PhD in 10 minutes

A few weeks ago Ilias Alexopoulos presented part of his PhD work on IoT performance Estimation.

Engineers involved in developing IoT either remote or not, have to deal with key parameters like power consumption, computation speed, or resources, depending on the cost function of each project.

The presenter making the introduction

The problem is to estimate the best performance according to the key project parameters of an implementation and more specifically of an algorithm with respect to different hardware. Each hardware can offer different kinds of optimizations so the combinations of each implementation involving algorithm variants and hardware optimization is unmanageable.

The framework flow
Presenting the Framework Flow

The work of this research is to establish a framework that can estimate this individual performance and provide guidance to the designer of the best hardware without the need of implementing the algorithms on any platform.

Presenting Conclusion and Challenges
Conclusion and Challenges

It is a long shot to achieve this goal, but research and progress are about challenges. Challenging methods, tools, or our limits to achieve more.

DEFEA 2023

This year gets exciting as new projects come up, and we meet interesting technology companies. This year we decided to visit DEFEA in Greece, to see the landscape of technology companies involved in the security and defense sectors.

AI Zerocaliber team in DEFEA 2023
AI Zerocaliber Team in DEFEA

It was interesting to see the different technologies demonstrated, but we also had the great pleasure to meet our friends of EM-Tech.

AI Zerocaliber and EM-Tech Selfie!

Overall our visit to DEFEA left us with good impressions along with a nice view of the technology landscape of the sector.

Building the FPGA Board

The second element of the TileSystem useful for edge processing is the FPGA board. This board interfaces tightly with the microcontroller of the system using a bus and also with the potential frontends for input or output.

As FPGAs are also hit by the component shortages in the semiconductor market, the design was based on AMD/Xilinx Spartan 6LX9 device, as this was in stock. The fact that the device is in a QFP package (as opposed to BGA) allows a less expensive PCB design with easier debugging, as all pins can be probed.

TileFPGA Board

The board was designed in less than 2 weeks and it came into our lab for verification. In order to test the board, we must connect it to our TileMCU through a backplane, and run the appropriate firmware that will load a valid configuration to the chip. A suitable test design with proper pin constraints was created.

After the assembly of the missing parts, the TileCUBE assembled with the microcontroller and the FPGA.

TileFPGA in Unconfigured State

The initial power-up lit our default LEDs (orange LED lit, means that the FPGA is unconfigured). We had to compile a test design with the updated pin-out from the Perseus CFE board to the TileFPGA. The design was placed at the SDCard. The firmware was adjusted to load this FPGA bitstream, so we can test the MCU and SDRAM interfaces.

FPGA in Configured State

After the FPGA was configured, we tested the Mini-FlexBus interface. We used the debugger to inspect the register area and confirmed the visibility (read operations). Registers were also written to verify that the interface is working as expected. We tested the LED state change (green color seen in the above photo) by changing the relevant bit in a register.

The next phase was to test the internal Block-RAMs. Initially the internal logic did not route the memories to the FlexBus interface (this was a design feature). the values seen in the memory space are 0xFFFF (due to the pull-ups inside the FPGA logic).

Block-RAM Access Enable and Test

Setting the respective enable bit in the control register the memory space can be written and the values are retained. Note that the default memory values seen by the Bus are 0xFFFF, but as soon as we step an instruction after the memory enable bit is set, the debugger refreshes the memory contents that are now zero.

These tests concluded the basic Mini-FlexBus interface and the internal Block-RAM interfaces. In the next post, we will test the SDRAM.

TileMCU FirmWare

The TileMCU Coldfire version completed its first set of tests, completing the integration of the USB stack from Freescale/NXP to the RTOS.

Using POSIX-style drivers (or any standard way of interfacing) we were able to replace the Serial input of the Command Line Interpreter (CLI) with the USB one.

The code change was a very simple one, replacing just the name of the driver.

Code Excerpt of Selectable Driver

So essentially we define a preprocessor macro with the name of the required driver. As both the USB-CDC and the Serial driver have the same API, they can be interchanged at will.

