/**************************************************************************** * * Copyright (C) 2013 PX4 Development Team. All rights reserved. * Author: Thomas Gubler * Julian Oes * * 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 * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * 3. Neither the name PX4 nor the names of its contributors may be * used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * ****************************************************************************/ /* @file U-Blox protocol implementation */ #include #include #include #include #include #include #include #include #include #include #include "ubx.h" #define UBX_CONFIG_TIMEOUT 100 UBX::UBX(const int &fd, struct vehicle_gps_position_s *gps_position) : _fd(fd), _gps_position(gps_position), _waiting_for_ack(false) { decode_init(); } UBX::~UBX() { } int UBX::configure(unsigned &baudrate) { _waiting_for_ack = true; /* try different baudrates */ const unsigned baudrates_to_try[] = {9600, 38400, 19200, 57600, 115200}; for (int baud_i = 0; baud_i < 5; baud_i++) { baudrate = baudrates_to_try[baud_i]; set_baudrate(_fd, baudrate); /* Send a CFG-PRT message to set the UBX protocol for in and out * and leave the baudrate as it is, we just want an ACK-ACK from this */ type_gps_bin_cfg_prt_packet_t cfg_prt_packet; /* Set everything else of the packet to 0, otherwise the module wont accept it */ memset(&cfg_prt_packet, 0, sizeof(cfg_prt_packet)); _clsID_needed = UBX_CLASS_CFG; _msgID_needed = UBX_MESSAGE_CFG_PRT; /* Define the package contents, don't change the baudrate */ cfg_prt_packet.clsID = UBX_CLASS_CFG; cfg_prt_packet.msgID = UBX_MESSAGE_CFG_PRT; cfg_prt_packet.length = UBX_CFG_PRT_LENGTH; cfg_prt_packet.portID = UBX_CFG_PRT_PAYLOAD_PORTID; cfg_prt_packet.mode = UBX_CFG_PRT_PAYLOAD_MODE; cfg_prt_packet.baudRate = baudrate; cfg_prt_packet.inProtoMask = UBX_CFG_PRT_PAYLOAD_INPROTOMASK; cfg_prt_packet.outProtoMask = UBX_CFG_PRT_PAYLOAD_OUTPROTOMASK; send_config_packet(_fd, (uint8_t*)&cfg_prt_packet, sizeof(cfg_prt_packet)); if (receive(UBX_CONFIG_TIMEOUT) < 0) { /* try next baudrate */ continue; } /* Send a CFG-PRT message again, this time change the baudrate */ cfg_prt_packet.clsID = UBX_CLASS_CFG; cfg_prt_packet.msgID = UBX_MESSAGE_CFG_PRT; cfg_prt_packet.length = UBX_CFG_PRT_LENGTH; cfg_prt_packet.portID = UBX_CFG_PRT_PAYLOAD_PORTID; cfg_prt_packet.mode = UBX_CFG_PRT_PAYLOAD_MODE; cfg_prt_packet.baudRate = UBX_CFG_PRT_PAYLOAD_BAUDRATE; cfg_prt_packet.inProtoMask = UBX_CFG_PRT_PAYLOAD_INPROTOMASK; cfg_prt_packet.outProtoMask = UBX_CFG_PRT_PAYLOAD_OUTPROTOMASK; send_config_packet(_fd, (uint8_t*)&cfg_prt_packet, sizeof(cfg_prt_packet)); if (UBX_CFG_PRT_PAYLOAD_BAUDRATE != baudrate) { set_baudrate(_fd, UBX_CFG_PRT_PAYLOAD_BAUDRATE); baudrate = UBX_CFG_PRT_PAYLOAD_BAUDRATE; } /* no ack is ecpected here, keep going configuring */ /* send a CFT-RATE message to define update rate */ type_gps_bin_cfg_rate_packet_t cfg_rate_packet; memset(&cfg_rate_packet, 0, sizeof(cfg_rate_packet)); _clsID_needed = UBX_CLASS_CFG; _msgID_needed = UBX_MESSAGE_CFG_RATE; cfg_rate_packet.clsID = UBX_CLASS_CFG; cfg_rate_packet.msgID = UBX_MESSAGE_CFG_RATE; cfg_rate_packet.length = UBX_CFG_RATE_LENGTH; cfg_rate_packet.measRate = UBX_CFG_RATE_PAYLOAD_MEASRATE; cfg_rate_packet.navRate = UBX_CFG_RATE_PAYLOAD_NAVRATE; cfg_rate_packet.timeRef = UBX_CFG_RATE_PAYLOAD_TIMEREF; send_config_packet(_fd, (uint8_t*)&cfg_rate_packet, sizeof(cfg_rate_packet)); if (receive(UBX_CONFIG_TIMEOUT) < 0) { /* try next baudrate */ continue; } /* send a NAV5 message to set the options for the internal filter */ type_gps_bin_cfg_nav5_packet_t cfg_nav5_packet; memset(&cfg_nav5_packet, 0, sizeof(cfg_nav5_packet)); _clsID_needed = UBX_CLASS_CFG; _msgID_needed = UBX_MESSAGE_CFG_NAV5; cfg_nav5_packet.clsID = UBX_CLASS_CFG; cfg_nav5_packet.msgID = UBX_MESSAGE_CFG_NAV5; cfg_nav5_packet.length = UBX_CFG_NAV5_LENGTH; cfg_nav5_packet.mask = UBX_CFG_NAV5_PAYLOAD_MASK; cfg_nav5_packet.dynModel = UBX_CFG_NAV5_PAYLOAD_DYNMODEL; cfg_nav5_packet.fixMode = UBX_CFG_NAV5_PAYLOAD_FIXMODE; send_config_packet(_fd, (uint8_t*)&cfg_nav5_packet, sizeof(cfg_nav5_packet)); if (receive(UBX_CONFIG_TIMEOUT) < 0) { /* try next baudrate */ continue; } type_gps_bin_cfg_msg_packet_t cfg_msg_packet; memset(&cfg_msg_packet, 0, sizeof(cfg_msg_packet)); _clsID_needed = UBX_CLASS_CFG; _msgID_needed = UBX_MESSAGE_CFG_MSG; cfg_msg_packet.clsID = UBX_CLASS_CFG; cfg_msg_packet.msgID = UBX_MESSAGE_CFG_MSG; cfg_msg_packet.length = UBX_CFG_MSG_LENGTH; /* Choose fast 5Hz rate for all messages except SVINFO which is big and not important */ cfg_msg_packet.rate[1] = UBX_CFG_MSG_PAYLOAD_RATE1_5HZ; cfg_msg_packet.msgClass_payload = UBX_CLASS_NAV; cfg_msg_packet.msgID_payload = UBX_MESSAGE_NAV_POSLLH; send_config_packet(_fd, (uint8_t*)&cfg_msg_packet, sizeof(cfg_msg_packet)); if (receive(UBX_CONFIG_TIMEOUT) < 0) { /* try next baudrate */ continue; } cfg_msg_packet.msgClass_payload = UBX_CLASS_NAV; cfg_msg_packet.msgID_payload = UBX_MESSAGE_NAV_TIMEUTC; send_config_packet(_fd, (uint8_t*)&cfg_msg_packet, sizeof(cfg_msg_packet)); if (receive(UBX_CONFIG_TIMEOUT) < 0) { /* try next baudrate */ continue; } cfg_msg_packet.msgClass_payload = UBX_CLASS_NAV; cfg_msg_packet.msgID_payload = UBX_MESSAGE_NAV_SVINFO; /* For satelites info 1Hz is enough */ cfg_msg_packet.rate[1] = UBX_CFG_MSG_PAYLOAD_RATE1_1HZ; send_config_packet(_fd, (uint8_t*)&cfg_msg_packet, sizeof(cfg_msg_packet)); if (receive(UBX_CONFIG_TIMEOUT) < 0) { /* try next baudrate */ continue; } cfg_msg_packet.msgClass_payload = UBX_CLASS_NAV; cfg_msg_packet.msgID_payload = UBX_MESSAGE_NAV_SOL; send_config_packet(_fd, (uint8_t*)&cfg_msg_packet, sizeof(cfg_msg_packet)); if (receive(UBX_CONFIG_TIMEOUT) < 0) { /* try next baudrate */ continue; } cfg_msg_packet.msgClass_payload = UBX_CLASS_NAV; cfg_msg_packet.msgID_payload = UBX_MESSAGE_NAV_VELNED; send_config_packet(_fd, (uint8_t*)&cfg_msg_packet, sizeof(cfg_msg_packet)); if (receive(UBX_CONFIG_TIMEOUT) < 0) { /* try next baudrate */ continue; } // cfg_msg_packet.msgClass_payload = UBX_CLASS_NAV; // cfg_msg_packet.msgID_payload = UBX_MESSAGE_NAV_DOP; // cfg_msg_packet.msgClass_payload = UBX_CLASS_RXM; // cfg_msg_packet.msgID_payload = UBX_MESSAGE_RXM_SVSI; _waiting_for_ack = false; return 0; } return -1; } int UBX::receive(unsigned timeout) { /* poll descriptor */ pollfd fds[1]; fds[0].fd = _fd; fds[0].events = POLLIN; uint8_t buf[32]; /* timeout additional to poll */ uint64_t time_started = hrt_absolute_time(); int j = 0; ssize_t count = 0; while (true) { /* pass received bytes to the packet decoder */ while (j < count) { if (parse_char(buf[j]) > 0) { /* return to configure during configuration or to the gps driver during normal work * if a packet has arrived */ if (handle_message() > 0) return 1; } /* in case we keep trying but only get crap from GPS */ if (time_started + timeout*1000 < hrt_absolute_time() ) { return -1; } j++; } /* everything is read */ j = count = 0; /* then poll for new data */ int ret = ::poll(fds, sizeof(fds) / sizeof(fds[0]), timeout); if (ret < 0) { /* something went wrong when polling */ return -1; } else if (ret == 0) { /* Timeout */ return -1; } else if (ret > 0) { /* if we have new data from GPS, go handle it */ if (fds[0].revents & POLLIN) { /* * We are here because poll says there is some data, so this * won't block even on a blocking device. If more bytes are * available, we'll go back to poll() again... */ count = ::read(_fd, buf, sizeof(buf)); } } } } int UBX::parse_char(uint8_t b) { switch (_decode_state) { /* First, look for sync1 */ case UBX_DECODE_UNINIT: if (b == UBX_SYNC1) { _decode_state = UBX_DECODE_GOT_SYNC1; } break; /* Second, look for sync2 */ case UBX_DECODE_GOT_SYNC1: if (b == UBX_SYNC2) { _decode_state = UBX_DECODE_GOT_SYNC2; } else { /* Second start symbol was wrong, reset state machine */ decode_init(); } break; /* Now look for class */ case UBX_DECODE_GOT_SYNC2: /* everything except sync1 and sync2 needs to be added to the checksum */ add_byte_to_checksum(b); /* check for known class */ switch (b) { case UBX_CLASS_ACK: _decode_state = UBX_DECODE_GOT_CLASS; _message_class = ACK; break; case UBX_CLASS_NAV: _decode_state = UBX_DECODE_GOT_CLASS; _message_class = NAV; break; // case UBX_CLASS_RXM: // _decode_state = UBX_DECODE_GOT_CLASS; // _message_class = RXM; // break; case UBX_CLASS_CFG: _decode_state = UBX_DECODE_GOT_CLASS; _message_class = CFG; break; default: //unknown class: reset state machine decode_init(); break; } break; case UBX_DECODE_GOT_CLASS: add_byte_to_checksum(b); switch (_message_class) { case NAV: switch (b) { case UBX_MESSAGE_NAV_POSLLH: _decode_state = UBX_DECODE_GOT_MESSAGEID; _message_id = NAV_POSLLH; break; case UBX_MESSAGE_NAV_SOL: _decode_state = UBX_DECODE_GOT_MESSAGEID; _message_id = NAV_SOL; break; case UBX_MESSAGE_NAV_TIMEUTC: _decode_state = UBX_DECODE_GOT_MESSAGEID; _message_id = NAV_TIMEUTC; break; // case UBX_MESSAGE_NAV_DOP: // _decode_state = UBX_DECODE_GOT_MESSAGEID; // _message_id = NAV_DOP; // break; case UBX_MESSAGE_NAV_SVINFO: _decode_state = UBX_DECODE_GOT_MESSAGEID; _message_id = NAV_SVINFO; break; case UBX_MESSAGE_NAV_VELNED: _decode_state = UBX_DECODE_GOT_MESSAGEID; _message_id = NAV_VELNED; break; default: //unknown class: reset state machine, should not happen decode_init(); break; } break; // case