This step by step guide shows how to log Sensor Data from a Soft-IP ADC interface within a SQLite-Database and how to plot these data on a web interface. In addition, it is demonstrated how to manage and change the FPGA Configuration with just a web browser.

Complex web interfaces for controlling and monitoring on embedded systems are standard today. Especially for low quantity FPGA applications, the development of these web applications is often time-consuming. To accelerate this process, it is important to use powerful web development frameworks with simple to use IDEs such as Django. A huge community on desktop site uses that and if the same version of Django runs on the embedded Linux, it is possible to benefit from their knowledge. Django has a comprehensive documentation with many demos. However, these demos are for typical Desktop- and Cloud- applications and not for embedded ones. The important part of embedded management web applications is the interaction between the web interface and Sensor- or FPGA-data.

To demonstrate this, the ADC converter (Analog Devices LTC2308) of a Terasic DE10-Nano- or DE10-Standard Board (Intel Cyclon V SoC-FPGA) with a Soft-IP interface is connected via the Lightweight HPS to FPGA Bridge to the Hard Processor System (HPS). On the ARM Cortex-A9 of the HPS my embedded Linux, called rsYocto, customized for Intel SoC-FPGA is running.

On rsYocto the Django Framework (Version 3.0.2) with all necessary components, like the Apache Webserver and the SQLite database, is pre-installed.

This approach is the monitoring and management of embedded FPGA systems with a web interface. This cannot be consider for low latency real-time applications. The advantage of the usage of SQLite and HTTP with Linux is that these are standard in the desktop world. It allows for example to connect the data with a cloud service by adding a few extensions.

• Features
  • Plotting the ADC convention voltage from a Soft-IP ADC
  • Uploading and managing of FPGA configuration files
  • Configuration of the FPGA fabric
  • Controlling a FPGA LED

The following sequence Diagram shows all involved actors and the data flow by reading an ADC Value to a SQLite Database. If an user opens the web page, Django plots the complete data into the web interface as shown below.

A HTTP GET-command (here by calling the URL http://127.0.1:8181/ADCtrigger) triggers the Django web application. It calls the “read Sensor” application. This is a python script, which reads the Soft-IP ADC Interface and returns the ADC convention. Then Django adds the value with a time stamp to the SQLite database.

To repeat and time sync the readout of the ADC a Shell script or the tool crontab can be considered.

In case an user is going to open the web application, Django loads the complete data of the ADC from the database and plots them graphically into the webpage.
This is one part of the final application. The interface for managing FPGA Configurations works similarly.

1. Project Preparations
2. Installing the finshed Web interface
3. Creating a new Django Project on the SoC-FPGA
4. Creating a new Django App to interact with the FPGA fabric
5. Testing the Web Appilcation
6. Reading of a Soft-IP ADC interface and writing the data into a SQLite datbase
7. Configuring the plotting of an ADC Channel
8. Reading and plotting the data time triggered

• Boot up rsYocto on your Intel SoC-FPGA Board by following the getting started Guide
• Setup Visual Studio Code Insider with this instruction guide
• On rsYocto (Version. 1.031+) are following compunets for this project pre-installed:
  • Django 3.0.2
  • rstools for accessing the FPGA fabric
  • During the boot are following modules connected to the Lightweight HPS to FPGA Bridge
    • PIO-Controller for controlling the on-Board LEDs on the Address offset 0x20
    • Analog Devices LTC2308 Interface IP on the Address offset 0x40

For installing and testing the final project do the following steps:

• Clone this repository by executing the following Linux Terminal command on rsYocto

  git clone https://github.com/robseb/Django2FPGAdemo.git

• Navigate inside the project folder

  cd DjangoFPGA/DjangoFPGA

• Generate an administration interface with your login information

  python3 manage.py createsuperuser

• Please follow: Testing the Web Appilcation

• Use the Linux Terminal, which is reachable inside Visual Studio Code Insider to create a new Django project with the name "DjangoFPGA" by executing the following command:

  django-admin startproject DjangoFPGA

  

• Note: Use in the drop-down menu (blue arrow) the point "sh" to access the Linux Terminal. In case the point is not there, press the “+”-icon to add it.

