laforge has submitted this change. ( https://gerrit.osmocom.org/c/osmo-trx/+/41231?usp=email ) Change subject: trx: Fix tx/rx-sps 4 for USRP1 devices ...................................................................... trx: Fix tx/rx-sps 4 for USRP1 devices The existing code sets the pingOffset variable to -7231(269 - 7500) with tx-sps = 4. The (apparent) correct value for pingOffset for tx/rx-sps 4 is 272. While I'm not completely sure how this patch works to fix the increased sps value, my theory is that the original OpenBTS TRX only supported a split sps setup(tx-sps=4, rx_sps=1 for sps=4), which created differing decimation rates between Tx and Rx on the board. In this case, apparently you needed to account for an advance in the timestamp for a correct output. With tx_sps == rx_sps, the decimation/sample rates will be the same, and(I guess) this advance doesn't need to be accounted for. Also changed a line in the initialization of the Rx end of the USRP device to use the correct decimation rate when tx/rx-sps == 4. Since osmo-trx won't allow nonequal values for tx-sps and rx-sps, I commented out the logic that selected pingOffset based on sps. I left it visible in the file for reference however. Tested & working on the URAN-1, a USRP1 clone designed for GSM. Change-Id: I3b08c23a3e7d4a226cd23b9fe42558f596a63257 --- M Transceiver52M/device/usrp1/USRPDevice.cpp 1 file changed, 8 insertions(+), 7 deletions(-) Approvals: laforge: Looks good to me, approved fixeria: Looks good to me, but someone else must approve; Verified diff --git a/Transceiver52M/device/usrp1/USRPDevice.cpp b/Transceiver52M/device/usrp1/USRPDevice.cpp index 63a9bcc..21cbd7e 100644 --- a/Transceiver52M/device/usrp1/USRPDevice.cpp +++ b/Transceiver52M/device/usrp1/USRPDevice.cpp @@ -75,18 +75,19 @@ * split sample rate Tx/Rx - 4/1 sps we need to need to * compensate for advance rather than delay. */ - if (tx_sps == 1) - pingOffset = 272; - else if (tx_sps == 4) - pingOffset = 269 - 7500; - else - pingOffset = 0; + pingOffset = 272; + + /* Split SPS (4/1) unsupported on USRP1 + * if(tx_sps == 4 && rx_sps == 1) + * pingOffset = 269 - 7500; + */ #ifdef SWLOOPBACK samplePeriod = 1.0e6/actualSampleRate; loopbackBufferSize = 0; gettimeofday(&lastReadTime,NULL); firstRead = false; + pingOffset = 0; #endif } @@ -101,7 +102,7 @@ m_uRx.reset(); try { m_uRx = usrp_standard_rx_sptr(usrp_standard_rx::make( - 0, decimRate * tx_sps, 1, -1, + 0, decimRate, 1, -1, usrp_standard_rx::FPGA_MODE_NORMAL, 1024, 16 * 8, rbf)); m_uRx->set_fpga_master_clock_freq(masterClockRate); -- To view, visit https://gerrit.osmocom.org/c/osmo-trx/+/41231?usp=email To unsubscribe, or for help writing mail filters, visit https://gerrit.osmocom.org/settings?usp=email Gerrit-MessageType: merged Gerrit-Project: osmo-trx Gerrit-Branch: master Gerrit-Change-Id: I3b08c23a3e7d4a226cd23b9fe42558f596a63257 Gerrit-Change-Number: 41231 Gerrit-PatchSet: 2 Gerrit-Owner: tempest <jackleea1b@gmail.com> Gerrit-Reviewer: Hoernchen <ewild@sysmocom.de> Gerrit-Reviewer: fixeria <vyanitskiy@sysmocom.de> Gerrit-Reviewer: laforge <laforge@osmocom.org> Gerrit-Reviewer: tnt <tnt@246tNt.com> Gerrit-Reviewer: ttsou <tom@tsou.cc> Gerrit-CC: pespin <pespin@sysmocom.de>