Null Packet Comms Arduino

This is an arduino library that implements a binary packet-based communication protocol on top of the arduino Serial library. This wrapper allows for robust generic data transfer between systems, it is heavily relied on for the Arduino UOS implementation.

The library exposes a class which is designed to mimic the Serial API, but using formatted packets.

NPC Arduino API

The following is the class structure for the library. This documents all the user-facing functions and members.

class NullPacketComms

Serial connection object to be handled via NPC protocol.

Public Functions

NullPacketComms()

Constructor to initialise the wrapper.

bool begin(uint32_t baud_rate)

Opens the connection to the UART port.

Parameters:

baud_rate – Standard UART baud rate to use.

Returns:

true if opened, false if unsupported baud.

void end()

Closes the connection to the UART port.

int available()

Number bytes waiting in the serial buffer.

Returns:

number of bytes.

bool readPacket(bool manual_ack = false)

Reads the next packet from the serial buffer.

Parameters:

manual_ack – (optional) Set true to respond ACK in client code.

Returns:

true if read success, false otherwise.

uint8_t writePacket(uint8_t target, uint8_t data[], uint8_t data_len)

Builds a data packet and sends it to the host system.

Parameters:

  • target – Of the system to respond to.

  • data – Payload array to populate into the packet.

  • data_len – Length of the payload array.

Returns:

Number of bytes successfully sent.

bool writeAck(uint8_t target, uint8_t ack_code)

Sends an ack packet in response to a resolved rx packet.

Parameters:

  • target – Address of system we are responding from.

  • ack_code – NACK error code or 0 for ACK.

Returns:

true if ack was sent successfully, else false.

Public Members

uint8_t target_

Stores the to address of the last rx packet.

uint8_t len_

Stores the payload length populated with the last rx packet.

uint8_t payload_[58]

Stores the payload from the last rx packet.

Changelog

Version 0.2.3

Date:

16-April-2023

  • Googletest framework updated to 1.13.0

  • Correcting incorrect syntax used for rst external hyperlink in docs.

  • Adding a check on CI build against the simple_example sketch to verify integration.

Version 0.2.2

Date:

31-December-2022

  • Fixing doc shields which inspected github workflows (see: issue).

  • Defining test data as constant where it is used as a constant.

Version 0.2.1

Date:

2-October-2022

  • Used Serial.available calls in preference to the nested NullPacketComms.available internally.

  • Sourcing doc metadata from library.properties. This fixes a issues from me forgetting to maintain conf.py.

Version 0.2.0

Date:

2-October-2022

  • Adding support for higher baud-rates 128000 to 2000000.

  • Googletest framework updated to 1.12.1.

  • Added waitOnAvailable private function to allow for dynamic delays pending next bytes.

  • Reduced idle time from 25ms to 1ms while waiting on buffer to accumulate. This improves responsiveness, especially at higher baud rates.

  • Error case for loss of start packet sync set to dynamically delay rather than blindly delay.

Version 0.1.2

Date:

18-April-2022

  • Explicit casting used on Serial.write calls to add support for platform cores with ambiguous prototypes.

  • Improvements to distributed docs.

Version 0.1.1

Date:

14-February-2022

  • Removing inclusion of files not required for the dist.

  • Fixing permalinks to docs.

Version 0.1.0

Date:

12-February-2022

  • Initial release of the redesigned API.