• Navigate with the Linux Terminal inside Visual Studio code to this project

  cd DjangoFPGA

• By default the Django web server is only reachable internally by the embedded Linux

• To access Django applications within your network do the following steps:

  1. Open the Django project settings file (settings.py) with Visual Studio Code (as shown above) and allow everybody to connect with the following lines:

     ALLOWED_HOSTS = [
      '*'
     ]

  2. After some change of the settings file a migration of the project is necessary:

     python3 manage.py migrate 

  • The output of this command should look like this:

    root@cyclone5:~/DjangoFPGA# python3 manage.py migrate
    Operations to perform:
    Apply all migrations: admin, auth, contenttypes, sessions
    Running migrations:
    Applying contenttypes.0001_initial... OK
    Applying auth.0001_initial... OK
    Applying admin.0001_initial... OK
    Applying admin.0002_logentry_remove_auto_add... OK
    Applying admin.0003_logentry_add_action_flag_choices... OK
    Applying contenttypes.0002_remove_content_type_name... OK
    Applying auth.0002_alter_permission_name_max_length... OK
    Applying auth.0003_alter_user_email_max_length... OK
    Applying auth.0004_alter_user_username_opts... OK
    Applying auth.0005_alter_user_last_login_null... OK
    Applying auth.0006_require_contenttypes_0002... OK
    Applying auth.0007_alter_validators_add_error_messages... OK
    Applying auth.0008_alter_user_username_max_length... OK
    Applying auth.0009_alter_user_last_name_max_length... OK
    Applying auth.0010_alter_group_name_max_length... OK
    Applying auth.0011_update_proxy_permissions... OK
    Applying sessions.0001_initial... OK

  3. Use the next command to start the web server (here on Port 8181)

     python3 manage.py runserver 0:8181

  • The output of this command should look like this:

    root@cyclone5:~/DjangoFPGA# python3 manage.py runserver 0:8181
    Watching for file changes with StatReloader
    Performing system checks...
    
    System check identified no issues (0 silenced).
    January 18, 2020 - 15:35:44
    Django version 3.0.2, using settings 'DjangoFPGA.settings'
    Starting development server at http://0:8181/
    Quit the server with CONTROL-C.

  • Note: The default port 8080 is used by the Apache web server

• Go with a web browser on a device inside this network (computer, tablet, smart-phone) to the URL:

   http://<iPv4-Address of the Board>:8181/ 

• If you see a rocket lunch your Django project works properly

  

• All HTTP-attaches are listed on the terminal as well

Every Django project requires at least one application (App). We will build an App to readout the Soft-IP ADC Interface (Analog Devices LTC2308) of a Terasic DE10-Standard- or Terasic DE10-Nano-Board and present the data in the web browser. As a second feature, we will build a management interface for changing the FPGA configuration.

• The following command adds a new app called "BoardInteraction" to the project.

  python3 manage.py startapp BoardInteraction

• Note: Be sure that this command is executed inside the project-folder (DjangoFPGA/)

• The project folder contains the following structure now:

  • All important files are marked

  

• Add this application to the Django project by adding the following line to the variable INSTALLED_APPS iniside settings.py:

  # Application definition
  INSTALLED_APPS = [
      'BoardInteraction.apps.BoardinteractionConfig', # Add this line 
      'django.contrib.admin',
      'django.contrib.auth',
      'django.contrib.contenttypes',
      'django.contrib.sessions',
      'django.contrib.messages',
      'django.contrib.staticfiles',
  ]

  • Note: This is a connection to the main-function BoardinteractionConfig() that is located in the "app.py" file
  • Migrate the project again

  python3 manage.py migrate 

• Add the following python code to the model file (DjangoFPGA/BoardInteraction/models.py)

  '''
  Django FPGA Interaction demo application - "models.py"
  '''
  from django.db import models
  from datetime import datetime
   #
   # Class for reading an analog Sensor 
   #
   class ADCSensorReading(models.Model):
       # Sensor value as Char Text Field type   
       reading = models.FloatField()         
       timestamp = models.DateTimeField(default=datetime.now, db_index=True)    # Time stamp
  
       def __unicode__(self):
           return self.reading
  
   # 
   # Class for connecting an Analog Devices LTC LTC2308 ADC Channel
   #
   class ADCchannel(models.Model):
       name     = models.CharField(max_length=200)          # a name for the Sensor on the ADC Channel
       slug     = models.SlugField(unique=True)             # an unique working handler name
       readings = models.ManyToManyField(ADCSensorReading)  # the sensor data object
       ch       = models.IntegerField() # the used ADC Channel Number
  
       def __unicode__(self):
           return self.name
  
   # 
   # FPGA .rbf Configuration File Database
   # 
   class FPGAconfFiles(models.Model):
       docfile = models.FileField(upload_to='FPGAconfigDatabase/%Y/%m/%d')      # local storge folder  
       timestamp = models.DateTimeField(default=datetime.now, db_index=True)    # Time stamp

