LoRa uplink and downlink

#1

Can someone could help me to understand this sketch and explain me how to receive downlink data :
#include “LoRaWan_APP.h”

/* OTAA para*/
uint8_t devEui[] = { 0x22, 0x32, 0x33, 0x00, 0x00, 0x88, 0x88, 0x02 };
uint8_t appEui[] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
uint8_t appKey[] = { 0x88, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88, 0x66, 0x01 };

/* ABP para*/
uint8_t nwkSKey[] = { 0x15, 0xb1, 0xd0, 0xef, 0xa4, 0x63, 0xdf, 0xbe, 0x3d, 0x11, 0x18, 0x1e, 0x1e, 0xc7, 0xda,0x85 };
uint8_t appSKey[] = { 0xd7, 0x2c, 0x78, 0x75, 0x8c, 0xdc, 0xca, 0xbf, 0x55, 0xee, 0x4a, 0x77, 0x8d, 0x16, 0xef,0x67 };
uint32_t devAddr = ( uint32_t )0x007e6ae1;

/LoraWan channelsmask, default channels 0-7/
uint16_t userChannelsMask[6]={ 0x00FF,0x0000,0x0000,0x0000,0x0000,0x0000 };

/LoraWan region, select in arduino IDE tools/
LoRaMacRegion_t loraWanRegion = ACTIVE_REGION;

/LoraWan Class, Class A and Class C are supported/
DeviceClass_t loraWanClass = CLASS_A;

/the application data transmission duty cycle. value in [ms]./
uint32_t appTxDutyCycle = 15000;

/OTAA or ABP/
bool overTheAirActivation = true;

/ADR enable/
bool loraWanAdr = true;

/* Indicates if the node is sending confirmed or unconfirmed messages */
bool isTxConfirmed = true;

/* Application port /
uint8_t appPort = 2;
/!

  • Number of trials to transmit the frame, if the LoRaMAC layer did not
  • receive an acknowledgment. The MAC performs a datarate adaptation,
  • according to the LoRaWAN Specification V1.0.2, chapter 18.4, according
  • to the following table:
  • Transmission nb | Data Rate
  • ----------------|-----------
  • 1 (first) | DR
  • 2 | DR
  • 3 | max(DR-1,0)
  • 4 | max(DR-1,0)
  • 5 | max(DR-2,0)
  • 6 | max(DR-2,0)
  • 7 | max(DR-3,0)
  • 8 | max(DR-3,0)
  • Note, that if NbTrials is set to 1 or 2, the MAC will not decrease
  • the datarate, in case the LoRaMAC layer did not receive an acknowledgment
    */
    uint8_t confirmedNbTrials = 4;

/* Prepares the payload of the frame */
static void prepareTxFrame( uint8_t port )
{
/*appData size is LORAWAN_APP_DATA_MAX_SIZE which is defined in “commissioning.h”.
*appDataSize max value is LORAWAN_APP_DATA_MAX_SIZE.
*if enabled AT, don’t modify LORAWAN_APP_DATA_MAX_SIZE, it may cause system hanging or failure.
*if disabled AT, LORAWAN_APP_DATA_MAX_SIZE can be modified, the max value is reference to lorawan region and SF.
*for example, if use REGION_CN470,
*the max value for different DR can be found in MaxPayloadOfDatarateCN470 refer to DataratesCN470 and BandwidthsCN470 in “RegionCN470.h”.
*/
appDataSize = 4;
appData[0] = 0x00;
appData[1] = 0x01;
appData[2] = 0x02;
appData[3] = 0x03;
}

