High Precision Triggers on Discovery 3

[dabes]

Hi All,

I'd like to output a simple sine wave that is triggered by a rising edge on one of the inputs. I'm currently using the following python code to achieve this:

I use the AnalogInTrigger detection setup shown below

#set up trigger
cSamples = 1024
hzRate = 100e6
dwf.FDwfAnalogInTriggerAutoTimeoutSet(hdwf, c_double(0)) #disable auto trigger
dwf.FDwfAnalogInTriggerSourceSet(hdwf, trigsrcDetectorAnalogIn) #one of the analog in channels
dwf.FDwfAnalogInTriggerTypeSet(hdwf, trigtypeEdge)
dwf.FDwfAnalogInTriggerChannelSet(hdwf, c_int(0)) # first channel
dwf.FDwfAnalogInTriggerLevelSet(hdwf, c_double(3.0)) # 0.0V
dwf.FDwfAnalogInTriggerConditionSet(hdwf, DwfTriggerSlopeRise) 
# relative to middle of the buffer, with time base/2 T0 will be the first sample
dwf.FDwfAnalogInTriggerPositionSet(hdwf, c_double(0.5*cSamples/hzRate)) 
dwf.FDwfAnalogInConfigure(hdwf, c_int(1), c_int(0))
# wait at least 2 seconds with Analog Discovery for the offset to stabilize, before the first reading after device open or offset/range change
time.sleep(2)
dwf.FDwfAnalogInConfigure(hdwf, c_int(0), c_int(1))

 

Followed by a loop structure to check the trigger on every iteration of the loop

while True:
    dwf.FDwfAnalogInStatus(hdwf, c_int(1), byref(sts))
    if sts.value == 2 : # done
        break

# Generating sine wave 
dwf.FDwfAnalogOutConfigure(hdwf, channel, c_int(1))
time.sleep(0.5)
dwf.FDwfAnalogOutConfigure(hdwf, channel, c_int(0))

 

Unfortunately this yields a large delay (~2.5ms) between the rising edge of the input, and the start of the sine waveform. Furthermore, this delay has some jitter to it (i.e. it is not a consistent delay).

Is there a better way to do this that doesn't require polling from FDwfAnalogInStatus? It would be helpful to be able to do this with a minimal delay bias and variance. 

[attila]

Hi @dabes

See the following example which directly starts the AWG on Trigger IO or Analog Input trigger: AnalogOut_Trigger.py