source: ResearchApps/PHY/WARPLAB/WARPLab7/M_Code_Examples/wl_example_siso_txrx_nodeSync.m

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% wl_example_siso_txrx_nodeSync.m
%
% This example illustrates how to synchronize multiple WARP v3 nodes
% to eliminate all frequency and timing offsets.
%
% Requirements:
%     - 2 WARP nodes (same hardware generation); 1 RF interface each
%     - Ether:
%         - 2 CM-MMCX modules; MMCX coax cable assemblies to connect the CM-MMCX I/O 
%           and a 2-pin twisted pair cable assembly to route the inter-node trigger
%         - 2 CM-PLL modules; CM-PLL connector 
%           (see:  http://warpproject.org/trac/wiki/HardwareUsersGuides/CM-PLL/Connectors#Cables )
%     - WARPLab 7.6.0 and higher
%
% More details on using this example are available on the WARP site:
%     http://warpproject.org/w/WARPLab/Examples
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Top Level Control Variables
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% External trigger mode requires a connection from the trigger output EXT_OUT_P0 on node 0
% to EXT_IN_P3 on node 1 (see http://warpproject.org/w/WARPLab/Examples for details)
%
USE_EXTERNAL_TRIGGER = true;

% To maintain constant phase offsets among nodes sharing an RF reference clock, bypass 
% wl_initNodes() which executes a reset of the MAX2829 transceivers that forces a re-tune 
% of the PLL that changes the inter-node phases.
%
% NOTE:  This has to be false the first time this script is run otherwise, the script will
%     not have the "nodes" variable populated.
%
BYPASS_INIT_NODES = false;

% RX variables
USE_AGC        = true;
ManualRxGainRF = 1;                    % Rx RF Gain in [1:3] (ignored if USE_AGC is true)
ManualRxGainBB = 15;                   % Rx Baseband Gain in [0:31] (ignored if USE_AGC is true)

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Set up the WARPLab experiment
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Create a vector of node objects
if ( ~BYPASS_INIT_NODES )

    nodes = wl_initNodes(2);

else 
    % This example assumes that the node is in the state from which it exits initNodes.
    % If the example does not run initNodes to keep the phase offsets constant, then we need
    % to issue a couple of commands to put the node in a known state.
    %

    % Set the transmit delay to zero
    wl_basebandCmd(nodes, 'tx_delay', 0);

    % Disable the buffers and RF interfaces for TX / RX
    wl_basebandCmd(nodes, ifc_ids.RF_ALL, 'tx_rx_buff_dis');
    wl_interfaceCmd(nodes, ifc_ids.RF_ALL, 'tx_rx_dis');
end


% Assign roles to the nodes (ie transmitter / receiver)
node_tx = nodes(1);
node_rx = nodes(2);


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Set up Trigger Manager
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Create a UDP broadcast trigger and primary node to be ready for it
eth_trig = wl_trigger_eth_udp_broadcast;
nodes.wl_triggerManagerCmd('add_ethernet_trigger', [eth_trig]);

% Read Trigger IDs into workspace
trig_in_ids  = wl_getTriggerInputIDs(node_tx);
trig_out_ids = wl_getTriggerOutputIDs(node_tx);

% For the transmit node, we will allow Ethernet to trigger the buffer baseband, the AGC, and debug0 
% (which is mapped to pin 8 on the debug header)
node_tx.wl_triggerManagerCmd('output_config_input_selection', [trig_out_ids.BASEBAND, trig_out_ids.EXT_OUT_P0], [trig_in_ids.ETH_A]);

if(USE_EXTERNAL_TRIGGER)
    % For the receive node, we will allow debug3 (mapped to pin 15 on the
    % debug header) to trigger the buffer baseband, and the AGC
    % Note that the below line selects both P0 and P3. This will allow the
    % script to work with either the CM-PLL (where output P0 directly
    % connects to input P0) or the CM-MMCX (where output P0 is usually
    % connected to input P3 since both neighbor ground pins).
    node_rx.wl_triggerManagerCmd('output_config_input_selection', [trig_out_ids.BASEBAND, trig_out_ids.AGC], [trig_in_ids.EXT_IN_P0, trig_in_ids.EXT_IN_P3]);
else
    node_rx.wl_triggerManagerCmd('output_config_input_selection', [trig_out_ids.BASEBAND, trig_out_ids.AGC], [trig_in_ids.ETH_A]);
end

