qmk-firmware/drivers/avr/serial.h

#pragma once

#include <stdbool.h>

// /////////////////////////////////////////////////////////////////
// Need Soft Serial defines in config.h
// /////////////////////////////////////////////////////////////////
// ex.
//  #define SOFT_SERIAL_PIN ??   // ?? = D0,D1,D2,D3,E6
//  OPTIONAL: #define SELECT_SOFT_SERIAL_SPEED ? // ? = 1,2,3,4,5
//                                               //  1: about 137kbps (default)
//                                               //  2: about 75kbps
//                                               //  3: about 39kbps
//                                               //  4: about 26kbps
//                                               //  5: about 20kbps
//
// //// USE simple API (using signle-type transaction function)
//   /* nothing */
// //// USE flexible API (using multi-type transaction function)
//   #define SERIAL_USE_MULTI_TRANSACTION
//
// /////////////////////////////////////////////////////////////////

// Soft Serial Transaction Descriptor
typedef struct _SSTD_t {
    uint8_t *status;
    uint8_t  initiator2target_buffer_size;
    uint8_t *initiator2target_buffer;
    uint8_t  target2initiator_buffer_size;
    uint8_t *target2initiator_buffer;
} SSTD_t;
#define TID_LIMIT(table) (sizeof(table) / sizeof(SSTD_t))

// initiator is transaction start side
void soft_serial_initiator_init(SSTD_t *sstd_table, int sstd_table_size);
// target is interrupt accept side
void soft_serial_target_init(SSTD_t *sstd_table, int sstd_table_size);

// initiator resullt
#define TRANSACTION_END 0
#define TRANSACTION_NO_RESPONSE 0x1
#define TRANSACTION_DATA_ERROR 0x2
#define TRANSACTION_TYPE_ERROR 0x4
#ifndef SERIAL_USE_MULTI_TRANSACTION
int soft_serial_transaction(void);
#else
int soft_serial_transaction(int sstd_index);
#endif

// target status
// *SSTD_t.status has
//   initiator:
//       TRANSACTION_END
//    or TRANSACTION_NO_RESPONSE
//    or TRANSACTION_DATA_ERROR
//   target:
//       TRANSACTION_DATA_ERROR
//    or TRANSACTION_ACCEPTED
#define TRANSACTION_ACCEPTED 0x8
#ifdef SERIAL_USE_MULTI_TRANSACTION
int soft_serial_get_and_clean_status(int sstd_index);
#endif