Library API
This section will describe the API of this library.
Payload encoder
The public API of the encoder class has these functions available:
namespace CayenneLPP
{
template <size_t static_size>
class CayenneLPP
{
public:
/**
* \brief Constructor, this class is now a template class
* and supposed to be initialized with template syntax.
* \example Initialize like this:
* CayenneLPP::CayenneLPP<100> enc_inst;
* Please note that this reserves a buffer of 100 bytes,
* you are free to go higher or lower, but keep in mind that
* a GPS measurement is the largest measurement and takes atleast 11-bytes to store.
*/
CayenneLPP();
/**
* \brief Since this class is initialized statically, there is nothing to clean up.
*/
~CayenneLPP();
/**
* \brief Reset the cursor back to zero.
*/
void reset(void);
/**
* \brief This gets the amount of bytes currently stored in the buffer
* \return The amount of bytes stored
*/
constexpr uint8_t getSize(void);
/**
* \brief This gets a pointer to the statically allocated internal buffer
* \return Pointer to the buffer
*/
constexpr uint8_t *getBuffer(void);
/**
* \brief Store a new measurement in the encoder buffer
* \return The cursor position in the internal buffer
*/
const uint8_t setMeasurement(const uint8_t channel,
const Measurement_t *measurement);
};
}
Reset function
The Reset function will reset the internal buffer byte counter to zero. If elements are added to the buffer after a call to reset, previous elements will be overwritten.Error checking
This function does not have error checking! As the buffer is statically assigned and no parameters are entered in to this function, error checking is not needed.
Parameters
This function does not accept parameters!
Return
This function returns void.
The buffer will not be emptied!
Please note that a call to reset will not empty buffer, it will only reset the counter to zero! All the old data will still be in the buffer after the reset call.
Usage
The function can be used by first initializing the class and then calling the reset() function:
#include <CayenneLPP.hpp>
#define BUF_SIZE 100
void main(){
CayenneLPP::CayenneLPP<BUF_SIZE> encoder;
encoder.reset();
}
getSize function
The getSize function will return the current amount of bytes stored in the buffer.Error checking
This function does not have error checking! As the buffer is statically assigned and no parameters are entered in to this function, error checking is not needed.
Parameters
This function does not accept parameters!
Return
This function returns the currently written amount of bytes in uint8_t format.
Usage
The function can be used by first initializing the class and then calling the getSize() function:
#include <CayenneLPP.hpp>
#define BUF_SIZE 100
void main(){
CayenneLPP::CayenneLPP<BUF_SIZE> encoder;
uint8_t size = encoder.getSize();
/* size should be 0, as the encoder has just been initialized */
Serial.println(size);
}
getBuffer function
The getBuffer function will return a pointer to the internal statically assigned buffer!Error checking
This function does not have error checking! As the buffer is statically assigned and no parameters are entered in to this function, error checking is not needed.
Parameters
This function does not accept parameters!
Return
This function returns a pointer to the internal statically assigned buffer in uint8_t * format.
Usage
The function can be used by first initializing the class and then calling the getBuffer() function:
#include <CayenneLPP.hpp>
#define BUF_SIZE 100
void main(){
CayenneLPP::CayenneLPP<BUF_SIZE> encoder;
uint8_t* buffer = encoder.getBuffer();
/* Should print nothing, as the buffer is empty! */
Serial.println(buffer);
}
setMeasurement function
The setMeasurement() function will store a new measurement inside the internal encoder buffer.Error checking
This function does dynamically error checks on the internal encoder buffer and the incoming parameters.
Parameters
This function accepts a channel and measurement parameter.
Return
This function returns the current buffer counter position.
Usage
The function can be used by first initializing the class and then calling the setMeasurement() function:
#include <CayenneLPP.hpp>
#define BUF_SIZE 100
#define CHANNEL 1
void main(){
CayenneLPP::CayenneLPP<BUF_SIZE> encoder;
CayenneLPP::Measurement_t measurement = CayenneLPP::SetDigitalOutput(1);
encoder.setMeasurement(1, measurement);
}
Measurement functions
The Measurement_t struct can be used without these functions, though it helps to use these functions as they do not introduce a run-time and space cost (as they are inline).
namespace CayenneLPP
{
static inline Measurement_t SetDigitalOutput(const uint8_t digital_output_val);
static inline Measurement_t SetDigitalInput(const uint8_t digital_input_val);
static inline Measurement_t SetPresence(const uint8_t presence_val);
static inline Measurement_t SetLuminosity(const uint16_t luminosity_val);
static inline Measurement_t SetAnalogOutput(const float analog_output_val);
static inline Measurement_t SetAnalogInput(const float analog_input_val);
static inline Measurement_t SetTemperature(const float temperature_val);
static inline Measurement_t SetRelativeHumidity(const float humidity_val);
static inline Measurement_t SetBarometricPressure(const float barometric_pressure_val);
static inline Measurement_t SetAcceleration(const float x,
const float y,
const float z);
static inline Measurement_t SetGyro(const float x,
const float y,
const float z);
static inline Measurement_t SetGPS(const float latitude,
const float longitude,
const float altitude);
static inline Measurement_t SetRawBit(const uint8_t raw_bit_val,
Measurement_t &prevMeasurement);
static inline Measurement_t SetRawByte(const uint8_t raw_byte_val);
static inline Measurement_t SetWord16(const uint16_t word16_val);
static inline Measurement_t SetWord32(const uint32_t word32_val);
static inline Measurement_t SetFloat32(const float float32_val);
}
Usage
All these functions are used the same way except for the SetRawBit function.
First initialize an empty Measurement_t struct and then call the Set... function to fill that struct with your required measurement:
#include <CayenneLPP.hpp>
void main() {
CayenneLPP::Measurement_t measurement;
measurement = CayenneLPP::SetDigitalOutput(1);
}
Measurement_t instance can then be reused when added to the encoder buffer:
#include <CayenneLPP.hpp>
#define BUF_SIZE 100
#define DIGITAL_TRANSMIT_CH 0
#define ANALOG_TRANSMIT_CH 1
void main() {
CayenneLPP::CayenneLPP<BUF_SIZE> encoder;
CayenneLPP::Measurement_t measurement;
measurement = CayenneLPP::SetDigitalOutput(1);
encoder.setMeasurement(DIGITAL_TRANSMIT_CH, &measurement);
measurement = CayenneLPP::SetAnalogOutput(2.3);
encoder.setMeasurement(ANALOG_TRANSMIT_CH, &measurement);
}
Usage of the SetRawBit function
The SetRawBit function requires one additional step to use, compared to the other helper functions.
It needs the old version of the measurement struct passed in to the parameters:
#include <CayenneLPP.hpp>
#define BUF_SIZE 100
#define DIGITAL_TRANSMIT_CH 0
#define ANALOG_TRANSMIT_CH 1
void main() {
CayenneLPP::CayenneLPP<BUF_SIZE> encoder;
CayenneLPP::Measurement_t measurement;
CayenneLPP::SetRawBit(1, &measurement);
}
Now the real party trick! Adding more bits...
#include <CayenneLPP.hpp>
#define BUF_SIZE 100
#define DIGITAL_TRANSMIT_CH 0
#define ANALOG_TRANSMIT_CH 1
void main() {
CayenneLPP::CayenneLPP<BUF_SIZE> encoder;
CayenneLPP::Measurement_t measurement;
for(uint8_t i = 0; i < 8; i++) {
const uint8_t bit_to_set = (i % 2); // Modulo 2 as example,
// could be digitalread
CayenneLPP::SetRawBit(bit_to_set, &measurement);
}
}