Problems with Things Network Downlink (LoRaWANStack.cpp)

Mbed OS
1

Hi, I’ve been having problems with trying to send data to a Things Network node. I’ve tracked it down to this section of code
if (_rx_msg.msg.mcps_indication.port != port || !(flags & received_flags)) {
return LORAWAN_STATUS_WOULD_BLOCK;
}
If I add an extra set of brackets to get this
if (_rx_msg.msg.mcps_indication.port != (port || !(flags & received_flags))) {
return LORAWAN_STATUS_WOULD_BLOCK;
}
it works OK, however I don’t understand why the extra set of brackets should make any difference.

Any suggestions?

Best wishes,

J

2

Hi Jeremy,
You are just changing the order of operation of the logic. Before the bracket, you would compare the port and rx_msg.msg.mcps_indication.port and then do a logical “or” with “!(flags & received_flags)”. After the bracket, you are comparing rx_msg.msg.mcps_indication.port and “(port || !(flags & received_flags)”. Therefore, the second work probably because you isolate the pin and then compare with the rx_msg.msg.mcps_indication.port.

-Peter

3

Hi Peter,

Thanks for the reply. I had spotted this almost immediately after I posted the message to the forum (it had been a long day) , but due to the permission required for the forum I couldn’t get back in and edit my post.

With hindsight I still think this code
(_rx_msg.msg.mcps_indication.port != port || !(flags & received_flags))
would be better written as
((_rx_msg.msg.mcps_indication.port != port) || !(flags & received_flags))
I’m not a great fan of having to remember precedence.

For those looking at the Things Network and Lorawan, the problem was I wasn’t sending the message to the right port, which under MBED is port 15. This is defined by the macro MBED_CONF_LORA_APP_PORT which is in the mbed_config.h file if you export the mbed project to uVision. I don’t think I found how to change it in the MBed cloud environment.

Thanks again,

Jeremy