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diff --git a/_site/feed.xml b/_site/feed.xml index f7141cf..1d1e03e 100644 --- a/_site/feed.xml +++ b/_site/feed.xml @@ -1 +1 @@ -<?xml version="1.0" encoding="utf-8"?><feed xmlns="http://www.w3.org/2005/Atom" ><generator uri="https://jekyllrb.com/" version="4.4.1">Jekyll</generator><link href="/feed.xml" rel="self" type="application/atom+xml" /><link href="/" rel="alternate" type="text/html" /><updated>2025-12-07T17:58:17+08:00</updated><id>/feed.xml</id><title type="html">ASCIIMX | Archive</title><author><name>Wickramage Don Sadeep Madurange</name></author><entry><title type="html">How I manage Suckless software packages</title><link href="/archive/suckless-software/" rel="alternate" type="text/html" title="How I manage Suckless software packages" /><published>2025-11-30T00:00:00+08:00</published><updated>2025-11-30T00:00:00+08:00</updated><id>/archive/suckless-software</id><author><name>Wickramage Don Sadeep Madurange</name></author><summary type="html"><![CDATA[Since suckless software requires users to modify the source code and recompile to customize, I need a way to maintain patches over the long term while retaining the ability to upgrade the software as new versions are released.]]></summary></entry><entry><title type="html">Neo4J A* search</title><link href="/archive/neo4j-a-star-search/" rel="alternate" type="text/html" title="Neo4J A* search" /><published>2025-09-14T00:00:00+08:00</published><updated>2025-09-14T00:00:00+08:00</updated><id>/archive/neo4j-a-star-search</id><author><name>Wickramage Don Sadeep Madurange</name></author><summary type="html"><![CDATA[Back in 2018, we used Neo4J graph database to track the movement of marine vessels. We were interested in the shortest path a ship could take through a network of about 13,000 route points. Algorithms based on graph theory, such as A* search, provide optimal solutions to such problems. In other words, the set of route points lends itself well to a model based on graphs.]]></summary></entry><entry><title type="html">MOSFETs as electronic switches</title><link href="/archive/mosfet-switches/" rel="alternate" type="text/html" title="MOSFETs as electronic switches" /><published>2025-06-22T00:00:00+08:00</published><updated>2025-06-22T00:00:00+08:00</updated><id>/archive/mosfet-switches</id><author><name>Wickramage Don Sadeep Madurange</name></author><summary type="html"><![CDATA[Recently, I needed a low-power circuit for one of my battery-operated projects. Much of the system’s power savings depended on its ability to electronically switch off components, such as servos, that draw high levels of quiescent currents. My search for a solution led me to MOSFETs, transistors capable of controlling circuits operating at voltages far above their own.]]></summary></entry><entry><title type="html">How to configure ATmega328P microcontrollers to run at 3.3V and 5V</title><link href="/archive/arduino-uno/" rel="alternate" type="text/html" title="How to configure ATmega328P microcontrollers to run at 3.3V and 5V" /><published>2025-04-10T00:00:00+08:00</published><updated>2025-04-10T00:00:00+08:00</updated><id>/archive/arduino-uno</id><author><name>Wickramage Don Sadeep Madurange</name></author><summary type="html"><![CDATA[This is a quick reference for wiring up ATmega328P ICs to run at 5V and 3.3V. While the 5V configuration is common, the 3.3V configuration can be useful in low-power applications and when interfacing with parts that themselves run at 3.3V. In this guide, the 5V setup is configured with a 16MHz crystal oscillator, while the 3.3V configuration makes use of an 8MHz crystal oscillator.]]></summary></entry><entry><title type="html">How to set up ATSAM3X8E microcontrollers for bare-metal programming in C</title><link href="/archive/arduino-due/" rel="alternate" type="text/html" title="How to set up ATSAM3X8E microcontrollers for bare-metal programming in C" /><published>2024-10-05T00:00:00+08:00</published><updated>2024-10-05T00:00:00+08:00</updated><id>/archive/arduino-due</id><author><name>Wickramage Don Sadeep Madurange</name></author><summary type="html"><![CDATA[This article is a step-by-step guide for programming bare-metal ATSAM3X8E chips found on Arduino Due boards. It also includes notes on the chip’s memory layout relevant for writing linker scripts. The steps described in this article were tested on an OpenBSD workstation.]]></summary></entry></feed>
