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Version vom 2. April 2018, 20:21 Uhr

Anleitung für einen schnell zusammengebauten Sensor-Knoten mit LoRa-Interface

Hardware-Stückliste

Ein auf der ESP32-Architektur basierendes Developer Board mit LoRa-Funkmodul (Detaillierte Vorstellung bei Heise), am besten mit OLED-Display, in Europa sind die Frequenzen um 433MHz oder 868MHz möglich. Unser erster Gateway arbeitet auf 868MHz. Preise je nach Quelle zwischen 10 USD und 35 EUR.
ESP32 mit LoRa Transceiver, WLAN
Sensor - wir wählen hier einen MQ-135, der eine recht allgemeine Aussage zur Luftqualität liefert (Benzol, Alkohol, Rauch, Ammoniak, Sulfide, Aromaten), ab 2 EUR beim Chinesen
Luftgütesensor MQ-135 mit AD-Wandler ADS1115 auf Bredboard
ADS1115 AD-Wandler mit I2C (eigentlich könnte das Developer-Board AD-Wandeln auch direkt selbst, aber der oben beschriebene Typ verträgt nur 3,3V am Eingang und der MQ-135 liefert zwischen 0 und 5V am Ausgang, je nach Konzentration)
- https://www.amazon.de/gp/product/B01N8ODF5C/
- https://www.amazon.de/gp/product/B01M0P86J9/
Optional Breadboard und Kabel

Entwicklungsumgebung einrichten

Arduino IDE. Das hier verwendete Entwicklungs-Board mit ESP32 lässt sich unter anderem mittels Arduino IDE programmieren
- https://www.arduino.cc/en/Main/Software
Eventuell braucht das entsprechende Betriebssystem einen Treiber für den auf dem Entwicklungs-Board vorhandenen USB-Serial-Converter
- https://www.silabs.com/products/development-tools/software/usb-to-uart-bridge-vcp-drivers
Arduino Core API für ESP32 installieren
- https://github.com/espressif/arduino-esp32
In der Arduino IDE Treiber fürs Board installieren

Software

Hier fehlt noch viel - die Messwerte auf dem Bild stammen von einem MQ-135 an einem Raspberry PI

C-Code (Arduino-Style) zum Auslesen des Sensors und Versenden des Ergebnisses per LoRaWAN
InfluxDB und Grafana
Verlauf der Sensor-Messwerte vom MQ-135

include <Arduino.h>

include <U8g2lib.h>

//https://github.com/olikraus/u8g2

include "esp_system.h"

include <lmic.h>
include <hal/hal.h>
include <SPI.h>

ifdef U8X8_HAVE_HW_I2C
include <Wire.h>
endif

// LoRaWAN NwkSKey, network session key // This is the default Semtech key, which is used by the prototype TTN // network initially. static const PROGMEM u1_t NWKSKEY[16] = { 0x2B, 0x7E, 0x15, 0x16, 0x28, 0xAE, 0xD2, 0xA6, 0xAB, 0xF7, 0x15, 0x88, 0x09, 0xCF, 0x4F, 0x3C };

// LoRaWAN AppSKey, application session key // This is the default Semtech key, which is used by the prototype TTN // network initially. static const u1_t PROGMEM APPSKEY[16] = { 0x2B, 0x7E, 0x15, 0x16, 0x28, 0xAE, 0xD2, 0xA6, 0xAB, 0xF7, 0x15, 0x88, 0x09, 0xCF, 0x4F, 0x3C };

// LoRaWAN end-device address (DevAddr) // See http://thethingsnetwork.org/wiki/AddressSpace static const u4_t DEVADDR = 0x03FF0001 ; // <-- Change this address for every node!

int sensorPin = 34; // select the input pin for the potentiometer int ledPin = 25; // select the pin for the LED int sensorValue = 0; // variable to store the value coming from the sensor int counter = 0;

// These callbacks are only used in over-the-air activation, so they are // left empty here (we cannot leave them out completely unless // DISABLE_JOIN is set in config.h, otherwise the linker will complain). void os_getArtEui (u1_t* buf) { } void os_getDevEui (u1_t* buf) { } void os_getDevKey (u1_t* buf) { }

uint8_t mydata[] = "Empty"; static osjob_t sendjob;

// Schedule TX every this many seconds (might become longer due to duty // cycle limitations). const unsigned TX_INTERVAL = 60;

