[Python] How to know that SCPI "STOP" command is working as intended

Good morning,

I am using a DPO7054 in order to read the voltage signal of 2 Single-Photon Avalanche Diodes. I have used a GPIB connection to setup the acquisition of "CURVE"s from the two channels that I use. Since I do correlation measurements I need both "CURVE"s to be taken at the same time, for that I added a "STOP" SCPI command before the acquisition. Nonetheless, I don't know if this way is bug free, like, how do I know that CHANNEL 1 stopped while CHANNEL 2 didn't acquire another waveform, how do I know that another frame was not updated?

The acquiring code look like this :

import pyvisa

rm = pyvisa.ResourceManager()
scope = rm.open_resource('GPIB0::1::INSTR') #Create an Instrument variable
data_list = []
for ind in range(5):
scope.write('START')
scope.write('STOP')
time.sleep(0.5)

# ---- [START] iterate over the available channels ----
for n in range(2):
scope.write(f"DATA:SOURCE {n}")
scope.query('*opc?') # '0' if not, '1' if yes
if ind==0:
scope.write("DATA:ENC RIB")
scope.write("DATA:BYT_Or MSB")
scope.write("DATA:WIDTH 1")
scope.write("DATA:START 0")
scope.write("DATA:STOP 1e10")
recordLength = int(scope.query("WFMO:NR_P?")) are actually available
scope.write("DATA:STOP {0}".format(recordLength)) #Set data stop

# Acquire waveform
scope.write("CURVE?")
data = scope.read_binary_values(datatype='b',
is_big_endian=True,
container=np.ndarray,
header_fmt='ieee',
expect_termination=True) # Reading binary data

opc = os.scope.query('*opc?')
while opc == 0:
print("CURVE not finished")
time.sleep(0.5)
opc

print("CURVE done")
data_list.append(data)


I hope I explained my problem correctly.

Thanks for your time.

PS : I also don't know if the OPC command is actually working, the print in the "whille opc == 0" loop are never called even if I take waveforms of multiple milliseconds, which takes some time to communicate along the GPIB connection.

Continue reading...