| /* |
| * gps.c |
| * |
| * A few utility functions to deal with low level GPS data |
| * |
| * |
| * Copyright (C) 2009 Sylvain Munaut <tnt@246tNt.com> |
| * |
| * This program is free software: you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License as published by |
| * the Free Software Foundation, either version 2 of the License, or |
| * (at your option) any later version. |
| * |
| * This program is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| * GNU General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program. If not, see <http://www.gnu.org/licenses/>. |
| */ |
| |
| #include "gps.h" |
| |
| |
| #define GET_FIELD_U(w, nb, pos) (((w) >> (pos)) & ((1<<(nb))-1)) |
| #define GET_FIELD_S(w, nb, pos) (((int)((w) << (32-(nb)-(pos)))) >> (32-(nb))) |
| |
| /* |
| * Unpacks GPS Subframe 1,2,3 payloads (3 * 8 words) |
| * |
| * Note: eph->sv_id is not filled here since not present in those subframes |
| * |
| * (no parity bit checking is done, only the lower 24 bits of each word |
| * are used) |
| */ |
| int |
| gps_unpack_sf123(uint32_t *sf, struct gps_ephemeris_sv *eph) |
| { |
| uint32_t *sf1 = &sf[0]; |
| uint32_t *sf2 = &sf[8]; |
| uint32_t *sf3 = &sf[16]; |
| |
| int iode1, iode2; |
| |
| eph->week_no = GET_FIELD_U(sf1[0], 10, 14); |
| eph->code_on_l2 = GET_FIELD_U(sf1[0], 2, 12); |
| eph->sv_ura = GET_FIELD_U(sf1[0], 4, 8); |
| eph->sv_health = GET_FIELD_U(sf1[0], 6, 2); |
| eph->l2_p_flag = GET_FIELD_U(sf1[1], 1, 23); |
| eph->t_gd = GET_FIELD_S(sf1[4], 8, 0); |
| eph->iodc = (GET_FIELD_U(sf1[0], 2, 0) << 8) | \ |
| GET_FIELD_U(sf1[5], 8, 16); |
| eph->t_oc = GET_FIELD_U(sf1[5], 16, 0); |
| eph->a_f2 = GET_FIELD_S(sf1[6], 8, 16); |
| eph->a_f1 = GET_FIELD_S(sf1[6], 16, 0); |
| eph->a_f0 = GET_FIELD_S(sf1[7], 22, 2); |
| |
| iode1 = GET_FIELD_U(sf2[0], 8, 16); |
| eph->c_rs = GET_FIELD_S(sf2[0], 16, 0); |
| eph->delta_n = GET_FIELD_S(sf2[1], 16, 8); |
| eph->m_0 = (GET_FIELD_S(sf2[1], 8, 0) << 24) | \ |
| GET_FIELD_U(sf2[2], 24, 0); |
| eph->c_uc = GET_FIELD_S(sf2[3], 16, 8); |
| eph->e = (GET_FIELD_U(sf2[3], 8, 0) << 24) | \ |
| GET_FIELD_U(sf2[4], 24, 0); |
| eph->c_us = GET_FIELD_S(sf2[5], 16, 8); |
| eph->a_powhalf = (GET_FIELD_U(sf2[5], 8, 0) << 24) | \ |
| GET_FIELD_U(sf2[6], 24, 0); |
| eph->t_oe = GET_FIELD_U(sf2[7], 16, 8); |
| eph->fit_flag = GET_FIELD_U(sf2[7], 1, 7); |
| |
| eph->c_ic = GET_FIELD_S(sf3[0], 16, 8); |
| eph->omega_0 = (GET_FIELD_S(sf3[0], 8, 0) << 24) | \ |
| GET_FIELD_U(sf3[1], 24, 0); |
| eph->c_is = GET_FIELD_S(sf3[2], 16, 8); |
| eph->i_0 = (GET_FIELD_S(sf3[2], 8, 0) << 24) | \ |
| GET_FIELD_U(sf3[3], 24, 0); |
| eph->c_rc = GET_FIELD_S(sf3[4], 16, 8); |
| eph->w = (GET_FIELD_S(sf3[4], 8, 0) << 24) | \ |
| GET_FIELD_U(sf3[5], 24, 0); |
| eph->omega_dot = GET_FIELD_S(sf3[6], 24, 0); |
| iode2 = GET_FIELD_U(sf3[7], 8, 16); |
| eph->idot = GET_FIELD_S(sf3[7], 14, 2); |
| |
| eph->_rsvd1 = GET_FIELD_U(sf1[1], 23, 0); |
| eph->_rsvd2 = GET_FIELD_U(sf1[2], 24, 0); |
| eph->_rsvd3 = GET_FIELD_U(sf1[3], 24, 0); |
| eph->_rsvd4 = GET_FIELD_U(sf1[4], 16, 8); |
| eph->aodo = GET_FIELD_U(sf2[7], 5, 2); |
| |
| /* Check & cross-validate iodc[7:0], iode1, iode2 */ |
| if ((iode1 != iode2) || (iode1 != (eph->iodc & 0xff))) |
| return -1; |
| |
| return 0; |
| } |
| |
| |
| /* |
| * Unpacks GPS Subframe 4 or 5 Almanac pages payload (8 words) |
| * |
| * (no parity bit checking is done, only the lower 24 bits of each word |
| * are used) |
| */ |
| int |
| gps_unpack_sf45_almanac(uint32_t *sf, struct gps_almanac_sv *alm) |
| { |
| alm->sv_id = GET_FIELD_U(sf[0], 6, 16); |
| |
| alm->e = GET_FIELD_U(sf[0], 16, 0); |
| alm->t_oa = GET_FIELD_U(sf[1], 8, 16); |
| alm->ksii = GET_FIELD_S(sf[1], 16, 0); |
| alm->omega_dot = GET_FIELD_S(sf[2], 16, 8); |
| alm->sv_health = GET_FIELD_U(sf[2], 8, 0); |
| alm->a_powhalf = GET_FIELD_U(sf[3], 24, 0); |
| alm->omega_0 = GET_FIELD_S(sf[4], 24, 0); |
| alm->w = GET_FIELD_S(sf[5], 24, 0); |
| alm->m_0 = GET_FIELD_S(sf[6], 24, 0); |
| alm->a_f0 = (GET_FIELD_S(sf[7], 8, 16) << 3) | \ |
| GET_FIELD_U(sf[7], 3, 2); |
| alm->a_f1 = GET_FIELD_S(sf[7], 11, 5); |
| |
| return 0; |
| } |
| |