diff --git a/gex/units/ADC.py b/gex/units/ADC.py
index 8208c42..11bf57a 100644
--- a/gex/units/ADC.py
+++ b/gex/units/ADC.py
@@ -23,6 +23,8 @@ CMD_STREAM_START = 26
 CMD_STREAM_STOP = 27
 CMD_SET_SMOOTHING_FACTOR = 28
 CMD_SET_SAMPLE_RATE = 29
+CMD_ENABLE_CHANNELS = 30
+CMD_SET_SAMPLE_TIME = 31
 
 EVT_CAPT_START = 50
 EVT_CAPT_MORE = 51
@@ -59,6 +61,7 @@ class ADC(gex.Unit):
         self._stream_listener = None
 
         self.channels = self.get_channels()
+        (_, self.sample_rate) = self.get_sample_rate()
 
     def _on_trig_capt(self, msg:TF_Msg):
         pp = gex.PayloadParser(msg.data)
@@ -122,7 +125,7 @@ class ADC(gex.Unit):
         Handle a trigger or stream start event.
 
         - EVT_CAPT_START
-          First frame payload: edge:u8, pretrig_len:u16, payload:tail
+          First frame payload: edge:u8, pretrig_len:u32, payload:tail
 
           Following are plain TF frames with the same ID, each prefixed with a sequence number in 1 byte.
           Type EVT_CAPT_MORE or EVT_CAPT_DONE indicate whether this is the last frame of the sequence,
@@ -139,7 +142,7 @@ class ADC(gex.Unit):
             self._trig_ts = evt.timestamp
             self._trig_buf = bytearray()
 
-            self._trig_pretrig_len = pp.u16()
+            self._trig_pretrig_len = pp.u32()
 
             self._trig_edge = pp.u8()
 
@@ -168,8 +171,16 @@ class ADC(gex.Unit):
         req = pp.u32()
         real = pp.float()
 
+        self.sample_rate = real
+
         return real
 
+    def set_sample_time(self, sample_time:int, confirm=True):
+        """ Set sample time. Values 0-7 """
+        pb = gex.PayloadBuilder()
+        pb.u8(sample_time)
+        self._send(CMD_SET_SAMPLE_TIME, pld=pb.close(), confirm=confirm)
+
     def get_sample_rate(self):
         """
         Get the current real sample rate as float.
@@ -219,7 +230,9 @@ class ADC(gex.Unit):
         """ Remove the trigger handler """
         self.on_trigger(None)
 
-    def setup_trigger(self, channel, level, count, edge='rising', pretrigger=0, holdoff=100, auto=False, confirm=True, handler=None):
+    def setup_trigger(self, channel, level, count,
+                      edge='rising', pretrigger=0, holdoff=100,
+                      auto=False, confirm=True, handler=None):
         """
         Configure a trigger.
 
@@ -247,7 +260,7 @@ class ADC(gex.Unit):
         pb.u8(channel)
         pb.u16(level)
         pb.u8(nedge)
-        pb.u16(pretrigger)
+        pb.u32(pretrigger)
         pb.u32(count)
         pb.u16(holdoff)
         pb.bool(auto)
@@ -301,6 +314,21 @@ class ADC(gex.Unit):
 
         self._send(cmd=CMD_FORCE_TRIGGER, confirm=confirm)
 
+    def set_active_channels(self, channels, confirm=True):
+        """
+        Set which channels should be active.
+        """
+
+        word = 0
+        for c in channels:
+            word |= 1 << c
+
+        pb = gex.PayloadBuilder()
+        pb.u32(word)
+
+        self._send(cmd=CMD_ENABLE_CHANNELS, pld=pb.close(), confirm=confirm)
+        self.channels = channels
+
     def _parse_buffer(self, buf):
         """
         Convert a raw buffer to a more useful format
@@ -311,7 +339,7 @@ class ADC(gex.Unit):
     def capture_in_progress(self):
         return self._stream_running or self._trig_buf is not None
 
-    def capture(self, count, timeout=30):
+    def capture(self, count, timeout=None):
         """
         Start a block capture.
         This is similar to a forced trigger, but has custom size and doesn't include any pre-trigger.
@@ -322,6 +350,10 @@ class ADC(gex.Unit):
         if self.capture_in_progress():
             raise Exception("Another capture already in progress")
 
+        if timeout is None:
+            timeout = 1 + float(count)/self.sample_rate * 2
+            #print("Timeout = %f" % timeout)
+
         pb = gex.PayloadBuilder()
         pb.u32(count)
 
diff --git a/main.py b/main.py
index 87f5bf9..58bd8f8 100644
--- a/main.py
+++ b/main.py
@@ -1,6 +1,7 @@
 #!/bin/env python3
 import time
 
+import numpy as np
 from matplotlib import pyplot as plt
 
 import gex
@@ -27,31 +28,47 @@ with gex.Client(transport) as client:
     if True:
         adc = gex.ADC(client, 'adc')
 
-        fs = adc.set_sample_rate(1000)
+        adc.set_active_channels([16])
+        fs = adc.set_sample_rate(30000)
 
-        data = None
+        for r in range(0,8):
+            adc.set_sample_time(r)
+            data = adc.capture(1000)
+            print("sr = %d" % r)
+            std = np.std(data)
+            print(std)
 
-        def capture(rpt):
-            global data
-            print("trig'd, %s" % rpt)
-            data = rpt.data
 
-        # adc.setup_trigger(channel=1,
-        #                   level=500,
-        #                   count=100,
-        #                   pretrigger=100,
-        #                   auto=False,
-        #                   edge="rising",
-        #                   holdoff=200,
-        #                   handler=capture)
         #
-        # adc.arm()
-        # time.sleep(2)
+        # global data
+        # data = None
+        #
+        # def capture(rpt):
+        #     global data
+        #     print("trig'd, %s" % rpt)
+        #     data = rpt.data
+        # #
+        # # adc.setup_trigger(channel=1,
+        # #                   level=700,
+        # #                   count=20000,
+        # #                   pretrigger=100,
+        # #                   auto=False,
+        # #                   edge="falling",
+        # #                   holdoff=200,
+        # #                   handler=capture)
+        #
+        # # adc.arm()
+        #
+        # data = adc.capture(1000)
+        #
+        # if data is not None:
+        #     plt.plot(data, 'r.', lw=1)
+        #     plt.show()
+        # else:
+        #     print("Nothing rx")
 
-        data = adc.capture(1000)
-        #plt.hist(data) #, 'r.', lw=1)
-        plt.magnitude_spectrum(data[:,0], Fs=fs, scale='dB', color='C1')
-        plt.show()
+        # plt.magnitude_spectrum(data[:,0], Fs=fs, scale='dB', color='C1')
+        # plt.show()
 
         # def lst(data):
         #     if data is not None:
@@ -60,7 +77,7 @@ with gex.Client(transport) as client:
         #         print("Closed.")
 
         # adc.stream_start(lst)
-        time.sleep(3)
+        # time.sleep(3)
         # adc.stream_stop()
         # print("Done.")