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BASIL Networks Blog BN'B | November 2019

3 Nov, 2019

Internet of Things (IoT) Security, Privacy, Safety -Platform Development Project Part-20

Part 20: IoT Core Platform Development;- Peripheral I/O Device Design
The IoT Embedded Core Platform -Peripheral Devices Real World Testing - Continued

"I can't change the direction of the wind, but I can adjust my sails to reach my destination" Jimmy Dean (August 10, 1928-June 13, 2010)

As we stated in past presentations in this series development costs are easily exceeded when the performance expectations and in that case performance requirements are not documented properly or the infamous "TBD".  This forces a direction change "AND" direction changes are commonly not listed as part of  performance expectations.  Sometimes the development "process" is faulty or just plain broken period.  The intent of this series in not to maintain the insanity of over budget development costs but to disrupt it in order to allow the creation of new habits that will give a solid foundation for engineering practices to be successful when starting a development project.

For the new designer that is taking on the learning of CPLD and FPGA design, "Each design completed is experience for the next lever of development."  There are only experiences and techniques that will bring you to the advanced level of applications.

IoT-Index Quick Links

Quick review to set the atmosphere for Part 20:
A lot of information was covered over the past 19 presentations of this series.  The progression from presenting an important explanation of safety, security and privacy of data, Internet basics from real basic to protocol complexities, conceptualizing a project development, presenting the need for secure accurate documentation as well storing that documentation where it is accessible during and after the product development cycle and of course the need to design in security and privacy during the conceptual development of a project.  

For review, the current Core Platform IoT development main focus is two fold, first an educational project development for the entrepreneurial mindset and the project applications of remote sensing and control incorporating safety, security and privacy over a wide range of peripherals including wireless.  This should be kept in mind since we will be designing in some redundancy for reliability and security.

The ITF development Project:
The ITF did create a change in direction, however did not change the desired results, this is not only common in development projects but is some cases required to meet the desired expectations.  The issues here are handling multiple projects, resources available and the changed timeline, just a short change in direction to complete the objective.  A validation that the real time product development process is far from being a linear process from conception to finished product.  

As we see this is a project within itself to show product development direction and expectations where resources are weighted and required for both product development, engineering performance testing and production.  The ADC-CHAN interface was selected since it was a "reuse" design and how it is to be modified to fit our application which would represent the standard peripheral interface to the IoT Core Platform CPU peripheral BUS requirements.  Initially presenting part of the Interface Test Fixture (ITF) to handle the remaining peripheral development for the series and continuing on with completing the  Interface Test Fixture (ITF) then go back to completing the ADC-CHAN Analog input design to insure the interface performance expectations.

OK, some information on re-use - With the ADC-CHAN design the reason it was easily presented was because it was a "Re-use" design so all the preliminary design work was completed.  Yes, this was selected with expectations to present the re-use with modifications vs the full design from scratch.  The full design process will be presented for CPLD#2 specifically from scratch to see what is involved with creating the design from start to finish and to review the reuse debate syndrome.  

Remember changing direction overnight does not mean changing goals our the final destination, it is just a better way to insure you will reach the desired destination.  In my years of exposure to the design arena as a designer,troubleshooter and mentor I have had the honor of experiencing innovative and passionate creators to realize that the creative thought process of an individual is not a linear step function, 1, 2, 3 ...N, probably because humans are not robots, that follow a preprogrammed set of processes as some may think of engineers.  The innovation of the human mind subconsciously is always performing scenarios to find the best solution for the task at hand and "developing habits along the way".

Over the past 40 plus years of being involved with product design, research, investigations and management so much has changed incorporating more tools to make manufacturing more controlled, design and development more accessible to all levels while increasing the level of knowledge for society adding more responsibility and accountability and freedom of innovation for individuals to take action and bring their ideas to fruition.

What we want to cover in Part 20:
In Part-16,17, 18 and 19 we addressed the issue of why we should consider testing of the peripherals (Proof of Design) PoD with a prototype build to insure when we interconnect several of the peripherals the throughput required for the applications will be met.  This allows the opportunity to change the development direction from the peripheral point of view if performance expectations become an issue. Developing a test methodology that will be used for testing peripherals for the platform keeping in mind peripheral throughput limitations. These are new habits being developed at a conscience mind set level that will connect to become the default critical thought process during development.  With that stated we will continue moving forward with detailing the Interface Test Fixture (ITF).

