Extracting text in Mendix using RegexReplaceAll

It’s a fairly common requirement to be able to extract text from a larger string.

Using Mendix, the easiest way I’ve found to do this is using the RegexReplaceAll Java action from the Community Commons module.

We use a regular expression extract the text, then return this selected text in the action.

For example, take the following string returned from the Nexmo SMS module.

--------- part [ 1 ] ------------Status [ 9 ] ...SUBMISSION FAILED!Message-Id [ null ] ...Error-Text [ Quota Exceeded - rejected ] ...Message-Price [ 0.03330000 ] ...Remaining-Balance [ 0.03200000 ]

If we want to extract the Error-Text we can use the following regular expression.

^.*Error-Text \[ (.*?) \].*$

Here we’re saying look for the text between the square brackets after the string Error-Text. We use round brackets to say we want to remember this matched text. We can then use the regular expression match position to return the matched text – in this case $1.

If we run this over our string we get the following

Quota Exceeded - rejected

To use this in a Mendix microflow, assume we have our status message in a String $StatusMessage that we pass into the Java action. This is our Haystack.

Next, we use the regular expression as a String for our Needle regex.

Finally, we say we want $1 as a String to be our Replacement.

We return the String as $Details.

This is what the microflow and action should look like.

View Robert Price’s Mendix Profile.

Building a simple air quality indicator

I demonstrated Using a bicolour LED with an NodeMCU in an earlier blog.

We now extend that code and instead of having a single LED, we have two. One LED will indicate the current levels of PM2.5, and the other LED will indicate the current levels of PM10. To do this we need to connect to the internet and download these levels from the Clean Air Eastbourne API. The API returns a single float as a string with the current value in µg/m3.

The wiring is very similar to the previous blog post, except we include an extra LED connected to D3 and D4 on the NodeMCU.

The code

The NodeMCU has support for WiFi built in thanks to it’s ESP8266 chip, so it’s very easy to go online in our in setup()loop() function we poll for values every 30 seconds. We turn these values into floats and compare our snapshot against the WHO annual guidelines limits, and UK annual legal limits. If we’re below WHO and UK limits, we show green. If we’re above WHO limits, but below UK limits, we show amber. If we’re above both WHO and UK limits, we show red.

#include <ESP8266WiFi.h>
#include <ESP8266HTTPClient.h>

// Wifi connection details
const char* ssid = "Wifi Network";
const char* password = "Wifi Password";

// Poll URLs
const char* PM10_URL = "http://api.eastbourneair.com/readings/906088-pm10";
const char* PM25_URL = "http://api.eastbourneair.com/readings/906088-pm25";

// How often to poll the website for updates (in microseconds)
const int POLL_DELAY = 30000;

// Limits for particulates from the WHO and UK.
// These are annual limits.
const float WHO_PM10 = 20.0;
const float WHO_PM25 = 10.0;
const float UK_PM10 = 40.0;
const float UK_PM25 = 25.0;

// The TriColour LEDs are wired to the following pins
int redPinPM10 = D2, greenPinPM10 = D1;
int redPinPM25 = D3, greenPinPM25 = D4;

void setup () {
  pinMode(redPinPM10, OUTPUT);
  pinMode(redPinPM25, OUTPUT);
  pinMode(greenPinPM10, OUTPUT);
  pinMode(greenPinPM25, OUTPUT);

  Serial.begin(115200);
  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.println("Connecting to Wifi...");
  }

}

void loop() {

  if (WiFi.status() == WL_CONNECTED) { //Check WiFi connection status

    HTTPClient http;  //Declare an object of class HTTPClient

    Serial.println("Getting PM10 data...");
    http.begin(PM10_URL);  //Specify request destination
    int httpCode = http.GET();                                        //Send the request
    if (httpCode > 0) { //Check the returning code

      String payload = http.getString();   //Get the request response payload
      Serial.println(payload);             //Print the response payload

      int reading = payload.toFloat();

      digitalWrite(redPinPM10, LOW);
      digitalWrite(greenPinPM10, LOW);
      if (reading >= WHO_PM10 && reading < UK_PM10) {  // turn the LED if over WHO limits, but under UK
        Serial.println("Over WHO guidelines ");
        digitalWrite(redPinPM10, HIGH);
        digitalWrite(greenPinPM10, HIGH);
      } else if (reading >= UK_PM10) {                 // turn the LED on if over UK limits
        Serial.println("Over UK limits");
        digitalWrite(redPinPM10, HIGH);
      } else {
        Serial.println("under limit");
        digitalWrite(greenPinPM10, HIGH);
      }
    } else {
      Serial.println("Unable to get data from API");
    }
    http.end();   //Close connection


