tiny_comm.h

/*!
 * @file
 * @brief Sends and receives payloads via UART.
 *
 * Packet structure:
 * [STX] [CRC MSB] [CRC LSB] [Payload (0-255 bytes)] [ETX]
 *
 * DLE is used to escape control characters sent as data/CRC.
 *
 * Payload integrity is protected by a 16-bit CRC (CRC-CCITT with a seed
 * of 0xFFFF).
 *
 * Buffers a single packet for send and a single packet for receive.
 */

#ifndef tiny_comm_h
#define tiny_comm_h

#include "hal/i_tiny_uart.h"
#include "i_tiny_comm.h"
#include "tiny_event.h"

typedef struct {
  i_tiny_comm_t interface;
  i_tiny_uart_t* uart;
  tiny_event_t on_receive;

  tiny_event_subscription_t send_complete;
  tiny_event_subscription_t byte_received;

  uint8_t* send_buffer;
  uint16_t send_crc;
  uint8_t send_buffer_size;
  uint8_t send_buffer_count;
  uint8_t send_buffer_offset;
  uint8_t send_state;
  bool send_escaped;

  // Makes sure we don't handle send complete
  // while we're setting up another send)
  volatile bool send_in_progress;

  uint8_t* receive_buffer;
  uint16_t receive_crc;
  uint16_t receive_calculated_crc;
  uint8_t receive_buffer_size;
  uint8_t receive_count;
  uint8_t receive_state;
  bool receive_escaped;

  // Makes sure we don't handle received bytes
  // while waiting for packet to be processed
  volatile bool received_packet_ready;
} tiny_comm_t;

/*!
 * Initializes a tiny comm instance.
 */
void tiny_comm_init(
  tiny_comm_t* self,
  i_tiny_uart_t* uart,
  uint8_t* send_buffer,
  uint8_t send_buffer_size,
  uint8_t* receive_buffer,
  uint8_t receive_buffer_size);

/*!
 * Runs the tiny comm instance. If any received packets
 * are pending, they will be published.
 */
void tiny_comm_run(tiny_comm_t* self);

#endif