Pattern generator frequency - Digital Discovery

[Limitha]

Hi,

I have been using python  to program the pattern generator of digilent digital discovery but when I am checking for the frequency of the generated output it is limited to 6KHz. I am writing here to know if there is anyway to use the device to its full potential like say 50 MHz? Thanks in advance.

Regards,

Limitha

[attila]

Hi @Limitha

It is possible to configure it up to 50MHz or the set system frequency / 2.
The FDwfDigitalOutDividerSet specifies the prescaler from 100MHz and FDwfDigitalOutCounterSet the low and high counts.
See the WF SDK manual and the samples/ py/ DigitalOut_Clock.py DigitalOut_Duty.py ... examples

[Limitha]

Hi @attila

I tried modifying the Digital_io.py code as shown,

 

from ctypes import *
from dwfconstants import *
import sys
import random
import pandas as pd

dwf = cdll.dwf

hdwf = c_int()
dwRead = c_uint32()
iDevId = c_int()
iDevRev = c_int()
hzSys = c_double()
devicename = create_string_buffer(64)
serialnum = create_string_buffer(16)  
    
dwf.FDwfEnum(c_int(0), byref(hdwf))
print("Number of Devices: "+str(hdwf.value))

dwf.FDwfEnumDeviceName (c_int(hdwf.value-1), devicename)
dwf.FDwfEnumSN (c_int(hdwf.value-1), serialnum)
dwf.FDwfEnumDeviceType (c_int(hdwf.value-1), byref(iDevId), byref(iDevRev))
print("------------------------------")
print("Device "+str(hdwf.value-1)+" : ")
print("\tName: \'" + str(devicename.value) + "' " + str(serialnum.value))
print("\tID: " + str(iDevId.value) + " rev: " + str(iDevRev.value))

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

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

dwf.FDwfAnalogIOChannelNodeSet(hdwf, c_int(0), c_int(0), c_double(1.8))

dwf.FDwfDigitalOutInternalClockInfo(hdwf, byref(hzSys))
print("Internal frequency is " + str(hzSys.value/1e6)+" MHz")

# enable output/mask on 8 LSB IO pins, from DIO 0 to 7
pin_status = c_uint32()  
  
# On DD the DIO-0 represents 24, 1 -> 25, 2 -> 26, 3 -> 27, 4 -> 28...
# Here for 28 it is the 5 bit which is set by 10000
pin=0x0010

dwf.FDwfDigitalIOOutputEnableSet(hdwf, c_int(pin)) 
dwf.FDwfDigitalIOOutputEnableGet(hdwf, byref(pin_status))
print("Pin value is " + bin(pin_status.value)[2:])

for i in range(int(hzSys.value)):
    data = str(random.randint(0, 50))
    # set value on enabled IO pins
    dwf.FDwfDigitalIOOutputSet(hdwf, c_int(int(data))) 
    
dwf.FDwfDigitalOutConfigure(hdwf, c_int(1))  

# fetch digital IO information from the device           
dwf.FDwfDigitalIOStatus(hdwf) 
# read state of all pins, regardless of output enable
dwf.FDwfDigitalIOInputStatus(hdwf, byref(dwRead)) 

#print(dwRead as bitfield (32 digits, removing 0b at the front)
print("Digital IO Pins: ", bin(dwRead.value)[2:].zfill(16))

dwf.FDwfDeviceClose(hdwf)

 

I guess the frequency is limited in this case yeah? So if I need to get a higher frequency I need to use the out configuration?

 

Regards,

Limitha 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[attila]

Hi @Limitha

You have used the digital-io functions for software control which have ~millisecond latency.
For high frequency use the earlier mentioned digital-out functions:

On 11/19/2021 at 3:26 PM, attila said:

Hi @Limitha

It is possible to configure it up to 50MHz or the set system frequency / 2.
The FDwfDigitalOutDividerSet specifies the prescaler from 100MHz and FDwfDigitalOutCounterSet the low and high counts.
See the WF SDK manual and the samples/ py/ DigitalOut_Clock.py DigitalOut_Duty.py ... examples

 

[Limitha]

Hi @attila

Thanks! Got you!

But I have another question. I want to read values from a csv file and give it as data into the pins can this be done in digital out functions? 

Regards,

Limitha

Edited November 22, 2021 by Limitha

[attila]

Hi @Limitha

See the DigitalOut_Custom.py DigitalOut_CustomBus.py examples

[Limitha]

Hi @attila,

 

Thank you so much for all the help!

 

Regards,

Limitha