The design process in this part includes:

Updating the IPD project documentation for the ITF (Interface Test Fixture) to keep track of the development process, "Documentation is a living process during development", a good habit to make!  The reference for the ITF is the functional block diagram Figure 16.1

Lets Get Started:
Some questions answered from our readers
"What happen to the series?,  "It has been a few months from part 19, are you going to continue the series?  
To answer the above two questions - YES the series will continue.   We own and maintain several on-line servers as well as off-line servers here in the lab and we were in the process of upgrading them to the latest and greatest compliant requirements.  This took longer than planned, HHMMmm I think I said that about product development timing some where, well again we have added another first hand experience to our portfolio. Cool

Are there any sponsors for this series?
All devices for this project have been selected by their specifications and there are no sponsors for any of the components or the designs.  The possibility of sponsors for this project was put on the table for discussion and in order to keep this development purely on component merit the decision was made not to have any advertisement or sponsors for this project.  We also discussed private sponsorship from grant funds however the complexities and timing would have postponed the project for over a year while looking for grant.  We are still open for a grant if the opportunity arises.

Have you decided on any video presentations for this project?
We are still discussing this possibility of a YouTube channel which is  not our first choice or just put the videos directly on one of our servers as an educational series.  BASIL Networks website new addition is a gallery for presentations and videos that we will be posting at the beginning the new year.  For those interested please contact us using the BASIL Networks Contact Form for more information on when this will be available.  All the video creation, editing and processing videos are in place at this time and we are experimenting with several ways to clearly present hardware, firmware and software techniques through a video presentation.

OK, a quick review of the documentation system we will be using, Yes again, Ok I'm sounding like management now, "are we there yet?" - so what does that all mean to this series?  This means that to assist this innovative development process that may change direction even get delayed at times from one development task to another a tracking system should meet the following requirements.

Product design documentation is not only for the designer it is for those that will follow the design when the designer moves on to other projects.  Product development with documentation is the Knowledge Base for growth and the leverage for reuse.

  1. Interactive - by second nature without thought
  2. Flexibility - being able to record changes and additions in real time.  
  3. Development Traceability - development changes that effect several project are easily traced and recorded in each project.
  4. Multiple Project Tracking - This is where we are now - being able to start and track new projects that will eventually interact with the product development at hand, hence: the IoT Core Platform development project.
    So, the ITF Project name given is- Universal_Peripheral_ITF previously
    AND-- We are going to make some more changes, again---

Repetition is the mother of retention,  wait a minute!..., I think I read that somewhere before in a different color. Cool


CPLD#2  I/O DataBUS Interface Registers Block Diagram:
OK, lets take the easy parts first, the Interface Data and Control Registers.  We will assign some tasks for these registers but hold off on assigning any bits or bit pattern until we actually implement then into the transfer sequence of the data.

From Figure 19.3 and Figure 19.4 the name of the registers have been assigned.  What we will create are the register bit widths, register functionality and data load path that defines the input side of the CPLD.  This will allow the flow control for the CPLD functionality.

OK, for those of you that have been following this series, a while back I stated that when you design a product you start from the output of what is desired and work toward the input to insure that you have all the necessary power to insure the transfer of power. This rule applies mainly for power supplies and power amplifiers since the drivers for each stage have to be capable of supplying power not just signal.  In the digital world there are only 1's and 0's and bits so we envision this approach a bit differently. Cool

The approach here is to insure there are enough input bits(pins) available to address all the required registers internal for the data transfer.  Since we defined the max on-board RAM to be 16Meg words, that dictates a 24 bit address.  The question is how do we want to address this data?  There are a few ways to do this, always start from address 0 to a final address specified by a counter register which would be the easiest of the implimentations.  However, looking forward much more control of the memory will be required when we get into the input data transfer mechanism.  Since we have designed these types of high speed interfaces over the years and have improved the process, (A polite way of saying that many shortcommings have been added to the experience port folio), the following register set for the memory data transfer is used as a starting point.

As a general preference rule for registers they are Read/Write type registers whenever possible.  Prior to 1981 before the initial PC was introduced peripherals with registers were always Read/Write.  The R/W gave a mechanism to test out specific logic for functionality. When the PC was introduced and the new associated controllers the read-only and write-only register sets were introduced.  Needless to say the complaints were compounded until some sort of reliability and multi-user programming methodology surfaced.  For software programmers a write only register is a Nightmare on Elm Street to keep track of in a multitasking environment.  OK back to the design.  Figure 20.0 shows the register breakdown of the on-board memory transfer section.

