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 index	Value		Meaning
0	01		Command byte for this packet.
1	XX		CO2 value in ppm, bits [15:8]
2	XX		CO2 value in ppm, bits [7:0]
3	XX		Internal temperature sensor data, bits 15:8 - T[15:8]
4	XX		Internal temperature sensor data, bits 7:0 - T[7:0]. $t, [\degree C] = \frac{T[15:0] - 400}{10}$
5	XX		Relative humidity data. Relative humidity,$[\%] = \frac{XX*100}{256}$
6	XX		Device battery voltage. $Voltage, [mV] = XX*8 + 1600$

Table 3

Payload index	Value		Meaning
0	01		Command byte for this packet.
1	06
2	5C		CO2, [ppm] = 0x065C = 1628.
3	02
4	8C		Temperature $t, [\degree C] = \frac{0x028C - 400}{10} = \frac{652 - 400}{10} = 25.2$
5	8B		Relative humidity,$[\%] = \frac{0x8B*100}{256} = \frac{139*100}{256} = 54.29$
6	DF		Device battery voltage. $Voltage, [mV] = 0xDF*8 + 1600 = 223 * 8 +1600 = 3384$

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: 0x0A.

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.