Acquiring Noisy and Incorrect Data using SCPI and Python

[diminDDL]

I am facing a major issue with the acquisition of data from the Red Pitaya 125-14 using SCPI commands and Python. Despite my best efforts, the acquired data looks extremely noisy and incorrect, which is causing me a lot of problems.

I have signal generator 1 connected to the oscilloscope channel 1 and have been using that for testing. However, despite my best efforts, the data I am acquiring is not accurate and contains a lot of noise.

I have attached the code and screenshots of the acquired data for reference. I would be grateful if anyone could take a look and suggest any potential solutions to the problem.

Code: Select all

import matplotlib.pyplot as plot
import sys
import redpitaya_scpi as scpi
import numpy as np
from time import sleep
import time

#Setup the connection to the Red Pitaya
IP = "rp-f0a29f.local"
rp_s = scpi.scpi(IP)

#Set the parameters for the signal generator
wave_form = 'SQUARE'
freq = 2000
ampl = 1
#Decimation factor
dec = 32

#Generate the signal
def set_generator(waveform, frequency, amplitude, offset):
    rp_s.tx_txt('GEN:RST')
    rp_s.tx_txt('SOUR1:FUNC ' + str(waveform).upper())
    rp_s.tx_txt('SOUR1:FREQ:FIX ' + str(frequency))
    rp_s.tx_txt('SOUR1:VOLT ' + str(amplitude))
    rp_s.tx_txt('SOUR1:VOLT:OFFS ' + str(offset))
    rp_s.tx_txt('OUTPUT1:STATE ON')
    rp_s.tx_txt('SOUR1:TRIG:INT')

set_generator(wave_form, freq, ampl, 0)
sleep(0.5)

#Define a function to sample the oscilloscope
def sample_oscilloscope():
    #Set the parameters for the acquisition
    rp_s.tx_txt('ACQ:RST')
    rp_s.tx_txt('ACQ:DATA:FORMAT ASCII')
    rp_s.tx_txt('ACQ:DATA:UNITS VOLTS')
    rp_s.tx_txt(f'ACQ:DEC {dec}')
    rp_s.tx_txt('ACQ:SOUR1:GAIN HV')
    rp_s.tx_txt('ACQ:TRIG:LEV 0.5')
    rp_s.tx_txt('ACQ:TRIG CH1_NE')
    rp_s.tx_txt('ACQ:START')
    sleep(0.1)

    #Wait for the acquisition to finish
    while 1:
        rp_s.tx_txt('ACQ:TRIG:STAT?')
        if rp_s.rx_txt() == 'TD':
            break
    #Read the data from the acquisition
    rp_s.tx_txt('ACQ:SOUR1:DATA?')
    print('Reading data...')
    #rp_s.tx_txt('ACQ:SOUR1:DATA:STA:N? 0,1000')
    buff_string = rp_s.rx_txt()
    print('Done reading data!') 

    #Convert the data to a list of floats
    buff_string = buff_string.strip('{}\n\r').replace("  ", "").split(',')
    buff = list(map(float, buff_string))

    return buff

buff = sample_oscilloscope()

#Plot the data
plot.plot(buff)
plot.ylabel('Voltage')
plot.show()

Here is the captured waveform (it looks correct on the web oscilloscope):

[redpitaya]

First of all, I would like to apologize for my late reply. We were representing Red Pitaya at Embedded World the previous week, so I didn't have time to read the support emails.

First, a few suggestions to make the code run faster:
- you have to set up the generator only once and then you can trigger it with the SOUR1:TRIG:INT command
- same with the ACQ, but you will need to run the following commands everytime you want to acquire data:

Code: Select all

rp_s.tx_txt('ACQ:TRIG:LEV 0.5')
rp_s.tx_txt('ACQ:START')	# try switching the ACQ, so that it matches this code
sleep(0.1)			# some delay due to higher decimation (it can be finetuned)
rp_s.tx_txt('ACQ:TRIG CH1_NE')
      

I have some additional questions:
- Which OS version are you using?
- What is the signal you are generating on the oscilloscope (or are you using the Red Pitaya's OUT1 as a generator)?
- Do you have 50 Ohm terminators near the inputs?