspberry Pi" | /usr/bin/gammu --sendsms TEXT +614123456789

Python Script

This python script will run every time a new SMS is received.

pi@raspberrypi ~ $ nano ~/smsReceived.py

Copy in the below code

import RPi.GPIO as GPIO
import time
import sys
import re


RED_LED =  21
GREEN_LED =  20
BLUE_LED =  16

GPIO.setmode(GPIO.BCM)
filename=str(sys.argv[1])                               #Gammu will pass the filename of the new SMS as an argument
complete_filename="/var/spool/gammu/inbox/"+filename    #we create the full path to the file here

GPIO.setup(RED_LED , GPIO.OUT)
GPIO.setup(GREEN_LED , GPIO.OUT)
GPIO.setup(BLUE_LED , GPIO.OUT)

sms_file=open(complete_filename,"r")
#read the contents of the SMS file
message=sms_file.read(160) #note that a not-parted SMS can be maximum 160 characters

#search the contents and perform an action. Rather than use 'find',
# we will use regular expression (re) so we can ignore case.
#Most smartphones will have the first letter capitalised
if re.search('red', message, re.IGNORECASE):
        GPIO.output(RED_LED , GPIO.HIGH)
        time.sleep(2)
        GPIO.output(RED_LED , GPIO.LOW)
elif re.search('green', message, re.IGNORECASE):
        GPIO.output(GREEN_LED , GPIO.HIGH)
        time.sleep(2)
        GPIO.output(GREEN_LED , GPIO.LOW)
elif re.search('blue', message, re.IGNORECASE):
        GPIO.output(BLUE_LED , GPIO.HIGH)
        time.sleep(2)
        GPIO.output(BLUE_LED , GPIO.LOW)



GPIO.cleanup()

To troubleshoot you can view the syslog

pi@raspberrypi ~ $ tail -f /var/log/syslog

BerryGPS, GSM, Raspberry Pi

Using a button and the GPIO on a Raspberry Pi to send a SMS

September 28, 2019 Mark Williams Leave a comment

In this guide we will show you how to send a SMS using a button connected to the GPIO pins of a Rasberry Pi Zero.

For this guide, the GSM modem we are using to send the SMS is the BerryGPS-GSM.

On the software side, we will be using Gammu, which is specifically designed to control phones and GSM modules.

Python will be used to monitor some buttons connected to GPIO pins and Gammu python bindings will be used to send a SMS.

Buttons are used here as an example, but you can use anything to trigger the SMS, E.g. Temperature sensor, water level sensor, light sensor, etc..

We have includes some LEDs so we can see when the buttons are pressed.

Wiring

We will be using the three bottom right GPIO pins on the Raspberry Pi header. These are GPIO 16, 20 and 21.
Each is connected to a button and different color LED as shown above. The internal pull-down resisters will be used on these GPIO.
3.3v and GND are connect to the power rails on the breadboard.
The resistors used are 330 Ohm and the GND pin (shorter pin) of the LEDs is connected to the GND power rail.

Continue reading Using a button and the GPIO on a Raspberry Pi to send a SMS →

BerryGPS, GSM

Real-time GPS tracking with a Raspberry Pi

July 16, 2019 Mark Williams Leave a comment

In this guide, we will show how to do real time tracking, use a BerryGPS-GSM and initialstate.com

Initialstate has some great tools to easily stream data from a Raspberry Pi to Initialstate.com and show this data within a dashboard using tiles. We will send longitude, latitude and speed. And use a BerryGPS-GSM to get these values and upload them via 3G.

You will need to create an account on Initialstate.com and then grab your access key which can be found under "My Settings"

BerryGPS-GSM setup

If you are using a BerryGPS-GSM, you can follow this guide to get the GPS working and get your Pi to connect to via 3G using PPP.

The above guide also shows how to make your Pi connect to the carrier network automatically when booted. You will need this if you plan to perform remote tracking(E.g. Asset tracking).

Install required libraries

pi@raspberrypi ~ $ sudo apt-get install python-pip
pi@raspberrypi ~ $ sudo pip install pynmea2
pi@raspberrypi ~ $ sudo pip install ISStreamer

Main Python Script

Here we will create the main script which will stream the GPS data to Initialstate.com.
The code below creates a separate thread which is used to monitor the serial port. This is needed because we have a pause in the main loop. The pause is there to limit how much data we upload over 3G.
If we did everything in the same thread during the pause, the serial buffer would fill up (it is FIFO) and when we get the next value from the buffer, it will be old by a few seconds. This happens every loop and eventually the data will be minutes or hours behind.

