Cayenne Low Power Payload

Overview

The Cayenne Low Power Payload (LPP) provides a convenient and easy way to send data over LPWAN networks such as LoRaWAN. The Cayenne LPP is compliant with the payload size restriction, which can be lowered down to 11 bytes, and allows the device to send multiple sensor data at one time.

Additionally, the Cayenne LPP allows the device to send different sensor data in different frames. In order to do that, each sensor data must be prefixed with two bytes:

Data Channel: Uniquely identifies each sensor in the device across frames, eg. “indoor sensor”
Data Type: Identifies the data type in the frame, eg. “temperature”.

Payload structure

1 Byte	1 Byte	N Bytes	1 Byte	1 Byte	M Bytes	...
Data1 Ch.	Data1 Type	Data1	Data2 Ch.	Data2 Type	Data2	...

Data Types

Data Types conform to the IPSO Alliance Smart Objects Guidelines, which identifies each data type with an “Object ID”. However, as shown below, a conversion is made to fit the Object ID into a single byte.

LPP_DATA_TYPE = IPSO_OBJECT_ID - 3200

Each data type can use 1 or more bytes to send the data according to the following table.

Type	IPSO	LPP	Hex	Data Size	Data Resolution per bit
Digital Input	3200	0	0	1	1
Digital Output	3201	1	1	1	1
Analog Input	3202	2	2	2	0.01 Signed
Analog Output	3203	3	3	2	0.01 Signed
Illuminance Sensor	3301	101	65	2	1 Lux Unsigned MSB
Presence Sensor	3302	102	66	1	1
Temperature Sensor	3303	103	67	2	0.1 °C Signed MSB
Humidity Sensor	3304	104	68	1	0.5 % Unsigned
Accelerometer	3313	113	71	6	0.001 G Signed MSB per axis
Barometer	3315	115	73	2	0.1 hPa Unsigned MSB
Gyrometer	3334	134	86	6	0.01 °/s Signed MSB per axis
GPS Location	3336	136	88	9	Latitude : 0.0001 ° Signed MSB
					Longitude : 0.0001 ° Signed MSB
					Altitude : 0.01 meter Signed MSB

Examples

Device with 2 temperature sensors

Payload (Hex)	03 67 01 10 05 67 00 FF
Data Channel	Type	Value
03 ⇒ 3	67 ⇒ Temperature	0110 = 272 ⇒ 27.2°C
05 ⇒ 5	67 ⇒ Temperature	00FF = 255 ⇒ 25.5°C

Device with temperature and acceleration sensors

Frame N

Payload (Hex)	01 67 FF D7
Data Channel	Type	Value
01 ⇒ 1	67 ⇒ Temperature	FFD7 = -41 ⇒ -4.1°C

Frame N+1

Payload (Hex)	06 71 04 D2 FB 2E 00 00
Data Channel	Type	Value
06 ⇒ 6	71 ⇒ Accelerometer	X: 04D2 = +1234 ⇒ +1.234G
		Y: FB2E = -1234 ⇒ -1.234G
		Z: 0000 = 0 ⇒ 0G

Example use

#include 'CayenneLPP.h';

#define MAX_SIZE 200; // depends on spreading factor and frequency used

CayenneLPP Payload(MAX_SIZE);

float celsius = -4.1;
float accel[] = {1.234, -1.234, 0};
float rh = 30;
float hpa = 1014.1;
float latitude = 42.3519;
float longitude = -87.9094;
float altitude:10

int size = 0;

Payload.reset();
size = Payload.addTemperature(0, celsius);

if (size == 0) {
    // not enough byte left to add the data
}

else {
    // add function returned current payload size
}


Payload.addAccelerometer(1, accel[0], accel[1], accel[2]);
Payload.addRelativeHumidity(3, rh);
Payload.addBarometricPressure(4, hpa);
Payload.addGPS(5, latitude, longitude, altitude);

// Call LoRaWAN library to send the frame
LORA_SEND(Payload.getBuffer(), Payload.getSize());

sse-engineering/cayennelpp