Sensors & WebThings

Philippe Coval <purl.org/rzr> #SFK20

$ whois Phil Coval

Software Engineer from Rennes, France
OpenSource Contributor, Mozilla Rep (IoT)
Involved in industry's OSS:
- Tizen (Intel), Yocto, IoTivity (Samsung)
Contact: https://purl.org/rzr
- Presentations, Videos, Social…
- Currently available for cooperation
- Link me from Fediverse or @RzrFreeFr

Agenda

My journey of playing with sensors
- Types, Tips and hints
- Examples use cases
How can it be improved for developers
Using sensors for IoT

Sensors vs Actuators

Sensor measures a physical variation
- and produce an output value
- eg: What is the temperature ?
Actuator produces a physical action
- "consumes" an input value (order)
- eg: Turn the light on

Sensor examples

Binary sensors:
- door sensor: open/closed
Analog sensors:
- humidity detector : 1.42v ~= 42%
Numerical sensors:
- tank level: [0,1,2]: none, some, full
Sensor fusion:
- air quality: healthy to hazardous
Devices or "services" sensors:
- Web, MQTT, LPWan, NOAA (weather radio)

System's I/O

GPIO : Binary
ADC : Analog
Digital:
- I2C: Inter-Integrated Circuit
- SPI: Serial Peripheral Interface
- UART: Universal async receiver-transmitter
Others: PWM, CAN, USB…

Prototyping

"Surface mount component" SMC
- Hard to soldier on PCB
Sensors modules are useful for prototyping
- Easy to wire
  - using dupont wires (bread board)
Daughters boards
- Arduino's shields
- Raspberry-Pi's Hats

Binary sensor

General purpose input/output (GPIO)
CPU's I/O usable from board's pins
can be configured dynamically as
- as input : (sensor)
- as output : (actuator)
Voltages: Low (0V) or High (Vcc)
- 5V (TTL) : eg: Arduino
- 3.3V (LVTTL) : eg: RaspberryPi
- 1.8V : eg: Edison

Analog Sensors

Numeric value (vs binary value on GPIO)
Need Analog to Digital Converter (ADC)
- Most Micro-controllers ship ADC units
- (Prefer Arduino to bare Raspberry Pi)
Translate a physical phenomena to voltage
Need to be converted software side
- range / quantification
Eg: gaz (MQ), proximity (HC-SR04)

Analog Sensor (yl-69)

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Digital sensors: I2C

Inter-Integrated Circuit (I2C) 1982
Serial communication bus
- Each device has a "slave" address
- 7bits -> 128 items
4 Wires:
- Serial Data Line (SDA)
- Serial Clock Line (SCL)
- VCC: +5V or +3.3V
- GND

I2C Setup on Pi

sudo raspi-config # Enable I2C
ls -l /dev/i2c* || sudo reboot
sudo apt-get install i2c-tools
/usr/sbin/i2cdetect -y 1
#|      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
#| 00:          -- -- -- -- -- -- -- -- -- -- -- -- --
#| 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
#| 20: -- -- -- 23 -- -- -- -- -- 29 -- -- -- -- -- --
#| 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
#| 40: 40 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
#| 50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
#| 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
#| 70: -- -- -- -- -- -- -- 77

Ambient light sensor

BH1750FVI IC from Rohm
- Digital 16bit Serial Output
- Wide range, High res [1 - 65535 lx]
Data sheet: bh1750fvi-e.pdf
- I2C protocol (address 0x23)
Drivers: more than 90 !!!
- https://libraries.io/search?q=bh1750

BH1750FVI Drivers

Arduino : 1 (+ community)
- https://arduinolibraries.info/libraries/bh1750-fvi
Mbed : ~1 of 51 entries
- https://os.mbed.com/search/?q=BH1750
Python : ~11
- https://pypi.org/search/?q=bh1750
Node.js : ~8
- https://www.npmjs.com/search?q=bh1750

Example (Node.js)

let BH1750 = require('@abandonware/bh1750');

const options = {
    device: '/dev/i2c1', // RPi I2C bus
    address: 0x23, // I2C address
    command: 0x10, // 1 lx resolution
    length: 2
};

let sensor = new BH1750(options);

sensor.readLight((value) => {
   console.log(value); // 42
});

bh1750 abandonware

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Environment

Temperature
- HTU21D by TE + humidity
- HTS221 by ST + humidity
- BMP085 by Bosh + pressure
Pressure (Barometric)
- LPS25HB from ST (in RPi sensehat)
AirQuality, Gaz, UV
- SDS011 (UART), MQ-X (Analog) …

