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SwapnilPandeSwapnilPande
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Implemented communications between Coral and Arduino (#36)
* Minimum working example of SPI communications between arduino and coral * Implemented communication with Arduino over SPI and created Arduino library to receive data * Started SPI comm protocol documentation * Fixed docs build issues * Documented SPI communications protocl * Changed travis file to only build on master branch
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‎.travis.yml

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cache: pip
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install:
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- "pip install sphinx sphinx_rtd_theme"
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- "pip install sphinx sphinx_rtd_theme recommonmark"
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- pip install -r requirements.txt
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- pip install pytest
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script:
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script:
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- docs/build.sh
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- pytest
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‎arduino/AnythingSensor/AnythingSensor.cpp

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#include "AnythingSensor.h"
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AnythingSensor* _instance = nullptr;
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AnythingSensor::AnythingSensor()
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{
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_instance = this;
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}
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bool AnythingSensor::begin()
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{
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// Create a temporary buffer with size 1 for reading config information
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AnythingSensor::buffer = new byte[4];
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AnythingSensor::bufferLength = 4;
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AnythingSensor::buffer[0] = 0;
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AnythingSensor::buffer[1] = 0;
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AnythingSensor::buffer[2] = 0;
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AnythingSensor::buffer[3] = 0;
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// Iniitliaze variables for ISR
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AnythingSensor::pos = 0;
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AnythingSensor::dataAvailable = false;
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spiInit();
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commInit();
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dataInit();
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return true;
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}
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void AnythingSensor::spiInit()
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{
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// Set our commState to the INIT state
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commState = INIT;
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// Set the signal pin to output mode
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pinMode(signalPin, OUTPUT);
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digitalWrite(signalPin, LOW);
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// Enable SPI in slave mode
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// Set Master In Slave Out as output
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pinMode(MISO, OUTPUT);
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// Set SPDR to 0x00
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SPDR = 0x00;
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// turn on SPI in slave mode
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SPCR |= _BV(SPE);
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// turn on interrupt for
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SPCR |= _BV(SPIE);
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}
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void AnythingSensor::commInit()
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{
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// Booleans to store the state of initialization
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bool initCompleted = false;
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bool startMessagedReceived = false;
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while(!initCompleted)
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{
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commState = INIT; // Ensure comm state is in init
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// First step of initialization, receive 4 0xFF messages from the Anything Sensor
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startMessagedReceived = false;
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while(!startMessagedReceived)
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{
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if(AnythingSensor::dataAvailable)
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{
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// Check that all of the data in the buffer is 0xFF
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if(AnythingSensor::buffer[0] == 0xFF &&
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AnythingSensor::buffer[1] == 0xFF &&
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AnythingSensor::buffer[2] == 0xFF &&
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AnythingSensor::buffer[3] == 0xFF)
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{
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startMessagedReceived = true;
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dataAvailable = false;
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}
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else
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{
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// Reset buffer to wait for new group of start bits
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AnythingSensor::buffer[0] = 0;
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AnythingSensor::buffer[1] = 0;
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AnythingSensor::buffer[2] = 0;
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AnythingSensor::buffer[3] = 0;
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AnythingSensor::dataAvailable = false;
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}
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}
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}
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Serial.println("Received starting message");
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// Second step involves sending two things to the Anything Sensor
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// First, a digital HIGH is sent on the signal pin to signal receipt of message
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// The Anything Sensor will request data transfer. In that transfer, 0x01 must
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// be sent by the slave
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Serial.println("Requesting sample data");
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// Write 0x01 to SPI output buffer to send to Anything Sensor
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requestData();
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// Check that all of the data in the buffer is 0x00
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// If it is, the initialization has been completed successfully
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// Else, we return to the beginning of the init process to try again
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if(AnythingSensor::buffer[0] == 0x00 &&
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AnythingSensor::buffer[1] == 0x00 &&
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AnythingSensor::buffer[2] == 0x00 &&
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AnythingSensor::buffer[3] == 0x00)
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{
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AnythingSensor::dataAvailable = false;
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initCompleted = true;
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Serial.println("Successfully Initialized");
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}
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}
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// Wait 1 second after init process
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delay(500);
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}
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void AnythingSensor::requestData()
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{
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// Write high to signal pin to signal ready to receive data
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digitalWrite(signalPin, HIGH);
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// Wait for data to be received from AnythingSensor
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while (!dataAvailable)
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{ }
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dataAvailable = false;
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digitalWrite(signalPin, LOW);
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}
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void AnythingSensor::dataInit()
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{
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requestData();
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Serial.print("Data initialized ");
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Serial.print(buffer[0]);
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Serial.print(" ");
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Serial.print(buffer[1]);
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Serial.print(" ");
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Serial.print(buffer[2]);
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Serial.print(" ");
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Serial.print(buffer[3]);
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Serial.print(" ");
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// We have received the new data from the Anything Sensor
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// This data stores the data type and length of the data
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// buffer[0] - datatype: currently only float is supported
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// buffer[1] - length of the data
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// buffer[2] - Unused
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// buffer[3] - Unused
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// Create a data array to store the data from the Anything Sensor
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dataLength = buffer[1];
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data = new float[dataLength];
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float test = 0.0;
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data[0] = 0;
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// Disable SPI interrupt while we resize buffer
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SPCR &= ~(_BV(SPIE));
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// Resize the buffer to the correct size for the streaming data
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delete[] buffer;
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bufferLength = 4*dataLength;
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buffer = new byte[bufferLength];
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// Re-enable SPI interrupt
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SPCR |= _BV(SPIE);
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Serial.println(dataLength);
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}
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bool AnythingSensor::read()
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{
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requestData();
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memcpy(data, buffer, bufferLength);
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}
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void AnythingSensor::_isr()
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{
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switch(commState)
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{
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case WAITING_FOR_HEADER:
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{
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byte header = SPDR;
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if(header == 0x10) // Heartbeat header, do nothing
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{ }
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else if(header == 0x20) // Message header, switch to receiving message
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{
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//Serial.println("Received Message header");
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commState = RECEIVING_MESSAGE;
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}
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else if(header == 0x30) // Config header, switch to receiving config state
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{
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// Reset heartbeat counter every time we receive config header
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// TODO This is a temporary, hacky solution
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// We are using this as a way to validate that both devices are in comms init
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// Currently, if the Arduino is requesting data while the Coral is in init mode,
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// the coral will interpret the data from the Arduino as the init sequence
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// Therefore, we need to have a different sequence that the Arduino sends as the heartbeat
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// than normal. Therefore, we make the heartbeat decrement instead of increment during the
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// init period
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// We need to add functionality such that the arduino recognizes the coral is in comm init
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// and resets its own comms
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commState = RECEIVING_CONFIG;
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}
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// else if(header == 0xFF) // Reset header, we need to reset comms with anything sensor
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// {
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// commState = INIT;
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// }
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break;
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}
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default: // This is used for the INIT, RECEIVING_CONFIG, or RECEIVING_MESSAGE states
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{
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AnythingSensor::buffer[pos] = SPDR;
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// Check if we've reached end of buffer
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// If at the end of buffer, we have received all of the data in this packet
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pos++;
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if(pos == bufferLength)
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{
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// State that new data available in the buffer
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dataAvailable = true;
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// Reset the position in the buffer to the beginning
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pos = 0;
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// We will always transition to the WAITING_FOR_HEADER STATE
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// after a message is received
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commState = WAITING_FOR_HEADER;
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}
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}
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}
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// Set the output register to the heartbeat counter and increment the heartbeat counter
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SPDR = heartbeatCounter;
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if(commState != INIT)
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heartbeatCounter++;
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else
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heartbeatCounter--;
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}
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int AnythingSensor::length()
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{
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return dataLength;
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}
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float AnythingSensor::get(int i)
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{
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return data[i];
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}
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// SPI interrupt routine
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ISR (SPI_STC_vect)
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{
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_instance -> _isr();
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}

