Added samplingrate getter so that one can retrieve the actual

sampling rate.

README.rst

@@ -80,6 +80,9 @@ and the analogue outputs, digital input and outputs synchronously::
       # are measured. Blocking call if no samples are available.
       getSampleFromBuffer()
 
+      # gets the actual sampling rate of the running acquisition
+      getSamplingRate()
+
       # stops the background acquisition
       stop()
 

examples/realtime_plot.py

@@ -37,6 +37,7 @@ def data_gen():
 c.open()
 print("ADC board:",c.get_board_name())
 c.start(8,250)
+print("Actual samplingrate =",c.getSamplingRate(),"Hz")
 
 # now let's plot the data
 fig, ax = plt.subplots()

examples/realtime_two_channel_plot.py

@@ -87,6 +87,11 @@ def getDataThread(qtPanningPlot1,qtPanningPlot2):
 # start data acquisition
 c.start(8,250)
 
+# gets the actual samplingrate from the board which
+# might be different to the requested because the
+# board is allowed to change it to a rate it can do.
+print("Actual samplingrate =",c.getSamplingRate(),"Hz")
+
 # start the thread getting the data
 t.start()
 

pyusbdux.cpp

@@ -2,7 +2,7 @@
  * pyusbdux
  *
  * Copyright (c) 1999,2000,2001 David A. Schleef <ds@schleef.org>
- *               2018 Bernd Porr <mail@berndporr.me.uk>
+ *               2019 Bernd Porr <mail@berndporr.me.uk>
  *
  * This file may be freely modified, distributed, and combined with
  * other software, as long as proper attribution is given in the
@@ -38,6 +38,7 @@ float samples[N_CHANS];
 unsigned int chanlist[N_CHANS];
 comedi_range* range_info[N_CHANS];
 lsampl_t maxdata[N_CHANS];
+comedi_cmd cmd;
 
 static const char errorDevNotOpen[] = "Comedi device not open. Use open() first.";
 static const char errorDisconnect[] = "Device error. Possible disconnect.";
@@ -54,6 +55,7 @@ void open(int comediDeviceNumber) {
 	if (strstr(comedi_get_board_name(dev),"usbdux") == NULL) {
 		throw "Not a USBDUX board.";
 	}
+	memset(&cmd,0,sizeof(comedi_cmd));
 }
 
 
@@ -99,7 +101,6 @@ void start(int n_channels, double fs) {
 		bytes_per_sample = sizeof(sampl_t);
 	}
 
-	comedi_cmd cmd;
 	memset(&cmd,0,sizeof(comedi_cmd));
         int ret = comedi_get_cmd_generic_timed(dev, subdevice, &cmd, n_chan, 1e9 / freq);
         if(ret<0){
@@ -169,10 +170,27 @@ int hasSampleAvailable() {
 	return ret > 0;
 }
 
+float getSamplingRate() {
+	float sampling_rate = 0;
+        // the timing is done channel by channel
+        // this means that the actual sampling rate is divided by
+        // number of channels
+        if ((cmd.convert_src ==  TRIG_TIMER)&&(cmd.convert_arg)) {
+                sampling_rate=((1E9 / cmd.convert_arg)/n_chan);
+        }
+
+        // the timing is done scan by scan (all channels at once)
+        // the sampling rate is equivalent of the scan_begin_arg
+        if ((cmd.scan_begin_src ==  TRIG_TIMER)&&(cmd.scan_begin_arg)) {
+                sampling_rate=1E9 / cmd.scan_begin_arg;
+        }
+	return sampling_rate;
+}
 
 void stop() {
 	if (dev == NULL) throw errorDevNotOpen;
 	comedi_cancel(dev,subdevice);
+	memset(&cmd,0,sizeof(comedi_cmd));
 }
 
 
@@ -232,4 +250,5 @@ void close() {
 	if (dev == NULL) throw errorDevNotOpen;
 	comedi_close(dev);
 	dev = NULL;
+	memset(&cmd,0,sizeof(comedi_cmd));
 }

pyusbdux.h

@@ -11,6 +11,8 @@ void start(int nChan, double fs);
 
 int hasSampleAvailable();
 
+float getSamplingRate();
+
 sample_p getSampleFromBuffer();
 
 void stop();

setup.py

@@ -21,7 +21,7 @@ def read(fname):
 
 
 setup (name = 'pyusbdux',
-       version = '1.5.7',
+       version = '1.6.0',
        author      = "Bernd Porr",
        author_email = "mail@berndporr.me.uk",
        url = "https://github.com/berndporr/pyusbdux",