RAK3172: "+EVT: TX_DONE", wait so long after "AT+SEND"

Why does it take so long to receive the return message “+EVT: TX_DONE” after sending the “AT+SEND” command? Is it possible to reduce this waiting time?

In my application, the uplink message is sent every 10 seconds. Initially, it takes about 6 seconds to receive “+EVT: TX_DONE”. However, after running for approximately 15 minutes, this waiting time increases to 12 seconds for the return message. Eventually, it reaches 19 seconds.

Surprisingly, at the moment of 19 seconds waiting time, I received a return message stated “Restricted_Wait_819_ms”. What does it mean?

Welcome to RAK forum @mctang ,

Based on the details you shared, it is likely you are sending a huge payload. The change on duration might be because of the change of DR.

In any case, the transmit interval of 10seconds (if really needed by your application) is not suited for LoRaWAN. Depending where you are, you will need to follow dutycycle or dwelltime rules on using the unlicensed frequency band. That’s why you see the Restricted_Wait is because you uplink to much and the FW is inhibiting you to uplink more.