Figure 20.0   CPLD #2 Register Functional Block Diagram

So, as we look at the register block diagram we see that the names have changed on the registers along with a different type of data transfer methodology.  Over the years designing data acquisition interface systems for updating and increasing ROI for capital equipment the following methodologies evolved allowing more control and flexibility to interfacing to the real world.  This modification is from the IBPD system that is approaching its ten year mark so we decided to present the new interface here that includes many of the features of a 16 bit digital logic analyzer as well as a straight digital I/O interface for testing peripherals.  The new additions are variable speed control via a DDS as well as data capture timing to measure propagation delays from BUS enable and data ready enable control lines.   Adding a pattern recognition to trigger data collection assists those oops it failed in the middle of a transfer bugs.

We also added a Start Address Register (SAR) and a Final Address Register (FAR) which allows addressing control for specified window of memory addresses for data transfer.  This type of feature is relatively common among more expensive data acquisition peripherals where multiple channels are designed in.  The SAR and FAR methodology compartmentalize the memory for multiple parameter testing of a peripheral by just programming the different parameters to the peripheral and it maintains the functional hardware setup with minimum changes.   We also added the clock timing control and the Programmed I/O functions that communicates with the Programmed Data I/O CPLD #1.   The timing and control for Enable and Data Ready lines incorporate a DDS AD9854 IC.  We used this chip for a few products several years ago and there are some other IC's that we will also look at however the 9854 has a dual DAC output that are phased controlled separately.  The price is in the USD $50 range for small quantities however it is one of the most versatile DDS IC on the market and will generate a clean 100MHz Sine, Triangle and Squarewave signals which incorporate two high speed DACs with a 14 bit phase control between the DACs.

The initial timing diagram for the memory transfer is still the same however there is added logic to handle the added features.  We will still start with the initial timing created in Figure 19.5   This timing will generally change as the CPLD#2 is designed and a full timing analysis is performed.  Propagation delays will change with addition to the CPLD when it is compiled.  This is one of the reasons that when using a dual CPLD design one CPLD will handle the critical timing part of a design and remains fixed in order to maintain performance.

CPLD#2 I/O Data BUS Register Setup Flow Diagram
The new memory data transfer changes also effect the way the CPLD is programmed as shown in the flow diagram in Figure 20.1 below.  The new additions require the setup of the ITF mode functions, Pattern recognition, speed of the transfer, default timing delays between enable and data available and a few other changes along the way. Performing a first pass design allows us to see how the internals are layed out and more importantly gives us an opportunity of fine tune the design for more flexibility.

Figure 20.1   CPLD #2  Program Flow Diagram Memory Data Transfer

ITF CPLD#2 Direct Memory Access Controller
Now that we have the preliminary registers and flow diagram identified it is time to start getting to the detailed design.  The first step is to insure we have enough pins in the CPLD that will accommodate all the changes to the design.  Table 20.0 below identifies the number of I/O pins required for the ITF Memory controller.  From the previous parts we selected the MAX-II series 144 pin TQFP CPLD series since there are 116 I/O Pins available on the chip.  There are several sizes of the MAX-II 144 Pin TQFP available depending on the number of LE (Logic Elements or Logical Units) in the selected chip.  We will hold off in picking a specific chip until we do the design.  The Quartus IDE will identify the LE's required to complete the design during compilation.

Name Pins Description
Data I/O Bridge 8 Data Transfer to/from Laptop or Desktop
Device Select 8 Device Select, Chip Enable, Read Setup, Write Setup,  R/W Control
MAIN Clock 2 Main Clock - 200 MHz Differential input
Memory Address 24 External Memory Chip address lines up to 16 Meg Words
Memory Data Bus 16 External Memory Data Bus 16 bit word
Memory Control 8 External Memory Control Lines , R/W and enable lines
CPLD#1 Data Interconnect 16 Inter-communications between CPLD#1 and CPLD#2 16 bit Data
CPLD#1 Data Control 10 Inter-communications between CPLD#1 and CPLD#2 Control lines 8 bits
Aux Latched Byte Input 8 Aux latched input
Aux Direct Byte Input 8 Aux direct sense input
Aux Control 4 Aux Input Control
CPLD#2 Pins Required 112 Total I/O Pins Available=116 Spare pins = 4