    Serial.println("Getting PM2.5 data...");
    http.begin(PM25_URL);  //Specify request destination
    httpCode = http.GET();                                            //Send the request
    if (httpCode > 0) { //Check the returning code

      String payload = http.getString();   //Get the request response payload
      Serial.println(payload);             //Print the response payload

      int reading = payload.toFloat();

      digitalWrite(redPinPM25, LOW);
      digitalWrite(greenPinPM25, LOW);
      if (reading >= WHO_PM25 && reading < UK_PM25) {  // turn the LED if over WHO limits, but under UK
        Serial.println("Over WHO guidelines ");
        digitalWrite(redPinPM25, HIGH);
        digitalWrite(greenPinPM25, HIGH);
      } else if (reading >= UK_PM25) {                 // turn the LED on if over UK limts
        Serial.println("Over UK limits");
        digitalWrite(redPinPM25, HIGH);
      } else {
        Serial.println("under limit");
        digitalWrite(greenPinPM25, HIGH);
      }
    } else {
      Serial.println("Unable to get data from API");
    }
    http.end();   //Close connection

  } else {
    Serial.println("Not connected to Wifi");
  }

  delay(POLL_DELAY);    // wait before we poll again.
}

Using a bicolour LED with a NodeMCU

This is a quick example on how to use a bicolour LED with a NodeMCU.

The bicolour LED has both red and green LEDs in a single package. There is a common cathode for both the red and green anodes. Applying a current to the red anode turns the red LED on. A current to green anode turns the green LED on. A current to both anodes creates yellow.

The circuit is very simple. We wire the red anode to D1 on the NodeMCU, the green anode to D2, protecting them both with a 220ohm resistor. The cathode is wired to ground.

Linking a bicolour LED to a NodeMCU

We program the NodeMCU using an Arduino sketch.

int redPin = D1, greenPin = D2;

void setup() {
  // set the pins to output mode
  pinMode(redPin, OUTPUT); 
  pinMode(greenPin, OUTPUT);
}

void loop() {
  // red
  digitalWrite(redPin, HIGH); delay(500);
  // yellow
  digitalWrite(greenPin, HIGH); delay(500);
  // green
  digitalWrite(redPin, LOW); delay(500);
  // off
  digitalWrite(greenPin, LOW); delay(500);
}

In the setup, we set D1 and D2 to both be outputs. We then turn D1 and D2 on and off in sequence every half a second to achieve a sequence of red, yellow, green, and off.

Running a SDS011 particulate sensor on a Mac using PHP

The Novafit SDS011 particulate sensor is an a very affordable sensor for detecting particulate pollution. It is capable of detecting both PM2.5 and PM10 with a relative error margin of +/- 10µg/m3.

It can output data via it’s serial port. The one I bought came with a serial to USB adaptor, allowing it to be plugged into my Mac. It did need a driver, and I used ch340g-ch34g-ch34x-mac-os-x-driver.

Data is sent at 9600 baud, with 8 data bits, no parity bit, and 1 stop bit. 10 bytes are sent at a time.

Byte Name Content
0 Message Header AA
1 Commander No C0
2 DATA 1 PM2.5 Low byte
3 DATA 2 PM2.5 High byte
4 DATA 3 PM10 Low byte
5 DATA 4 PM10 High byte
6 DATA 5 ID byte 1
7 DATA 6 ID byte 2
8 Check-sum DATA 1+DATA 2+..+DATA 6
9 Message tail AB

PM2.5 (μg /m3) = ((PM2.5 High byte *256) + PM2.5 low byte)/10
PM10 (μg /m3) = ((PM10 high byte*256) + PM10 low byte)/10

We can read this using PHP. The following PHP script can be run on the command line and outputs the PM2.5 and PM10 levels every 2 seconds to a terminal window.

<?php
exec('stty -f /dev/cu.wchusbserial1420 9600 raw');
while (true) {
    $handle = @fopen( '/dev/cu.wchusbserial1420', 'r' ); # Open device for Read access
    if ($handle) {
        $binarydata = fread( $handle, 10 ); # Read data from device
        $data = unpack('H2header/H2commander/vpm25/vpm10/Sid/H2checksum/H2tail', $binarydata);
        echo sprintf("PM2.5: %dµg/m³\nPM10:  %dµg/m³\n", $data['pm25']/10, $data['pm10']/10);
        fclose ($handle); # Close device file
    } else {
        echo "Unable to connect to pollution sensor\n";
    }
    sleep(2);
}

The device is used by reading the 10 bytes it returns each message from the USB device. We can use PHP’s unpack function to break the binary data returned into an associative array for ease of use. We do have to do divide the PM2.5 and PM10 results by 10 to get their real values though. This can then be echo’d to the terminal.