JS driver for BMPx8x

var bmp085 = require('@abandonware/bmp085-sensor');

var sensor = bmp085({address: 0x77, mode: 3});

sensor.calibrate(function (err, data) {
  // ...
  sensor.read(function (err, data) {
  console.log(data);
  // { pressure: 29.9, temp: 42.0 }
  });
});

bmp085 abandonware

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Motion sensors

Accelerometer, Gyroscope, (+Magnetic)
- Fusion to avoid drift
- Accurate Orientation, Compass
Several devices:
- LSM9DS1 by ST (with mag)
- MMA845X by NXP (3 Axis)
- FXOS8700Q (shipped in NXP K64F)
- MPU6050 by TDK (6DoF Gyro+Accel)

FXOS8700Q (Mbed)

#include "mbed.h"
#include "FXOS8700Q.h"

I2C i2c(PTE25, PTE24); // K64F's pins for SDA SDC

FXOS8700QAccelerometer acc(i2c, FXOS8700CQ_SLAVE_ADDR1);

motion_data_units_t v;

acc.enable();

acc.getAxis(v);

printf("X=%f Y=%f Z=%f\n", v.x, v.y, v.z);

LSM9DS1 IMU

The IMU (inertial measurement unit) sensor
- combination of three sensors
- each with an x, y and z axis.
- 9 dof (degrees of freedom) sensor.
Shipped in RPi Sensehat
Supported by python module:
- set_imu_config(compass, gyro, accel)
- get_compass/orientation/accelerometer

Sensehat webthings

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Drivers mess

Many drivers from community
- use custom API to do same thing
  - highlevel: start, read, fail, stop
For many languages and platforms:
- Linux: Node.js, python
- RTOS: C/C++ (Arduino, Mbed, NuttX)
+ Mobile phones API for sensors
- GPS, Orientation…
Even in web browsers !

Sensor API for Web

(Mobiles') Sensors exposed to browsers
- with Sensor API
W3C Specification:
- to drive consistency across sensor APIs
- set of interfaces
- enable new use cases,
- speed-up and ease specification
- implementation of new sensors

The Web and beyond

Web is platform agnostic
- Programmable: server or client side
Use JavaScript interpreted language
- in browser, headless (Node)
- also supported in Micro Controllers (MCU)

generic-sensor-lite

Lightweight JS implementation of W3C spec
https://github.com/rzr/generic-sensors-lite/
provide high level API
support many Sensors
- devices and/or simulators
target constrained devices (MCU)
Several JavaScript runtimes are supported
- Develop on Linux using Node.js
- Deploy to MCU running IoT.js

Generic Sensor flow

Create new Sensor objects
- with options (frequency)
Add callbacks functions
- onerror, onreading…
start: loop on reading
- object's values are updated on each read
- onreading() callback called
- wait next read (frequency opt)
stop

Simulator example

// file: example.js
var GenericSensors = require('generic-sensors-lite');

var sensor = new GenericSensors.Geolocation({frequency: 0.42});

sensor.onreading = function() {
 console.log("[" + this.latitude + "," + this.longitude + "]");
 this.stop();
};

sensor.start()

# Run JS application with Node.js
node example.js
[ 4.20180308, 2.20200923]

Creating new driver

Example: Sensor color
- Ready to be added to generic-sensor-lite
  - without any adaptation
Supports:
- I2C sensor TCS34725
- Simulator
https://github.com/rzr/color-sensor-js/

var sensor = new ColorSensor({controller: "tcs34725"}) // I2C
sensor.onreading = function () {
  console.log('{"color": "' + this.color + '"}') // #badc0d
}
sensor.start()

Color sensor demo

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Sensors devices

Aligned to W3C specs
- AmbientLight (BH1750)
- Temperature (BMPX8X or HTU21D)
Inspired by W3C specs
- Humidity (HTU21D)
- Color (TCS34725)

Simulators

Accelerometer
Battery
Geolocation
Orientation
Proximity
more?

IoT.js : JS runtime

Use JerryScript interpreter (ES 5.1)
Low footprint: Flash=180+KB RAM=26KB
Built in Modules:
- I/O: GPIO, ADC, I2C, SPI, UART, PWM
- Sys: Net, FS/ROM, Crypto…
External JS modules from community
Support: Linux, Tizen, NuttX, TizenRT

Sensor script on MCU

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NuttX RTOS

RTOS Committed to comply standards
- POSIX, ANSI C (like Unix, GNU/Linux)
- File based IO (/dev), BSD sockets (uIP)
Released by Gregory Nutt in 2007
Incubated by Apache Foundation
Base of derived projects:
- TizenRT, PX4, Sony Spresense
IoT.js supports NuttX (watch NuttX2020Con)

Deploy JS app to MCU

Import IoT.js as NuttX application
Deploy application to ROMFS
- example.js : main (loop) + js modules
Add startup script (NSH)
- start interpreter:
- iotjs "/rom /… /example.js"
Build firmware for supported MCU
- I use ST Nucleo F746ZG
Watch https://nuttx.events 2020

Going online?

