Connect LoPy LoRa with Semtech Board

[nikkson]

Hello,

I am trying to connect Semtech LoRa development board with LoPy. I am sending 9 bytes of payload from Semtech board each 2 seconds. Format of the packet that is sent from Semtech board is: first 4 bytes are unsigned int (used for packet ID), other 5 bytes are dummy.

I am able to receive packets on LoPy, but with following problems:

• Not able to receive each packet, but every second (packet loss is 50%)
• Able to extract packet ID properly only if reading first two bytes: _LORA_PKG_FORMAT = "H" (unsigned short int, 2 bytes). If I put _LORA_PKG_FORMAT = "I" (unsigned int, 4 bytes), it is decoded as garbage.

Code that I used for reception is given below:

import pycom
import socket
import time
import struct
from network import LoRa
pycom.heartbeat(False)
pycom.rgbled(0xffffff)
_LORA_PKG_FORMAT = "I"
lora = LoRa(mode=LoRa.LORA,
frequency=868000000,
power_mode=LoRa.ALWAYS_ON,
tx_power=14,
bandwidth=LoRa.BW_125KHZ,
sf=10,
preamble=8,
coding_rate=LoRa.CODING_4_6,
tx_iq=False,
rx_iq=False,
public=False)

s = socket.socket(socket.AF_LORA, socket.SOCK_RAW)
s.setblocking(False)
while True:
rxBuf = s.recv(9)
if (len(rxBuf) > 0)
rxData = struct.unpack(_LORA_PKG_FORMAT, rxBuf)
print(rxData)

Does anyone have an idea what should be done to receive each packet and to properly decode all four bytes?

Cheers, Nikola