experimental version busing the built-in DAC (kinda broken)

UNITS.INI

@@ -2,6 +2,9 @@
 ## GEX v1.0.0 on STM32F072-HUB
 ## built Jun 15 2018 at 13:45:28
 
+# Overwrite this file to change settings.
+# Press the LOCK button to save them to Flash.
+
 [UNITS]
 # Create units by adding their names next to a type (e.g. DO=A,B),
 # remove the same way. Reload to update the unit sections below.
@@ -31,7 +34,7 @@ TOUCH=
 # Simple PWM output
 PWMDIM=
 # Two-channel analog output with waveforms
-DAC=
+DAC=dac
 
 [SPI:spi@2]
 # Peripheral number (SPIx)
@@ -55,7 +58,7 @@ first-bit=MSB
 # SS port name
 port=A
 # SS pins (comma separated, supports ranges)
-pins=4
+pins=3
 
 [ADC:adc@4]
 # Enabled channels, comma separated
@@ -73,7 +76,7 @@ frequency=1000
 # - defines the maximum pre-trigger size (divide by # of channels)
 # - captured data is sent in half-buffer chunks
 # - buffer overrun aborts the data capture
-buffer_size=512
+buffer_size=800
 
 # Enable continuous sampling with averaging
 # Caution: This can cause DAC output glitches
@@ -81,4 +84,17 @@ averaging=N
 # Exponential averaging coefficient (permil, range 0-1000 ~ 0.000-1.000)
 # - used formula: y[t]=(1-k)*y[t-1]+k*u[t]
 # - not available when a capture is running
-avg_factor=800
+avg_factor=80
+
+[DAC:dac@1]
+# Enabled channels (1:A4, 2:A5)
+ch1_enable=Y
+ch2_enable=N
+# Enable output buffer
+ch1_buff=Y
+ch2_buff=Y
+# Superimposed noise type (NONE,WHITE,TRIANGLE) and nbr. of bits (1-12)
+ch1_noise=NONE
+ch1_noise-level=3
+ch2_noise=NONE
+ch2_noise-level=3

main.py

@@ -7,13 +7,7 @@ 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
+use_native_dac = True
 
 class ADG:
     def __init__(self, client:gex.Client):
@@ -48,8 +42,7 @@ class ADG:
         if freq is not None:
             self.set_frequency(freq)
 
-#with gex.Client(gex.TrxRawUSB()) as client:
-with gex.Client(gex.TrxSerialThread('/dev/ttyACM0')) as client:
+with gex.Client(gex.TrxRawUSB()) as client:
     # ===============================================
       
     # Delay between adjusting input and starting the measurement. 
@@ -61,62 +54,57 @@ with gex.Client(gex.TrxSerialThread('/dev/ttyACM0')) as client:
     # db shift compensation (spread through the frequency sweep to adjust for different slopes)
     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 demo == 'HP':
+    if False:
       # highpass filter example (corner 340 Hz)
       settling_time_s = (4700*100e-9)*10
-      max_allowed_shift_db = 5.6
-      allowed_shift_compensation = -5
+      max_allowed_shift_db = 5
+      allowed_shift_compensation = -4.5
     
-    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':
+    if True:
       # lowpass filter example (corner 340 Hz)
       settling_time_s = (4700*100e-9)*10
-      max_allowed_shift_db = .5
-      allowed_shift_compensation = 5
-      f_1 = 4500
-      f_step_end = 100
+      max_allowed_shift_db = 1
+      allowed_shift_compensation = 1.2
     
-    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
+    f_0 = 10
+    f_1 = 5000
+    f_step = 50
     
     # Retry on failure
     retry_count = 5
-    retry_delay_s = settling_time_s*2
+    retry_delay_s = settling_time_s*10
     
     # Initial sample granularity
     samples_per_period = 60
     capture_periods = 10
     
     # Parameters for automatic params adjustment
-    max_allowed_sample_rate = 65000
-    max_allowed_nr_periods = 100
-    min_samples_per_period = 16
+    max_allowed_sample_rate = 36000
+    max_allowed_nr_periods = 80
+    min_samples_per_period = 4
     
     # ===============================================
     
-    #allowed_shift_compensation /= (f_1 - f_0) / f_step
+    allowed_shift_compensation /= (f_1 - f_0) / f_step
     
     adc = gex.ADC(client, 'adc')
     
+    dac = None
+    gen = None
+    
+    if use_native_dac:
+        print('Using native GEX DAC')
+        dac = gex.DAC(client, 'dac')
+        dac.waveform(1, 'SINE')
+    else:
+        print('Using AD9833 via SPI')
         gen = ADG(client)
         gen.initialize()
 
@@ -124,25 +112,19 @@ with gex.Client(gex.TrxSerialThread('/dev/ttyACM0')) as client:
     table = []
     
     last_db = None
-    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)
+    for f in range(f_0, f_1, f_step):
+      
+        if use_native_dac:
+            dac.set_frequency(1, f)
+        else:
             gen.set_frequency(f)
         
-        max_allowed_shift_db = begin_allowedshift + allowed_shift_compensation * ((f - f_0) / (f_1 - f_0))
+        max_allowed_shift_db += allowed_shift_compensation
 
         # 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)
                 
@@ -183,6 +165,7 @@ with gex.Client(gex.TrxSerialThread('/dev/ttyACM0')) as client:
 
           y1 = np.max(t[:,0]) - np.min(t[:,0])
           y2 = np.max(t[:,1]) - np.min(t[:,1])
+          print("\x1b[90mU %f, Y %f\x1b[0m" % (y1, y2))
           gain_raw = y2/y1
           gain_db = 20*math.log10(gain_raw)
           
@@ -214,6 +197,9 @@ with gex.Client(gex.TrxSerialThread('/dev/ttyACM0')) as client:
         if not suc:
           last_db = last_db_in_fail
 
+    if use_native_dac:
+        dac.dc(1, 2000)
+    else:
         gen.wfm_dc()
     
     t = np.reshape(np.array(table), [int(len(table) / 3), 3])
@@ -222,18 +208,17 @@ with gex.Client(gex.TrxSerialThread('/dev/ttyACM0')) as client:
     gains = t[:, 1]
     phases = t[:, 2]
 
-    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.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()
     plt.show()