LoPy with TTN Nano Gateway and Arduino (and RFM95) with LMIC lib

[Clemens]

I'm trying to connect an Adafruit Feather M0 with RFM95 as node via a LoPy as nano gateway to the TTN. What I did till now and what is working:

LoPy as TTN Nano Gateway

I updated my LoPy to the latest firmware version and installed the nano gateway software along this tutorial.

In config.py I used this (default) LoRa settings

# for EU868
LORA_FREQUENCY = 868100000
LORA_GW_DR = "SF7BW125" # DR_5
LORA_NODE_DR = 5

• the LoPy is showing up in the TTN console
• it receives packages, but unfortunately not the data from my node ;-) the incoming "foreign" packages are specified in the TTN console as, so this seems to be a working setup:
  -- frequency: 868.1
  -- mod: lora
  -- CR: 4/5
  -- data rate: SF7 BW125
• so I assume the gateway is working but not in combination with my node! :-(

Arduino / Adafruit Feather M0 with RFM95

I installed the Arduino-LMIC library from Matthijs Kooijman following this tutorial mostly, and with the help of some threads here [1] [2]. For details see https://community.hiveeyes.org/t/testing-adafruit-feather-m0-lora-rfm95-and-ttn/528

After installation I could send data to a public TTN gateway ("full" TTN Gateway, not a single channel) with a range of 1 km!

Addaption Nano Gateway

For working with the Nano Gateway I had to reduce the available channels in the LMIC code. I used the ttn-abp.ino example and commented all frequency lines out exept one:

LMIC_setupChannel(0, 868100000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI);
// specify only the single (!) channel matching with the LoPy nano gateway!
// uncomment all other  
//    LMIC_setupChannel(1, 868300000, DR_RANGE_MAP(DR_SF12, DR_SF7B), BAND_CENTI); 
//    LMIC_setupChannel(2, 868500000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI); 
//    
//    LMIC_setupChannel(7, 867900000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI); 
//    LMIC_setupChannel(8, 868800000, DR_RANGE_MAP(DR_FSK,  DR_FSK),  BAND_MILLI); 

following this advice. https://forum.pycom.io/topic/1635/lorawan-gateway-using-lopy-and-sx1276-node/2

So I think I have done all necessary steps but the data of the Arduino/Feather/LMIC device is not showing up at TTN.

I have in both configuration files a frequency of 868.1 MHz. I wonder hwo can I check or change the other parameters like CR: 4/5 or data rate: SF7 BW125 to match or did I oversee an other point I have to adapt?

[Clemens]

I think I have found the solution after some research on the TTN board:
https://www.thethingsnetwork.org/forum/t/can-lmic-1-6-be-set-up-to-use-a-single-channel-and-sf/5207/11

Beside uncommenting the non fitting channels you have to

• disable the (other) default channels and
• announce a fix spreading factor matching that on the LoPy / nano gateway

Now it is working! Great!

[Clemens]

In addition a nice explanation from Andreas Spiess

https://youtu.be/Ya-QlEaonLU?t=5m25s