spektrum_rc.cpp

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/**
 * @file spektrum_rc.cpp
 *
 * This is a driver for a Spektrum satellite receiver connected to a Snapdragon
 * on the serial port. By default port J12 (next to J13, power module side) is used.
 */

#include <string.h>

#include <px4_platform_common/tasks.h>
#include <px4_platform_common/posix.h>
#include <px4_platform_common/getopt.h>

#include <lib/rc/dsm.h>
#include <drivers/drv_rc_input.h>
#include <drivers/drv_hrt.h>

#include <uORB/uORB.h>
#include <uORB/topics/input_rc.h>

// Snapdraogon: use J12 (next to J13, power module side)
#define SPEKTRUM_UART_DEVICE_PATH "/dev/tty-3"

#define UNUSED(x) (void)(x)

extern "C" { __EXPORT int spektrum_rc_main(int argc, char *argv[]); }


namespace spektrum_rc
{

volatile bool _task_should_exit = false;
static bool _is_running = false;
static px4_task_t _task_handle = -1;

int start();
int stop();
int info();
void usage();
void task_main(int argc, char *argv[]);

void fill_input_rc(uint16_t raw_rc_count, uint16_t raw_rc_values[input_rc_s::RC_INPUT_MAX_CHANNELS],
           hrt_abstime now, bool frame_drop, bool failsafe, unsigned frame_drops, int rssi,
           input_rc_s &input_rc);

void task_main(int argc, char *argv[])
{
    const char *device_path = SPEKTRUM_UART_DEVICE_PATH;
    int ch;
    int myoptind = 1;
    const char *myoptarg = NULL;

    while ((ch = px4_getopt(argc, argv, "d:", &myoptind, &myoptarg)) != EOF) {
        switch (ch) {
        case 'd':
            device_path = myoptarg;
            break;

        default:
            break;
        }
    }

    int uart_fd = dsm_init(device_path);

    if (uart_fd < 1) {
        PX4_ERR("dsm init failed");
        return;
    }

    orb_advert_t rc_pub = nullptr;

    // Use a buffer size of the double of the minimum, just to be safe.
    uint8_t rx_buf[2 * DSM_BUFFER_SIZE];

    _is_running = true;
    uint16_t raw_rc_values[input_rc_s::RC_INPUT_MAX_CHANNELS];
    uint16_t raw_rc_count = 0;

    // Main loop
    while (!_task_should_exit) {

        int newbytes = ::read(uart_fd, &rx_buf[0], sizeof(rx_buf));

        if (newbytes < 0) {
            PX4_WARN("read failed");
            continue;
        }

        if (newbytes == 0) {
            continue;
        }

        const hrt_abstime now = hrt_absolute_time();

        bool dsm_11_bit;
        unsigned frame_drops;
        int8_t dsm_rssi;

        // parse new data
        bool rc_updated = dsm_parse(now, rx_buf, newbytes, &raw_rc_values[0], &raw_rc_count,
                        &dsm_11_bit, &frame_drops, &dsm_rssi, input_rc_s::RC_INPUT_MAX_CHANNELS);
        UNUSED(dsm_11_bit);

        if (rc_updated) {

            input_rc_s input_rc = {};

            fill_input_rc(raw_rc_count, raw_rc_values, now, false, false, frame_drops, dsm_rssi,
                      input_rc);

            if (rc_pub == nullptr) {
                rc_pub = orb_advertise(ORB_ID(input_rc), &input_rc);

            } else {
                orb_publish(ORB_ID(input_rc), rc_pub, &input_rc);
            }
        }

        // sleep since no poll for qurt
        usleep(10000);

    }

    orb_unadvertise(rc_pub);
    dsm_deinit();

    _is_running = false;
}

void fill_input_rc(uint16_t raw_rc_count, uint16_t raw_rc_values[input_rc_s::RC_INPUT_MAX_CHANNELS],
           hrt_abstime now, bool frame_drop, bool failsafe, unsigned frame_drops, int rssi,
           input_rc_s &input_rc)
{
    input_rc.input_source = input_rc_s::RC_INPUT_SOURCE_QURT;

    input_rc.channel_count = raw_rc_count;

    if (input_rc.channel_count > input_rc_s::RC_INPUT_MAX_CHANNELS) {
        input_rc.channel_count = input_rc_s::RC_INPUT_MAX_CHANNELS;
    }

    unsigned valid_chans = 0;

    for (unsigned i = 0; i < input_rc.channel_count; ++i) {
        input_rc.values[i] = raw_rc_values[i];

        if (raw_rc_values[i] != UINT16_MAX) {
            valid_chans++;
        }
    }

    input_rc.timestamp = now;
    input_rc.timestamp_last_signal = input_rc.timestamp;
    input_rc.rc_ppm_frame_length = 0;

    /* fake rssi if no value was provided */
    if (rssi == -1) {

        input_rc.rssi = 255;

    } else {
        input_rc.rssi = rssi;
    }

    if (valid_chans == 0) {
        input_rc.rssi = 0;
    }

    input_rc.rc_failsafe = failsafe;
    input_rc.rc_lost = (valid_chans == 0);
    input_rc.rc_lost_frame_count = frame_drops;
    input_rc.rc_total_frame_count = 0;
}

int start(int argc, char *argv[])
{
    if (_is_running) {
        PX4_WARN("already running");
        return -1;
    }

    _task_should_exit = false;

    _task_handle = px4_task_spawn_cmd("spektrum_rc_main",
                      SCHED_DEFAULT,
                      SCHED_PRIORITY_DEFAULT,
                      2000,
                      (px4_main_t)&task_main,
                      (char *const *)argv);

    if (_task_handle < 0) {
        PX4_ERR("task start failed");
        return -1;
    }

    return 0;
}

int stop()
{
    if (!_is_running) {
        PX4_WARN("not running");
        return -1;
    }

    _task_should_exit = true;

    while (_is_running) {
        usleep(200000);
        PX4_INFO(".");
    }

    _task_handle = -1;
    return 0;
}

int info()
{
    PX4_INFO("running: %s", _is_running ? "yes" : "no");

    return 0;
}

void
usage()
{
    PX4_INFO("Usage: spektrum_rc {start|info|stop}");
}

} // namespace spektrum_rc


int spektrum_rc_main(int argc, char *argv[])
{
    int myoptind = 1;

    if (argc <= 1) {
        spektrum_rc::usage();
        return 1;
    }

    const char *verb = argv[myoptind];


    if (!strcmp(verb, "start")) {
        return spektrum_rc::start(argc - 1, argv + 1);
    }

    else if (!strcmp(verb, "stop")) {
        return spektrum_rc::stop();
    }

    else if (!strcmp(verb, "info")) {
        return spektrum_rc::info();
    }

    else {
        spektrum_rc::usage();
        return 1;
    }
}