Metal detection: building the detector
Fabien Le Mentec turns a bench-validated BFO stage into a field-ready metal detector using scavenged parts and straightforward fabrication. He moves the circuit from breadboard to a through-hole prototyping PCB, swaps the Arduino Nano for a lower-power Mini, and builds an ABS control box with buttons and a buzzer. The build uses a 2S LiPo pack with a 5V LDO and a nonmagnetic coil mount, with practical notes on tradeoffs and safety.
Metal detection: beat frequency oscillator
Plan Introduction Theory Electronics Software Tests ReferencesNext part: building the detector 1. IntroductionThis article discusses the implementation of a beat frequency oscillator (BFO) stage for metal detector. While they are mentioned here and there, the article does not detail other important electronic stages such as the power supply, and user interface, the coil or the detector frame. I may write other articles on these topics, and other detection methods.Before...
An absolute position encoder VHDL core
In this article, Fabien Le Mentec explains how to implement a unique VHDL core addressing absolute position encoder interfaces. He reviews existing instruments in use or being developed and considers their specific requirements. He also looks for details in current implementations and considers the projects to come so that the implementation can be designed to be extensible. The VHDL core dubbed absenc features both ENDAT, BISS and SSI interface. Due to its architecture, new interfaces are easily added. Also, the 3 interfaces can be enabled at synthesis while 1 is selected at runtime. As much as possible, resources common to the different interfaces are shared (counters, comparators…).
Handling latency in data acquisition systems
In recent projects, I found myself working with data acquisition systems. For instance: PCIe/10GbE readouts for 2D XRay detectors (RASHPA slides, RASHPA paper) instruments mixing 1D signal acquisition and triggering, microcontroller based system for audio transmission: (NRF spearker)
Improving the Reload2 active load
IntroductionWith another colleague at work, we are currently developing an electronic board that will eventually be powered over Ethernet. To gain more experience with this technology, we prototyped a standalone power supply stage.
We want to test this stage with different load profiles. While we already have professional grade active loads at work, I had previously read about the Reload2 product from Arachnidlabs, a low cost active load sold on Hackaday:
OOKLONE: a cheap RF 433.92MHz OOK frame cloner
Fabien Le Mentec built a pocket device that listens to and clones 433.92MHz OOK frames, automating the tedious reverse engineering of cheap wireless outlets. The prototype uses a Moteino with an RFM69 to sample demodulated OOK data, stores pulse durations in SRAM, and replays frames; the code and hardware notes are available on GitHub along with limitations and next steps.
Reverse engineering wireless wall outlets
Fabien Le Mentec reverse engineers a cheap set of wireless wall outlets to add them to his BANO home automation while avoiding uncertified mains hardware. He uses PCB inspection to identify a Holtek MCU and RF83C, captures 433.92 MHz OOK signals with an RTL-SDR and ookdump, then replays commands using an RFM22 in direct mode controlled by an ATmega328P. The post explains frame structure and links to a working GitHub implementation.
A wireless door monitor based on the BANO framework
Fabien Le Mentec built a battery-powered wireless door monitor and a reusable node framework called BANO to monitor doors across seven floors without wired links. The post highlights BANO's 17-byte key,value protocol, the node runtime that enables wake-on-interrupt low-power operation, and practical RF choices like the NRF905 plus a 330 µF cap to handle coin-cell transmission peaks. It includes source, PCB, and base station notes.
Using the C language to program the am335x PRU
Assembly-language PRU development is tedious and error prone, so Fabien Le Mentec shows how to use TI's PRU C toolchain to simplify the workflow. He walks through installing the CGT package, integrating the compiler with a modified prussdrv loader to honor the _c_int00 start symbol, and provides a BeagleBone Black example with build scripts and sources on GitHub. The post also covers inline assembly constraints and code-size tradeoffs.
Using the Beaglebone PRU to achieve realtime at low cost
Fabien Le Mentec shows how the BeagleBone Black's PRU coprocessors can run hard realtime control loops, removing the need for an FPGA or dedicated microcontroller. He walks through Linux setup, device tree enabling, assembler and loader tools, and a timer example that reads ADCs and drives PWM from PRU code. The post highlights community SDKs and a recent TI Code Composer Studio option for C-based PRU development.
