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Harald Welte gerrit-no-reply at lists.osmocom.orgReview at https://gerrit.osmocom.org/6697 host/trxcon/scheduler: implement SCH decoding Change-Id: Ic5e7416271d647752cd1aaf90de51fa48286798e --- M src/host/trxcon/sched_lchan_desc.c M src/host/trxcon/sched_lchan_handlers.c 2 files changed, 73 insertions(+), 2 deletions(-) git pull ssh://gerrit.osmocom.org:29418/osmocom-bb refs/changes/97/6697/1 diff --git a/src/host/trxcon/sched_lchan_desc.c b/src/host/trxcon/sched_lchan_desc.c index 93927a6..1ff6e14 100644 --- a/src/host/trxcon/sched_lchan_desc.c +++ b/src/host/trxcon/sched_lchan_desc.c @@ -44,6 +44,10 @@ uint32_t fn, enum trx_lchan_type chan, uint8_t bid, sbit_t *bits, uint16_t nbits, int8_t rssi, float toa); +int rx_sch_fn(struct trx_instance *trx, struct trx_ts *ts, + uint32_t fn, enum trx_lchan_type chan, uint8_t bid, + sbit_t *bits, uint16_t nbits, int8_t rssi, float toa); + const struct trx_lchan_desc trx_lchan_desc[_TRX_CHAN_MAX] = { { TRXC_IDLE, "IDLE", @@ -69,8 +73,11 @@ 0x00, LID_DEDIC, 0x00, 0x00, - /* We already have clock indications from TRX */ - NULL, NULL, + /** + * We already have clock indications from TRX, + * but we also need BSIC (BCC / NCC) value. + */ + rx_sch_fn, NULL, }, { TRXC_BCCH, "BCCH", diff --git a/src/host/trxcon/sched_lchan_handlers.c b/src/host/trxcon/sched_lchan_handlers.c index 2c2cb6a..41e60d8 100644 --- a/src/host/trxcon/sched_lchan_handlers.c +++ b/src/host/trxcon/sched_lchan_handlers.c @@ -34,6 +34,7 @@ #include <osmocom/core/msgb.h> #include <osmocom/core/fsm.h> +#include <osmocom/gsm/gsm_utils.h> #include <osmocom/coding/gsm0503_coding.h> #include "l1ctl_proto.h" @@ -159,3 +160,66 @@ /* TODO: AGC, TA loops */ return 0; } + +static void decode_sb(struct gsm_time *time, uint8_t *bsic, uint8_t *sb_info) +{ + uint8_t t3p; + uint32_t sb; + + sb = (sb_info[3] << 24) + | (sb_info[2] << 16) + | (sb_info[1] << 8) + | sb_info[0]; + + *bsic = (sb >> 2) & 0x3f; + + /* TS 05.02 Chapter 3.3.2.2.1 SCH Frame Numbers */ + time->t1 = ((sb >> 23) & 0x01) + | ((sb >> 7) & 0x1fe) + | ((sb << 9) & 0x600); + + time->t2 = (sb >> 18) & 0x1f; + + t3p = ((sb >> 24) & 0x01) | ((sb >> 15) & 0x06); + time->t3 = t3p * 10 + 1; + + /* TS 05.02 Chapter 4.3.3 TDMA frame number */ + time->fn = gsm_gsmtime2fn(time); +} + +int rx_sch_fn(struct trx_instance *trx, struct trx_ts *ts, + uint32_t fn, enum trx_lchan_type chan, uint8_t bid, + sbit_t *bits, uint16_t nbits, int8_t rssi, float toa) +{ + sbit_t payload[2 * 39]; + struct gsm_time time; + uint8_t sb_info[4]; + uint8_t bsic; + int rc; + + /* Obtain payload from burst */ + memcpy(payload, bits + 3, 39); + memcpy(payload + 39, bits + 3 + 39 + 64, 39); + + /* Attempt to decode */ + rc = gsm0503_sch_decode(sb_info, payload); + if (rc) { + LOGP(DSCH, LOGL_DEBUG, "Received bad SCH burst at fn=%u\n", fn); + return rc; + } + + /* Decode BSIC and TDMA frame number */ + decode_sb(&time, &bsic, sb_info); + + LOGP(DSCH, LOGL_DEBUG, "Received SCH: bsic=%u, fn=%u, sched_fn=%u\n", + bsic, time.fn, trx->sched.fn_counter_proc); + + /* Check if decoded frame number matches */ + if (time.fn != fn) { + LOGP(DSCH, LOGL_ERROR, "Decoded fn=%u does not match " + "fn=%u provided by scheduler\n", time.fn, fn); + return -EINVAL; + } + + return 0; +} -- To view, visit https://gerrit.osmocom.org/6697 To unsubscribe, visit https://gerrit.osmocom.org/settings Gerrit-MessageType: newchange Gerrit-Change-Id: Ic5e7416271d647752cd1aaf90de51fa48286798e Gerrit-PatchSet: 1 Gerrit-Project: osmocom-bb Gerrit-Branch: master Gerrit-Owner: Harald Welte <laforge at gnumonks.org>