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https://github.com/meshcore-dev/MeshCore.git
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141 lines
5 KiB
C++
141 lines
5 KiB
C++
#pragma once
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#include "helpers/bridges/BridgeBase.h"
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#include <Stream.h>
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#ifdef WITH_RS232_BRIDGE
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/**
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* @brief Bridge implementation using RS232/UART protocol for packet transport
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*
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* This bridge enables mesh packet transport over serial/UART connections,
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* allowing nodes to communicate over wired serial links. It implements a simple
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* packet framing protocol with checksums for reliable transfer.
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*
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* Features:
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* - Point-to-point communication over hardware UART
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* - Fletcher-16 checksum for data integrity verification
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* - Magic header for packet synchronization and frame alignment
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* - Duplicate packet detection using SimpleMeshTables tracking
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* - Configurable RX/TX pins via build defines
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* - Fixed baud rate at 115200 for consistent timing
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*
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* Packet Structure:
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* [2 bytes] Magic Header (0xC03E) - Used to identify start of RS232Bridge packets
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* [2 bytes] Payload Length - Length of the mesh packet payload
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* [n bytes] Mesh Packet Payload - The actual mesh packet data
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* [2 bytes] Fletcher-16 Checksum - Calculated over the payload for integrity verification
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*
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* The Fletcher-16 checksum is calculated over the mesh packet payload and provides
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* error detection capabilities suitable for serial communication where electrical
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* noise, timing issues, or hardware problems could corrupt data. The checksum
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* validation ensures only valid packets are forwarded to the mesh.
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*
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* Configuration:
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* - Define WITH_RS232_BRIDGE to enable this bridge
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* - Define WITH_RS232_BRIDGE_RX with the RX pin number
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* - Define WITH_RS232_BRIDGE_TX with the TX pin number
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*
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* Platform Support:
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* Different platforms require different pin configuration methods:
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* - ESP32: Uses HardwareSerial::setPins(rx, tx)
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* - NRF52: Uses HardwareSerial::setPins(rx, tx)
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* - RP2040: Uses SerialUART::setRX(rx) and SerialUART::setTX(tx)
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* - STM32: Uses HardwareSerial::setRx(rx) and HardwareSerial::setTx(tx)
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*/
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class RS232Bridge : public BridgeBase {
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public:
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/**
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* @brief Constructs an RS232Bridge instance
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*
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* @param serial The hardware serial port to use
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* @param mgr PacketManager for allocating and queuing packets
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* @param rtc RTCClock for timestamping debug messages
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*/
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RS232Bridge(Stream &serial, mesh::PacketManager *mgr, mesh::RTCClock *rtc);
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/**
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* Initializes the RS232 bridge
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*
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* - Validates that RX/TX pins are defined
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* - Configures UART pins based on target platform
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* - Sets baud rate to 115200 for consistent communication
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* - Platform-specific pin configuration methods are used
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*/
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void begin() override;
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/**
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* @brief Main loop handler for processing incoming serial data
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*
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* Implements a state machine for packet reception:
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* 1. Searches for magic header bytes for packet synchronization
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* 2. Reads length field to determine expected packet size
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* 3. Validates packet length against maximum allowed size
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* 4. Receives complete packet payload and checksum
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* 5. Validates Fletcher-16 checksum for data integrity
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* 6. Creates mesh packet and forwards if valid
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*/
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void loop() override;
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/**
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* @brief Called when a packet needs to be transmitted over serial
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*
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* Formats the mesh packet with RS232 framing protocol:
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* - Adds magic header for synchronization
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* - Includes payload length field
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* - Calculates Fletcher-16 checksum over payload
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* - Transmits complete framed packet
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* - Uses duplicate detection to prevent retransmission
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*
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* @param packet The mesh packet to transmit
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*/
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void onPacketTransmitted(mesh::Packet *packet) override;
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/**
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* @brief Called when a complete valid packet has been received from serial
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*
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* Forwards the received packet to the mesh for processing.
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* The packet has already been validated for checksum integrity
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* and parsed successfully at this point.
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*
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* @param packet The received mesh packet ready for processing
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*/
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void onPacketReceived(mesh::Packet *packet) override;
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private:
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/**
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* RS232 Protocol Structure:
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* - Magic header: 2 bytes (packet identification)
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* - Length field: 2 bytes (payload length)
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* - Payload: variable bytes (mesh packet data)
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* - Checksum: 2 bytes (Fletcher-16 over payload)
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* Total overhead: 6 bytes
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*/
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/**
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* @brief The total overhead of the serial protocol in bytes.
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* Includes: MAGIC_WORD (2) + LENGTH (2) + CHECKSUM (2) = 6 bytes
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*/
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static constexpr uint16_t SERIAL_OVERHEAD = BRIDGE_MAGIC_SIZE + BRIDGE_LENGTH_SIZE + BRIDGE_CHECKSUM_SIZE;
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/**
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* @brief The maximum size of a complete packet on the serial line.
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*
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* This is calculated as the sum of:
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* - MAX_TRANS_UNIT + 1 for the maximum mesh packet size
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* - SERIAL_OVERHEAD for the framing (magic + length + checksum)
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*/
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static constexpr uint16_t MAX_SERIAL_PACKET_SIZE = (MAX_TRANS_UNIT + 1) + SERIAL_OVERHEAD;
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/** Hardware serial port interface */
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Stream *_serial;
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/** Buffer for building received packets */
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uint8_t _rx_buffer[MAX_SERIAL_PACKET_SIZE];
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/** Current position in the receive buffer */
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uint16_t _rx_buffer_pos = 0;
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};
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#endif
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