API Reference

OSynaptic-TX exposes three headers. The recommended entry point is ostx_sensor.h.

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ostx_sensor.h — Tier A (dynamic strings)

ostx_sensor_pack()

int ostx_sensor_pack(
    ostx_u32        aid,        /* agent ID */
    const char     *sensor_id,  /* NUL-terminated, max 8 chars */
    const char     *unit,       /* NUL-terminated, max 8 chars (UCUM) */
    ostx_u8         tid,        /* transaction ID 0–255 */
    ostx_u32        ts_sec,     /* Unix timestamp seconds */
    ostx_i32        scaled,     /* value × OSTX_VALUE_SCALE */
    ostx_u8        *out         /* output buffer, at least OSTX_PACKET_MAX bytes */
);

Returns: Packet length in bytes on success, 0 on error (sensor_id or unit too long, output buffer too small, unit validation failed).

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ostx_static.h — Tier B (Flash-stored descriptor)

OSTX_STATIC_DEFINE() macro

OSTX_STATIC_DEFINE(name, aid, sensor_id_literal, unit_literal);

Declares a static const ostx_static_t name placed in program memory. No SRAM is used for the descriptor itself.

ostx_static_pack()

int ostx_static_pack(
    const ostx_static_t *desc,  /* descriptor created with OSTX_STATIC_DEFINE */
    ostx_u8              tid,
    ostx_u32             ts_sec,
    ostx_i32             scaled,
    ostx_u8             *out
);

Returns: Packet length in bytes, or 0 on error.

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ostx_stream.h — Tier C (streaming callback)

Emit callback type

typedef void (*ostx_emit_fn)(ostx_u8 byte, void *ctx);

ostx_stream_pack()

void ostx_stream_pack(
    const ostx_static_t *desc,
    ostx_u8              tid,
    ostx_u32             ts_sec,
    ostx_i32             scaled,
    ostx_emit_fn         emit,
    void                *ctx
);

No return value — the emit callback is called once per output byte. If emit is NULL, the call is a no-op.

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ostx_config.h — Configuration

See Configuration Macros for the full table.

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Data Types

Type	Underlying type	Description
ostx_u8	unsigned char	Byte
ostx_u32	unsigned long	32-bit unsigned (both 16-bit and 32-bit platforms)
ostx_i32	signed long	32-bit signed
ostx_static_t	struct	Flash-stored sensor descriptor (opaque; use OSTX_STATIC_DEFINE)

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Stack Usage Summary (AVR, -Os)

Tier	Function	Stack peak
A	ostx_sensor_pack()	~137 B
B	ostx_static_pack()	~51 B
C	ostx_stream_pack()	~21 B

Excluding the user's stack frame for the emit callback (Tier C), which is typically 2–8 B for a simple Serial.write().