//downlink data handle function example
void downLinkDataHandle(McpsIndication_t *mcpsIndication)
{
Serial.printf("+REV DATA:%s,RXSIZE %d,PORT %d\r\n",mcpsIndication->RxSlot?“RXWIN2”:“RXWIN1”,mcpsIndication->BufferSize,mcpsIndication->Port);
Serial.print("+REV DATA:");
for(uint8_t i=0;iBufferSize;i++)
{
Serial.printf("%02X",mcpsIndication->Buffer[i]);
}
Serial.println();
uint32_t color=mcpsIndication->Buffer[0]<<16|mcpsIndication->Buffer[1]<<8|mcpsIndication->Buffer[2];
#if(LoraWan_RGB==1)
turnOnRGB(color,5000);
turnOffRGB();
#endif
}

void setup() {
Serial.begin(115200);
Mcu.begin();
deviceState = DEVICE_STATE_INIT;
}

void loop()
{
switch( deviceState )
{
case DEVICE_STATE_INIT:
{
#if(LORAWAN_DEVEUI_AUTO)
LoRaWAN.generateDeveuiByChipID();
#endif
LoRaWAN.init(loraWanClass,loraWanRegion);
break;
}
case DEVICE_STATE_JOIN:
{
LoRaWAN.join();
break;
}
case DEVICE_STATE_SEND:
{
prepareTxFrame( appPort );
LoRaWAN.send();
deviceState = DEVICE_STATE_CYCLE;
break;
}
case DEVICE_STATE_CYCLE:
{
// Schedule next packet transmission
txDutyCycleTime = appTxDutyCycle + randr( -APP_TX_DUTYCYCLE_RND, APP_TX_DUTYCYCLE_RND );
LoRaWAN.cycle(txDutyCycleTime);
deviceState = DEVICE_STATE_SLEEP;
break;
}
case DEVICE_STATE_SLEEP:
{
LoRaWAN.sleep(loraWanClass);
break;
}
default:
{
deviceState = DEVICE_STATE_INIT;
break;
}
}
}

Thanks
Eric

#2

Hi Eric
First of all you need to understand how your LoRa messages are to be received and processed. Who’s gateway are you going to use? How is this gateway connected to data management solutions like The Things Network?
What country are you in and what frequency plan will you be using?

I run exactly this code and have my own TTN gateway mounted on the roof of my house. It is connected to TTN in Australia as I live in New Zealand. I use AU915 frequency plan so had to set this up in Arduino under Tools–> LORaWAN region

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My TTN router/modem is a Micro Tik wAP LR9 which I can thoroughly recommend. I have a link to the setup to connect to TTN at LoRa Gateway Setup
Note this router specifically supports TTN
image
Now that I have a gateway I need to set up applications in TTN. I will leave you to find this but it is also covered by my WiKi, the only change is to use Activation Mode Over the air (OTAA).

It will allow you to create the devEUI, appEUI, and appKEY, all of which you copy to the OTAA settings in the ino file you showed above. Compile and load into your LoRa node (Heltec LoRa OLED (V3)) in my case and you should start to see message arrive at your gateway and application. the gateway will show encrypted messages, your application in TTN will show decrypted messages.

If using someone else’s gateway good luck as you will probably need to contact them to find out their frequency plan, their network server etc and then figure out how to get an account with their network provider so you can access your messages.

I then use Node-Red to receive these messages from TTN using MQTT

image

You need your username and security key to pull this data from TTN.

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I write simple functions to pull the data from the payload for example my temperature value is sent as ‘degreesC’ in the payload so my function is:

var value = msg.payload.uplink_message.decoded_payload.degreesC;
value1 = parseFloat((value).toFixed(3));
msg.payload = value1;
msg.topic = "TempH1";
return msg;

I then send this value to InfluxDB my database and display all values in Chronograph.

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My DHT22 sensors are playing up so ignore the temperature and humidity from those

1 Like
#3

Thank you very much for all the usefull explanations.
I achieve an uplink connection from the wifi-lora-32-v3 node to ttn through my dragino lora gateway. Now i would like to expriment and understand the downlink. I’m trying to use ttn schedule downlink :

image
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But i receive nothing at the node as the serial port print nothing about this.

In the sketch, downLinkDataHandle is defined but seems to be not used …
Eric