Max Payload size in mDot_LoRa_Connect_Example

[Zia Syed]

Hi,

I know the Lora payload size is 256 bytes, but i am not able to send more than 12 characters over using the mBed Lora Connect Example. https://developer.mbed.org/teams/MultiTech/code/mDot_LoRa_Connect_Example/

See below the code and the output. Any suggestion on what i am doing wrong here?
Thanks

std::string data_str = “Aquickbrownfox”;
printf(“Payload Size %d”,data_str.size());
if ((ret = dot->send(data)) != mDot::MDOT_OK) {
logError(“failed to send”, ret, mDot::getReturnCodeString(ret).c_str());
} else {
logInfo(“successfully sent data to gateway”);

}

Console:
Payload Size 14 [ERROR] Data exceeds datarate max payload

[Jason Reiss]

256 is the maximum physical LoRa packet size. It is not the max payload size, 242 bytes. That is the maximum allowed in the LoRaWAN protocol and a limitation of the SxRadio chips.

There are also regional regulations to consider. Regions may restrict dwell time or duty-cycle. EU restrict by duty cycle and US by 400 ms dwell time.

See https://www.lora-alliance.org/portals/0/specs/LoRaWAN%20Specification%201R0.pdf for limits according to datarate per region.

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