Here we do this on compile time. Another option would be to mirror both interfaces and have at the same time either USB or Serial I/O. For now, we decided to keep it simple as we have to test the rest of the boards to complete our hydrophone system.

USB Enumeration

At first, the USB enumeration was checked to see if the basics worked. Then we opened with our terminal the respective virtual serial port and start testing the CLI.

CLI Test Example

The CLI was tested to ensure that there were no problems using it and testing some other functions like the SD Card mounting and FAT access.

As we have completed the first phase of testing we can move on to the next boards for testing. We will return back to this board to test the Mini-FlexBus interface with the FPGA.

Building the MCU Board

The concept of a flexible and scalable system is a usual requirement for many applications. We initially started this flexibility by integrating MCUs with FPGAs on the same board. These created the initial Perseus Family Platform boards that we used for the development of applications.

Later on, during the MARI-Sense project, it was evident that the form factor should be more compact while features should be more selectable. In that spirit, we created the TileCubeTM System. Toward implementation of the platform, we designed boards for a complete hydrophone system, including microcontroller boards, FPGAs, and analog front-ends.

Due to component shortages, we were forced to design and use existing parts that we had in stock for the boards. Some boards are already designed with higher-performance microcontrollers waiting to have the new parts in hand. The flexibility of the system allows using different MCU boards in a backward-compatible manner.

The first board of the Tile System is the microcontroller. This version is based on Coldfire MCF52258.

CAD Model of TileMCU_CF

Soon the boards arrived to our lab and we started the board bring-up process and testing.

Actual TileMCU_CF Sample

We confirmed the firmware configuration changes to support the new I/O assignment and installed COFILOS to test the system. Soon we had a system working with serial communications, command line interface (CLI), etc.

First Light (Blinking) of Firmware

Next steps were to verify the SDCard interface and we tried the first time the Digilent Digital Discovery tool for capturing SPI data.

SDCard SPI Checks

Finally, we confirmed the proper operation of the SDCard and through the CLI we sneaked into the first sector of the device.

SDCard First Sector

Initially, the same board was designed with another microcontroller in mind, but due to component shortages, we had to re-spin the board with Coldfire. It was a fast race to quickly redesign the board, build it and make it work, within our deadlines. This gave us the motivation to complete the rest of the boards with the same speed, so we can see the full system ready and explore the potential of the system.

If you are interested in this platform feel free to contact us.

Embedded Online Conference 2022

This year we will present how to create heterogeneous embedded platforms using Coldfire or Kinetis microcontrollers and FPGAs. We will touch on some interesting points related to such implementations.

EOC2022 Compact Heterogenous Computing Platforms
Compact Heterogeneous Computing Platforms

We hope that you will enjoy this talk and the small demonstration of integration between MCUs and FPGAs.

Edge Computing for Maritime IoT @BTS

“Breaking The Surface 2021” event was very successful and interesting. Many scientists of all over thw world presented the latest developments in archeology, marine robotics, sensing and other applications.

We were honored to present our maritime IoT platforms and share our knowledge on embedded system design and hardware acceleration.

BTS Tutorial

We discussed things like power management, showcasing the power management board for the MARI-Sense ASV, hardware acceleration, and versatile heterogeneous platforms.

Ready for the Tutorial with all Hardware
Power Management GUI
Power Management GUI

For more details see the following link.

Tutorial 2 Intro – AI Zerocaliber: Edge Computing for Maritime IoT – Breaking the Surface (


For anyone attending the multi-disciplinary conference of “Breaking The Surface 2021” event, I will be giving a tutorial on multiple topics on using embedded computing in maritime applications.

Hydrophone Processing System
Hydrophone Processing System

For more details see the following link.

Tutorial 2 Intro – AI Zerocaliber: Edge Computing for Maritime IoT – Breaking the Surface (

EMD2021: Smart-Float

European Maritime Day in Cyprus 2021

In Larnaca, 17-21 June 2021, there was this great event, where we had the opportunity to show our latest developments for the MARI-Sense project in collaboration with CMMI.

On Sunday 21 of June, at Europe Square CMMI and MARI-Sense exhibited various vehicles for maritime applications.