Table 20.0  CPLD #2 I/O Pin Requirements

Since the Memory controller is contained within a single CPLD we can begin this CPLD design independently.  This is the main interconnect  to a Desktop or Laptop computer via the USB port to 16 bit bridge chip which we will cover in another part of the ITF development.  The changes in the memory controller came up during a discussion for other types of interface peripherals that may be used on the IoT Core Platform.  The addition of a security ID feature as well as digital pattern recognition at the bit level to start and end a data transfer process add flexibility for future development/

For the MAX-II CPLD design we will be using Quartus 9.1sp2 and 18.1 Prime.  At the time of this writing the Windows 10 release for 19.1 was not available.  This also gives the opportunity to compare the two.. The first issue found is the printer setup.  We have an HP Designjet T120 with the roll attachment for C and D size drawings.   This works great in Quartus 9.1 especially when p[rinting from ANSI B size to ANSI C and D sizes.   When we attempted to do the same in release 18.1 the page selection is totally out of sync with the sizes.. When we migrate from 9.1 to 18.1 the C size ends uyp to be a letter size even whern the default printer is the Designjet.  The size that works is Super C/A2 for release 18.1 which appears to be an Architectual-C.  The selection for C&D size are standard ANSI sheets and the ARCH sizes are larger, this is not a problem for the roll paper since it cuts to size.   I will download 19.1 for windows when it is available and runs some test on it for compatibility.   

OK, the CPLD#2 first pass is shown below in FIgure 20.2  and we find that it is possible to fit a lot of the control for the memory transfer into CPLD2 adding the extra features that gives us a 16 bit logic analyzer type memory buffer device as well as a other features for a programmed control 16 bit test fixture that includes a DMA control feature for CPLD #1.  

As a design preference it is a good idea to do a preliminary pin assignment layout of the chip to get a feel of how the PCB will handle the traces.  Pin assignment does effect the timing due to the internal matrix propagation times.   We have learned over the years that a good portion of system integration problems arise due to propagation delays and some type of timing problems with the interconnects of FPGA's, CPLD.s matrix and associated support IC's.  A preliminary layout and pin assignment will show the first pass at the propagation delays inside the CPLD / FPGA which gives the opportunity to change the design to accommodate the performance requirements.  There are ways to work around matrix timing issues and if we run into to them during development we will present them.  One of the ways is to use the next size up on the CPLD part number that has more Logic Elements and Pins if available.  These chips have a larger internal connection matrix and will allow more flexible optimization and shorter propagation delays.

Figure 20.2   CPLD #2  Design

Creating CPLD Pin Assignment Templates
OK, for the first time assigning pins for FPGA's and CPLD's my preference is to use a spreadsheet model that identifies the fixed pins then fill in the blanks.  All programmable Logic IC from all of the manufacturers have their own fixed pin assignments so this is a critical strategy to insure that the assignments do not conflict with fixed pins.  Below is the template for the MAX-II 1270 LE 144 TQFP model that we will be using here.  The design only uses about 50% of the Logic Units, however this allows for future assignments.  There is only a few spare pins, however we added an additional 16 pin input port just to make it easier if future modifications require more I/O pins.   Figure 20.3 and Figure 20.4 shows the blank spreadsheet pin assignments sued by number and by name.  There are a few signal names left in since we have performed similar tasks on several designs over the years.  You can download the Xcell spreadsheet and are free to use it.  The PCB schematic capture and footprints will be available when we get to that section of the series.  Click on each spreadsheet to see the assignments for the first pass of the CPLD.

Figure 20.3  CPLD #2  MAX-II Pin Assignment by Number Design Template

Figure 20.4 CPLD #2  MAX-II Pin Assignment by Name Design Template

The file in Quartus the holds the pin assignments is a simple text file that can be opened by any text editor.  For this design it is "" and contains helpful information on how the unused pins and the I/O pins should be connected.  The file is organized by Pin Number 1-144 so it would be more efficient to fill in the By number spreadsheet first then fill in the by name template.  For the by name template I just input a clean spreadsheet and input the text file skipping all the previous lines up to pin one of the assignments.  Sorting them by pin name insures that all the pins are assigned.  Then just cut and past the name grouped into the By Name template spreadsheet.   The spreadsheet template for grouping the pins by name allows the designer to organize the layout of the PCB to fit the pin assignments and allow pin swapping to make the layout traces easier to route.