// Pin mapping const lmic_pinmap lmic_pins = {

   .nss = 6,
   .rxtx = LMIC_UNUSED_PIN,
   .rst = 5,
   .dio = {2, 3, 4},

};

void onEvent (ev_t ev) {

   Serial.print(os_getTime());
   Serial.print(": ");
   switch(ev) {
       case EV_SCAN_TIMEOUT:
           Serial.println(F("EV_SCAN_TIMEOUT"));
           break;
       case EV_BEACON_FOUND:
           Serial.println(F("EV_BEACON_FOUND"));
           break;
       case EV_BEACON_MISSED:
           Serial.println(F("EV_BEACON_MISSED"));
           break;
       case EV_BEACON_TRACKED:
           Serial.println(F("EV_BEACON_TRACKED"));
           break;
       case EV_JOINING:
           Serial.println(F("EV_JOINING"));
           break;
       case EV_JOINED:
           Serial.println(F("EV_JOINED"));
           break;
       case EV_RFU1:
           Serial.println(F("EV_RFU1"));
           break;
       case EV_JOIN_FAILED:
           Serial.println(F("EV_JOIN_FAILED"));
           break;
       case EV_REJOIN_FAILED:
           Serial.println(F("EV_REJOIN_FAILED"));
           break;
           break;
       case EV_TXCOMPLETE:
           Serial.println(F("EV_TXCOMPLETE (includes waiting for RX windows)"));
           if(LMIC.dataLen) {
               // data received in rx slot after tx
               Serial.print(F("Data Received: "));
               Serial.write(LMIC.frame+LMIC.dataBeg, LMIC.dataLen);
               Serial.println();
           }
           // Schedule next transmission
           os_setTimedCallback(&sendjob, os_getTime()+sec2osticks(TX_INTERVAL), do_send);
           break;
       case EV_LOST_TSYNC:
           Serial.println(F("EV_LOST_TSYNC"));
           break;
       case EV_RESET:
           Serial.println(F("EV_RESET"));
           break;
       case EV_RXCOMPLETE:
           // data received in ping slot
           Serial.println(F("EV_RXCOMPLETE"));
           break;
       case EV_LINK_DEAD:
           Serial.println(F("EV_LINK_DEAD"));
           break;
       case EV_LINK_ALIVE:
           Serial.println(F("EV_LINK_ALIVE"));
           break;
        default:
           Serial.println(F("Unknown event"));
           break;
   }

}

void do_send(osjob_t* j){

   // Check if there is not a current TX/RX job running
   if (LMIC.opmode & OP_TXRXPEND) {
       Serial.println(F("OP_TXRXPEND, not sending"));
   } else {
       // Prepare upstream data transmission at the next possible time.
       LMIC_setTxData2(1, mydata, sizeof(mydata)-1, 0);
       Serial.println(F("Packet queued"));
   }
   // Next TX is scheduled after TX_COMPLETE event.

}

/*

 U8glib Example Overview:
   Frame Buffer Examples: clearBuffer/sendBuffer. Fast, but may not work with all Arduino boards because of RAM consumption
   Page Buffer Examples: firstPage/nextPage. Less RAM usage, should work with all Arduino boards.
   U8x8 Text Only Example: No RAM usage, direct communication with display controller. No graphics, 8x8 Text only.

/

// U8g2 Contructor List (Frame Buffer) // The complete list is available here: https://github.com/olikraus/u8g2/wiki/u8g2setupcpp

U8G2_SSD1306_128X64_NONAME_F_SW_I2C u8g2(U8G2_R0, /* clock=*/ 15, /* data=*/ 4, /* reset=*/ 16);

void u8g2_prepare(void) {

 u8g2.setFont(u8g2_font_6x10_tf);
 //https://github.com/olikraus/u8g2/wiki/fntgrpx11
 u8g2.setFontRefHeightExtendedText();
 u8g2.setDrawColor(1);
 u8g2.setFontPosTop();
 u8g2.setFontDirection(0);