RXM: // switch (b) { // case UBX_MESSAGE_RXM_SVSI: // _decode_state = UBX_DECODE_GOT_MESSAGEID; // _message_id = RXM_SVSI; // break; // // default: //unknown class: reset state machine, should not happen // decode_init(); // break; // } // break; case CFG: switch (b) { case UBX_MESSAGE_CFG_NAV5: _decode_state = UBX_DECODE_GOT_MESSAGEID; _message_id = CFG_NAV5; break; default: //unknown class: reset state machine, should not happen decode_init(); break; } break; case ACK: switch (b) { case UBX_MESSAGE_ACK_ACK: _decode_state = UBX_DECODE_GOT_MESSAGEID; _message_id = ACK_ACK; break; case UBX_MESSAGE_ACK_NAK: _decode_state = UBX_DECODE_GOT_MESSAGEID; _message_id = ACK_NAK; break; default: //unknown class: reset state machine, should not happen decode_init(); break; } break; default: //should not happen because we set the class warnx("UBX Error, we set a class that we don't know"); decode_init(); // config_needed = true; break; } break; case UBX_DECODE_GOT_MESSAGEID: add_byte_to_checksum(b); _payload_size = b; //this is the first length byte _decode_state = UBX_DECODE_GOT_LENGTH1; break; case UBX_DECODE_GOT_LENGTH1: add_byte_to_checksum(b); _payload_size += b << 8; // here comes the second byte of length _decode_state = UBX_DECODE_GOT_LENGTH2; break; case UBX_DECODE_GOT_LENGTH2: /* Add to checksum if not yet at checksum byte */ if (_rx_count < _payload_size) add_byte_to_checksum(b); _rx_buffer[_rx_count] = b; /* once the payload has arrived, we can process the information */ if (_rx_count >= _payload_size + 1) { //+1 because of 2 checksum bytes /* compare checksum */ if (_rx_ck_a == _rx_buffer[_rx_count-1] && _rx_ck_b == _rx_buffer[_rx_count]) { return 1; } else { decode_init(); return -1; warnx("ubx: Checksum wrong"); } return 1; } else if (_rx_count < RECV_BUFFER_SIZE) { _rx_count++; } else { warnx("ubx: buffer full"); decode_init(); return -1; } break; default: break; } return 0; //XXX ? } int UBX::handle_message() { int ret = 0; switch (_message_id) { //this enum is unique for all ids --> no need to check the class case NAV_POSLLH: { // printf("GOT NAV_POSLLH MESSAGE\n"); if (!_waiting_for_ack) { gps_bin_nav_posllh_packet_t *packet = (gps_bin_nav_posllh_packet_t *) _rx_buffer; _gps_position->lat = packet->lat; _gps_position->lon = packet->lon; _gps_position->alt = packet->height_msl; _gps_position->eph_m = (float)packet->hAcc * 1e-3f; // from mm to m _gps_position->epv_m = (float)packet->vAcc * 1e-3f; // from mm to m /* Add timestamp to finish the report */ _gps_position->timestamp_position = hrt_absolute_time(); /* only return 1 when new position is available */ ret = 1; } break; } case NAV_SOL: { // printf("GOT NAV_SOL MESSAGE\n"); if (!_waiting_for_ack) { gps_bin_nav_sol_packet_t *packet = (gps_bin_nav_sol_packet_t *) _rx_buffer; _gps_position->fix_type = packet->gpsFix; _gps_position->s_variance_m_s = packet->sAcc; _gps_position->p_variance_m = packet->pAcc; _gps_position->timestamp_variance = hrt_absolute_time(); } break; } // case NAV_DOP: { //// printf("GOT NAV_DOP MESSAGE\n"); // gps_bin_nav_dop_packet_t *packet = (gps_bin_nav_dop_packet_t *) _rx_buffer; // // _gps_position->eph_m = packet->hDOP; // _gps_position->epv = packet->vDOP; // // _gps_position->timestamp_posdilution = hrt_absolute_time(); // // _new_nav_dop = true; // // break; // } case NAV_TIMEUTC: { // printf("GOT NAV_TIMEUTC MESSAGE\n"); if (!