How to Obtain a Finished ITF:
Our plans when the ITF is finished, is to offer an ITF to the public that has many more features than the one being developed for this presentation.  We already have completed two different PoD products to get ready for manufacturing and offering custom development for contract manufacturing companies and the entrepreneur small company that want to setup a development test base for future and present development contracts.  Please use the BASIL Networks Contact Form to be put on a mailing list when we are ready to supply the manufacturing prints if you are interested in purchasing the entire system manufactured and tested.


OK, this is a lot to present in a single part as with most of the parts of this series as we dive deeper into the designs.  This update to the ITF section adds a single channel DMA controller as well as a Digital Logic Analyse for monitoring CPU BUS timing.  This becomes a very useful reuse design since not all designs will survive the reuse environment as we mentioned previously, only about 5% will be a true total Plug'N'Play reuse.  Experience has shown that FPGA and CPLD designs that incorporate the simplest of modifications have the risk of reduced performance, it is the nature of the beast.  We selected the larger of the MAX-II Logic Units to allow optimization and future additions if required.

The next part of this series will be addressing the timing for this CPLD #2.  The pin assignments will most likely change when we get into the PCB layout and we will come back to the timing performance as we change the pin assignment for a clean PCB layout.

CPLD#1 will cover all the serial hardware protocols we will be adding to the ITF.  The main serial protocols will be a very high speed serial protocol to address the various serial A/D converters and other serial sensing interface IC's.  We will be considering adding a TCP/IP Ethernet controller for the standard interface to the desktop or laptop or internal LAN network.  

Changing poor engineering habits are difficult however not impossible to correct.   Humans are very flexible they all have the ability of learning anything with applied effort, the only impasse is the mind set that if negative will defeat any attempt to grow and instill fear of learning.  The key is to acknowledge the initial behavior, no it will not change overnight - it took a while to become rooted.  Bringing the development behavior to the surface and acknowledging the behavior is the first step in this series to bring the development process to a winning level.   What this series will present by the successful development mind set to complete a Core IoT Platform development process as a winning process to insure success in any project development taken on.

BASIL Networks will be developing educational class room video modules to discuss engineering and project management principles by active example with hardware, software and lab experiments as we continue on with the series.  All hardware and software designed during this series will be available through our on-line video tutorials along with the class materials.

As the series progresses the author, Sal Tuzzo will be available for discussion through the BASIL Networks Contact Form for those that want to apply this series to conduct their own experiments.  I will always be appreciative for the private comments sent through the contact form for suggestions and advice during the development of this series.  This is a growing opportunity for everyone entering into product development as well as a great review for us "well seasoned" in the field to just refresh our human DRAM.

It is recommended for those that have specific questions to use the BASIL Networks Contact Form to separate them from getting lost in the general comments for each blog presentation.  For all specific design request or contracts please feel free to contact us.

Part 21+ Preliminary Outline"Design the ITF: -Continued

Reference Links:

ITF Selected Components

MAX-II EPM1270T144C5  Pin Assignment Template

BOM Spreadsheet and Component datasheets ZIP file

PGA281 Programmable gain Amplifier Datasheet
IS66WVE4M16EBLL 64Mbit (4M x16) Pseudo SRAM Datasheet
Alliance Memory AS1C8M16PL 128Mbit (8Meg x16) Pseudo SRAM

Intel®/Altera® Quartus Download 9.1 sp2 from Archives
Intel®/Altera® Quartus Lite 18.x Download

Requirements Traceability Matrix  (RTM)
Project Management
Mezzanine Board

The majority of Internet scheme and protocol information are from a few open public information sources on the net, IETF (Internet Engineering Task Force) RFC's that explain details on the application of the protocols used for both IPv4 and IPv6 as well as experimental protocols for the next generation Internet and the Network Sorcery web site.  The remaining of this series on the IoT platform will be from BASIL Networks MDM (Modular Design Methodology) applied with the Socratic teaching method.   Thank You - expand your horizon- Sal Tuzzo

Network Sorcery:
The Internet Engineering task Force: IETF - RFC references

Memory Segmentation
The Memory Management Unit (MMU)
Virtual Address Space
Virtual Addresses and Page Tables
Extended Memory

Previous Part 19 IoT Core Platform - Peripheral I/O Development - Peripheral Device Real World Testing -Continued(June 17, 2019)

Next Part 21 IoT Core Platform - Peripheral I/O Development - Peripheral Device Real World Testing -Continued(Mar 23rd, 2020)



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