add sallen key preset 2

main.py

@@ -7,6 +7,14 @@ from matplotlib import pyplot as plt
 import gex
 import time
 
+# Two presets defined for demoing the plotter with a high-pass and low-pass RC filter
+# made of 1 kOhm and 100 nF
+
+#demo = 'HP'
+demo = 'LP'
+#demo = 'LP2'
+#demo = 'LP3' # LT1112 sallenkey at 1 kHz
+
 class ADG:
     def __init__(self, client:gex.Client):
         self.client = client
@@ -40,7 +48,8 @@ class ADG:
         if freq is not None:
             self.set_frequency(freq)
 
-with gex.Client(gex.TrxRawUSB()) as client:
+#with gex.Client(gex.TrxRawUSB()) as client:
+with gex.Client(gex.TrxSerialThread('/dev/ttyACM0')) as client:
     # ===============================================
       
     # Delay between adjusting input and starting the measurement. 
@@ -51,43 +60,60 @@ with gex.Client(gex.TrxRawUSB()) as client:
     max_allowed_shift_db = 5
     # db shift compensation (spread through the frequency sweep to adjust for different slopes)
     allowed_shift_compensation = -4.5
-        
     
-    if False:
-      # highpass filter example (corner 340 Hz)
-      settling_time_s = (4700*100e-9)*10
-      max_allowed_shift_db = 5
-      allowed_shift_compensation = -4.5
+    # Frequency sweep parameters
+    f_0 = 5
+    f_1 = 6000
     
+    f_step = 5
+    f_step_begin = 5
+    f_step_end = 200
     
-    if True:
+    if demo == 'HP':
+      # highpass filter example (corner 340 Hz)
+      settling_time_s = (4700*100e-9)*10
+      max_allowed_shift_db = 5.6
+      allowed_shift_compensation = -5
+
+    if demo == 'LP':
+      # lowpass filter example (corner 340 Hz)
+      settling_time_s = (4700*100e-9)*10
+      max_allowed_shift_db = .5
+      allowed_shift_compensation = 2
+         
+    if demo == 'LP2':
       # lowpass filter example (corner 340 Hz)
       settling_time_s = (4700*100e-9)*10
-      max_allowed_shift_db = 1
-      allowed_shift_compensation = 1.2
+      max_allowed_shift_db = .5
+      allowed_shift_compensation = 5
+      f_1 = 4500
+      f_step_end = 100
+         
+    if demo == 'LP3':
+      # lowpass filter example (corner 340 Hz)
+      settling_time_s = 0.05
+      max_allowed_shift_db = .5
+      allowed_shift_compensation = 5
+      f_1 = 10000
+      f_step_end = 250
     
-     
-    # Frequency sweep parameters
-    f_0 = 5
-    f_1 = 5000
-    f_step = 15
     
     # Retry on failure
     retry_count = 5
-    retry_delay_s = settling_time_s*10
+    retry_delay_s = settling_time_s*2
     
     # Initial sample granularity
     samples_per_period = 60
     capture_periods = 10
     
     # Parameters for automatic params adjustment
-    max_allowed_sample_rate = 36000
-    max_allowed_nr_periods = 80
-    min_samples_per_period = 4
+    max_allowed_sample_rate = 65000
+    max_allowed_nr_periods = 100
+    min_samples_per_period = 16
     
     # ===============================================
     
-    allowed_shift_compensation /= (f_1 - f_0) / f_step
+    #allowed_shift_compensation /= (f_1 - f_0) / f_step
     
     adc = gex.ADC(client, 'adc')
     
@@ -98,16 +124,25 @@ with gex.Client(gex.TrxRawUSB()) as client:
     table = []
     
     last_db = None
-    for f in range(f_0, f_1, f_step):
+    f = f_0
+    first = True
+    begin_allowedshift = max_allowed_shift_db
+    while f <= f_1:
+        if not first:
+          f_step = round(f_step_begin + ((f - f_0) / (f_1 - f_0)) * (f_step_end - f_step_begin))
+          f += f_step          
+        first = False      
+      
         #dac.set_frequency(1, f)
-        gen.set_frequency(f)
+        gen.set_frequency(f)        
         
-        max_allowed_shift_db += allowed_shift_compensation
+        max_allowed_shift_db = begin_allowedshift + allowed_shift_compensation * ((f - f_0) / (f_1 - f_0))
 
         # Adjust measurement parameters
         while True:
             desiredf = f*samples_per_period
             if desiredf > max_allowed_sample_rate:
+                desiredf = max_allowed_sample_rate
                 oldspp = samples_per_period
                 samples_per_period = math.ceil(samples_per_period * 0.9)
                 
@@ -187,17 +222,18 @@ with gex.Client(gex.TrxRawUSB()) as client:
     gains = t[:, 1]
     phases = t[:, 2]
 
-    plt.figure()
-    plt.ylabel('Gain (dB)')
-    plt.xlabel('Frequency (Hz)')
-    plt.semilogx(freqs, gains)  # Bode magnitude plot
-    plt.grid()
-
-    plt.figure()
-    plt.ylabel('Phase (deg)')
-    plt.xlabel('Frequency (Hz)')
-    plt.semilogx(freqs, phases)  # Bode phase plot
-    plt.grid()
+    fig = plt.figure()
+    ax1 = fig.add_subplot(211)
+    ax1.set_ylabel('Gain (dB)')
+    ax1.semilogx(freqs, gains)  # Bode magnitude plot
+    ax1.grid()
+
+    ax2 = fig.add_subplot(212)
+    ax2.set_ylabel('Phase (deg)')
+    ax2.set_xlabel('Frequency (Hz)')
+    ax2.semilogx(freqs, phases)  # Bode phase plot
+    ax2.grid()
+    
     plt.show()