• Create an user who can do the login to the admin site. Run the following command:

  python3 manage.py createsuperuser

• Enter an Username, an Email-Address and a Passwort

  Password: **********
  Password (again): *********
  Superuser created successfully.

• Allow the Admin to access all database models by adding the following code lines to the Admin-file (DjangoFPGA/BoardInteraction/admin.py)

  '''
  Django FPGA Interaction demo application  - "admin.py"
  '''
  
  from django.contrib import admin
  from BoardInteraction.models import ADCSensorReading, ADCchannel, FPGAconfFiles
  
  # Allow access to all ADC data models and FPGA configuration files inside the SQLite Database
  admin.site.register(ADCchannel)
  admin.site.register(ADCSensorReading)
  admin.site.register(FPGAconfFiles) 
  
  # Personalisation of the admin page
  admin.site.site_header = 'rsYocto'                                         # Headline title           
  admin.site.index_title = 'Django FPGA interaction Demo Administration'     # Sub-Headline title       
  admin.site.site_title = 'rsYocto'                                          # HTML Headline

• Save all open files
• To generate a SQLite database with these settings execude the following Linux Shell commands (DjangoFPGA/):

  python3 manage.py makemigrations
  python3 manage.py migrate
  python3 manage.py migrate --run-syncdb

• Start the Django Server

  python3 manage.py runserver 0:8181

• Open the following URL with a web browser:

  http://<iPv4-Address of the Board>:8181/admin 

• The Yocto Login Screen should appear:

• Use your login credentials to login

• Here are all created databases accessible
• At this point it is possible to add the sensor data manuelly

• To view this data in a graphic the library plotly is used

  • That is an easy way to implement such kind of UI-elemets to a web page.
  • In the same way it is possible to add any kind of diagramms to this web App (please follow the official documentation

• To display something on a web page it is necessary to add some lines of code to the "views.py"-file (DjangoFPGA/AccSensor/views.py):

  '''
  Django FPGA Interaction demo application  - "views.py"
  '''
  
  from django.http import Http404
  from django.shortcuts import render, HttpResponse, HttpResponseRedirect
  from .models import ADCSensorReading
  from subprocess import call
  
  # use "pip install plotly" to add this package
  from plotly.graph_objs import Scatter
  from plotly.offline import plot 
  import plotly.graph_objects as go
  
  
  # For accessing the FPGA configuration
  from subprocess import call
  
  # For working with a file upload box 
  from .forms import DocumentForm
  from .models import FPGAconfFiles
  
  # For accessing the the Project settings
  from django.conf import settings
  
  # import trigger function for reading the ADC
  from BoardInteraction.services import ReadADCchannel
  
  
  # 
  # Called in case the user opened the main web page of the App
  # the complete UI will be built and transmitted to the web browser
  #
  def detail(request):
  
      # Handle file upload for the FPGA configuration file
      if request.method == 'POST':
          form = DocumentForm(request.POST, request.FILES)
          if form.is_valid(): 
              # Upload the File to the Database
              newdoc = FPGAconfFiles(docfile = request.FILES['docfile'])
              newdoc.save()
              # Write FPGA Configuration
              call('FPGA-writeConfig -f '+settings.BASE_DIR+"/"+newdoc.docfile.url, shell=True)
      else:
          form = DocumentForm() 
  
      # Load all stored FPGA configuration files
      try:
          FPGAconfigFiles = FPGAconfFiles.objects.all()
      except ADCSensorReading.DoesNotExist:   
          raise Http404("FPGA Configuration data does not exist")
  
      # Load the ADC Value database
      try:
          adcChvalue = ADCSensorReading.objects.all() 
      except ADCSensorReading.DoesNotExist:        
          raise Http404("ADC data does not exist")  # In case of an Error display an Error 404 Screeen
  