Using the Beaglebone PRU to achieve realtime at low cost
Fabien Le Mentec shows how the BeagleBone Black's PRU coprocessors can run hard realtime control loops, removing the need for an FPGA or dedicated microcontroller. He walks through Linux setup, device tree enabling, assembler and loader tools, and a timer example that reads ADCs and drives PWM from PRU code. The post highlights community SDKs and a recent TI Code Composer Studio option for C-based PRU development.
Using the C language to program the am335x PRU
Assembly-language PRU development is tedious and error prone, so Fabien Le Mentec shows how to use TI's PRU C toolchain to simplify the workflow. He walks through installing the CGT package, integrating the compiler with a modified prussdrv loader to honor the _c_int00 start symbol, and provides a BeagleBone Black example with build scripts and sources on GitHub. The post also covers inline assembly constraints and code-size tradeoffs.
C Programming Techniques: Function Call Inlining
Fabien Le Mentec shows how you can keep clean C interfaces while recovering the cycles lost to function call overhead. The post demonstrates static inline and header inclusion techniques, then compares generated ARM assembly for an inlined versus non inlined bit test. Read it to see concrete assembly differences, compiler hints, and the practical trade off between speed and code size on embedded targets.
Metal detection: building the detector
Fabien Le Mentec turns a bench-validated BFO stage into a field-ready metal detector using scavenged parts and straightforward fabrication. He moves the circuit from breadboard to a through-hole prototyping PCB, swaps the Arduino Nano for a lower-power Mini, and builds an ABS control box with buttons and a buzzer. The build uses a 2S LiPo pack with a 5V LDO and a nonmagnetic coil mount, with practical notes on tradeoffs and safety.
Metal detection: beat frequency oscillator
Plan Introduction Theory Electronics Software Tests ReferencesNext part: building the detector 1. IntroductionThis article discusses the implementation of a beat frequency oscillator (BFO) stage for metal detector. While they are mentioned here and there, the article does not detail other important electronic stages such as the power supply, and user interface, the coil or the detector frame. I may write other articles on these topics, and other detection methods.Before...
Reverse engineering wireless wall outlets
Fabien Le Mentec reverse engineers a cheap set of wireless wall outlets to add them to his BANO home automation while avoiding uncertified mains hardware. He uses PCB inspection to identify a Holtek MCU and RF83C, captures 433.92 MHz OOK signals with an RTL-SDR and ookdump, then replays commands using an RFM22 in direct mode controlled by an ATmega328P. The post explains frame structure and links to a working GitHub implementation.
Interfacing LINUX with microcontrollers
Fabien presents a practical pattern: put Internet- facing logic on a Linux board and keep time-critical I/O on a microcontroller, using a Raspberry Pi and a Teensy 3.0. He introduces MASL, a reusable userspace library that hides master-slave details and shows how to use userspace SPI, sysfs GPIO and epoll for programming, reset and event-driven signaling with working code examples.
Using a RTLSDR dongle to validate NRF905 configuration
I am currently working on a system to monitor the garage door status from my flat. Both places are 7 floors apart, and I need to send the data wirelessly. I chose to operate on the 433MHz carrier, and I ordered 2 PTR8000 modules: http://www.electrodragon.com/w/NRF905_Transceiver_433MHz-Wireless_ModuleThe PTR8000 is based on the dual band sub 1GHz NRF905 chipset from NORDICSEMI: http://www.nordicsemi.com/eng/Products/Sub-1-GHz-RF/nRF905I...OOKLONE: a cheap RF 433.92MHz OOK frame cloner
Fabien Le Mentec built a pocket device that listens to and clones 433.92MHz OOK frames, automating the tedious reverse engineering of cheap wireless outlets. The prototype uses a Moteino with an RFM69 to sample demodulated OOK data, stores pulse durations in SRAM, and replays frames; the code and hardware notes are available on GitHub along with limitations and next steps.
An absolute position encoder VHDL core
In this article, Fabien Le Mentec explains how to implement a unique VHDL core addressing absolute position encoder interfaces. He reviews existing instruments in use or being developed and considers their specific requirements. He also looks for details in current implementations and considers the projects to come so that the implementation can be designed to be extensible. The VHDL core dubbed absenc features both ENDAT, BISS and SSI interface. Due to its architecture, new interfaces are easily added. Also, the 3 interfaces can be enabled at synthesis while 1 is selected at runtime. As much as possible, resources common to the different interfaces are shared (counters, comparators…).