% For the receive node, we enable the debounce circuity on the debug 3 input
% to deal with the fact that the signal may be noisy.
node_rx.wl_triggerManagerCmd('input_config_debounce_mode', [trig_in_ids.EXT_IN_P0, trig_in_ids.EXT_IN_P3], true); 

% Since the debounce circuitry is enabled, there will be a delay at the
% receiver node for its input trigger. To better align the transmitter and
% receiver, we can artifically delay the transmitters trigger outputs that
% drive the buffer baseband and the AGC.
node_tx.wl_triggerManagerCmd('output_config_delay', [trig_out_ids.EXT_OUT_P0], 0);
node_tx.wl_triggerManagerCmd('output_config_delay', [trig_out_ids.BASEBAND], 62.5);     % 62.5ns delay
node_rx.wl_triggerManagerCmd('output_config_delay', [trig_out_ids.AGC], 3000);          % 3000ns delay


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Set up the Interface parameters
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Get IDs for the interfaces on the boards.  
%
% NOTE:  This example assumes each board has the same interface capabilities (ie 2 RF 
%   interfaces; RFA and RFB).  Therefore, we only need to get the IDs from one of the boards.
%
ifc_ids = wl_getInterfaceIDs(node_tx);

% Set the Transmit and Receive interfaces
%     Transmit from RFA of one node to RFA of the other node
%
% NOTE:  Variables are used to make it easier to change interfaces.
% 
RF_TX         = ifc_ids.RF_A;                    % Transmit RF interface
RF_RX         = ifc_ids.RF_A;                    % Receive RF interface

RF_RX_VEC     = ifc_ids.RF_A;                    % Vector version of transmit RF interface
RF_TX_VEC     = ifc_ids.RF_A;                    % Vector version of receive RF interface

% Set the RF center frequency on all interfaces
%     - Frequency Band  :  Must be 2.4 or 5, to select 2.4GHz or 5GHz channels
%     - Channel         :  Must be an integer in [1,11] for BAND = 2.4; [1,23] for BAND = 5
%
wl_interfaceCmd(nodes, ifc_ids.RF_ALL, 'channel', 2.4, 11);

% Set the RX gains on all interfaces or use AGC
%     - Rx RF Gain      :  Must be an integer in [1:3]
%     - Rx Baseband Gain:  Must be an integer in [0:31]
% 
% NOTE:  The gains may need to be modified depending on your experimental setup
%
if(USE_AGC)
    wl_interfaceCmd(nodes, ifc_ids.RF_ALL, 'rx_gain_mode', 'automatic');
    wl_basebandCmd(nodes, 'agc_target', -10);
else
    wl_interfaceCmd(nodes, ifc_ids.RF_ALL, 'rx_gain_mode', 'manual');
    wl_interfaceCmd(nodes, ifc_ids.RF_ALL, 'rx_gains', ManualRxGainRF, ManualRxGainBB);
end

% Set the TX gains on all interfaces
%     - Tx Baseband Gain:  Must be an integer in [0:3] for approx [-5, -3, -1.5, 0]dB baseband gain
%     - Tx RF Gain      :  Must be an integer in [0:63] for approx [0:31]dB RF gain
% 
% NOTE:  The gains may need to be modified depending on your experimental setup
% 
wl_interfaceCmd(nodes, ifc_ids.RF_ALL, 'tx_gains', 3, 30);


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Set up the Baseband parameters
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Get the sample frequency from the board
ts      = 1 / (wl_basebandCmd(nodes(1), 'tx_buff_clk_freq'));

% Read the maximum I/Q buffer length.  
%
% NOTE:  This example assumes that each board has the same baseband capabilities (ie both nodes are 
%   the same WARP hardware version, for example WARP v3).  This example also assumes that each RF 
%   interface has the same baseband capabilities (ie the max number of TX samples is the same as the 
%   max number of RF samples). Therefore, we only need to read the max I/Q buffer length of node_tx RFA.
% 
maximum_buffer_len = wl_basebandCmd(node_tx, RF_TX, 'tx_buff_max_num_samples');

% Set the transmission / receptions lengths (in samples)
%     See WARPLab user guide for maximum length supported by WARP hardware 
%     versions and different WARPLab versions.
%
tx_length    = 2^15;
rx_length    = tx_length;

