A downlink string is a combination of Hex values that triggers the configuration of a device OTA. The downlink string should be sent to the device to effect changes in parameter settings.
Here's an example of a downlink string created with Reference to section 7.2.3 of the SensorData/SensorNode Sigfox LoRa Integration document.
The table below shows an example of how the downlink (12) to set Digital Input parameters for a SensorNode OTA was derived
Downlink 12 at default DEC value 12
Binary to Hex
Set Global Max Alarm rate to 1 hour: using the minute
range of 129-255. 60 mins = DEC value 134 derived from the range
– i.e. 129=10 minutes, 130=20 minutes, 131=30 minutes…etc
All Alarm Statuses for digital inputs Set to OFF (Binary)0000 0000
Set Debounce period to 30 seconds
Disable Debounce for DI2
Disable Debounce for DI3
Set Pull Direction to Pulldown on Digital Input1 Binary 0000 0011*
*Some Documents have the hour range, if an hour range is available for the device being configured then the minute range only applies up to 59 minutes.
*All Binary inputs are set in reverse from right to left i.e. 0011 (inputs 1 & 2 are set to Active; 3 & 4 are Inactive)
*The form taken by Time values being configured should follow absolute values. E.g. the Alarm rate can not be set to 5h:30min:10sec. In this case we will have to round off the time to 6 hours or 5 hours, whichever suits your requirements best. Thus setting the Alarm rate to 5 hours - 300 mins (DEC:158=HEX:9E)