Using the Beaglebone PRU to achieve realtime at low cost
Fabien Le Mentec shows how the BeagleBone Black's PRU coprocessors can run hard realtime control loops, removing the need for an FPGA or dedicated microcontroller. He walks through Linux setup, device tree enabling, assembler and loader tools, and a timer example that reads ADCs and drives PWM from PRU code. The post highlights community SDKs and a recent TI Code Composer Studio option for C-based PRU development.
Using the C language to program the am335x PRU
Assembly-language PRU development is tedious and error prone, so Fabien Le Mentec shows how to use TI's PRU C toolchain to simplify the workflow. He walks through installing the CGT package, integrating the compiler with a modified prussdrv loader to honor the _c_int00 start symbol, and provides a BeagleBone Black example with build scripts and sources on GitHub. The post also covers inline assembly constraints and code-size tradeoffs.
C Programming Techniques: Function Call Inlining
Fabien Le Mentec shows how you can keep clean C interfaces while recovering the cycles lost to function call overhead. The post demonstrates static inline and header inclusion techniques, then compares generated ARM assembly for an inlined versus non inlined bit test. Read it to see concrete assembly differences, compiler hints, and the practical trade off between speed and code size on embedded targets.
Using a RTLSDR dongle to validate NRF905 configuration
I am currently working on a system to monitor the garage door status from my flat. Both places are 7 floors apart, and I need to send the data wirelessly. I chose to operate on the 433MHz carrier, and I ordered 2 PTR8000 modules: http://www.electrodragon.com/w/NRF905_Transceiver_433MHz-Wireless_ModuleThe PTR8000 is based on the dual band sub 1GHz NRF905 chipset from NORDICSEMI: http://www.nordicsemi.com/eng/Products/Sub-1-GHz-RF/nRF905I...OOKLONE: a cheap RF 433.92MHz OOK frame cloner
Fabien Le Mentec built a pocket device that listens to and clones 433.92MHz OOK frames, automating the tedious reverse engineering of cheap wireless outlets. The prototype uses a Moteino with an RFM69 to sample demodulated OOK data, stores pulse durations in SRAM, and replays frames; the code and hardware notes are available on GitHub along with limitations and next steps.
Interfacing LINUX with microcontrollers
Fabien presents a practical pattern: put Internet- facing logic on a Linux board and keep time-critical I/O on a microcontroller, using a Raspberry Pi and a Teensy 3.0. He introduces MASL, a reusable userspace library that hides master-slave details and shows how to use userspace SPI, sysfs GPIO and epoll for programming, reset and event-driven signaling with working code examples.
Metal detection: beat frequency oscillator
Plan Introduction Theory Electronics Software Tests ReferencesNext part: building the detector 1. IntroductionThis article discusses the implementation of a beat frequency oscillator (BFO) stage for metal detector. While they are mentioned here and there, the article does not detail other important electronic stages such as the power supply, and user interface, the coil or the detector frame. I may write other articles on these topics, and other detection methods.Before...
A wireless door monitor based on the BANO framework
Fabien Le Mentec built a battery-powered wireless door monitor and a reusable node framework called BANO to monitor doors across seven floors without wired links. The post highlights BANO's 17-byte key,value protocol, the node runtime that enables wake-on-interrupt low-power operation, and practical RF choices like the NRF905 plus a 330 µF cap to handle coin-cell transmission peaks. It includes source, PCB, and base station notes.
Reverse engineering wireless wall outlets
Fabien Le Mentec reverse engineers a cheap set of wireless wall outlets to add them to his BANO home automation while avoiding uncertified mains hardware. He uses PCB inspection to identify a Holtek MCU and RF83C, captures 433.92 MHz OOK signals with an RTL-SDR and ookdump, then replays commands using an RFM22 in direct mode controlled by an ATmega328P. The post explains frame structure and links to a working GitHub implementation.
[ C Programming Techniques: integer type optimization ]
Microcontroller integer width can make or break ISR performance on AVR. In this post Fabien Le Mentec compares using uint8_t versus unsigned int for a timer counter on an ATmega328P and shows how the smaller type cuts instruction and cycle count in the ISR. He also walks through the trade offs: reduced capacity, volatile access costs, and simple portability fixes such as uint_fast8_t or an architecture-aware typedef.