NodeMCU WiFi setup

NodeMCU devices have WiFi built in, and it’s easy to configure using Lua.

One of the easiest examples of setting this up was on Limpkin’s blog. I took this and tweaked it slightly so it works with the more recent Lua wifi module.

station_cfg={}
station_cfg.ssid="Rob's iPhone"
station_cfg.pwd="secret password"
wifi.setmode(wifi.STATION)
wifi.sta.config(station_cfg)
wifi.sta.connect()
tmr.alarm(1, 1000, 1, function()
    if wifi.sta.getip() == nil then
        print("IP unavailable, Waiting...")
    else
        tmr.stop(1)
        print("ESP8266 mode is: " .. wifi.getmode())
        print("The module MAC address is: " .. wifi.ap.getmac())
        print("Config done, IP is "..wifi.sta.getip())
    end
end)

Upload this using luatool or similar as the init.lua file that runs when the NodeMCU powers up.

In this example, the script tries to connect to my iPhone hotspot. We use tmr.alarm to check once a second if we have an IP address. If we don’t, we let the user know. If we do, we stop the timer from continually executing, and print out some of our wifi configuration details.

It’s at this point we could start using the connection to talk to the internet if we needed to.

Using an i2c 128×64 OLED display with Lua on a NodeMCU

Small 128×64 OLED i2c displays can picked up for just over £3 on Amazon, and they are great for interfacing with a NodeMCU IoT device.

Wiring is simple…

  • NodeMCU 3.3v – OLED VCC
  • NodeMCU GND – OLED GND
  • NodeMCU D1 – OLED SDA
  • NodeMCU D2 – OLED SCL or SCK

Wiring an i2c OLED display to a NodeMCU

Your NodeMCU firmware must have been compiled with the i2c and u8g modules included. If you need to add these, see my previous post – NodeMCU Lua setup using a Mac. It also explains how to upload the example Lua code below.

The u8g module comes with some great examples. I’ve taken some of the relevant parts for a simple two page Lua script that prints out two alternating screens of text.

sda = 1 -- SDA Pin
scl = 2 -- SCL Pin

function init_display(sda,scl) --Set up the u8glib lib
     sla = 0x3C
     i2c.setup(0, sda, scl, i2c.SLOW)
     disp = u8g.ssd1306_128x64_i2c(sla)
     disp:setFont(u8g.font_6x10)
     disp:setFontRefHeightExtendedText()
     disp:setDefaultForegroundColor()
     disp:setFontPosTop()
end

function updateDisplay(func)
  -- Draws one page and schedules the next page, if there is one
  local function drawPages()
    func()
    if (disp:nextPage() == true) then
      node.task.post(drawPages)
    end
  end
  -- Restart the draw loop and start drawing pages
  disp:firstPage()
  node.task.post(drawPages)
end

function drawScreen1()
     disp:drawFrame(2,2,126,62)
     disp:drawFrame(5,5,121,57)
     disp:drawStr(5, 20, "  RobertPrice.co.uk")
     disp:drawStr(5, 35, "    @robertprice")
end

function drawScreen2()
     disp:drawFrame(2,2,126,62)
     disp:drawFrame(5,5,121,57)
     disp:drawStr(5, 20, "  NodeMCU OLED Test")
     disp:drawStr(5, 35, "   12th July 2017")
end

local drawDemo = { drawScreen1, drawScreen2 }

function demoLoop()
  -- Start the draw loop with one of the demo functions
  local f = table.remove(drawDemo,1)
  updateDisplay(f)
  table.insert(drawDemo,f)
end

init_display(sda,scl)
demoLoop()
tmr.alarm(4, 5000, 1, demoLoop)

This may look a bit complex for just displaying text, but it aims to be reusable. We use the tmr.alarm to avoid bogging the CPU down in a loop.

NodeMCU driving an i2c OLED display

I’ve tried this with two different i2c OLED displays, and they both work.

NodeMCU Lua setup using a Mac

I recently bought a NodeMCU. This is a small ESP8266 based card with built in WiFi, MicroUSB, and a Lua interpreter that can be used for developing IoT (Internet of Things) devices.