      ### Plot the ADC Values #####
  
      # Plot the latest 100 data points in time order 
      adcData = adcChvalue.order_by('-timestamp')[:100]
      
      # pre-process the ADC data of the database
      y_data= []
      x_data= []
  
      for b in adcData:
          y_data.append(b.reading)
          x_data.append(b.timestamp)
  
      # create a new line plot element 
      fig = go.Figure()
      fig.add_trace(go.Scatter(x=x_data, y=y_data, name='Sensor Voltage',
                              line = dict(color='royalblue', width=4, dash='dashdot')))
      # Edit the layout
      fig.update_layout(title='Plot of recorded ADC data from a Soft IP-interface',
                      xaxis_title='Time (UTC)  [HH:MM:SS]',
                      yaxis_title='ADC Voltage (V)')
  
      # store the plot object 
      plot_div = plot(fig, output_type='div', include_plotlyjs=False)
  
      # render the HTML template with all values
      return render(request, "BoardInteraction/DisplayTemplate.html", context=
      { 
          'plot_div': plot_div,           # Plot object 
          'obj':adcData,                  # ADC raw data 
          'documents': FPGAconfigFiles,   # FPGA Configuration files 
          'form': form                    # Upload File form
      })

• For displaying the FPGA Configuration management interface extend the views.py-file with the following lines of python code

  #
  # If the user select a FPGA Configuration file this function will be called 
  # to insert the file to the data base and the FPGA will be configured with it
  #
  def change_FPGAconfiguration(request):
      # <URL>/?subjectID=<Configuration file path>
      subjectID = request.GET.get("subjectID")
  
      # Write this file on the FPGA fabric 
      call('FPGA-writeConfig -f '+settings.BASE_DIR+"/"+subjectID, shell=True)
  
      # Relaod the main app page again 
      return HttpResponseRedirect(request.META.get('HTTP_REFERER', '/'))
  
  
  #
  # If the user select the rool back to the boot FPGA Configuration this function will be called 
  #
  def change_FPGAconfigurationBack(request):
      # <URL>/?subjectID=<Configuration file path>
      subjectID = request.GET.get("subjectID")
  
      # Write the FPGA fabric back to the boot state
      call('FPGA-writeConfig -r', shell=True)
  
      # Relaod the main app page again 
      return HttpResponseRedirect(request.META.get('HTTP_REFERER', '/'))

  • These are two event functions, which are triggered in the case a FPGA-Configuration button was pressed

• To allow to collect and update the ADC Sensor data add the following function to the "views.py"-file

  #
  # ADC Store data trigger function 
  #
  def ADCtrigger(request):
      ReadADCchannel()
      return HttpResponse('')

• With these functions two events are declared, this allows to control the FPGA LED 0 with a push button:

  • Add them to the "views.py"-file as well

   #
   # Function to turn FPGA LED 0 on called in case the ON-button was pressed 
   #
   def LED0_ON(request):
       # Turn FPGA LED0 on 
       call('FPGA-writeBridge -lw 20 -b 0 1 -b', shell=True)
       # Relaod the main app page again 
       return HttpResponseRedirect(request.META.get('HTTP_REFERER', '/'))
  
  
   #
   # Function to turn FPGA LED 0 off called in case the OFF-button was pressed 
   #
   def LED0_OFF(request):
       # Turn FPGA LED0 off
       call('FPGA-writeBridge -lw 20 -b 0 0 -b', shell=True)
       # Relaod the main app page again 
       return HttpResponseRedirect(request.META.get('HTTP_REFERER', '/'))

• The render-function uses the "DisplayTemplate.html" HTML file to build the canvas of the web interface

• Django only looks for this kind of template file in this folder structure: /templates//

• That meens, that this file must be located here:

  DjangoFPGA/BoardInteraction/templates/BoardInteraction/DisplayTemplate.html

  • Creat the file with all folders with Visual Studio Code Insider

• For building a simple UI add the following to the HTML file:

  <!-- Django FPGA Interaction demo application - DisplayTemplate.html -->
  <!DOCTYPE HTML>
  <html>
    <head>
      <!--Load the ploty Library script -->
      <script src="https://cdn.plot.ly/plotly-latest.min.js"></script>
      <meta charset="utf-8">
      </script>
      <title>rsYocto Django Demo</title>
    </head>
    <body>
      <center>
      <p><embed src="https://raw.githubusercontent.com/robseb/rsyocto/rsYocto-1.03/doc/symbols/rsYoctoLogo.jpg?raw=true" width="300" height="120" title="rsYocto Logo" /></p>
      <h2>Simple Django demo application for using a web interface to control and access the FPGA fabric</h2>
      <br>
      <!--Load the ploty UI-->
      <h3>FPGA IP data plot </h3>
  
      {% autoescape off %}
      {{ plot_div }}
      {% endautoescape %}
      <br>  
  
      <!--Show the FPGA Configuration File upload box-->
      <h3>Chnage the FPGA Configuration </h3>
      <form action="{% url 'main' %}" method="post" enctype="multipart/form-data">
            {% csrf_token %}
            <p>{{ form.non_field_errors }}</p>
            <p>{{ form.docfile.label_tag }} {{ form.docfile.help_text }}</p>
            <p>
                {{ form.docfile.errors }}
                {{ form.docfile }}
            </p>
            <p><input type="submit" value="Upload"/></p>
        </form>
        <!--Show a list of all stored FPGA configuration files-->
        <br>
        <h3>FPGA configuration manager </h3>
        <h4>List of all saved FPGA configuration files</h4>
        {% if documents %}
        <ul>
          <table  border="1">
            <tr>
              <th>File Name</th>
              <th>Upload Date</th>
              <th>Load to the FPGA fabric</th>
            </tr>
          {% for document in documents %}
                <tr>
                  <td>{{document.docfile.name}}</td>
                  <td>{{document.timestamp}}</td>
                  <td><a href="{% url 'scriptFPGAconf' %}?subjectID={{document.docfile.url}}">Configure FPGA</a></td>
                </tr>
          {% endfor %}
          <tr>
            <td>Bootloader FPGA Configuration</td>
            <td>-</td>
            <td><a href="{% url 'BootloaderFPGAconf' %}">Roll back</a></td>
          </tr>
      </table>
  
        </ul>
      {% else %}
          <p>No documents.</p>
      {% endif %}
        <!--Create two push buttons to control the FPGA LED 0-->
        <br>
        <h4>FPGA LED 0 Control </h4>
        <button onclick="location.href='{% url 'scriptLED0N' %}'">LED 0 ON</button>
        <button onclick="location.href='{% url 'scriptLED0F' %}'">LED 0 OFF</button>
        </center>
      </body>
  </html>  

• To show a File Upload box for the selecting of a FPGA configuration file these steps are requiered

• Create inside the App the new file "form.py" (DjangoFPGA/BoardInteraction/forms.py)

• Add the following code to this file

  '''
  Django FPGA Interaction demo application - "form.py"
  '''
  from django import forms
  
  # 
  # Build the Upload File Box for selecting 
  # a FPGA configuration file 
  #
  class DocumentForm(forms.Form):
  
      docfile = forms.FileField(
          label='Select a ".rbf"- FPGA configuration file',
          help_text='Click Upload to save the file and configure the FPGA fabric'
      )

• By default nothing will be routed to the front page of this application (http://:8181/)
• To link the front page to the App, add the following lines of code to the global url configuration file (DjangoFPGA/DjangoFPGA/urls.py):

  # DjangoFPGA URL Configuration
  from django.contrib import admin
  from django.urls import path
  
  # Include the "BoardInteraction" App  
  from BoardInteraction import views
  
  # URL linkages of this project 
  urlpatterns = [
  
      # UI 
      path('', views.detail,name="main"),                 # Front page -> linked to the "BoardInteraction" App 
      path('admin/', admin.site.urls),                    # /admin     -> Admin interface
  
      # HPS LED 0 
      path('LED0_ON',views.LED0_ON,name="scriptLED0N"),   # /LED0_ON   -> triggered by pushing the LED0 ON Button 
      path('LED0_OFF',views.LED0_OFF,name="scriptLED0F"), # /LED0_OFF  -> triggered by pushing the LED0 OFF Button 
  
      # e.g. views.LED0_ON is the name of the viewer function  
      # With e.g. the name="scriptLED0N" the linkage is taken to the HTML event handler: '{% url 'scriptLED0N' %}'
  
      # FPGA Configuration 
      path('FPGA',views.change_FPGAconfiguration,name="scriptFPGAconf"),
      path('BOOTFPGA',views.change_FPGAconfigurationBack,name="BootloaderFPGAconf"),
  