_waiting_for_ack) { gps_bin_nav_timeutc_packet_t *packet = (gps_bin_nav_timeutc_packet_t *) _rx_buffer; //convert to unix timestamp struct tm timeinfo; timeinfo.tm_year = packet->year - 1900; timeinfo.tm_mon = packet->month - 1; timeinfo.tm_mday = packet->day; timeinfo.tm_hour = packet->hour; timeinfo.tm_min = packet->min; timeinfo.tm_sec = packet->sec; time_t epoch = mktime(&timeinfo); _gps_position->time_gps_usec = (uint64_t)epoch * 1000000; //TODO: test this _gps_position->time_gps_usec += (uint64_t)(packet->time_nanoseconds * 1e-3f); _gps_position->timestamp_time = hrt_absolute_time(); } break; } case NAV_SVINFO: { // printf("GOT NAV_SVINFO MESSAGE\n"); if (!_waiting_for_ack) { //this is a more complicated message: the length depends on the number of satellites. This number is extracted from the first part of the message const int length_part1 = 8; char _rx_buffer_part1[length_part1]; memcpy(_rx_buffer_part1, _rx_buffer, length_part1); gps_bin_nav_svinfo_part1_packet_t *packet_part1 = (gps_bin_nav_svinfo_part1_packet_t *) _rx_buffer_part1; //read checksum const int length_part3 = 2; char _rx_buffer_part3[length_part3]; memcpy(_rx_buffer_part3, &(_rx_buffer[_rx_count - 1]), length_part3); //definitions needed to read numCh elements from the buffer: const int length_part2 = 12; gps_bin_nav_svinfo_part2_packet_t *packet_part2; char _rx_buffer_part2[length_part2]; //for temporal storage uint8_t satellites_used = 0; int i; for (i = 0; i < packet_part1->numCh; i++) { //for each channel /* Get satellite information from the buffer */ memcpy(_rx_buffer_part2, &(_rx_buffer[length_part1 + i * length_part2]), length_part2); packet_part2 = (gps_bin_nav_svinfo_part2_packet_t *) _rx_buffer_part2; /* Write satellite information in the global storage */ _gps_position->satellite_prn[i] = packet_part2->svid; //if satellite information is healthy store the data uint8_t unhealthy = packet_part2->flags & 1 << 4; //flags is a bitfield if (!unhealthy) { if ((packet_part2->flags) & 1) { //flags is a bitfield _gps_position->satellite_used[i] = 1; satellites_used++; } else { _gps_position->satellite_used[i] = 0; } _gps_position->satellite_snr[i] = packet_part2->cno; _gps_position->satellite_elevation[i] = (uint8_t)(packet_part2->elev); _gps_position->satellite_azimuth[i] = (uint8_t)((float)packet_part2->azim * 255.0f / 360.0f); } else { _gps_position->satellite_used[i] = 0; _gps_position->satellite_snr[i] = 0; _gps_position->satellite_elevation[i] = 0; _gps_position->satellite_azimuth[i] = 0; } } for (i = packet_part1->numCh; i < 20; i++) { //these channels are unused /* Unused channels have to be set to zero for e.g. MAVLink */ _gps_position->satellite_prn[i] = 0; _gps_position->satellite_used[i] = 0; _gps_position->satellite_snr[i] = 0; _gps_position->satellite_elevation[i] = 0; _gps_position->satellite_azimuth[i] = 0; } _gps_position->satellites_visible = satellites_used; // visible ~= used but we are interested in the used ones /* set timestamp if any sat info is available */ if (packet_part1->numCh > 0) { _gps_position->satellite_info_available = true; } else { _gps_position->satellite_info_available = false; } _gps_position->timestamp_satellites = hrt_absolute_time(); } break; } case NAV_VELNED: { // printf("GOT NAV_VELNED MESSAGE\n"); if (!