\ No newline at end of file +<?xml version="1.0" encoding="utf-8"?><feed xmlns="http://www.w3.org/2005/Atom" ><generator uri="https://jekyllrb.com/" version="4.4.1">Jekyll</generator><link href="/feed.xml" rel="self" type="application/atom+xml" /><link href="/" rel="alternate" type="text/html" /><updated>2025-12-07T18:28:47+08:00</updated><id>/feed.xml</id><title type="html">ASCIIMX | Archive</title><author><name>Wickramage Don Sadeep Madurange</name></author><entry><title type="html">How I manage Suckless software packages</title><link href="/archive/suckless-software/" rel="alternate" type="text/html" title="How I manage Suckless software packages" /><published>2025-11-30T00:00:00+08:00</published><updated>2025-11-30T00:00:00+08:00</updated><id>/archive/suckless-software</id><author><name>Wickramage Don Sadeep Madurange</name></author><summary type="html"><![CDATA[Since suckless software requires users to modify the source code and recompile to customize, I need a way to maintain patches over the long term while retaining the ability to upgrade the software as new versions are released.]]></summary></entry><entry><title type="html">Neo4J A* search</title><link href="/archive/neo4j-a-star-search/" rel="alternate" type="text/html" title="Neo4J A* search" /><published>2025-09-14T00:00:00+08:00</published><updated>2025-09-14T00:00:00+08:00</updated><id>/archive/neo4j-a-star-search</id><author><name>Wickramage Don Sadeep Madurange</name></author><summary type="html"><![CDATA[Back in 2018, we used Neo4J graph database to track the movement of marine vessels. We were interested in the shortest path a ship could take through a network of about 13,000 route points. Algorithms based on graph theory, such as A* search, provide optimal solutions to such problems. In other words, the set of route points lends itself well to a model based on graphs.]]></summary></entry><entry><title type="html">MOSFETs as electronic switches</title><link href="/archive/mosfet-switches/" rel="alternate" type="text/html" title="MOSFETs as electronic switches" /><published>2025-06-22T00:00:00+08:00</published><updated>2025-06-22T00:00:00+08:00</updated><id>/archive/mosfet-switches</id><author><name>Wickramage Don Sadeep Madurange</name></author><summary type="html"><![CDATA[Recently, I needed a low-power circuit for one of my battery-operated projects. Much of the system’s power savings depended on its ability to electronically switch off components, such as servos, that draw high levels of quiescent currents. My search for a solution led me to MOSFETs, transistors capable of controlling circuits operating at voltages far above their own.]]></summary></entry><entry><title type="html">How to configure ATmega328P microcontrollers to run at 3.3V and 5V</title><link href="/archive/arduino-uno/" rel="alternate" type="text/html" title="How to configure ATmega328P microcontrollers to run at 3.3V and 5V" /><published>2025-04-10T00:00:00+08:00</published><updated>2025-04-10T00:00:00+08:00</updated><id>/archive/arduino-uno</id><author><name>Wickramage Don Sadeep Madurange</name></author><summary type="html"><![CDATA[This is a quick reference for wiring up ATmega328P ICs to run at 5V and 3.3V. While the 5V configuration is common, the 3.3V configuration can be useful in low-power applications and when interfacing with parts that themselves run at 3.3V. In this guide, the 5V setup is configured with a 16MHz crystal oscillator, while the 3.3V configuration makes use of an 8MHz crystal oscillator.]]></summary></entry><entry><title type="html">How to set up ATSAM3X8E microcontrollers for bare-metal programming in C</title><link href="/archive/arduino-due/" rel="alternate" type="text/html" title="How to set up ATSAM3X8E microcontrollers for bare-metal programming in C" /><published>2024-10-05T00:00:00+08:00</published><updated>2024-10-05T00:00:00+08:00</updated><id>/archive/arduino-due</id><author><name>Wickramage Don Sadeep Madurange</name></author><summary type="html"><![CDATA[This article is a step-by-step guide for programming bare-metal ATSAM3X8E chips found on Arduino Due boards. It also includes notes on the chip’s memory layout relevant for writing linker scripts. The steps described in this article were tested on an OpenBSD workstation.]]></summary></entry></feed>
\ No newline at end of file diff --git a/_site/posts.xml b/_site/posts.xml index b37a595..88c0c52 100644 --- a/_site/posts.xml +++ b/_site/posts.xml @@ -1 +1 @@ -<?xml version="1.0" encoding="utf-8"?><feed xmlns="http://www.w3.org/2005/Atom" ><generator uri="https://jekyllrb.com/" version="4.4.1">Jekyll</generator><link href="/posts.xml" rel="self" type="application/atom+xml" /><link href="/" rel="alternate" type="text/html" /><updated>2025-12-07T17:58:17+08:00</updated><id>/posts.xml</id><title type="html">ASCIIMX</title><author><name>Wickramage Don Sadeep Madurange</name></author></feed>