I had trouble getting it working initially, so I wanted to share how I fixed this on a Mac.

Install Mac drivers

If you’re not using a Mac, you can skip this part.

You plug the NodeMCU into the Mac via USB. The Mac won’t support this by default, and you need to install a driver. The driver you need to install is the Silcon Labs CP210x USB to UART Bridge.

Once installed, plug in the NodeMCU and check that the device /dev/tty.SLAB_USBtoUART exists.

To connect to the NodeMCU, you’ll need some tools. To test, download CoolTerm. In Options, for Port select SLAB_USBtoUART, and for Baudrate select 115200.

If you are lucky you’ll get a prompt, if not you may need to build and install some new firmware.

If you do get a prompt type…

print "Hello";

… and Lua should echo “Hello” back to you.

Build and install the NodeMCU firmware

If you need to build new firmware, there is a very useful online site called NodeMCU-Build.com that I used to build the firmware with the right modules I wanted for my project.

Once you’ve build the firmware, you’ll need to install the Python esptool.py to flash the firmware to the NodeMCU.

git clone https://github.com/themadinventor/esptool.git
cd esptool
sudo python ./setup.py install

Check the flash size of your NodeMCU.

To flash the firmware hold down “FLASH” and press “RST” on the NodeMCU, then use the following command (remembering to disconnect CoolTerm first if connected)…

esptool.py --port /dev/tty.SLAB_USBtoUART write_flash -fm dio 0x00000 ~/Downloads/nodemcu-master-12-modules-2017-07-07-21-24-03-float.bin

As esptool.py runs, you should see something like this…

esptool.py v2.0.1
Connecting........_
Detecting chip type... ESP8266
Chip is ESP8266
Uploading stub...
Running stub...
Stub running...
Configuring flash size...
Auto-detected Flash size: 4MB
Flash params set to 0x0240
Compressed 754992 bytes to 505060...
Wrote 754992 bytes (505060 compressed) at 0x00000000 in 44.5 seconds (effective 135.6 kbit/s)...
Hash of data verified.

Leaving...
Hard resetting...

Connect to it using CoolTerm, then press the “RST” button. You should see some messy characters, then something like following (depending on what you built into your firmware)…

NodeMCU custom build by frightanic.com
.branch: master
.commit: c8ac5cfb912ff206b03dd7c60ffbb2dafb83fe5e
.SSL: true
.modules: adc,bit,cron,crypto,encoder,file,gpio,http,i2c,net,node,ow,pcm,sjson,sntp,spi,struct,tmr,u8g,uart,websocket,wifi,tls
 build .built on: 2017-07-12 09:30
 powered by Lua 5.1.4 on SDK 2.1.0(116b762)
lua: cannot open init.lua
>

Upload Lua code to the NodeMCU

The best way to get Lua code onto the NodeMCU is to use the Python luatool.

git clone https://github.com/4refr0nt/luatool
cd luatool

To test we’ll upload a simple Lua script that will blink the NodeMCU’s onboard LED, save this as “blink.lua”.

LED_PIN = 0

gpio.mode(LED_PIN, gpio.OUTPUT)
value = true

tmr.alarm(0, 500, 1, function ()
    gpio.write(LED_PIN, value and gpio.HIGH or gpio.LOW)
    value = not value
end)

Upload it to the NodeMCU using the following command (making sure Coolterm is disconnected first)…

python luatool/luatool.py --port /dev/tty.SLAB_USBtoUART --src blink.lua --dest init.lua --dofile

You should see the following…

->file.open("init.lua", "w") -> ok
->file.close() -> ok
->file.remove("init.lua") -> ok
->file.open("init.lua", "w+") -> ok
->file.writeline([==[LED_PIN = 0]==]) -> ok
->file.writeline([==[]==]) -> ok
->file.writeline([==[gpio.mode(LED_PIN, gpio.OUTPUT)]==]) -> ok
->file.writeline([==[value = true]==]) -> ok
->file.writeline([==[]==]) -> ok
->file.writeline([==[tmr.alarm(0, 500, 1, function ()]==]) -> ok
->file.writeline([==[gpio.write(LED_PIN, value and gpio.HIGH or gpio.LOW)]==]) -> ok
->file.writeline([==[value = not value]==]) -> ok
->file.writeline([==[end)]==]) -> ok
->file.flush() -> ok
->file.close() -> ok
->dofile("init.lua") -> send without check
--->>> All done <<<--

The onboard LED on the NodeMCU should now be blinking.

