When using FDwfDigitalOutPlayDataSet with large sample values results in corrupted signals

[RRahul]

When trying to play a pattern in an infinite loop with a sample frequency of 8MHz and 6,000,000 samples a corrupted signal appears at the beginning of every period. My pattern is still visible but before the rising edge there are some signals which seem to be random. Additionally what is the format for the data for example to have one line be constant 0 while the other lines are doing some clock signals

CODE:

"""

   DWF Python Example

   Author:  Digilent, Inc.

   Revision:  2022-02-11

 

   Requires:          

       Python 2.7, 3

"""

 

from ctypes import *

from dwfconstants import *

import sys

import time

 

if sys.platform.startswith("win"):

    dwf = cdll.dwf

elif sys.platform.startswith("darwin"):

    dwf = cdll.LoadLibrary("/Library/Frameworks/dwf.framework/dwf")

else:

    dwf = cdll.LoadLibrary("libdwf.so")

 

hdwf = c_int()

sts = c_ubyte()

 

version = create_string_buffer(16)

dwf.FDwfGetVersion(version)

print("DWF Version: "+str(version.value))

 

dwf.FDwfParamSet(DwfParamOnClose, c_int(1)) # 0 = run, 1 = stop, 2 = shutdown

 

print("Opening first device")

dwf.FDwfDeviceOpen(c_int(-1), byref(hdwf))

 

if hdwf.value == 0:

    print("failed to open device")

    szerr = create_string_buffer(512)

    dwf.FDwfGetLastErrorMsg(szerr)

    print(str(szerr.value))

    quit()

 

dwf.FDwfDeviceAutoConfigureSet(hdwf, c_int(0))# 0 = the device will be configured only when calling FDwf###Configure

 

print("Configuring Digital Out...")

 

hzPlay = 10e6

# for infinite playback fill the entire 256MiByte memory

nSamples = 6000000

rgbSamples= (c_ubyte*int(nSamples))()

 

for i in range(len(rgbSamples)):

    if i < 3000000:

        rgbSamples[i]=1

    else:

        rgbSamples[i] = 0

 

dwf.FDwfDigitalOutRunSet(hdwf, c_double(nSamples / float(hzPlay)))

dwf.FDwfDigitalOutRepeatSet(hdwf, c_int(0)) # infinite repeats

 

# enable play mode for the wanted signals

for i in range(8):

    dwf.FDwfDigitalOutEnableSet(hdwf, c_int(i), c_int(1)) # enable

    dwf.FDwfDigitalOutTypeSet(hdwf, c_int(i), DwfDigitalOutTypePlay)

    dwf.FDwfDigitalOutIdleSet(hdwf, c_int(i), DwfDigitalOutIdleLow)

 

print("Samples:"+str(nSamples)+" Rate:"+str(hzPlay)+"Hz "+" Period:"+str(nSamples/hzPlay)+"s")

dwf.FDwfDigitalOutPlayRateSet(hdwf, c_double(hzPlay)) # play sample rate

# set play data array of 8 bit samples

dwf.FDwfDigitalOutPlayDataSet(hdwf, byref(rgbSamples), c_int(8), c_int(int(nSamples)))

 

print("Arming Digital Out...")

dwf.FDwfDigitalOutConfigure(hdwf, c_int(1))

time.sleep(100)

dwf.FDwfDeviceCloseAll()

 

test.py

Edited September 11 by RRahul

[attila]

At DwfDigitalOutIdle level

[RRahul]

"""
   DWF Python Example
   Author:  Digilent, Inc.
   Revision:  2024-08-21

   Requires:                       
       Python 2.7, 3
   Description:
   Generates a custom pattern
"""

from ctypes import *
from dwfconstants import *
import sys
import time
import numpy
import matplotlib.pyplot as plt


if sys.platform.startswith("win"):
    dwf = cdll.dwf
elif sys.platform.startswith("darwin"):
    dwf = cdll.LoadLibrary("/Library/Frameworks/dwf.framework/dwf")
else:
    dwf = cdll.LoadLibrary("libdwf.so")

hdwf = c_int()

version = create_string_buffer(16)
dwf.FDwfGetVersion(version)
print("DWF Version: "+str(version.value))

# continue running after device close
dwf.FDwfParamSet(DwfParamOnClose, 0) # 0 = run, 1 = stop, 2 = shutdown

print("Opening first device")
dwf.FDwfDeviceOpen(-1, byref(hdwf))

if hdwf.value == 0:
    print("failed to open device")
    szerr = create_string_buffer(512)
    dwf.FDwfGetLastErrorMsg(szerr)
    print(str(szerr.value))
    quit()

# the device will only be configured when FDwf###Configure is called
dwf.FDwfDeviceAutoConfigureSet(hdwf, 0) 
dwf.FDwfParamSet(hdwf,DwfParamDigitalVoltage,1800)

PIXEL_TIME =12
LINE_TIME = 128*PIXEL_TIME
FRAME_TIME=4096*LINE_TIME

pin = 0
hzRate = 8e6
data_py = [0]*32000
for i in range(12000):
    data_py[i] =1
cBits = len(data_py)
print(cBits)
# digital-in
hzDI = c_double()



hzSys = c_double()
dwf.FDwfDigitalOutInternalClockInfo(hdwf, byref(hzSys))
print("DigitanOut base freq: "+str(hzSys.value/1e6)+"MHz")
# how many bytes we need to fit this many bits, (+7)/8
rgbdata = (c_ubyte*((cBits+7)>>3))(0) 
# array to bits in byte array
for i in range(cBits):
    if data_py[i] != 0:
        rgbdata[i>>3] |= 1<<(i&7)
        
# generate pattern
dwf.FDwfParamSet(hdwf, DwfParamDigitalVoltage, 1800)
dwf.FDwfDigitalOutEnableSet(hdwf, pin, 1)
dwf.FDwfDigitalOutIdleSet(hdwf, pin, DwfDigitalOutIdleLow)
dwf.FDwfDigitalOutTypeSet(hdwf, pin, DwfDigitalOutTypeCustom)
# 100kHz sample rate
dwf.FDwfDigitalOutDividerSet(hdwf, pin, int(hzSys.value/hzRate))
 # set sample rate
dwf.FDwfDigitalOutDataSet(hdwf, pin, byref(rgbdata), cBits)
dwf.FDwfDigitalOutRepeatSet(hdwf, c_int(0))
dwf.FDwfDigitalOutRunSet(hdwf, c_double(cBits/hzRate)) 
dwf.FDwfDigitalOutConfigure(hdwf, 1)

Lastly, why is this code not producing an maximum output of around 1.8 V instead of 3.3 V

 

[attila]

Use FDwfDeviceParamSet for opened device and FDwfParamSet as initial/generic option, should be used before device open call.

 

[RRahul]

@attila Using the SDK, how do you trigger an output from a raspberry pi Pico producing an clock signal connected to high speed input 1 on the rising edge. For clarification when the input reads a clock edge it should produce the desired output and hold the last value until the next clock edge 

[attila]

Hi @RRahul

This is currently not supported. What clock frequency would you want to run this at?

[RRahul]

Then how do triggers work in digital output 

 

[RRahul]

the clock frequency was 2kHz