Basic noise/jitter test script

readme.org

 #+TITLE: marcos_client
 
-(NEED TO UPDATE THIS FILE)
+(NEED TO UPDATE THIS FILE -- SOME OF THE DESCRIPTIONS ARE OBSOLETE)
 
 Python-based MaRCoS GUI and associated tests.
 
@@ -11,14 +11,12 @@ See the [[https://github.com/vnegnev/marcos_extras/wiki][MaRCoS wiki]] for info;
   - Install =msgpack= for Python manually or via the package manager of your choice.
 
   - Clone the repo and copy =local_config.py.example= to =local_config.py=.
-  
+
   - Edit =local_config.py= to suit your network and hardware setup.
 
   - Run =test_server.py= and make sure no errors are returned.
 
-  - Run =test_acquire.py= to test the hardware in a basic acquisition.
-
-  - Run =test_experiment.py= to test the experiment API.
+  - Run =test_noise.py= to generate some simple pulses and view their properties on an oscilloscope.
 
   - Import experiment.py in your higher-level MRI scripts.
 

test_noise.py

+#!/usr/bin/env python3
+
+import numpy as np
+import matplotlib.pyplot as plt
+import experiment as ex
+from local_config import grad_board
+
+import pdb
+st = pdb.set_trace
+
+def test_jitter(
+        rf_pulse_freq = 2, # MHz
+        rf_pulse_start_time = 10, # us
+        rf_pulse_length = 2, # us
+        rf_amp=0.8, # fraction of full-scale
+        rf_interval=5, # us, delay between start of first and start of
+                       # second pulse - must be bigger than pulse
+                       # length
+        grad_pulse_start_time = 10, # us
+        grad_pulse_length = 40, # us
+        grad_interval=80, # us
+        grad_amp=0.2, # fraction of full-scale
+        loops=10,
+        print_loops=False,
+        plot_sequence=False,
+        experiment_kwargs={}):
+    """Two successive pulses, with an adjustable interval between them.
+
+    Trigger an oscilloscope from the TX gate or first pulse, and look
+    at the second pulse, with a suitable hold-off time so that
+    triggering is reliable. Over many repetitions, the timing jitter
+    will be visible.
+    """
+    tx_gate_start_time = 0
+    tx_gate_length = 0.1
+
+    rf_data = (
+        rf_pulse_start_time + np.array([0, rf_pulse_length, rf_interval, rf_pulse_length + rf_interval]),
+        np.array([rf_amp, 0, rf_amp, 0])
+    )
+
+    grad_data = (
+        grad_pulse_start_time + np.array([0, grad_pulse_length, grad_interval, grad_pulse_length + grad_interval]),
+        np.array([grad_amp, 0, grad_amp, 0])
+    )
+
+    gpa_fhdo_offset_time = 10 if grad_board == "gpa-fhdo" else 0
+
+    event_dict = {'tx0': rf_data,
+                  'tx1': rf_data,
+                  'grad_vx': grad_data,
+                  'grad_vy': grad_data,
+                  'grad_vz': grad_data,
+                  'grad_vz2': grad_data,
+                  'tx_gate': (tx_gate_start_time + np.array([0, tx_gate_length]), np.array([1, 0]))}
+
+    exp = ex.Experiment(lo_freq=rf_pulse_freq, gpa_fhdo_offset_time=gpa_fhdo_offset_time, **experiment_kwargs)
+    exp.add_flodict(event_dict)
+
+    if plot_sequence:
+        exp.plot_sequence()
+        plt.show()
+
+    for k in range(loops):
+        exp.run()
+        if print_loops and k % 1000 == 0:
+            print(f"Loop {k}")
+
+    exp.close_server(only_if_sim=True)
+
+if __name__ == "__main__":
+    # slowed down to suit VN's setup, due to GPA-FHDO communication chip being dead
+    experiment_kwargs = {'init_gpa': True, 'grad_max_update_rate': 0.1}
+    loops = int(1e6)
+
+    # Enable the test that you want to run below
+
+    # RF pulses close together, gradient pulses further apart, rf and grad start simultaneously (default)
+    if False:
+        test_jitter(loops=loops, experiment_kwargs=experiment_kwargs) # many loops
+
+    # RF and gradient pulses start almost simultaneously (RF offset to avoid SPI noise), second pulses happen at an adjustable interval
+    if True:
+        interval=100000 # 100ms
+        amp = 0.2
+        test_jitter(loops=loops, rf_pulse_start_time=10.5,
+                    rf_interval=interval, rf_amp=amp,
+                    grad_interval=interval, grad_amp=amp,
+                    experiment_kwargs=experiment_kwargs) # many loops