To Capture Pulse triggered at specific interval in Analog Discovery 2

[Rohit_Verma]

I need to capture a pulse (High to low), which stays for appx 600us, then goes back high.

I need to capture for a given interval of time, the no. of pulses triggered.

time interval maybe : 1ms, 1 s, 5s etc.

Been using the DigitalIn_PulseTrigger.py & DigitalIn_trigger.py, but couldn't understand if it is behaving as expected:

--------------

while True:
    dwf.FDwfDigitalInStatus(hdwf, c_int(1), byref(sts))
    print("Status:", str(sts.value))
    if sts.value == 2 : # done
        break

------------

Not sure about the value to be compared here, as for 1 sec or for 5 sec, i am seeing the break in appx same time here.

=> Also tried with AnalogIn_sample.py but i think it is not able to detect the drop in voltage for such short duration.

Any help will be appreciated.

 

Thanks,

Rohit

[attila]

Hi @Rohit_Verma

You could perform recording either on analog or digital-in and count the edges/pulses in software.

[Rohit_Verma]

2 minutes ago, attila said:

Hi @Rohit_Verma

You could perform recording either on analog or digital-in and count the edges/pulses in software.

Hi @attila,

Thanks for quick response,

Actually i need the count in the file itself, need for some automation project work..

Checking with DigitalIn_PulseTrigger.py as of now, but not sure about the value "2" below:

    print("Status:", str(sts.value))
    if sts.value == 2 : # done          <------------ What does this 2 signify, what else can we write here???

What does this signify ?

=> Also, please confirm if my understanding about these functions is right :

dwf.FDwfDigitalInTriggerResetSet(hdwf, c_int(0), c_int(0), c_int(0), c_int(1<<7))  <----  Reset at Falling edge on pin DIO7 
dwf.FDwfDigitalInTriggerSet(hdwf, c_int(1<<7), c_int(0), c_int(0), c_int(0))  <------- generate trigger at low state of Pin DIO7(in my case it around 600 us) attach snippet of negative pulse.

=> what value should be placed here to count number of negative pulse for some interval ??

 

Thanks,

[attila]

Hi @Rohit_Verma

1. The following lines are to wait for the capture to finish.
while True:
    dwf.FDwfDigitalInStatus(hdwf, c_int(1), byref(sts))
    if sts.value == DwfStateDone : # 2
        break

2. If you want to trigger on DIO-7 negative pulse length use:
dwf.FDwfDigitalInTriggerResetSet(hdwf, c_int(0), c_int(0), c_int(0), c_int(1<<7)) # low, high, rise, fall
dwf.FDwfDigitalInTriggerSet(hdwf, c_int(1<<7), c_int(0), c_int(0), c_int(0)) # low, high, rise, fall
dwf.FDwfDigitalInTriggerLengthSet(hdwf, c_double(5e-4), c_double(7e-4), c_int(0)) # 500-700us
dwf.FDwfDigitalInTriggerCountSet(hdwf, c_int(1), c_int(0))

3. If you want to precisely count the pulse rate use the record to collect a fixed number of samples and count the pulses in you script.
You could use the sync capture mode and rely on the available samples, see DigitalIn_Sync.py and the following post. This will be software controlled start/stop so it will have a uncertainty of milliseconds.

 

[Rohit_Verma]

50 minutes ago, attila said:

Hi @Rohit_Verma

1. The following lines are to wait for the capture to finish.
while True:
    dwf.FDwfDigitalInStatus(hdwf, c_int(1), byref(sts))
    if sts.value == DwfStateDone : # 2
        break

2. If you want to trigger on DIO-7 negative pulse length use:
dwf.FDwfDigitalInTriggerResetSet(hdwf, c_int(0), c_int(0), c_int(0), c_int(1<<7)) # low, high, rise, fall
dwf.FDwfDigitalInTriggerSet(hdwf, c_int(1<<7), c_int(0), c_int(0), c_int(0)) # low, high, rise, fall
dwf.FDwfDigitalInTriggerLengthSet(hdwf, c_double(5e-4), c_double(7e-4), c_int(0)) # 500-700us
dwf.FDwfDigitalInTriggerCountSet(hdwf, c_int(1), c_int(0))

3. If you want to precisely count the pulse rate use the record to collect a fixed number of samples and count the pulses in you script.
You could use the sync capture mode and rely on the available samples, see DigitalIn_Sync.py and the following post. This will be software controlled start/stop so it will have a uncertainty of milliseconds.