      # ADC Sensor Trigger
      path('ADCtrigger',views.ADCtrigger,name="scriptADCtrigger")
  ]

  • Save all open files

• Now all configurations of the user elements are done and it is time to test this state

• Import the Python pip-package "plotly" using for the plotting of the data:

  pip install plotly

• Execude the following Linux Shell commands again (DjangoFPGA/):

  python3 manage.py makemigrations
  python3 manage.py migrate
  python3 manage.py migrate --run-syncdb

• Start the Django Server

  python3 manage.py runserver 0:8181

• Open the following URL with a web browser:

  http://<iPv4-Address of the Board>:8181/admin 

• The front page should now look like this:

  

• Test the Webinterface:

  • Change the FPGA configuration (the required type is described here)

• Turn the FPGA LED ON or OFF

At this point the ADC plot is empty, because no application has written to the database. This will be solved in the next steps.

As it is shwon in the sequence diagram above the readout of the FPGA data is triggered by calling the URL http://127.0.1:8181/ADCtrigger. Then the web interface starts an application to collect the ADC sensor data into the database.

To implement that two extensions of the project are required:

1. A function handler, that calls this application and writes the received values to the database

• Create a new python file called “services.py” (DjangoFPGA/BoardInteraction/services.py)
• Add the following code to it:

  '''
  Django FPGA Interaction demo application  - "sevices.py"
  '''
  import subprocess
  
  from BoardInteraction.models import ADCSensorReading, ADCchannel 
  
  # For accessing the Project settings
  from django.conf import settings
  
  #
  # Start a python application to read the ADC value 
  # and write the value to a database
  #
  def ReadADCchannel():
      # For every activ ADC Channel 
      for sensor in ADCchannel.objects.all():   
          adc_u = 0
          # Start the Python Script "adcReadChannel.py" to read the ADC Channel
          try: 
              adc_u = float(subprocess.check_output(['python3',settings.BASE_DIR+'/BoardInteraction/adcReadChannel.py',str(sensor.ch)],stderr=subprocess.STDOUT, timeout=None))
          except ValueError:
              adc_u = 0
              subprocess.call('echo Value Error ', shell=True)
  
          # Write the value to the database
          ADCSensorReading.reading = adc_u 
  
          newreading = ADCSensorReading(reading= ADCSensorReading.reading)
          newreading.save()
          sensor.readings.add(newreading)
          sensor.save()
  
      return True

2. An application to read an ADC Channel of the Soft-IP ADC interface

• service.py will call the following python script to read the ADC

  Django2FPGAdemo/DjangoFPGA/BoardInteraction/adcReadChannel.py 
  

• Create this file "adcReadChannel.py" on this location and add the following lines to it

  #!/usr/bin/env python
  # coding: utf-8
  
  '''
  @disc:  Single Shoot ADC Channel readout (Analog Devices LTC2308)
          Fast way over the virtual memory
  
  @date:   21.01.2020
  @device: Intel Cyclone V 
  @author: Robin Sebastian
           (https://github.com/robseb)
  '''
  import os
  import time
  import math
  import sys
  # 
  # This demo uses the python class "devmen" (https://github.com/kylemanna/pydevmem)
  # be sure that this file is on the same directory 
  #
  import devmem
  
  # the Lightweight HPS-to-FPGA Bus base address offset
  HPS_LW_ADRS_OFFSET = 0xFF200000 
  
  # LTC2308 Address offset
  ADC_ADDRES_OFFSET = 0x40
  
  # Register set of the LTC2308
  ADC_CMD_REG_OFFSET  = 0x0
  ADC_DATA_REG_OFFSET = 0x4
  
  
  ### FIFO Convention Data Size for average calculation
  FIFO_SIZE = 255 # MAX=1024 
  
  if __name__ == '__main__':
  
      # Read selected ADC Channel as input argument [1]
      # python3 adcReadChannl <CH> 
      ch = 0
      ch_selet = str(sys.argv[1])
  
      try: 
          ch = int(ch_selet)
      except ValueError:
          ch = 0
  
      if(not(ch >=0 and ch < 6)):
          ch = 0
  
      # open the memory Access to the Lightweight HPS-to-FPGA bridge
      #                  (Base address, byte length to acceses, interface)
      de = devmem.DevMem(HPS_LW_ADRS_OFFSET, ADC_ADDRES_OFFSET+0x8, "/dev/mem")
  
