roboclaw_main.cpp

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/**
 * @file roboclaw_main.cpp
 *
 * RoboClaw Motor Driver
 *
 * references:
 * http://downloads.ionmc.com/docs/roboclaw_user_manual.pdf
 *
 */

#include <px4_platform_common/px4_config.h>
#include <px4_platform_common/log.h>
#include <px4_platform_common/module.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

#include <parameters/param.h>

#include <arch/board/board.h>
#include "RoboClaw.hpp"

static bool thread_running = false;     /**< Deamon status flag */
px4_task_t deamon_task;

/**
 * Deamon management function.
 */
extern "C" __EXPORT int roboclaw_main(int argc, char *argv[]);

/**
 * Mainloop of deamon.
 */
int roboclaw_thread_main(int argc, char *argv[]);

/**
 * Print the correct usage.
 */
static void usage();

static void usage()
{
    PRINT_MODULE_USAGE_NAME("roboclaw", "driver");

    PRINT_MODULE_DESCRIPTION(R"DESCR_STR(
### Description

This driver communicates over UART with the [Roboclaw motor driver](http://downloads.ionmc.com/docs/roboclaw_user_manual.pdf).
It performs two tasks:

 - Control the motors based on the `actuator_controls_0` UOrb topic.
 - Read the wheel encoders and publish the raw data in the `wheel_encoders` UOrb topic

In order to use this driver, the Roboclaw should be put into Packet Serial mode (see the linked documentation), and
your flight controller's UART port should be connected to the Roboclaw as shown in the documentation. For Pixhawk 4,
use the `UART & I2C B` port, which corresponds to `/dev/ttyS3`.

### Implementation

The main loop of this module (Located in `RoboClaw.cpp::task_main()`) performs 2 tasks:

 1. Write `actuator_controls_0` messages to the Roboclaw as they become available
 2. Read encoder data from the Roboclaw at a constant, fixed rate.

Because of the latency of UART, this driver does not write every single `actuator_controls_0` message to the Roboclaw
immediately. Instead, it is rate limited based on the parameter `RBCLW_WRITE_PER`.

On startup, this driver will attempt to read the status of the Roboclaw to verify that it is connected. If this fails,
the driver terminates immediately.

### Examples

The command to start this driver is:

 $ roboclaw start <device> <baud>

`<device>` is the name of the UART port. On the Pixhawk 4, this is `/dev/ttyS3`.
`<baud>` is te baud rate.

All available commands are:

 - `$ roboclaw start <device> <baud>`
 - `$ roboclaw status`
 - `$ roboclaw stop`
    )DESCR_STR");
}

/**
 * The deamon app only briefly exists to start
 * the background job. The stack size assigned in the
 * Makefile does only apply to this management task.
 *
 * The actual stack size should be set in the call
 * to task_create().
 */
int roboclaw_main(int argc, char *argv[])
{

    if (argc < 4) {
        usage();
    }

    if (!strcmp(argv[1], "start")) {

        if (thread_running) {
            printf("roboclaw already running\n");
            /* this is not an error */
            return 0;
        }

        RoboClaw::taskShouldExit = false;
        deamon_task = px4_task_spawn_cmd("roboclaw",
                         SCHED_DEFAULT,
                         SCHED_PRIORITY_MAX - 10,
                         2000,
                         roboclaw_thread_main,
                         (char *const *)argv);
        return 0;

    } else if (!strcmp(argv[1], "stop")) {

        RoboClaw::taskShouldExit = true;
        return 0;

    } else if (!strcmp(argv[1], "status")) {

        if (thread_running) {
            printf("\troboclaw app is running\n");

        } else {
            printf("\troboclaw app not started\n");
        }

        return 0;
    }

    usage();
    return 1;
}

int roboclaw_thread_main(int argc, char *argv[])
{
    printf("[roboclaw] starting\n");

    // skip parent process args
    argc -= 2;
    argv += 2;

    if (argc < 2) {
        printf("usage: roboclaw start <device> <baud>\n");
        return -1;
    }

    const char *deviceName = argv[1];
    const char *baudRate = argv[2];

    // start
    RoboClaw roboclaw(deviceName, baudRate);

    thread_running = true;

    roboclaw.taskMain();

    // exit
    printf("[roboclaw] exiting.\n");
    thread_running = false;
    return 0;
}