The access key below is not a valid key, it is just an example. You will need to replace it with your own key.

pi@raspberrypi ~ $ nano ~/GPStracker.py

#! /usr/bin/python

from gps import *
from time import *
import threading
import datetime
from ISStreamer.Streamer import Streamer

gpsd = None  #Setup global variable 

#Setup the Initialstate stream, give it a bucket name and the access key
streamer = Streamer(bucket_name="GPS_Tracker20190713", bucket_key="GPS_Tracker20190713", access_key="ist_W4aHj0eCkMjCD8JVpp3AMsKomys8NaD")


class GPSDcollector(threading.Thread):
   def __init__(self, threadID):
      threading.Thread.__init__(self)
      self.threadID = threadID
      global gpsd #bring it in scope
      gpsd = gps(mode=WATCH_ENABLE) #Start GPSD
      self.running = True #Start running this thread
   def run(self):
      global gpsd
      while gpsdThread.running:
        gpsd.next() 
        
if __name__ == '__main__':
  gpsdThread = GPSDcollector(1) # create a thread to collect data
  try:
    gpsdThread.start() # start it up
    while True:
        print 'GPS ' , gpsd.utc,'--> CPU time->',datetime.datetime.now().time() ,
        if (gpsd.fix.longitude<>0) and (gpsd.fix.longitude<>'nan'): #Only upload data if it is valid
          streamer.log("Location", "{lat},{lon}".format(lat=gpsd.fix.latitude,lon=gpsd.fix.longitude))
          streamer.log("speed",gpsd.fix.speed)
        print '  lat    ' , gpsd.fix.latitude,
        print '  lon   ' , gpsd.fix.longitude,
        print '  speed ', gpsd.fix.speed

        sleep(5)
  except (KeyboardInterrupt, SystemExit): #when you press ctrl+c
    print "\nKilling Thread..."
    gpsdThread.running = False
    gpsdThread.join() # wait for the thread to finish what it's doing
  print "Done.\nExiting."

Start the script automatically on boot

If you are doing remote monitoring, you would want the script to run on boot. To do this, we will create a small script which will start the main python program.

pi@raspberrypi ~ $ nano ~/GPStrackerStart.sh

copy in the below lines;

#!/bin/bash
sleep 15
python /home/pi/GPStracker.py &

The pause above is there to give the Pi time to boot and connect via PPP.

Make the script executable;

pi@raspberrypi ~ $ chmod +x ~/GPStrackerStart.sh

We will use cron to start the script every time the Pi boots;

pi@raspberrypi ~ $ crontab -e

Add the below line to the bottom

@reboot /home/pi/GPStrackerStart.sh &

Get a GPS fix in seconds using assisted GPS on a Raspberry Pi with a BerryGPS-GSM

July 14, 2019 Mark Williams Leave a comment

Typically, a GPS module can take a few minutes to get Time To First Fix(TTFF), or even longer if you are in built up areas(+20mins). This is because the Almanac needs to be downloaded from satellites before a GPS fix can be acquired and only a small portion of the Almanac is sent in each GPS update.

Assisted GPS speeds this up significantly by downloading ephemeris, almanac, accurate time and satellite status over the network, resulting in faster TTTF, in a few seconds. This is very similar how to GPS works on a smartphone.

The BerryGPS-GSM supports assisted GPS. The below video shows a comparison between assisted and normal GPS.

Assisted GPS takes 19secs to get a fix
Normal GPS takes 8min 22Sec to get a fix

How does the BerryGPS-GSM do this?

The two main components on the BerryGPS-GSM are;

uBlox CAM-M8 GPS module
uBlox SARA-U201 cellular modem

The SARA-U201 can be configured to download GPS assist data and then pass this over the the GPS module. These two components speak to each other via i2c.

This assist data is downloaded by the SARA-U201 modem (not the Pi), therefore the modem needs to create an internal PDP (Packet Data Protocol) connection.

Once the PDP connection is made, the SARA-U201 will reach out to uBlox AssitNow servers and download the latest assist data. A valid token is needed to perform this, all BerryGPS-GSM have had this token pre-configured.

Continue reading Get a GPS fix in seconds using assisted GPS on a Raspberry Pi with a BerryGPS-GSM →

BerryGPS

New Product: BerryGPS-GSM - Global 3G/2G cellular modem with GPS + SIM

June 28, 2019 Mark Williams Leave a comment

We have released a new product:

BerryGPS-GSM - Global 3G/2G cellular modem with GPS + SIM

This is an all in one module which can provide location tracking and GSM services such as data, text and SMS to your project. It comes in the same form factor as a Raspberry Pi Zero, which makes it nice and compact when used with a Raspberry Pi Zero.

The two main components that make this board great are;

uBlox CAM-M8 GPS module (Same GPS found on BerryGPS-IMU)
uBlox SARA-U201 GSM for GSM connectivity, which has global coverage.

Both of these modules working together results in obtaining a GPS fix in secs, using Assisted GPS.

BerryGPS

BerryGPS-IMU used by Plastic Monkeys in CanSat competition

June 18, 2019 Mark Williams Leave a comment

Along with other sponsors, we are happy to congratulate Plastic Monkeys team for placing 3rd (out of over 70 teams taking part) in the CanSats in Europe Polish Competition.

A CanSat is a type of sounding rocket payload used to teach space technology. It is similar to the technology used in miniaturized satellites.

In CanSat competitions, the payload is required to fit inside the volume of a typical soda can (66mm diameter and 115mm height).

A BerryGPS-IMU was used to provide location tracking for this project.