‎arduino/AnythingSensor/AnythingSensor.h

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#include "Arduino.h"
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//#include "AnythingSensorData.h"
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enum SPIState
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{
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INIT,
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WAITING_FOR_HEADER,
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RECEIVING_CONFIG,
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RECEIVING_MESSAGE
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};
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class AnythingSensor
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{
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private:
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// Stores the sensor data collected from the Anything Sensor
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// The memory for this is dynamically allocated when the communication is established
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// because the Anything Sensor communicates the data size to the Arduino
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volatile byte* buffer;
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volatile int bufferLength;
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// Position in the buffer the ISR is currently writing to
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volatile int pos;
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volatile bool dataAvailable;
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volatile byte heartbeatCounter = 0xFF;
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// Stores the data after it is converted to floating point
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float* data;
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// Stores the length of the buffer
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int dataLength;
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// This is the pin that the Arduino will send a signal to the
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// coral board over.
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int signalPin = 9;
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volatile SPIState commState;
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void spiInit();
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void commInit();
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void dataInit();
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void requestData();
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public:
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// Default constructor
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AnythingSensor();
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bool begin();
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bool end();
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bool read();
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int length();
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void _isr();
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float get(int i);
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};

‎arduino/test_spi.ino/test_spi.ino.ino

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#include "pins_arduino.h"
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#include "AnythingSensor.h"
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AnythingSensor sensor = AnythingSensor();
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void setup()
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{
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Serial.begin (9600); // debugging
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Serial.println("Beginning comms");
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sensor.begin();
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}
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// main loop - wait for flag set in interrupt routine
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void loop (void)
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{
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sensor.read();
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for(int i = 0; i < sensor.length(); i++)
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{
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Serial.print(sensor.get(i));
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Serial.print(" ");
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}
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Serial.println(" ");
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delay(10);
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//
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} // end of loop

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