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		sAQI bits 8:1 – sAQI[8:1].
2	XX	Bit 7	sAQI bit 0 – sAQI[0]. Result value is calculated as: $sAQI = sAQI[8:0] * 16$
		Bits 6:2	AQI bits 4:0 – AQI[4:0]. Result value is calculated as: $AQI = AQI[4:0] * 16$
		Bits 1:0	CO2eq bits 9:8 – CO2eq[9:8].
3	XX		CO2eq bits 7:0 – CO2eq[7:0]. Result value is calculated as: $CO2eq, [ppm] = CO2eq[9:0] * 32$
4	XX		VOC bits 7:0 – VOC[7:0]. Result value is calculated as: $VOC, [ppm] = VOC[7:0]*4$
5	XX		Relative humidity data. Relative humidity,$[\%] = \frac{XX*4}{10}$
6	XX		Pressure data, bits 10:3 – P[10:3].
7	XX	Bits 7:5	Pressure data, bits 2:0 – P[2:0]. Result value is calculated as: $P, [hPa] = \frac{P[10:0] * 40 + 30000}{100}$
		Bits 4:0	Temperature data, bits 10:6 – T[10:6].
8	XX	Bits 7:2	Temperature data, bits 5:0 – T[5:0]. Result value is calculated as: $t, [\degree C] = \frac{T[10:0] - 400}{10}$
	XX	Bits 1:0	Air quality related parameters accuracy: 0: Sensor data is unreliable (Sensor stabilization); 1: Low accuracy, to reach higher accuracy please expose sensor once to good air (for about hour) and bad air for auto- trimming; 2: Medium accuracy: auto-trimming ongoing; 3: High accuracy.
9	XX		Device battery voltage. $Voltage, [mV] = XX*8 + 1600$

Table 3

Payload index	Value		Meaning
0	01		Command byte for this packet.
1	07		sAQI[8:1] = 0x07.
2	A4	Bit 7	sAQI[0] = 0x01. $sAQI = sAQI[8:0] * 16 = 0x0F * 16 = 240$
		Bits 6:2	$AQI = AQI[4:0] * 16 = 0x09 * 16 = 144$
		Bits 1:0	CO2eq[9:8] = 0x00.
3	4C		CO2eq[7:0] = 0x4C $CO2eq, [ppm] = CO2eq[9:0] * 32 = 0x4C * 32 = 2432$
4	03		$VOC, [ppm] = VOC[7:0]*4 = 0x03*4 = 12$
5	53		Relative humidity,$[\%] = \frac{0x53*4}{10} = 33.2$
6	C9		P[10:3] = 0xC9.
7	A9	Bits 7:5	P[2:0] = 0x05 $P, [hPa] = \frac{P[10:0] * 40 + 30000}{100} = \frac{0x64D * 40 + 30000}{100} = 945.2$
		Bits 4:0	Temperature data, bits 10:6 – T[10:6].
8	E3	Bits 7:2	Temperature data, bits 5:0 – T[5:0] $t, [\degree C] = \frac{T[10:0] - 400}{10} = \frac{0x278 - 400}{10} = 23.2$
		Bits 1:0	Air quality related parameters accuracy: 3
9	CD		$Voltage, [mV] = CD*8 + 1600 = 205 * 8 + 1600 = 3240$

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.

Example command sent from server: 0x12;

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