\ No newline at end of file +<?xml version="1.0" encoding="utf-8"?><feed xmlns="http://www.w3.org/2005/Atom" ><generator uri="https://jekyllrb.com/" version="4.4.1">Jekyll</generator><link href="/posts.xml" rel="self" type="application/atom+xml" /><link href="/" rel="alternate" type="text/html" /><updated>2025-12-07T18:28:47+08:00</updated><id>/posts.xml</id><title type="html">ASCIIMX</title><author><name>Wickramage Don Sadeep Madurange</name></author></feed>
\ No newline at end of file diff --git a/_site/projects/fpm-door-lock/index.html b/_site/projects/fpm-door-lock/index.html index 96b1d2e..8557376 100644 --- a/_site/projects/fpm-door-lock/index.html +++ b/_site/projects/fpm-door-lock/index.html @@ -60,12 +60,12 @@ attached to the interior door knob. The MCU must be installed at the back of the door to prevent unauthorized users from tampering with it.</p> <p>When no one is interacting with the lock, the MCU is in deep sleep. The sensor -and the servo each draw 13.8 mA and 4.6 mA of quiescent currents. To prevent -this idle current draw, the MCU employs MOSFETs to cut off power to them before +and the servo each draw 13.8mA and 4.6mA of quiescent currents. To prevent this +idle current draw, the MCU employs MOSFETs to cut off power to them before entering deep sleep. Doing so is crucial for conserving the battery.</p> <p>Without power, the sensor remains in a low-power state, drawing approximately -2.9 μA through a separate power rail. When a finger comes into contact with the +2.9μA through a separate power rail. When a finger comes into contact with the sensor, the sensor triggers a pin change interrupt, waking up the MCU. The MCU activates a MOSFET, which in turn activates the sensor. Over UART, the MCU unlocks the sensor and issues commands to scan and match the fingerprint.</p> @@ -95,7 +95,7 @@ page.</p> <h2 id="the-pcb">The PCB</h2> <p>For this project, I designed a custom PCB and had it fabricated by JLCPCB. Like -the software, the circuit is chiefly concerned with optimizing power +the software, the circuit is primarily concerned with optimizing power consumption and extending battery life.</p> <table style="border: none; width: 100%"> @@ -114,33 +114,32 @@ consumption and extending battery life.</p> </tr> </table> -<p>To that end, the principal components of the circuit are the 2N7000 and +<p>Consequently, the principal components of the circuit are the 2N7000 and NDP6020P field-effect transistors. They switch power electronically to the servo and the fingerprint sensor, the two most power-hungry parts of the circuit. The two MP1584EN buck converters play an axial role in efficiently regulating power to the MCU and the sensor.</p> -<p>The ATmega328P typically operates at 5 V with a 16 MHz crystal oscillator. To +<p>The ATmega328P typically operates at 5V with a 16MHz crystal oscillator. To further reduce power consumption, I modified the ATmega328P’s fuses to run at -3.3 V with an 8 MHz crystal oscillator.</p> +3.3V with an 8MHz crystal oscillator.</p> <p>The bottom right area of the PCB isolates the power supply of the servo from the rest of the circuit. This shields components such as the MCU from the -servo’s high current draw, which can exceed 1 A. The IN4007 diode in slot U2 +servo’s high current draw, which can exceed 1A. The IN4007 diode in slot U2 serves as a flyback diode, protecting the MOSFET from reverse currents generated by the servo.</p> -<p>Lastly, the 56 kΩ and 10 kΩ resistors in slots R10 and R11 form a voltage -divider circuit. Its output is fed to the ADC of the MCU, which measures the -supply voltage by comparing it to the internal bandgap reference voltage.</p> +<p>Lastly, the 56kΩ and 10kΩ resistors in slots R10 and R11 form a voltage divider +circuit. Its output is fed to the ADC of the MCU, which measures the supply +voltage by comparing it to the internal bandgap reference voltage.</p> <h2 id="epilogue">Epilogue</h2> <p>This project began nearly a year ago when I attempted to unlock our door wirelessly by writing to the UART ports of two MCUs connected to inexpensive -433 MHz RF transceivers, as if there were an invisible wire between them. -Although I failed, it led me down a rabbit hole of RF communications, MOSFETs, -PCB design, and low-power circuits.</p> +433MHz RF transceivers. Although I failed, it led me down a rabbit hole of RF +communications, MOSFETs, PCB design, and low-power circuits.</p> <p>During the project, I reinvented the wheel many times. I implemented a low-level network stack using only RF modules and an 8-bit microcontroller, |