_waiting_for_ack) { gps_bin_nav_velned_packet_t *packet = (gps_bin_nav_velned_packet_t *) _rx_buffer; _gps_position->vel_m_s = (float)packet->speed * 1e-2f; _gps_position->vel_n_m_s = (float)packet->velN * 1e-2f; _gps_position->vel_e_m_s = (float)packet->velE * 1e-2f; _gps_position->vel_d_m_s = (float)packet->velD * 1e-2f; _gps_position->cog_rad = (float)packet->heading * M_DEG_TO_RAD_F * 1e-5f; _gps_position->vel_ned_valid = true; _gps_position->timestamp_velocity = hrt_absolute_time(); } break; } // case RXM_SVSI: { // printf("GOT RXM_SVSI MESSAGE\n"); // const int length_part1 = 7; // char _rx_buffer_part1[length_part1]; // memcpy(_rx_buffer_part1, _rx_buffer, length_part1); // gps_bin_rxm_svsi_packet_t *packet = (gps_bin_rxm_svsi_packet_t *) _rx_buffer_part1; // // _gps_position->satellites_visible = packet->numVis; // _gps_position->counter++; // _last_message_timestamps[RXM_SVSI - 1] = hrt_absolute_time(); // // break; // } case ACK_ACK: { // printf("GOT ACK_ACK\n"); gps_bin_ack_ack_packet_t *packet = (gps_bin_ack_ack_packet_t *) _rx_buffer; if (_waiting_for_ack) { if (packet->clsID == _clsID_needed && packet->msgID == _msgID_needed) { ret = 1; } } } break; case ACK_NAK: { // printf("GOT ACK_NAK\n"); warnx("UBX: Received: Not Acknowledged"); /* configuration obviously not successful */ ret = -1; break; } default: //we don't know the message warnx("UBX: Unknown message received: %d-%d\n",_message_class,_message_id); ret = -1; break; } // end if _rx_count high enough decode_init(); return ret; //XXX? } void UBX::decode_init(void) { _rx_ck_a = 0; _rx_ck_b = 0; _rx_count = 0; _decode_state = UBX_DECODE_UNINIT; _message_class = CLASS_UNKNOWN; _message_id = ID_UNKNOWN; _payload_size = 0; } void UBX::add_byte_to_checksum(uint8_t b) { _rx_ck_a = _rx_ck_a + b; _rx_ck_b = _rx_ck_b + _rx_ck_a; } void UBX::add_checksum_to_message(uint8_t* message, const unsigned length) { uint8_t ck_a = 0; uint8_t ck_b = 0; unsigned i; for (i = 0; i < length-2; i++) { ck_a = ck_a + message[i]; ck_b = ck_b + ck_a; } /* The checksum is written to the last to bytes of a message */ message[length-2] = ck_a; message[length-1] = ck_b; } void UBX::send_config_packet(const int &fd, uint8_t *packet, const unsigned length) { ssize_t ret = 0; /* Calculate the checksum now */ add_checksum_to_message(packet, length); const uint8_t sync_bytes[] = {UBX_SYNC1, UBX_SYNC2}; /* Start with the two sync bytes */ ret += write(fd, sync_bytes, sizeof(sync_bytes)); ret += write(fd, packet, length); if (ret != (int)length + (int)sizeof(sync_bytes)) // XXX is there a neater way to get rid of the unsigned signed warning? warnx("ubx: config write fail"); }