137 lines
3.4 KiB
C
137 lines
3.4 KiB
C
#ifndef LAYER1_RX_H
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#define LAYER1_RX_H
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#include <liquid/liquid.h>
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#include "modcod.h"
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#include "correlator.h"
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#include "results.h"
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typedef enum {
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RX_STATE_ACQUISITION,
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RX_STATE_HEADER,
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RX_STATE_DATA,
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} rx_state_t;
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typedef enum {
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RX_EVT_PACKET_RECEIVED,
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RX_EVT_PREAMBLE_FOUND,
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RX_EVT_HEADER_ERROR,
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RX_EVT_CHECKSUM_ERROR,
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} rx_evt_t;
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typedef void (*rx_callback_t)(rx_evt_t evt, uint8_t *packet_data, size_t packet_len);
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typedef struct
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{
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// Input channel filter
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firfilt_crcf channel_filter;
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// AGC
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agc_crcf agc;
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float noise_floor_level;
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// NCOs for carrier frequency offset correction
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nco_crcf carrier_coarse_nco;
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nco_crcf carrier_fine_nco;
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// Forward error correction objects
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fec hdr_fec;
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// Demodulators
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modem hdr_demod;
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modem payload_demod;
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// symbol timing synchronizer
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symsync_crcf symsync;
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// preamble correlator
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correlator_ctx_t preamble_correlator;
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// Receiver state
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rx_state_t state;
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// Callback function to notify user of certain events
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rx_callback_t callback;
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// Precalcuated header lengths
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unsigned int hdr_len_symbols;
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unsigned int hdr_len_enc_bytes;
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// Information from the decoded header
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uint16_t payload_len_symbols;
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uint16_t payload_len_bytes;
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uint16_t payload_crc;
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uint16_t payload_len_enc_bytes;
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modcod_t modcod;
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} layer1_rx_t;
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/*!
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* \brief Initialize the receiver.
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*
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* \param rx Pointer to the receiver context.
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* \param callback Function to be called on receiver events.
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* \returns The result of the initialization.
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*/
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result_t layer1_rx_init(layer1_rx_t *rx, rx_callback_t callback);
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/*!
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* \brief Shut the receiver down. Frees all memory.
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*
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* \param rx Pointer to the receiver context.
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* \returns The result of the shutdown.
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*/
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result_t layer1_rx_shutdown(layer1_rx_t *rx);
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/*!
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* \brief Process the given block of samples.
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*
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* Runs the whole receiver chain for the given samples. This includes timing-
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* and frequency synchronization, preamble search, header demodulation and
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* decoding and payload demodulation and decoding.
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*
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* On specific events, most notably when a packet is successfully decoded, the
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* callback function passed to \ref layer1_rx_init() will be called. See \ref
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* rx_evt_t for possible events.
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*
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* \param rx Pointer to the receiver context.
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* \param samples Pointer to the samples to process.
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* \param sample_count Number of samples to process.
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* \returns The result of the shutdown.
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*/
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result_t layer1_rx_process(layer1_rx_t *rx, const float complex *samples, size_t sample_count);
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/*!
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* \brief Determine whether the receiver is currently receiving a packet.
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*
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* This function can be used to identify idle periods where packet transmission
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* is possible. Switching to TX while this function returns true will very
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* probably result in a collision with packet corruption.
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*
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* \param rx Pointer to the receiver context.
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* \returns Whether the receiver is currently receiving a packet.
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*/
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bool layer1_rx_is_busy(const layer1_rx_t *rx);
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/*!
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* \brief Retrieve the coarsely estimated carrier frequency.
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*
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* The carrier frequency is measured in radians per sample in the RRC-filtered baseband domain, i.e. the sampling rate is SYMBOL_RATE * RRC_SPS.
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*
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* \param rx Pointer to the receiver context.
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* \returns The estimated carrier frequency in the RRC-filtered domain.
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*/
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float layer1_rx_get_coarse_carrier_frequency(const layer1_rx_t *rx);
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#endif // LAYER1_RX_H
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