C++ UARTDriver::read方法代码示例

/*
  run detection step for one GPS instance. If this finds a GPS then it
  will fill in drivers[instance] and change state[instance].status
  from NO_GPS to NO_FIX.
 */
void
AP_GPS::detect_instance(uint8_t instance)
{
    AP_GPS_Backend *new_gps = NULL;
    AP_HAL::UARTDriver *port = instance==0?hal.uartB:hal.uartE;
    struct detect_state *dstate = &detect_state[instance];

    if (port == NULL) {
        // UART not available
        return;
    }

    uint32_t now = hal.scheduler->millis();

    state[instance].instance = instance;
    state[instance].status = NO_GPS;

    // record the time when we started detection. This is used to try
    // to avoid initialising a uBlox as a NMEA GPS
    if (dstate->detect_started_ms == 0) {
        dstate->detect_started_ms = now;
    }

    if (now - dstate->last_baud_change_ms > 1200) {
        // try the next baud rate
		dstate->last_baud++;
		if (dstate->last_baud == sizeof(_baudrates) / sizeof(_baudrates[0])) {
			dstate->last_baud = 0;
		}
		uint32_t baudrate = pgm_read_dword(&_baudrates[dstate->last_baud]);
		port->begin(baudrate, 256, 16);		
		dstate->last_baud_change_ms = now;
        send_blob_start(instance, _initialisation_blob, sizeof(_initialisation_blob));
    }

    send_blob_update(instance);

    while (port->available() > 0 && new_gps == NULL) {
        uint8_t data = port->read();
        /*
          running a uBlox at less than 38400 will lead to packet
          corruption, as we can't receive the packets in the 200ms
          window for 5Hz fixes. The NMEA startup message should force
          the uBlox into 38400 no matter what rate it is configured
          for.
        */
        if ((_type[instance] == GPS_TYPE_AUTO || _type[instance] == GPS_TYPE_UBLOX) &&
            pgm_read_dword(&_baudrates[dstate->last_baud]) >= 38400 && 
            AP_GPS_UBLOX::_detect(dstate->ublox_detect_state, data)) {
            hal.console->print_P(PSTR(" ublox "));
            new_gps = new AP_GPS_UBLOX(*this, state[instance], port);
        } 
		else if ((_type[instance] == GPS_TYPE_AUTO || _type[instance] == GPS_TYPE_MTK19) &&
                 AP_GPS_MTK19::_detect(dstate->mtk19_detect_state, data)) {
			hal.console->print_P(PSTR(" MTK19 "));
			new_gps = new AP_GPS_MTK19(*this, state[instance], port);
		} 
		else if ((_type[instance] == GPS_TYPE_AUTO || _type[instance] == GPS_TYPE_MTK) &&
                 AP_GPS_MTK::_detect(dstate->mtk_detect_state, data)) {
			hal.console->print_P(PSTR(" MTK "));
			new_gps = new AP_GPS_MTK(*this, state[instance], port);
		}
#if GPS_RTK_AVAILABLE
        else if ((_type[instance] == GPS_TYPE_AUTO || _type[instance] == GPS_TYPE_SBP) &&
                 AP_GPS_SBP::_detect(dstate->sbp_detect_state, data)) {
            hal.console->print_P(PSTR(" SBP "));
            new_gps = new AP_GPS_SBP(*this, state[instance], port);
        }
#endif // HAL_CPU_CLASS
#if !defined( __AVR_ATmega1280__ )
		// save a bit of code space on a 1280
		else if ((_type[instance] == GPS_TYPE_AUTO || _type[instance] == GPS_TYPE_SIRF) &&
                 AP_GPS_SIRF::_detect(dstate->sirf_detect_state, data)) {
			hal.console->print_P(PSTR(" SIRF "));
			new_gps = new AP_GPS_SIRF(*this, state[instance], port);
		}
		else if (now - dstate->detect_started_ms > 5000) {
			// prevent false detection of NMEA mode in
			// a MTK or UBLOX which has booted in NMEA mode
			if ((_type[instance] == GPS_TYPE_AUTO || _type[instance] == GPS_TYPE_NMEA) &&
                AP_GPS_NMEA::_detect(dstate->nmea_detect_state, data)) {
				hal.console->print_P(PSTR(" NMEA "));
				new_gps = new AP_GPS_NMEA(*this, state[instance], port);
			}
		}
#endif
	}

	if (new_gps != NULL) {
        state[instance].status = NO_FIX;
        drivers[instance] = new_gps;
        timing[instance].last_message_time_ms = now;
	}
}

//.........这里部分代码省略.........
    case SERIAL_CONTROL_DEV_TELEM1:
        port = hal.uartC;
        lock_channel(MAVLINK_COMM_1, exclusive);
        break;
    case SERIAL_CONTROL_DEV_TELEM2:
        port = hal.uartD;
        lock_channel(MAVLINK_COMM_2, exclusive);
        break;
    case SERIAL_CONTROL_DEV_GPS1:
        port = hal.uartB;
        gps.lock_port(0, exclusive);
        break;
    case SERIAL_CONTROL_DEV_GPS2:
        port = hal.uartE;
        gps.lock_port(1, exclusive);
        break;
    default:
        // not supported yet
        return;
    }

    if (exclusive) {
        // force flow control off for exclusive access. This protocol
        // is used to talk to bootloaders which may not have flow
        // control support
        port->set_flow_control(AP_HAL::UARTDriver::FLOW_CONTROL_DISABLE);
    }

    // optionally change the baudrate
    if (packet.baudrate != 0) {
        port->begin(packet.baudrate);
    }

    // write the data
    if (packet.count != 0) {
        if ((packet.flags & SERIAL_CONTROL_FLAG_BLOCKING) == 0) {
            port->write(packet.data, packet.count);
        } else {
            const uint8_t *data = &packet.data[0];
            uint8_t count = packet.count;
            while (count > 0) {
                while (port->txspace() <= 0) {
                    hal.scheduler->delay(5);
                }
                uint16_t n = port->txspace();
                if (n > packet.count) {
                    n = packet.count;
                }
                port->write(data, n);
                data += n;
                count -= n;
            }
        }
    }

    if ((packet.flags & SERIAL_CONTROL_FLAG_RESPOND) == 0) {
        // no response expected
        return;
    }

    uint8_t flags = packet.flags;

more_data:
    // sleep for the timeout
    while (packet.timeout != 0 &&
            port->available() < (int16_t)sizeof(packet.data)) {
        hal.scheduler->delay(1);
        packet.timeout--;
    }

    packet.flags = SERIAL_CONTROL_FLAG_REPLY;

    // work out how many bytes are available
    int16_t available = port->available();
    if (available < 0) {
        available = 0;
    }
    if (available > (int16_t)sizeof(packet.data)) {
        available = sizeof(packet.data);
    }

    // read any reply data
    packet.count = 0;
    memset(packet.data, 0, sizeof(packet.data));
    while (available > 0) {
        packet.data[packet.count++] = (uint8_t)port->read();
        available--;
    }

    // and send the reply
    _mav_finalize_message_chan_send(chan,
                                    MAVLINK_MSG_ID_SERIAL_CONTROL,
                                    (const char *)&packet,
                                    MAVLINK_MSG_ID_SERIAL_CONTROL_LEN,
                                    MAVLINK_MSG_ID_SERIAL_CONTROL_CRC);
    if ((flags & SERIAL_CONTROL_FLAG_MULTI) && packet.count != 0) {
        hal.scheduler->delay(1);
        goto more_data;
    }
}