How to set a fix DR / Spreading Factor or Output Power
Introduction
User might want to set Fix DR or Spreading Factor to get the maximum distance. This can be down via AT Command, Or Downlink Command (in case the device is of the latest Dragino LoRaWAN stack as specify here: End Device AT or Downlink Command.
The mapping for DataRate and Spreading Factor are different for each frequency band. User can refer the LoRaWAN regional parameter to see how the map. For exampl, look at page 22, we can know that the DR0 for US915 band is SF10,125Khz.
In our STM32 base LoRaWAN end node, user can use below command to change set fix DR.
AT+ADR=0 // Disable ADR so server won't be able to change the DR on the sensor
AT+DR=0 // Set the DR to the required DataRate.
AT+TXP=50 // Manually set to highest power to 20dB. ( manually bypass 14dB limit in EU868 frequency)
For AS923 frequency band, the uplinkdwelltime will effect the setting of DR. Please see this link for more: AS923 UplinkDwellTime