Aktuelle Version vom 5. April 2018, 19:27 Uhr

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

Hintergrund

Projekt LoRa

Hardware-Stückliste

Luftgütesensor MQ-135 mit AD-Wandler ADS1115 auf Breadboard

Gesamtaufbau (Der separate AD-Wandler ist nötig, da der AD-Wandler auf dem Board nur maximal 3,3V verträgt.)

Name	Regierungszeit	Beschaffung
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.	http://www.heltec.cn/project/wifi-lora-32/ https://www.amazon.de/gp/product/B078M74NNN/ https://www.amazon.de/gp/product/B076T28KWG/ https://www.thethingsnetwork.org/forum/t/big-esp32-sx127x-topic-part-1/10247 https://de.aliexpress.com/item/ESP32-0-96-Inch-Blue-OLED-Display-Bluetooth-WIFI-CP2102-LoRa-Kit-32-Module-Internet-Development/32840325780.html
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	https://wiki.c3re.de/index.php/Umweltmessnetz/Sensorstation https://de.aliexpress.com/item/New-MQ135-MQ-135-Air-Quality-Sensor-Hazardous-Gas-Detection-Module-For-Arduino-M2-PromotionHot-New/32502221002.html https://www.amazon.de/dp/B06Y53QNP3/
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)	ca. 10 EUR	https://www.amazon.de/gp/product/B01N8ODF5C/ https://www.amazon.de/gp/product/B01M0P86J9/
Optional Breadboard und Kabel für Versuchsaufbau	ca. 10 EUR	https://www.amazon.de/Jumper-Wire-Mit-Breadboard-Female-Female/dp/B073X7GZ1P/ https://www.amazon.de/Elegoo-Breadboard-Solderless-Distribution-Verbindungsblöcke/dp/B01MCRZFE5/ https://www.amazon.de/Elegoo-Female-Female-Male-Female-Steckbrücken-Drahtbrücken-bunt/dp/B01EV70C78/

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

C-Code (Arduino-Style) zum Auslesen des Sensors und Versenden des Ergebnisses per LoRaWAN

 #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>
 
 #include <Wire.h>
 
 #include <Adafruit_ADS1015.h>
 
 Adafruit_ADS1115 ads;  /* Use this for the 16-bit version */
 
 // 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 ledPin = 25;      // select the pin for the LED
 int16_t 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.
 }
 
 
 // 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);
 
 
 
 #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 setup(void) {
   ads.begin();
   
   u8g2.begin();
   u8g2.setFont(u8g2_font_6x10_tf);
   //https://github.com/olikraus/u8g2/wiki/fntgrpx11
   u8g2.setFontRefHeightExtendedText();
   u8g2.setDrawColor(1);
   u8g2.setFontPosTop();
   u8g2.setFontDirection(0);
   
   pinMode(ledPin, OUTPUT);
   Serial.begin(115200);
   Serial.println("Programm gestartet!");
 
 //  // 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();
   u8g2_bitmap_modes(0);
   
   int16_t sensorValue;
 
   sensorValue = ads.readADC_SingleEnded(0);
   
   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);
 }

InfluxDB und Grafana
Verlauf der Sensor-Messwerte vom MQ-135