Keep-alive

How to decode the keep-alive packet and how to set new keep-alive period

Keep-alive command explanation

Periodically sent message which contains the most important device data.

The data is described in Table 3. In Table 4 example packet is given.

Payload	Value		Meaning
0	01		Command byte for this packet.
1	XX		Internal temperature sensor data, bits 15:8 – T[15:8].
2	XX		Internal temperature sensor data, bits 7:0 - T[7:0]. $t,[ \degree C] = \frac{T[15:0] - 400 }{10}$
3	XX		Relative Humidity data. $RH, [ \%] = \frac{XX*100}{256}$
4	XX		Device battery voltage. $Vb, [mV] = XX * 8 + 1600$
5	XX	Bits 7:3	Reserved.
		Bit 2	External thermistor operational status: 1: Thermistor connection is broken; 0: The thermistor is properly connected.
		Bits 1:0	External thermistor temperature data, bits 9:8 - T[9:8]
6	XX		External thermistor temperature data, bits 7:0 - T[7:0]. The measurement resolution is $0.1 \degree C$ . $t, [\degree C] = \frac{T[9:0]}{10}$

Table 3

Payload	Value		Meaning
0	01		Command byte for this packet.
1	02		Internal temperature sensor data, bits 15:8 – T[15:8].
2	88		Temperature data, bits 7:0. $t,[ \degree C] = \frac{648 - 400 }{10} = 24.8$
3	80		Relative humidity, $RH, [\%] = \frac{128 * 100}{256} = 50$
4	AB		Battery voltage, $Vb, [mV] = 171 * 8 + 1600 = 2968$
5	02	Bits 7:3	Reserved.
		Bit 2	External thermistor operational status: 1: Thermistor connection is broken; 0: The thermistor is properly connected.
		Bits 1:0	External thermistor temperature data, bits 9:8 - T[9:8]
6	9C		External thermistor temperature data, bits 7:0 - T[7:0]. $t, [\degree C] = \frac{0x29C}{10} = \frac{668}{10} = 66.8$

Table 4

Set keep-alive period command explanation

Sets the period of the device keep-alive command messages. See table 5 for details.

Byte index	Bit index	Hex value – Meaning
0	-	02 – The command will set the device keep-alive period.
1	-	XX – keep-alive period in minutes. Value 0x00 isn’t applicable. Default value: 0x03.

Table 5

Example command, [Hex]: 020A

The example sets the keep-alive period to 10 minutes.

Note that the keep-alive period must respect the LoRaWAN messages duty cycle limitations. Otherwise the message will be sent when this is allowed. Also, the bigger keep-alive period, the less battery discharge. In most of cases, min. allowed period is 3 minutes and recommended values are 10 minutes or greater.

Get keep-alive period command explanation

This command is used to get the device keep-alive command messages period. Server sends the command code and the response is sent from the device together with next keep-alive command. The sent command request and the received command response are described in Table 6. The keep-alive in the response is omitted for clarity.

Byte index	Bit index	Sent request	Received response
0	-	12 – The command code.	12 – The command code.
1	-		XX – device keep-alive period in minutes.

Table 6

Example command sent from server: 0x12;

Example command response: 0x1209 – Device keep-alive period is 9 minutes.