The underwater remote controlled robotic vehicle (ROV) has the capability to provide underwater images or use manipulators to perform delicate actions as required for research or other applications.

EMD2021: CMMI ROV Exhibit
Front view of the CMMI’s Robotic Underwater Vehicle

A smart-boat is also developed named “Kerkouros” from the ancient Cyprus ship with oars. “Kerkouros” is under development with the ultimate goal to be an autonomous surface vehicle; a challenging task for the development team.

EMD2021: Smart-Boat "Kerkouros" Exhibit
Prototype of Autonomous Smart Boat Developed at CMMI

For helping development efforts for the MARI-Sense project another platform was exhibited, the Smart-Float. The Smart Float will be used as a technology evaluation platform, where different sensors will be mounted and tested along with radio links, like WiFi, LoRa, thrusters, maneuverability, or other technologies and embedded systems. This platform will help improve the know-how of the team and will lead to new improved models. The main advantage of this platform is its low-cost and large transport capacity (more than 20Kgr net for payload). The team is already thinking of other potential applications where this platform can be used effectively. AI Zerocaliber Ltd is involved with this platform from the concept phases till now, helping with the hull and system design, and specific embedded components.

EMD2021: Smart-Float
Smart-Float Platform Shown During EMD-2021 Event

For more information on the MARI-Sense project you may check the project’s website.

MARI-Sens Logo

A quick view of the MSO44 in action

Going from TDS3012 to MSO44

In the past 18 years I have been using a 100MHz two channel oscilloscope TDS3012B from Tektronix, which was using the new at the time Digital Phosphor technology (DPO). With a bandwidth of 100MHz back then it was sufficient for embedded design and debugging. I was missing the serial decode capabilities, but I was able to program a Python script for this purpose. For more information see my article in CodeProject.

Debugging a system with Atmel AVR and Xilinx Spartan (5K gates) device
Debugging a system with Atmel AVR and Xilinx Spartan (5K gates) device

Back then it served me very well, although in some cases I would like to have four channels to help me resolve some problems. Not a showstopper anyway, I have been used to have less than ideal equipment. Recently the ethernet interface failed and this reduced the capabilities of my old instrument. In addition, my newer embedded boards started using SDRAMs or HDMI and the signal bandwidth of the scope was below my debugging needs. I had to guess the clock phase on my FPGA-SDRAM interface looking to sinewaves on my scope and trying an educated guess for the correct PLL phase delay. Fortunately, the first guess for the phase difference was correct, so this went smooth and my SDRAM worked fine without much hassle. The old floppy also prohibited data transfers or firmware updates.

According to Altium Designer research about new PCB designs, the trend is to go to boards with 500MHz. Although this might seem a little high for microcontrollers, I started feeling the pressure to go above 100MHz and for some newer serial protocols even higher. I had a SDRAM 133MHZ, but DDR starts to be more mainstream even for embedded systems. Purchasing a scope is an investment for the next 10 years and hence the capabilities should match at a great extent the future requirements. If we go to platform FPGA boards, like Ultra96 or PynQ, there are serial interfaces that can achieve clock frequencies above the 100MHz limit. So, I thought that my next scope should be certainly at the range of 350MHz. So, I decided to move on to a new scope like the MSO44 from Tektronix. A big thanks to Vector Technologies which helped me with my decision. In the next paragraphs, I will present some of the features from my preliminary tests of the new instrument. I still keep my TDS3012B around, as a secondary instrument for field work.

Last days of my TDS3012B Sitting on my lab, while expecting the MSO44.
Last days of my TDS3012B Sitting on my lab, while expecting the MSO44.

Thank you TDS3012B for your service all these years!!


The new instrument has four analog channels. This alone is an important upgrade. I can check full SPI bus with enables and clocks or combination of analog and digital lines on my board. A rarely used more than 4 channels unless I had to deal with a digital parallel bus.  Even then looking at some control signals and one of the data could give you an idea of the situation. Nevertheless, an analog probe can be replaced by a digital counterpart with 8-channels digital inputs and used as a logic analyzer. You lose one analog channel for this, but it is a reasonable compromise. Other vendors provide this functionality without the analog probe loss, but I do not believe or remember a case in the past that this would be an issue.

