loratap.h

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/*
This file is part of LoRaTap Copyright (C) 2017 Erik de Jong
 
LoRaTap is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
 
LoRaTap is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.
 
You should have received a copy of the GNU General Public License
along with LoRaTap.  If not, see <http://www.gnu.org/licenses/>.
*/
 
#include <stdint.h>
 
/*
        Values are big-endian
 
        Field details
        lt_version      LoRaTap header version, current version is 0.
        lt_padding      Unused, for boundary alignment.
        lt_length       LoRaTap header length, field used to allow expansion in future versions. Each version can append header parameters.
                        So, whilst parsing, these parameters can be skipped if not defined for older versions by skipping to the offset of lt_length starting from the beginning of the header.
        channel         Channel information
        rssi            RSSI information
        sync_word       Sync word for received packet, value 0x34 is reserved for LoRaWAN packets
*/
 
typedef enum sf { SF7=7, SF8, SF9, SF10, SF11, SF12 } sf_t;
 
typedef struct __attribute__((__packed__)) loratap_channel {
        uint32_t                        frequency;      /* LoRa frequency (Hz) */
        uint8_t                         bandwidth;      /* Channel bandwidth (KHz) in 125 KHz steps */
        uint8_t                         sf;           /* LoRa SF (sf_t) [7, 8, 9, 10, 11, 12] */
} loratap_channel_t;
 
typedef struct __attribute__((__packed__)) loratap_rssi {
        uint8_t                         packet_rssi;    /* LoRa packet RSSI, if snr >= 0 then dBm value is -139 + packet_rssi, otherwise dBm value is -139 + packet_rssi * .25 */
        uint8_t                         max_rssi;       /* LoRa receiver max RSSI (dBm value is -139 + rssi) */
        uint8_t                         current_rssi;   /* LoRa receiver current RSSI (dBm value is -139 + rssi) */
        uint8_t                         snr;            /* LoRa SNR (dB value is (snr[two's complement])/4) */
} loratap_rssi_t;
 
typedef struct __attribute__((__packed__)) loratap_header {
        uint8_t                         lt_version;     /* LoRatap header version */
        uint8_t                         lt_padding;
        uint16_t                        lt_length;      /* LoRatap header length */
        loratap_channel_t              channel;
        loratap_rssi_t                    rssi;
        uint8_t                         sync_word;      /* LoRa radio sync word [0x34 = LoRaWAN] */
} loratap_header_t;