sts_protocol.h

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#pragma once
 
#include <stdint.h>
 
/* --- Protocol Structural Constants --- */
#define STS_HEADER                0xFFU
#define STS_HEADER_SIZE           2U
#define STS_CHECKSUM_SIZE         1U
#define STS_LENGTH_FIXED_OVERHEAD 2U   /* ID + Checksum */
#define STS_PKT_FIXED_TOTAL       4U   /* Header(2) + ID(1) + Length(1) */
#define STS_MIN_PACKET_SIZE       6U   /* Header(2)+ID(1)+Len(1)+Inst(1)+CS(1) */
#define STS_MAX_PACKET_SIZE       255U /* Max total byte limit */
 
/* --- Packet Layout Indices --- */
#define STS_IDX_HEADER_1          0U
#define STS_IDX_HEADER_2          1U
#define STS_IDX_ID                2U
#define STS_IDX_LENGTH            3U
#define STS_IDX_INSTRUCTION       4U 
#define STS_IDX_STATUS            4U 
#define STS_IDX_PARAM_START       5U
 
/* --- Protocol Limits --- */
#define STS_MAX_ID                254U
#define STS_MAX_PARAM_LEN         253U
#define STS_HARDWARE_OK           0x00U
#define STS_MAX_INSTRUCTION       0x05U /* Range: 0x01 (Ping) to 0x05 (Reset) */
#define STS_MIN_PKT_LEN_VAL       2U    /* Min 'Length' byte: Status + Checksum */
 
/* --- Protocol Element Sizes --- */
#define STS_ACK_BASE_LEN          6U  
#define STS_REG_ADDR_LEN          1U  
#define STS_DATA_LEN_8BIT         1U  
#define STS_DATA_LEN_16BIT        2U  
 
/* --- Derived Parameter Lengths --- */
#define STS_WRITE8_PARAM_LEN      (STS_REG_ADDR_LEN + STS_DATA_LEN_8BIT)   /* 2U */
#define STS_WRITE16_PARAM_LEN     (STS_REG_ADDR_LEN + STS_DATA_LEN_16BIT)  /* 3U */
#define STS_READ_CMD_PARAM_LEN    (STS_REG_ADDR_LEN + STS_DATA_LEN_8BIT)   /* 2U */
typedef enum {
    STS_OK = 0,               
    STS_ERR_NULL_PTR,         
    STS_ERR_INVALID_LEN,      
    STS_ERR_INVALID_PARAM,    
    STS_ERR_BUF_TOO_SMALL,    
    STS_ERR_TIMEOUT,          
    STS_ERR_HEADER,            
    STS_ERR_ID_MISMATCH,      
    STS_ERR_CHECKSUM,         
    STS_ERR_MALFORMED,        
    STS_ERR_HARDWARE,         
    STS_ERR_TX_FAIL,          
    STS_ERR_RX_FAIL,
    STS_ERR_BUSY              
} sts_result_t;
 
sts_result_t sts_calculate_checksum(const uint8_t* pkt_buf, uint16_t pkt_len, uint8_t* checksum_out);
 
sts_result_t sts_create_packet(uint8_t id, uint8_t instruction, const uint8_t* param_buf, uint16_t param_len, uint8_t* pkt_buf, uint16_t pkt_buf_size);
 
sts_result_t sts_parse_response(uint8_t expected_id, const uint8_t* rx_buf, uint16_t rx_len,  uint8_t* param_buf, uint16_t param_buf_size,uint16_t* param_len);