}

define opennetlogobw_width 64
define opennetlogobw_height 64

static unsigned char opennetlogobw_bits[] = {

  0x00, 0x00, 0x80, 0xff, 0x1f, 0x00, 0x00, 0x00, 0x00, 0x00, 0xf8, 0x07,
  0xfc, 0x03, 0x00, 0x00, 0x00, 0x00, 0x0f, 0x00, 0x00, 0x1f, 0x00, 0x00,
  0x00, 0xe0, 0x01, 0x00, 0x00, 0x78, 0x00, 0x00, 0x00, 0x38, 0x00, 0x00,
  0x00, 0xc0, 0x03, 0x00, 0x00, 0x0e, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x1c, 0x00, 0x00, 0x00, 0xc0, 0xff,
  0x3f, 0x00, 0x70, 0x00, 0x00, 0x00, 0xf8, 0x00, 0xf0, 0x03, 0xc0, 0x00,
  0x00, 0x00, 0x0f, 0x00, 0x00, 0x0f, 0x80, 0x01, 0x00, 0xc0, 0x01, 0x00,
  0x00, 0x38, 0x00, 0x03, 0x00, 0x40, 0x00, 0x00, 0x00, 0xe0, 0x00, 0x06,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0x03, 0x1c, 0x00, 0x00, 0x00, 0xfc,
  0x03, 0x00, 0x06, 0x38, 0x00, 0x00, 0xc0, 0xff, 0x7f, 0x00, 0x1c, 0x30,
  0x00, 0x00, 0x78, 0x00, 0xe0, 0x01, 0x38, 0x60, 0x00, 0x00, 0x0e, 0x00,
  0x00, 0x07, 0x60, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x1c, 0xc0, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x30, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0xe0, 0x80, 0x01, 0x00, 0x00, 0x00, 0xfe, 0x07, 0x80, 0x01, 0x01,
  0x00, 0x00, 0xc0, 0x07, 0x3c, 0x00, 0x03, 0x00, 0x00, 0x00, 0x60, 0x00,
  0xe0, 0x00, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0x01, 0x06, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x0c, 0x00, 0x00, 0x00, 0x00, 0x00, 0xe0, 0x00, 0x18, 0x00, 0x00,
  0x00, 0x00, 0x00, 0xfe, 0x07, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x06,
  0x1c, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x38, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x60, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x78, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0xfe, 0x01, 0x80, 0x1f, 0x00, 0x00, 0x00, 0x00, 0xff, 0x03,
  0xc0, 0x3f, 0x00, 0x00, 0x00, 0x00, 0xff, 0x07, 0xe0, 0x7f, 0x00, 0x00,
  0x00, 0x00, 0xff, 0x07, 0xe0, 0x7f, 0x00, 0x00, 0x00, 0x02, 0xff, 0x07,
  0xe0, 0xff, 0x00, 0x00, 0x00, 0x04, 0xfe, 0x03, 0xe0, 0x7f, 0x00, 0x00,
  0x00, 0x0c, 0xfc, 0x03, 0xe0, 0x7f, 0x00, 0x00, 0x00, 0x38, 0xf0, 0x00,
  0xc0, 0x3f, 0x80, 0x00, 0x00, 0x78, 0x00, 0x00, 0x00, 0x06, 0xc0, 0x00,
  0x00, 0xf0, 0x01, 0x00, 0x01, 0x00, 0x60, 0x00, 0x00, 0xf0, 0x07, 0x10,
  0x1e, 0x00, 0x78, 0x00, 0x00, 0xe0, 0x3f, 0x0f, 0xf8, 0x07, 0x7e, 0x00,
  0x00, 0xe0, 0xff, 0x07, 0xf0, 0xff, 0x7f, 0x00, 0x00, 0xe0, 0xff, 0x07,
  0xc0, 0xff, 0x7f, 0x00, 0x00, 0xe0, 0xff, 0x03, 0x80, 0xff, 0x3f, 0x00,
  0x00, 0xe0, 0xff, 0x01, 0x00, 0xff, 0x3f, 0x00, 0x00, 0xf0, 0xff, 0x01,
  0x00, 0xfe, 0x3f, 0x00, 0x00, 0xf8, 0xff, 0x00, 0x00, 0xfe, 0x3f, 0x00,
  0x00, 0xfe, 0xff, 0x00, 0x00, 0xfc, 0x7f, 0x00, 0x80, 0xff, 0xff, 0x00,
  0x00, 0xfc, 0x7f, 0x00, 0xe0, 0x03, 0xff, 0x00, 0x00, 0xfe, 0xff, 0x00,
  0x04, 0x00, 0xf8, 0x00, 0x00, 0xfe, 0xff, 0x00, 0x00, 0x00, 0xf0, 0x00,
  0x00, 0xff, 0xff, 0x01, 0x00, 0x00, 0xe0, 0x00, 0x00, 0x3f, 0xe0, 0x01,
  0x00, 0x00, 0xc0, 0x00, 0x80, 0x0f, 0x80, 0x03, 0x00, 0x00, 0x80, 0x00,
  0xc0, 0x03, 0x00, 0x06, 0x00, 0x00, 0x80, 0x00, 0xe0, 0x00, 0x00, 0x08,
  0x00, 0x00, 0x00, 0x01, 0x30, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00,
  0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00  };

void u8g2_bitmap_modes(uint8_t transparent) {

 const uint8_t frame_size = 24;

 u8g2.setDrawColor(1);// Black
 u8g2.drawXBMP(0, 0, opennetlogobw_width, opennetlogobw_height, opennetlogobw_bits);