 

Thanks @attila ,

I have copied the aboveset of commands and below is the output:

---------------
DWF Version: b'3.17.1'
Opening first device
DigitanIn base freq: 100.0MHz
Waiting for acquisition...
Status: 5
Status: 5
Status: 5
Status: 5
Status: 5
Status: 3
Status: 3
Status: 3
Status: 3
Status: 2
   done

---------------

=> Now my concern is the value that is being returned in status variable.

==> Because i need to validate this for different time intervals, that is:

1st case: Negative pulse at every 1 sec

2nd Case: Negative Pulse at every 100msec.

3rd Case: Negative Pulse at every 5 sec.

Likewise, i need to store 6-7 cases, and need to validate the same in file only.

I am attaching the full DigitalIn_PulseTrigger.py file here.

Please let me know what should be the best way to validate the same (Without using the software).

 

Thanks again,

Rohit

DigitalIn_PulseTrigger.py

Edited January 7, 2022 by Rohit_Verma

[attila]

Hi @Rohit_Verma

To measure time between captures you can use something like this.
For quick captures also set the sample rate high, divider to low, like to 1.

...
dwf.FDwfDigitalInDividerSet(hdwf, c_int(int(1))) 
...
print("Waiting for acquisition...")
dwf.FDwfDigitalInConfigure(hdwf, c_bool(0), c_bool(1))
try:
    while True:
        start = time.time()
        while True:
            dwf.FDwfDigitalInStatus(hdwf, c_int(1), byref(sts))
            if sts.value == 2 : # done
                break
        print("elapsed: "+str((time.time()-start)*1000)+"ms")
except KeyboardInterrupt: # Ctrl+C
    pass
...

 

[Rohit_Verma]

Hi @attila,

 

Thanks so much for your valuable input, i am able to detect the Negative pulse now.

However, just for one case i need some more input please?

=> I want to generate a pulse on 1 DIO pin and  my code is such that, it's response i can check from another pin.

Been using below logic:

def GeneratingSignal():
#For GPIO1, generating 1ms pulse
    dwf.FDwfDigitalOutRunSet(hdwf, c_double(1)) # 1ms run
    dwf.FDwfDigitalOutRepeatSet(hdwf, c_int(1)) # once
    dwf.FDwfDigitalOutIdleSet(hdwf, c_int(0), c_int(0)) # 1=DwfDigitalOutIdleLow, low when not running 
    dwf.FDwfDigitalOutCounterInitSet(hdwf, c_int(0), c_int(1), c_int(0)) # initialize high on start
    dwf.FDwfDigitalOutCounterSet(hdwf, c_int(0), c_int(1), c_int(1)) # low/high count zero, no toggle during run
    dwf.FDwfDigitalOutEnableSet(hdwf, c_int(0), c_int(1))
    print("Generating 1s pulse")
    dwf.FDwfDigitalOutConfigure(hdwf, c_int(1))
    #time.sleep(1)
    dwf.FDwfDigitalOutReset(hdwf)

 

But i need to validate no. of pulses, lets say 5 pulses of 1ms, to validate the scenario.

However i am getting some random values if i call this func, GenerateSignal(), is it because of some latency,?

How can i rectify this ??

[attila]

Hi @Rohit_Verma

See the examples WF SDK / samples/ py/ DigitalOut_Pulse.py DigitalOut_Pins.py DigitalOut_Duty.py DigitalOut_Phase.py ...