px4io_serial.cpp

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 *   Copyright (c) 2013-2015 PX4 Development Team. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
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 *    used to endorse or promote products derived from this software
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/**
 * @file px4io_serial.cpp
 *
 * Serial interface for PX4IO
 */

#include "px4io_driver.h"

#include <px4_arch/px4io_serial.h>

static PX4IO_serial *g_interface;

device::Device
*PX4IO_serial_interface()
{
    return new ArchPX4IOSerial();
}

PX4IO_serial::PX4IO_serial() :
    Device("PX4IO_serial"),
    _pc_txns(perf_alloc(PC_ELAPSED, "io_txns")),
#if 0
    _pc_retries(perf_alloc(PC_COUNT,    "io_retries  ")),
    _pc_timeouts(perf_alloc(PC_COUNT,   "io_timeouts ")),
    _pc_crcerrs(perf_alloc(PC_COUNT,    "io_crcerrs  ")),
    _pc_protoerrs(perf_alloc(PC_COUNT,  "io_protoerrs")),
    _pc_uerrs(perf_alloc(PC_COUNT,      "io_uarterrs ")),
    _pc_idle(perf_alloc(PC_COUNT,       "io_idle     ")),
    _pc_badidle(perf_alloc(PC_COUNT,    "io_badidle  ")),
#else
    _pc_retries(nullptr),
    _pc_timeouts(nullptr),
    _pc_crcerrs(nullptr),
    _pc_protoerrs(nullptr),
    _pc_uerrs(nullptr),
    _pc_idle(nullptr),
    _pc_badidle(nullptr),
#endif
    _bus_semaphore(SEM_INITIALIZER(0))
{
    g_interface = this;
}

PX4IO_serial::~PX4IO_serial()
{
    /* kill our semaphores */
    px4_sem_destroy(&_bus_semaphore);

    perf_free(_pc_txns);
    perf_free(_pc_retries);
    perf_free(_pc_timeouts);
    perf_free(_pc_crcerrs);
    perf_free(_pc_protoerrs);
    perf_free(_pc_uerrs);
    perf_free(_pc_idle);
    perf_free(_pc_badidle);

    if (g_interface == this) {
        g_interface = nullptr;
    }
}

int
PX4IO_serial::init(IOPacket *io_buffer)
{
    _io_buffer_ptr = io_buffer;
    /* create semaphores */
    // in case the sub-class impl fails, the semaphore is cleaned up by destructor.
    px4_sem_init(&_bus_semaphore, 0, 1);

    return 0;
}

int
PX4IO_serial::write(unsigned address, void *data, unsigned count)
{
    uint8_t page = address >> 8;
    uint8_t offset = address & 0xff;
    const uint16_t *values = reinterpret_cast<const uint16_t *>(data);

    if (count > PKT_MAX_REGS) {
        return -EINVAL;
    }

    px4_sem_wait(&_bus_semaphore);

    int result;

    for (unsigned retries = 0; retries < 3; retries++) {
        _io_buffer_ptr->count_code = count | PKT_CODE_WRITE;
        _io_buffer_ptr->page = page;
        _io_buffer_ptr->offset = offset;
        memcpy((void *)&_io_buffer_ptr->regs[0], (void *)values, (2 * count));

        for (unsigned i = count; i < PKT_MAX_REGS; i++) {
            _io_buffer_ptr->regs[i] = 0x55aa;
        }

        _io_buffer_ptr->crc = 0;
        _io_buffer_ptr->crc = crc_packet(_io_buffer_ptr);

        /* start the transaction and wait for it to complete */
        result = _bus_exchange(_io_buffer_ptr);

        /* successful transaction? */
        if (result == OK) {

            /* check result in packet */
            if (PKT_CODE(*_io_buffer_ptr) == PKT_CODE_ERROR) {

                /* IO didn't like it - no point retrying */
                result = -EINVAL;
                perf_count(_pc_protoerrs);
            }

            break;
        }

        perf_count(_pc_retries);
    }

    px4_sem_post(&_bus_semaphore);

    if (result == OK) {
        result = count;
    }

    return result;
}

int
PX4IO_serial::read(unsigned address, void *data, unsigned count)
{
    uint8_t page = address >> 8;
    uint8_t offset = address & 0xff;
    uint16_t *values = reinterpret_cast<uint16_t *>(data);

    if (count > PKT_MAX_REGS) {
        return -EINVAL;
    }

    px4_sem_wait(&_bus_semaphore);

    int result;

    for (unsigned retries = 0; retries < 3; retries++) {

        _io_buffer_ptr->count_code = count | PKT_CODE_READ;
        _io_buffer_ptr->page = page;
        _io_buffer_ptr->offset = offset;

        _io_buffer_ptr->crc = 0;
        _io_buffer_ptr->crc = crc_packet(_io_buffer_ptr);

        /* start the transaction and wait for it to complete */
        result = _bus_exchange(_io_buffer_ptr);

        /* successful transaction? */
        if (result == OK) {

            /* check result in packet */
            if (PKT_CODE(*_io_buffer_ptr) == PKT_CODE_ERROR) {

                /* IO didn't like it - no point retrying */
                result = -EINVAL;
                perf_count(_pc_protoerrs);

                /* compare the received count with the expected count */

            } else if (PKT_COUNT(*_io_buffer_ptr) != count) {

                /* IO returned the wrong number of registers - no point retrying */
                result = -EIO;
                perf_count(_pc_protoerrs);

                /* successful read */

            } else {

                /* copy back the result */
                memcpy(values, &_io_buffer_ptr->regs[0], (2 * count));
            }

            break;
        }

        perf_count(_pc_retries);
    }

    px4_sem_post(&_bus_semaphore);

    if (result == OK) {
        result = count;
    }

    return result;
}