A quick view of the MSO44 in action
A quick view of the MSO44 in action

The next major upgrade is the bandwidth of 500MHz. Hey, I can check my SDRAM clock easily now… I want to check at some point my HDMI signals (at 250MHz). The 500MHz though can be used also for RF applications at 433MHz, through the spectrum analyzer feature. Really neat.

The arbitrary function generator feature is really useful as with one instrument I can also exercise my circuits. I plan to use this feature for testing the Hydrophone Analog Front End and the FPGA data capture.

I am not going to stay at the UI features most instruments in this category have recently, the large touchscreen etc. Having a large screen estate is important to view multiple signals.

One important aspect of the new generation of instruments is that they offer upgrades by license. So, you can upgrade the bandwidth or some features (more serial busses decoding etc) by purchasing them later according to your needs or projects. This provides a more viable solution where you start with some specific requirements and you can scale up the instrument according to your needs later-on.

Serial Decode

The instrument supports serial decoding of common protocols like RS232, I2C or SPI. This is useful for debugging peripherals or components to your microcontroller. To test this feature  I tried an I2C interface on one of my boards. The abundance of screen area is useful to put all the signals without too much clutter and in addition have the serial bus decoding.

Serial Bus decode of an I2C bus
Serial Bus decode of an I2C bus

Web Interface

Connectivity is important, so the instrument comes with a bunch of USB ports and an ethernet port for network. This is what I used with a web browser to mirror my MSO screen to my desktop PC. Extremely helpful if you want to control the instrument from the same place as you control your debugger. No need to turn your chair around to turn knobs.

MSO screen view on my desktop PC
MSO screen view on my desktop PC

Jitter Tests

On one of my boards, I knew that there is some jitter on my clock. So, I decided to test the DPO capabilities and look in more detail on this signal. I can see the probability of states clearly. I want to delve more on this feature in the future.

Clock Jitter seen through DPO
Clock Jitter seen through DPO

Spectrum Analyzer

Yes, many engineers would say that this is the FFT button or feature found on most of the scopes, so what’s the big deal. Well, nope. The FFT feature exists in the math menu and is not the same with the spectrum analyzer feature, which works like a spectrum analyzer. I mean you need to setup video bandwidth, resolution bandwidth and so on, as you would do in an actual spectrum analyzer. In addition, changing the time domain signal (scaling-resolution) does not affect the spectrum and vice-versa. I read about this feature on the website when looking at the specifications and I was keen to see it in action. Having worked with spectrum analyzers in the past, I got pretty familiar with the parameters. This feature exists inside the channel settings (tap on your channel and select spectrum tab). Testing this feature, I tried a remote of 433MHz. The probe was attached at the antenna signal on the receiver side.

Spectrum of a remote at 433MHz
Spectrum of a remote at 433MHz

I even went further. I have some LoRa devices working at 433MHz and wanted to confirm that this is their center frequency. As LoRa uses broadband transmission, I set-up my instrument to capture and hold the maximum level. So after a while transmitting, the spectrum started to show activity, by filling bands.

Spectrum max hold at 433MHz LoRa transmission
Spectrum max hold at 433MHz, LoRa transmission

Arbitrary Function Generator

Providing stimulus to your circuits is essential when designing and testing analog to digital converters. Applying some basic stimulus may help you check design elements and ensure that the basics work. For more thorough testing you will need a dedicated instrument. In this case the arbitrary function generator is used for the first line of defense. Here a sinc function is output and its spectrum is displayed.

Arbitrary Function Generator and Spectrum
Arbitrary Function Generator and Spectrum


I will need to spend lots of time to test every aspect of the new instrument. I am already using it in my projects, and I am getting used to it. Albeit the complexity of the functions, I can navigate around, put the right settings without hassle, giving me time and insight and let me be productive. I have a long queue of things that needs development and testing that this instrument will help me a lot.

Our laboratory is now massively upgraded and ready to win the next battles!