Ethics: Please consider privacy and security
Several protocols:
- MQTT, CoAP, HTTP, WebSockets
Web Of Things (aka WoT)
- W3C's Working group
- Link devices (sensors, actuators)
FLOSS: WebThings smart-home platform

WebThings

Smart-home platform born in Mozilla ET lab
- with privacy by design
- inspired by W3C WebOfThings (WoT)
Framework to build webthings (REST API)
- Mozilla IoT schema (in JSON)
- JS (Node or IoT.js), Python, Rust, C++…
Mozilla WebThings gateway
- UI to control webthings from browser
- + addons: generic-sensors-adapter for Pi

WebThings REST API

$ make -C generic-sensors-lite/example/webthing/ start

make runtime=iotjs start
make -C example/webthing runtime=iotjs start

curl -s  http://localhost:8888/properties
#| { (...) "illuminance":123., "celsius":42., "color":"#c0a175" (...) }

Webthings addon:

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Summary

Sensors drivers
- Can use uniform API: W3C Generic Sensors
generic-sensor-lite implements spec in JS
- work on MCU (with IoT.js)
- or full OS (with Node.js)
WebThings SmartHome with Privacy by Design
- Use webthing API
- to connect devices to gateway
- or its sensors w/ generic-sensors addon

Feedback welcome

https://github.com/rzr/webthing-iotjs/wiki/Sensor
https://github.com/rzr/generic-sensors-lite
https://github.com/rzr/generic-sensors-webthing
Thanks: #SFK20, @MozillaReps/@WebThingsIO
License: CC-BY-SA-4.0 @ https://purl.org/rzr/

Extra demos

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Video Playback

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Extra: Wearable

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https://flossk.org/events/sfk-2020-conference/

https://sfk.flossk.org/?schedule=sensing-reality-with-wot-on-microcontrollers#

https://sfk.flossk.org.www412.your-server.de/#program

Workshop – Sensing reality with WoT on Microcontrollers

Working with sensors or actuators can be a good exercise to get into the Internet of Things. Even if the community has provided many drivers you can use on various system, from cheap Arduino DIY boards to full GNU/Linux boxes, the lack of unification can appear chaotic to developers.

To solve fragmentation of implementations W3C proposed “Generic Sensors API” which is worth to be supported; while JavaScript is totally capable capable of addressing low end targets (using Node.js or IoT.js powered by JerryScript engine).

Application developers will be happy to use an easy and lightweight toolbox, hiding the integration’s complexity (keep lower level tasks to data-sheet readers).

The slot is 55 minutes. You should leave some time for Q&A, 5-10 mins. So you're left with a circa 45 min video presentation.

https://sfk.flossk.org/?schedule=sensing-reality-with-wot-on-microcontrollers# #SFK20 I'll speak about #Sensors and #WebThings on #Sun20200927 at @flosskosova's online conference as @MozillaReps and @WebThingsIO contributor

Playlist

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Sensors & WebThings

Philippe Coval <purl.org/rzr> #SFK20

$ whois Phil Coval

Agenda

Sensors vs Actuators

Sensor examples

System's I/O

Prototyping

Binary sensor

Analog Sensors

Analog Sensor (yl-69)

Digital sensors: I2C

I2C Setup on Pi

Ambient light sensor

BH1750FVI Drivers

Example (Node.js)

bh1750 abandonware

Environment

JS driver for BMPx8x

bmp085 abandonware

Motion sensors

FXOS8700Q (Mbed)

LSM9DS1 IMU

Sensehat webthings

Drivers mess

Sensor API for Web

The Web and beyond

generic-sensor-lite

Generic Sensor flow

Simulator example

Creating new driver

Color sensor demo

Sensors devices

Simulators

IoT.js : JS runtime

Sensor script on MCU

NuttX RTOS

Deploy JS app to MCU

Going online?

WebThings

WebThings

WebThings REST API

Webthings addon:

Summary

Feedback welcome

Extra demos

Video Playback

Extra: Wearable

More

Playlist