  
      # Set FIFO size for ADC value averaging
      de.write(ADC_ADDRES_OFFSET+ADC_DATA_REG_OFFSET,[FIFO_SIZE])
  
      # Enable the convention with the selected Channel
      de.write(ADC_ADDRES_OFFSET+ADC_CMD_REG_OFFSET, [(ch <<1) | 0x00])
      de.write(ADC_ADDRES_OFFSET+ADC_CMD_REG_OFFSET, [(ch <<1) | 0x01])
      de.write(ADC_ADDRES_OFFSET+ADC_CMD_REG_OFFSET, [(ch <<1) | 0x00])
  
      timeout = 300 #ms
      # Wait until convention is done or a timeout occurred
      while (not(timeout == 0)):
          if(de.read(ADC_ADDRES_OFFSET+ADC_CMD_REG_OFFSET,1)[0] & (1<<0)): 
              break
  
          timeout = timeout -1
          time.sleep(.001) # delay 1ms 
  
      # calculate the average of the FIFO
      rawValue = 0
      for i in range(FIFO_SIZE): 
          rawValue = rawValue+ (de.read(ADC_ADDRES_OFFSET+ADC_DATA_REG_OFFSET,1))[0]
  
      value = rawValue / FIFO_SIZE
  
      # Convert ADC Value to Volage
      volage = round(value/1000,2)
      # print the Value
      print(str(volage))

This Django application needs a new database entry for all ADC Channels to read. This will be stored inside the database “ADCchannel“. This is only possible by hand as an Admin with the admin interface.

• Start the Django Server

  python3 manage.py runserver 0:8181

• Open the following URL with a web browser:

  http://<iPv4-Address of the Board>:8181/admin 

• On the Admin page select +-Icon in the menu "Ad cchannels"

• Inside the opend view press the "ADD AD CCHANNEL" Button

  

• Then insert the following to the web form to add a new Sensor to the ADC Channel

  • Name: The name of the Sensor
  • Slug: A unique ID for the Sensor
  • Reading: The databebase with all sensor values
  • CH: The choosed ADC Channel

• Press save
• Note: It is necessary to add one sensor value to the "readings" at least

• Open the Application with the following URL on a web browser:

  http://<iPv4-Address of the Board>:8181/ 

At this point only one ADC Value is inside the plot. To manually read the ADC channel it is possible to open the following URL with a web browser:

http://<iPv4-Address of the Board>:8181/ADCtrigger 

Then reload the application page. The new collected value is plotted now too.

To automatically read the ADC Channel in a time interval are two approaches shown here

1. Usage of a shell script

• For example, run the following Linux shell script to read the ADC every 100 milliseconds for 500 times

  #!/bin/sh
  # Run script
  echo "*********************************"
  echo "read ADC Channel every 100ms "
  
  for nvar in {1..500}
  do
    curl -s http://127.0.0.1:8181/ADCtrigger
  
    sleep  0.1
  done 
  
  echo "*********************************"

2. Usage of the Linux task automation tool crontab

• This is on rsYocto pre-installed

• A good documentation is availablehere

• Open the "crontab" configuration file

  sudo nano /etc/crontab

• Insert the following line to it

   * * * * * root curl -s http:/127.0.0.1:8181/ADCtrigger

  • The Sensor will read this every minute
  • Note: To execute this change a restart of Linux is required

• Refresh the management interface to recognize the time synced plotting of the ADC data

• rsyocto; Robin Sebastian,M.Sc. (LinkedIn)

Django2FPGAdemo and rsyocto are self-developed projects in which no other companies are involved. It is specifically designed to serve students and the Linux/FPGA open-source community with its publication on GitHub and its open-source MIT license. In the future, rsyocto will retain its open-source status and it will be further developed.

Due to the enthusiasm of commercial users, special features for industrial, scientific and automotive applications were developed and ready for the implementation in a highly optimazed closed commercial version. Partnerships as an embedded SoC-FPGA design service to fulfil these specific commercial requirements are offered. It should help, besides students with the rsyocto open-source version, commercial users, as well.

For commercial users, please visit the rsyocto embedded service provider website: rsyocto.com