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GitHub Repository: Ardupilot/ardupilot
 Path: blob/master/libraries/AP_ADSB/sagetech-sdk/sgDecodeAck.c
Views: 1799
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/**

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 * @copyright Copyright (c) 2021 Sagetech, Inc. All rights reserved.

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 *

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 * @file   sgDecodeAck.c

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 * @author jimb

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 *

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 * @date   Feb 10, 2021

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 *

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 * This file receives a raw Acknowledge message buffer and

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 * parses the payload into a data struct.

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 */

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#include <string.h>

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#include <stdbool.h>

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#include <math.h>

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#include "sg.h"

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#include "sgUtil.h"

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#define SG_ACK_XPNDR_FAIL 0x01

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#define SG_ACK_SYSTEM_FAIL 0x02

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#define SG_ACK_CRYPTO_FAIL 0x04

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#define SG_ACK_WOW 0x08

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#define SG_ACK_MAINT 0x10

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#define SG_ACK_ALT_SOURCE 0x20

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#define SG_ACK_OP_MODE 0xC0

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typedef struct __attribute__((packed))

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{

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    uint8_t start;

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    uint8_t type;

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    uint8_t id;

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    uint8_t payloadLen;

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    uint8_t ackType;

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    uint8_t ackId;

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    uint8_t state;

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    uint8_t alt[3];

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    uint8_t checksum;

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} ack_t;

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/*

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 * Documented in the header file.

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 */

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bool sgDecodeAck(uint8_t *buffer, sg_ack_t *ack)

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{

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    ack_t sgAck;

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    memcpy(&sgAck, buffer, sizeof(ack_t));

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    ack->ackType = sgAck.ackType;

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    ack->ackId = sgAck.ackId;

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    ack->failXpdr = (sgAck.state & SG_ACK_XPNDR_FAIL) > 0;

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    ack->failSystem = (sgAck.state & SG_ACK_SYSTEM_FAIL) > 0;

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    ack->failCrypto = (sgAck.state & SG_ACK_CRYPTO_FAIL) > 0;

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    ack->wow = (sgAck.state & SG_ACK_WOW) > 0;

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    ack->maint = (sgAck.state & SG_ACK_MAINT) > 0;

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    ack->isHostAlt = (sgAck.state & SG_ACK_ALT_SOURCE) > 0;

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    ack->opMode = (sgAck.state & SG_ACK_OP_MODE) >> 6;

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    int32_t int24 = toInt32(sgAck.alt);

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    // Bitmask altitude field to determine if alt = invalid

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    if ((int24 & 0x00FFFFFF) == 0x00800000)

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    {

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        ack->alt = 0;

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        ack->altValid = false;

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    }

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    else

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    {

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        ack->alt = int24;

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        ack->altValid = true;

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    }

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    return true;

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}

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