RPiSensorFramework

Application framework for a sensor array using Raspberry Pi nodes. This is to be used as a changeable/adaptable baseline, with the intention of developers modifying it as needed.

Notes:

maximum node ID is 256 as it must fit within one byte.

Output/input ports must be in BCM form.

This project uses pigpio

Information is read using polling. Threading can be used if the developer has access to a multicore Raspberry Pi.

Example program

The example program will load all three node types as objects on a single Raspberry Pi. Therefore, one needs to comment out the #include "Node.cpp" from the various subclasses to avoid including the Node class three times in a single program. When deployed, each node will require only its specific class and the Node class.

Example program (main.cpp) uses only SPI for communication, and is therefore limited to 2 connections per node as the RPi has 2 only SPI ports.

run the program using sudo ./Main. Sudo required to initialise pigpio daemon.

The Raspberry Pi will have to be connected in spi loopback mode i.e. connect the MOSI pin to the MISO.

Handlers

Bridge control handler

This handler checks that the target node belongs to the bridge, which reduces flooding in the network, before forwarding to the target node.

Sensor control handler

This checks that the node is the target node, and then executes the command.

Bridge data handler

Forwards data to control node.

Control data handler

Unpacks data and stores in a repository, using Data objects. (see Data class in Control folder).

Communication packets

Received packets are read from the rx_buffer, which is refreshed whenever sent out of the node via spi (spiXfer). A list of basic commands are defined in the Node.hpp file. The developer can add to these, and should add the relevant actions to the switch statements in the Control and Sensor classes.

1. Control packet

1.1 Bridge control packet

The control packet received by the bridge node from the control node is made up of 4 bytes:

0	1	2	3
'c' - indicates control pkt	sensor ID - byte indicating target node ID	bridge ID - byte indicating target bridge ID	cmd - command to be executed

1.2 Sensor control packet

The control packet received by the sensor node from the bridge node is made up of 3 bytes:

0	1	2
'c' - indicates control pkt	sensor ID - byte indicating target node ID	cmd - command to be executed

2. Data packet

The data packet is made up as follows:

0	1	2	3 -> 2+sz
'd' - indicates data pkt	sensor ID - ID of sensor that recorded data	sz - size of data in packet	data

If a 'd' is found in the data (e.g. the ASCII integer), the next byte will be analysed. If this byte is not in the range of a typical sz byte, the data will continue to be read as normal. Otherwise, the device will read in the next byte as the sz (size) of data to follow.

An end-of-packet indicator may not be neccesary as the sz bit could be used for this purpose.

No target ID is needed, as the only target for a data packet (denoted by 'd') is the control node.

Data Handling

Data packets are converted into data objects, which are stored in an array in the Control node program. This array can either be written to permanent storage or uploaded to cloud storage, depending on the user's needs. The data object contains a function for displaying the specific sample, made up of the source sensor node ID, the time at which the sample was recorded and the data sample itself. The data class can be modified to meet developer's needs.

class Data
{
protected:
    //ID of sensor from which data was received
    int sensorID;
    //time at which sample was received by the control node
    BYTE* time; //may need string
    //the data (possibly formatted) corresponding to the sample.
    BYTE dataSample[64];
    //size of sample stored in data array
    int size;

public:
    //Constructor
    Data(int ID, BYTE* t, BYTE* sample, unsigned int sz);
    string toString();
    //returns the ID of the sensor that recorded the sample.
    int getID();
    //displays a particular sample
    void printSample();
};