Could you share how you're setting up LO sharing in your code, as well as how you're setting the system clock on the N321?
The functions "configure_channels" and "set_lo_hw_exports" are used to set up the LO sharing. The functions "sync_sources" and "sync_all_devices" are used to set up the system clock on the N321. How do you measure the relative delay? We are measuring the offset of the LO's by just measuring the phase difference of the RF coming out of the Ettus with an Oscilloscope (picture attached as Scope_Trace_SingleStream_LO.png <https://mail.google.com/mail/u/0?ui=2&ik=34abf4583b&attid=0.1&permmsgid=msg-a:r-1207093291428225864&view=att&disp=safe&realattid=f_lijcykt50>). Yellow is Channel 1, Green is Channel 2; using a single streamer we still appear to have a 2.64ns delta or ~135 degree phase shift. Thanks Marcus and Rob for your assistance. Michael Toussaint def sync_sources(usrp): logging.info('Setting Sync Sources') usrp.set_sync_source(clock_source = 'gpsdo', time_source = 'gpsdo') def sync_all_devices(hw_info): logging.info('Syncing All Devices') mb_with_gps_locked = -1 while 1: time.sleep(1.0) all_ref_locked = True for board in range(hw_info.usrp.get_num_mboards()): all_ref_locked = all_ref_locked and \ hw_info.usrp.get_mboard_sensor('ref_locked', board).to_bool() if (mb_with_gps_locked == -1) and \ hw_info.usrp.get_mboard_sensor('gps_locked', board).to_bool(): mb_with_gps_locked = board if all_ref_locked: logging.info('All Devices are REF locked') break logging.info('GPS Locked on MB #%d', mb_with_gps_locked) time.sleep(1.0) hw_info.usrp.set_time_next_pps( uhd.types.TimeSpec( hw_info.usrp.get_mboard_sensor('gps_time', mb_with_gps_locked).to_int() + 1.0) ) time.sleep(1.0) def configure_channels(usrp, rf_type, hw_info): rf_channel_index = None set_rf_rate = None set_rf_freq = None set_rf_gain = None set_rf_lo_source = None get_rf_lo_source = None get_rf_lo_freq = None get_rf_lo_freq_range = None if (rf_type == 'rx'): if (len(hw_info.rx_channel_index) > 0): rf_channel_index = hw_info.rx_channel_index set_rf_rate = usrp.set_rx_rate set_rf_freq = usrp.set_rx_freq set_rf_gain = usrp.set_rx_gain set_rf_lo_source = usrp.set_rx_lo_source get_rf_lo_source = usrp.get_rx_lo_source get_rf_lo_freq = usrp.get_rx_lo_freq get_rf_lo_freq_range = usrp.get_rx_lo_freq_range else: return elif (rf_type == 'tx'): if (len(hw_info.tx_channel_index) > 0): rf_channel_index = hw_info.tx_channel_index set_rf_rate = usrp.set_tx_rate set_rf_freq = usrp.set_tx_freq set_rf_gain = usrp.set_tx_gain set_rf_lo_source = usrp.set_tx_lo_source get_rf_lo_source = usrp.get_tx_lo_source get_rf_lo_freq = usrp.get_tx_lo_freq get_rf_lo_freq_range = usrp.get_tx_lo_freq_range else: return logging.info('Configuring %s Channels', rf_type.upper()) for rf_ch_name, rf_ch_index in rf_channel_index.items(): logging.info('Configuring %s channel %s (channel #%d)', rf_type.upper(), rf_ch_name, rf_ch_index) ch_def = hw_info.channel_def[rf_ch_name] # LO Channel Setup current_lo_name = 'unknown' current_lo_src = 'unknown' if ch_def.lo_inputs is not None: logging.info(' Setting %s LO for Channel %s (#%d)', rf_type.upper(), rf_ch_name, rf_ch_index) set_rf_lo_source(ch_def.lo_inputs.source, ch_def.lo_inputs.name, rf_ch_index) current_lo_name = ch_def.lo_inputs.name logging.info(' (#%d) Requested %s LO name %s, src %s', rf_ch_index, rf_type.upper(), ch_def.lo_inputs.name, ch_def.lo_inputs.source) else: logging.info(' No %s LO inputs for Channel %s (#%d)', rf_type.upper(), rf_ch_name, rf_ch_index) current_lo_name = 'lo1' current_lo_src = get_rf_lo_source(current_lo_name, rf_ch_index) logging.info(' (#%d) Current %s LO name %s, src %s', rf_ch_index, rf_type.upper(), current_lo_name, current_lo_src) rf_lo_freq = get_rf_lo_freq(current_lo_name, rf_ch_index) logging.info(' (#%d) [%s] Current %s LO freq %d', rf_ch_index, current_lo_name, rf_type.upper(), rf_lo_freq) rf_lo_freq_range = get_rf_lo_freq_range( current_lo_name, rf_ch_index) temp = ' (#%d) [%s] Current %s LO freq range' + \ ' [%d, %d] step %d' logging.info(temp, rf_ch_index, current_lo_name, rf_type.upper(), rf_lo_freq_range.start(), rf_lo_freq_range.stop(), rf_lo_freq_range.step()) logging.info(' Setting Sampling Rate %s', hw_info.fs) set_rf_rate(hw_info.fs, rf_ch_index) logging.info(' Setting Center Freq %s', hw_info.fc) tr = set_rf_freq(uhd.libpyuhd.types.tune_request(hw_info.fc), rf_ch_index) logging.info(' (#%d) %s Tune Result:', rf_ch_index, rf_type.upper()) log_tune_result(tr) logging.info(' Setting %s Gain: %2.3f db', rf_type.upper(), ch_def.gain) set_rf_gain(ch_def.gain, rf_ch_index) def set_lo_hw_exports(usrp, node_name, dirx, lo_enabled, output_array): """Set LO HW Exports""" if (lo_enabled is None) or (output_array is None): return logging.info('Setting %s LO Export Enabled for %s', dirx.upper(), node_name) if dirx.lower() == 'rx': usrp.set_rx_lo_export_enabled(lo_enabled, 'lo1', 0) enable_val = usrp.get_rx_lo_export_enabled('lo1') elif dirx.lower() == 'tx': usrp.set_tx_lo_export_enabled(lo_enabled, 'lo1', 0) enable_val = usrp.get_tx_lo_export_enabled('lo1') else: logging.warning('Invalid direction %s', dirx) return logging.info(' %s LO Export Enabled = %s, requested %s', dirx.upper(), enable_val, lo_enabled) temp_path = 'blocks/0/Radio#0/dboard/' + \ f'{dirx.lower()}_frontends/' + \ '0/los/lo1/lo_distribution/LO_OUT_{}/export' logging.info('Setting %s LO HW Outputs for %s', dirx.upper(), node_name) for out_num in range(len(output_array)): hw_lo_export_path = temp_path.format(out_num) if usrp.get_tree().exists(hw_lo_export_path): usrp.get_tree().access_bool(hw_lo_export_path).set( output_array[out_num]) logging.info(' %s LO HW Export Out[%d] = %s, %s %s', dirx.upper(), out_num, usrp.get_tree().access_bool( hw_lo_export_path).get(), 'requested', output_array[out_num]) else: logging.warning(' %s LO HW Export Out[%d] does not exist', dirx.upper(), out_num) On Thu, May 25, 2023 at 6:45 AM Rob Kossler <rkoss...@nd.edu> wrote: > On Thu, May 25, 2023 at 3:54 AM Michael Toussaint > <mtoussa...@chaosinc.com> wrote: > > > > Used a single streamer and saw the delay slightly improve to between 2.5 > - 3 ns. > > > > Any other suggestions to improve the delay to match the results from the > knowledge base, https://kb.ettus.com/USRP_N320/N321_LO_Distribution? > > How do you measure the relative delay? >
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