API Reference

OSynaptic-RX exposes five header modules. The recommended entry point for new projects is osrx_sensor.h.

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osrx_sensor.h — All-in-one decode (recommended)

osrx_sensor_recv()

int osrx_sensor_recv(const osrx_u8        *packet,
                     int                   len,
                     osrx_packet_meta     *meta,
                     osrx_sensor_field    *field);

Decode header + body + validate both CRCs in a single call.

Parameter	Direction	Description
packet	in	Raw frame bytes from your transport
len	in	Number of bytes in packet
meta	out	Decoded header fields; always populated on return
field	out	Decoded sensor fields; populated only when return value is nonzero

Returns: 1 on full success (structural parse + both CRCs pass), 0 otherwise.

meta->crc8_ok and meta->crc16_ok are set independently. A return value of 0 may still have a valid CRC-8 if only CRC-16 failed (or vice versa).

osrx_sensor_unpack()

int osrx_sensor_unpack(const osrx_u8     *body,
                       int                body_len,
                       osrx_sensor_field *out);

Parse a body slice "sid|unit|b62" into osrx_sensor_field only (no header decode, no CRC).

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osrx_parser.h — Streaming byte accumulator

OSRXParser struct

typedef struct {
    osrx_u8   buf[OSRX_PACKET_MAX]; /* accumulation buffer */
    int       len;                   /* number of bytes accumulated so far */
    osrx_frame_cb fn;                /* user callback */
    void     *ctx;                   /* user context pointer */
} OSRXParser;

RAM footprint: 102 bytes at default OSRX_PACKET_MAX=96.

Function table

Function	Signature	Description
osrx_parser_init	(OSRXParser *p, osrx_frame_cb cb, void *ctx)	Initialise parser; register callback
osrx_feed_byte	(OSRXParser *p, osrx_u8 b) → int	Push one byte. Returns 0 on overflow/reset, 1 otherwise
osrx_feed_done	(OSRXParser *p) → int	Signal frame end; parse + callback. Returns 1 if structurally valid
osrx_feed_bytes	(OSRXParser *p, const osrx_u8 *data, int len) → int	Feed all bytes then call osrx_feed_done in one call
osrx_parser_reset	(OSRXParser *p)	Discard accumulated bytes without parsing

Callback signature

typedef void (*osrx_frame_cb)(
    const osrx_packet_meta  *meta,   /* header fields, always valid */
    const osrx_sensor_field *field,  /* sensor fields; NULL for non-sensor frames */
    const osrx_u8           *raw,    /* raw frame bytes */
    int                      raw_len,
    void                    *ctx     /* user context from osrx_parser_init() */
);

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osrx_packet.h — Header-only decoder

int osrx_packet_decode(const osrx_u8    *packet,
                       int               len,
                       osrx_packet_meta *out);

Decodes only the 13-byte header. Does not parse body or validate CRCs. Useful when you only need aid, tid, and ts_sec.

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osrx_b62.h — Base62 decoder

osrx_i32 osrx_b62_decode(const char *s, int len, int *ok);

Parameter	Description
s	Pointer to Base62 string (need not be NUL-terminated)
len	Number of significant characters to decode
ok	Set to 1 on success, 0 on invalid character or overflow

Returns: Decoded signed 32-bit integer. Result is valid only when *ok == 1.

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osrx_crc.h — CRC primitives

osrx_u8  osrx_crc8 (const osrx_u8 *data, int len,
                    osrx_u8 poly,  osrx_u8  init);

osrx_u16 osrx_crc16(const osrx_u8 *data, int len,
                    osrx_u16 poly, osrx_u16 init);

Both use bit-loop implementation: zero bytes of RAM, no lookup table.

Algorithm	Call	Standard check value
CRC-8/SMBUS	osrx_crc8(data, len, 0x07, 0x00)	0xF4 for "123456789"
CRC-16/CCITT-FALSE	osrx_crc16(data, len, 0x1021, 0xFFFF)	0x29B1 for "123456789"

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Data Structures

osrx_packet_meta

typedef struct {
    osrx_u32 aid;        /* agent ID (32-bit, big-endian decoded) */
    osrx_u8  tid;        /* transaction ID */
#if !OSRX_NO_TIMESTAMP
    osrx_u64 ts_sec;     /* Unix timestamp seconds */
#endif
    int      crc8_ok;    /* 1 = body CRC-8 passed */
    int      crc16_ok;   /* 1 = frame CRC-16 passed */
    int      body_offset;/* byte offset of body within packet */
    int      body_len;   /* length of body slice in bytes */
} osrx_packet_meta;

osrx_sensor_field

typedef struct {
    char      sensor_id[OSRX_ID_MAX];   /* NUL-terminated sensor ID, e.g. "T1" */
    char      unit[OSRX_UNIT_MAX];      /* NUL-terminated unit, e.g. "Cel" */
    osrx_i32  scaled;                   /* fixed-point value × OSRX_VALUE_SCALE */
} osrx_sensor_field;

Getting the real value:

double real = (double)field.scaled / OSRX_VALUE_SCALE;  /* float */
long   whole = (long)(field.scaled / OSRX_VALUE_SCALE); /* integer part */
long   frac  = (long)labs(field.scaled % OSRX_VALUE_SCALE); /* fractional part */

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Stack Usage Summary (AVR, -Os)

Function	Stack peak
osrx_sensor_recv()	~41 B (direct path)
osrx_feed_done() + callback chain	~55 B
osrx_crc8() / osrx_crc16()	~4 B
osrx_b62_decode()	~8 B