}

void draw(void) {

 u8g2_prepare();
 u8g2_bitmap_modes(0);

}

void setup(void) {

 u8g2.begin();
 pinMode(ledPin, OUTPUT);
 pinMode(sensorPin, INPUT);
 Serial.begin(115200);
 Serial.println("Programm gestartet!");

   #ifdef VCC_ENABLE
   // For Pinoccio Scout boards
   pinMode(VCC_ENABLE, OUTPUT);
   digitalWrite(VCC_ENABLE, HIGH);
   delay(1000);
   #endif

   // LMIC init
   os_init();
   // Reset the MAC state. Session and pending data transfers will be discarded.
   LMIC_reset();

   // Set static session parameters. Instead of dynamically establishing a session
   // by joining the network, precomputed session parameters are be provided.
   #ifdef PROGMEM
   // On AVR, these values are stored in flash and only copied to RAM
   // once. Copy them to a temporary buffer here, LMIC_setSession will
   // copy them into a buffer of its own again.
   uint8_t appskey[sizeof(APPSKEY)];
   uint8_t nwkskey[sizeof(NWKSKEY)];
   memcpy_P(appskey, APPSKEY, sizeof(APPSKEY));
   memcpy_P(nwkskey, NWKSKEY, sizeof(NWKSKEY));
   LMIC_setSession (0x1, DEVADDR, nwkskey, appskey);
   #else
   // If not running an AVR with PROGMEM, just use the arrays directly 
   LMIC_setSession (0x1, DEVADDR, NWKSKEY, APPSKEY);
   #endif

   // Set up the channels used by the Things Network, which corresponds
   // to the defaults of most gateways. Without this, only three base
   // channels from the LoRaWAN specification are used, which certainly
   // works, so it is good for debugging, but can overload those
   // frequencies, so be sure to configure the full frequency range of
   // your network here (unless your network autoconfigures them).
   // Setting up channels should happen after LMIC_setSession, as that
   // configures the minimal channel set.
   LMIC_setupChannel(0, 868100000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI);      // g-band
   LMIC_setupChannel(1, 868300000, DR_RANGE_MAP(DR_SF12, DR_SF7B), BAND_CENTI);      // g-band
   LMIC_setupChannel(2, 868500000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI);      // g-band
   LMIC_setupChannel(3, 867100000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI);      // g-band
   LMIC_setupChannel(4, 867300000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI);      // g-band
   LMIC_setupChannel(5, 867500000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI);      // g-band
   LMIC_setupChannel(6, 867700000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI);      // g-band
   LMIC_setupChannel(7, 867900000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI);      // g-band
   LMIC_setupChannel(8, 868800000, DR_RANGE_MAP(DR_FSK,  DR_FSK),  BAND_MILLI);      // g2-band
   // TTN defines an additional channel at 869.525Mhz using SF9 for class B
   // devices' ping slots. LMIC does not have an easy way to define set this
   // frequency and support for class B is spotty and untested, so this
   // frequency is not configured here.

   // Disable link check validation
   LMIC_setLinkCheckMode(0);

   // Set data rate and transmit power (note: txpow seems to be ignored by the library)
   LMIC_setDrTxpow(DR_SF7,14);

   // Start job
   do_send(&sendjob);

}

void loop(void) {

 digitalWrite(ledPin, LOW);
 u8g2.clearBuffer();
 draw();
 sensorValue = analogRead(sensorPin);
 u8g2.setFont(u8g2_font_6x10_tf);
 char c[64];
 String str;
 str = String(sensorValue);
 Serial.println(str);
 str.getBytes(mydata, 64);
 // mydata will be sent in do_send() which is also called in case we receive a EV_TXCOMPLETE event
 str.toCharArray(c, 64);
 u8g2.drawStr(75,0, "Sensor");
 u8g2.drawStr(75,10, "readout:");
 u8g2.drawStr(75,20, c);
 u8g2.drawStr(75,34, "LoRaWAN");
 u8g2.drawStr(75,44, "message");
 str = String(counter);
 Serial.println(str);
 str.toCharArray(c, 64);
 u8g2.drawStr(75,54, c);
 counter++;
 u8g2.sendBuffer();
 delay(2500);
 digitalWrite(ledPin, HIGH);
 delay(2500);

} </syntaxhighlight>