% Check the transmission length
if (tx_length > maximum_buffer_len) 
    error('Node supports max transmission length of %d samples.  Requested %d samples.', maximum_buffer_len, tx_length); 
end

% Set the length for the transmit and receive buffers based on the transmission length
wl_basebandCmd(nodes, 'tx_length', tx_length);
wl_basebandCmd(nodes, 'rx_length', rx_length);


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Signal processing to generate transmit signal
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% First generate the preamble for AGC. 
%     NOTE:  The preamble corresponds to the short symbols from the 802.11a PHY standard
%
shortSymbol_freq = [0 0 0 0 0 0 0 0 1+i 0 0 0 -1+i 0 0 0 -1-i 0 0 0 1-i 0 0 0 -1-i 0 0 0 1-i 0 0 0 0 0 0 0 1-i 0 0 0 -1-i 0 0 0 1-i 0 0 0 -1-i 0 0 0 -1+i 0 0 0 1+i 0 0 0 0 0 0 0].';
shortSymbol_freq = [zeros(32,1);shortSymbol_freq;zeros(32,1)];
shortSymbol_time = ifft(fftshift(shortSymbol_freq));
shortSymbol_time = (shortSymbol_time(1:32).')./max(abs(shortSymbol_time));
shortsyms_rep    = repmat(shortSymbol_time,1,30);
preamble         = shortsyms_rep;
preamble         = preamble(:);


t = [0:ts:((tx_length - length(preamble) - 1))*ts].';      % Create time vector(Sample Frequency is ts (Hz))

sinusoid  = 0.6 * exp(j*2*pi * 2e6 * t);                   % Create 2 MHz sinusoid

tx_data   = [preamble; sinusoid];


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Transmit and receive signal using WARPLab
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Transmit IQ data to the TX node
wl_basebandCmd(node_tx, RF_TX_VEC, 'write_IQ', tx_data(:));

% Enabled the RF interfaces for TX / RX
wl_interfaceCmd(node_tx, RF_TX, 'tx_en');
wl_interfaceCmd(node_rx, RF_RX, 'rx_en');

% Enable the buffers for TX / RX
wl_basebandCmd(node_tx, RF_TX, 'tx_buff_en');
wl_basebandCmd(node_rx, RF_RX, 'rx_buff_en');

% Send the Ethernet trigger to start the TX
eth_trig.send();

% Read the IQ data from the RX node 
rx_IQ    = wl_basebandCmd(node_rx, RF_RX_VEC, 'read_IQ', 0, rx_length);

% Disable the buffers and RF interfaces for TX / RX
wl_basebandCmd(nodes, ifc_ids.RF_ALL, 'tx_rx_buff_dis');
wl_interfaceCmd(nodes, ifc_ids.RF_ALL, 'tx_rx_dis');

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Visualize results
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
tVec = [0:ts:((tx_length -1 )*ts)]*1e6;

sampStart = 5000;
sampEnd = tx_length;
htxt = [];

figure(1);clf;
subplot(3,1,1)
plot(tVec(sampStart:sampEnd),real(tx_data(sampStart:sampEnd)),'b')
htxt(end+1) = ylabel('Amplitude');
htxt(end+1) = title('Transmitted I Waveform');
axis([tVec(sampStart) tVec(sampEnd) -1 1]);
grid on;

subplot(3,1,2)
plot(tVec(sampStart:sampEnd),real(rx_IQ(sampStart:sampEnd,:)), 'r')
htxt(end+1) = ylabel('Amplitude');
htxt(end+1) = title('Received I Waveform');
axis([tVec(sampStart) tVec(sampEnd) -1 1]);
grid on;

subplot(3,1,3)
phase_diff = unwrap(angle(rx_IQ(sampStart:sampEnd))) - unwrap(angle(tx_data(sampStart:sampEnd)));
plot(tVec(sampStart:sampEnd), phase_diff)
axis tight
myAxis = axis;

if(myAxis(4)-myAxis(3) < 2*pi)
    %Zoom out to at least a 2*pi range of angles
    axis([myAxis(1), myAxis(2), mean(myAxis(3:4))-pi, mean(myAxis(3:4))+pi]);

end

grid on;
htxt(end+1) = title('Tx-Rx Phase Offset');
htxt(end+1) = ylabel('Phase Difference (radians)');
htxt(end+1) = xlabel('Time (us)');

set(htxt, 'FontWeight', 'bold');