generate wave voltage output (Python)

[jo_dkt]

Hey Guys,

im using Python with an NI USB-6366. My task ist to create a voltage with a waveform (sine and saw). Both should have an offset, frequency and amplitude that can change according to your own settings. I am using a oscilloscope to view my results. I already createt a few saw waveforms but they all had a way to high frequency. If i changed the frequency to something lower, the output would not generate the whole wave. There might be a problem with my clock timing but i am not sure. 

My 2nd problem is that the waves i generate dont generate continuously. They generate just a few times (only generate with a high frequency). 

My Code: 

# Continuous write single channel

from re import I

import numpy as np

import matplotlib.pyplot as plt

import time

import nidaqmx

from nidaqmx.stream_writers import (AnalogSingleChannelWriter)

from nidaqmx import constants

from nidaqmx.constants import AcquisitionType

import math

#variables

global rate_outcfg

global counter_limit

global voltage

global stream

global counter

global v_inc

global i

num_samples = 4294967295

rate_outcfg = 500

len_list = 101

v_inc = 0.01

task = nidaqmx.Task()

counter = 0

i = 0

offset = 0    

amplitude = 3

#Voltage list

voltage = np.empty((len_list,))

voltage [:] = -v_inc

while counter < len_list:  

    voltage[i:] = voltage[i:] + v_inc

    counter = counter + 1

    i = i+1

voltage_fin = voltage[:] * amplitude + offset

#voltage = np.array([0.2, 0.4, 0.6, 0.8, 1])

#voltage = np.array([0, 0.5, 1, 1.5, 2, 2.5, 3])

print(voltage_fin)

def SAW ():

    task = nidaqmx.Task()

    task.ao_channels.add_ao_voltage_chan("Dev1/ao0")

    task.timing.cfg_samp_clk_timing(rate = rate_outcfg, sample_mode = AcquisitionType.CONTINUOUS) #, samps_per_chan = num_samples)

    stream = AnalogSingleChannelWriter(task.out_stream, auto_start=True)

    stream.write_many_sample(voltage_fin, timeout = 10.0)

    nidaqmx.Task.start()

SAW ()

task.close()  

Sorry for my bad english (not mother tongue).

all the help is greatly appreciated.

Best reagrds,

Jo_dkt