The NodeMCU executes the init.lua script by default, so when we upload we tell luatool to upload our blink.lua script as init.lua.

Analysing Beat The Street data using R

Beat The Street is a game currently running in East Sussex with the aim of increasing the amount of walking and cycling people do. Players are given a free Beat The Street card that they tap on Beat Boxes to record their journeys. At least 2 different Beat Boxes must be tapped in the space of an hour for points to be recorded. Each 2nd box tapped within an hour of the last earns at least 10 points.

While there isn’t an officially documented API to the Beat The Street data, the website itself is built using JSON feeds we can use to extract data ourselves. There can be multiple schemes running at once. I’m playing in East Sussex which is scheme 47, we’ll need this ID shortly.

Firstly we’ll need to login as this sets a cookie that identifies us for subsequent calls.

library(httr)
loginurl <- "https://beatthestreet.me/api/Login?schemeId=47"
loginbody <- list(Username = "Your Username", Password = "Your Password", RememberMe = "false")
r <- POST(loginurl, body = loginbody, encode = "form", verbose())

We can use R's httr library to handle the login for us. We POST our details to the form. I'm using the verbose() option for debugging, but that's optional.

Now we are logged in, we should have a cookie set identifying us, so we can request a record of our journeys so far.

swipesurl <- "https://beatthestreet.me/api/UserCardSwipesWidget?schemeId=47"
r <- GET(swipesurl, accept_json())
cont <- content(r, as = "parsed", type="application/json")

The returned JSON data is an array of objects looking like this.

[
    {
        "SwipeDatetime":"2017-07-11T07:18:38",
        "Name":"E019",
        "Description":"E.Sussex",
        "Line1":
        "N/A",
        "Line2":"N/A",
        "Line3":"N/A",
        "Postcode":"ES1",
        "City":"E.Sussex",
        "Points":10
    },{
        "SwipeDatetime":"2017-07-11T07:14:40",
        "Name":"E024",
        "Description":"E.Sussex",
        "Line1":"N/A",
        "Line2":"N/A",
        "Line3":"N/A",
        "Postcode":"ES1",
        "City":"E.Sussex",
        "Points":0
    }
]

We can parse this by calling content().

The values are all strings apart from "Points" which is an integer. However, sometimes Beat The Street returns a null value, which we'll want to convert to an R NA. We can do this by applying a small utility function over the data to convert any nulls to NA.

nullToNA <- function(x) {
    x[sapply(x, is.null)] <- NA
    return(x)
}
cont <- lapply(cont, nullToNA)

Now we can convert our data to a data.frame, cast the "SwipeDatetime" as a DateTime, and add in an extra field called "Date" that's just the Date without the time.

library(plyr)
swipes <- ldply(cont, data.frame)
swipes$SwipeDatetime <- as.POSIXct(swipes$SwipeDatetime, format = "%Y-%m-%dT%H:%M:%S")
swipes$Date <- as.Date(swipes$SwipeDatetime)

Now we have our data in usable format, we can extract some useful information.

I can plot a graph of how many Beat Boxes I've tapped each day.

library(ggplot2)
ggplot(swipes, aes(Date)) + geom_bar(stat="count") + ggtitle("Beat Boxes Visited Per Day") + ylab("Visits") + xlab("Date") + theme(axis.text.x = element_text(angle = 90, hjust = 1))

Number of Beat Boxes visited by day

Or I can plot which Beat Boxes I visit most.

swipesFrame <- data.frame(sort(table(swipes$Name)))
ggplot(data=swipesFrame, aes(x=Var1, y=Freq)) + geom_bar(stat="identity") + ggtitle("Most Visited Beat Boxes") + ylab("Visits") + xlab("Beat Box") + theme(axis.text.x = element_text(angle = 90, hjust = 1))

Most visited Beat Boxes

I can even plot this onto a map assuming I have the latitude and longitudes of the Beat Boxes already available in a data.frame called "beatboxes", and the map in "map". The larger the frequency of visit, the larger the plotted point on the map.

library(ggmap)
swipeFrameLatLng <- merge(swipesFrame, beatboxes, by.x = "Var1", by.y="id")
ggmap(map) + geom_point(data = swipeFrameLatLng, aes(x = longitude, y = latitude, color="Red", size=Freq*10)) + ylab("") + xlab("") + guides(colour = "colorbar",size = "none")

Most visited Beat Boxes map

Using file_get_contents to PUT JSON data over HTTPS to a webservice

It’s possible to use PHP’s file_get_contents to PUT JSON data to a RESTful webservice if you don’t want to use cURL.

In this example I’m going to try to add or update a person using the NationBuilder API.

Firstly, we need the URL of the webservice, and the data you want to update as a JSON string.

$access_token = 'set access token here';
$nation = 'set nation name here';
$url = "/$nation.nationbuilder.com/api/v1/people/push?access_token=$access_token";
// details we want to update
$data = [
    'person' => [
        'email_opt_in' => true,
        'do_not_contact' => false,
        'do_not_call' => false,
        'first_name' => 'Robert',
        'last_name' => 'Price',
        'email' => '[email protected]',
        'home_address' => [
            'zip' => 'AB1 2CD'
        ],
        'bio' => 'Software developer - robertprice.co.uk'
    ]
];
$json_data = json_encode($data);

Now we need to setup a stream_context so file_get_contents knows how to handle the request.

Even though we’re PUTing data over HTTPS, we need to use the http context. We set method to PUTContent-type to application/json, Accept to application/json, Connection to close, and Content-length to the length of our JSON string. We’re PUTing this data over HTTP1.1 so we set the to 1.1. We’re sending the JSON in the body of the request, so we set this in the content.

As we are using HTTPS, we need to configure the ssl settings. In this case I’m not going to verify the peer or the peer name.

$context = stream_context_create([
    'http' => [
        'method' => 'PUT',
        'header' => "Content-type: application/json\r\n" .
                    "Accept: application/json\r\n" .
                    "Connection: close\r\n" .
                    "Content-length: " . strlen($json_data) . "\r\n",
        'protocol_version' => 1.1,
        'content' => $json_data
    ],
    'ssl' => [
        'verify_peer' => false,
        'verify_peer_name' => false
    ]
]);

Finally we PUT the data by calling file_get_contents. NationBuilder returns a JSON response to this call, so we can decode that and echo a confirmation message to the screen.

$rawdata = file_get_contents($url, false, $context);
if ($rawdata === false) {
    exit("Unable to update data at $url");
}
$data = json_decode($rawdata, true);
if (JSON_ERROR_NONE !== json_last_error()) {
    exit("Failed to parse json: " . json_last_error_msg());
}
echo "Updated details for {$data['person']['first_name']} {$data['person']['last_name']}\n";

The full code for this, and some other examples of querying NationBuilder using PHP, can be found in my NationBuilder People In Nation – GitHub repository.

You may also be interested in my previous article on POSTing JSON to Web Service.

Using a motion sensor on a Raspberry Pi with PHP

Adding a motion sensor to a Raspberry Pi is easy. In this article I’ll show you how to use it with PHP.

The HC-SR501 is a pyroelectric infrared PIR motion sensor module, that connects to the Raspberry Pi using just 3 wires.

Connect GND to GND on the Pi, VCC to +5V on the Pi, and OUT to GPIO 17 on the Pi. That’s all that’s needed.

Added a HC-SR501 motion detector to a Raspberry Pi

To use the sensor with PHP we use the PHPi library. This library supports event driven bindings for the Raspberry Pi GPIO. We install this using Composer.

composer require calcinai/phpi

To use the PHPi library we need to bring it in using the autoloader, and add some namespace shortcuts.

require 'vendor/autoload.php';

use Calcinai\PHPi\Pin;
use Calcinai\PHPi\Pin\PinFunction;

We then create a board

$board = \Calcinai\PHPi\Factory::create();

We now need to declare that we’re using GPIO pin 17 for input.

$pin = $board->getPin(17)
             ->setFunction(PinFunction::INPUT)
             ->setPull(Pin::PULL_UP);

As this is event driven programming, we need to listen to the pin to see when it changes. When the pin goes high, we know motion has been detected and we can do something. In this example, we’ll just write a message to the screen.

$pin->on('level.high', function() {
        echo "Motion detected\n";
});

Finally we start the start the loop running, so the script is listening and reacting to events.

$board->getLoop()->run();

Putting it all together

Here’s the final working PHP to detect motion using the HC-SR501

<?php

require 'vendor/autoload.php';

use Calcinai\PHPi\Pin;
use Calcinai\PHPi\Pin\PinFunction;

$board = \Calcinai\PHPi\Factory::create();

$pin = $board->getPin(17) //BCM pin number
             ->setFunction(PinFunction::INPUT)
             ->setPull(Pin::PULL_UP);

$pin->on('level.high', function() {
        echo "Motion detected\n";
});

$board->getLoop()->run();