FPM lock journal style.

author: Sadeep Madurange <sadeep@asciimx.com> 2025-12-26 16:53:45 +0800
committer: Sadeep Madurange <sadeep@asciimx.com> 2025-12-26 21:43:43 +0800
commit: e04ce2ab6ca82d0014bec8b217215f35b436ff25 (patch)
tree: 4fdc82fb2bf46de34213cf7b2d3f1a5abed0b7be /_site/log
parent: 9b95f811472a15280e67f99c90c0013987b32ee2 (diff)
download: www-e04ce2ab6ca82d0014bec8b217215f35b436ff25.tar.gz
21 files changed, 141 insertions, 191 deletions
diff --git a/_site/log/fpm-door-lock/breadboard.jpg b/_site/log/fpm-door-lock-lp/breadboard.jpg
index 2bf47a9..2bf47a9 100644
--- a/_site/log/fpm-door-lock/breadboard.jpg
+++ b/_site/log/fpm-door-lock-lp/breadboard.jpg
diff --git a/_site/log/fpm-door-lock/footprint.png b/_site/log/fpm-door-lock-lp/footprint.png
index 5511bf1..5511bf1 100644
--- a/_site/log/fpm-door-lock/footprint.png
+++ b/_site/log/fpm-door-lock-lp/footprint.png
diff --git a/_site/log/fpm-door-lock/gerber.zip b/_site/log/fpm-door-lock-lp/gerber.zip
index 19a9d19..19a9d19 100644
--- a/_site/log/fpm-door-lock/gerber.zip
+++ b/_site/log/fpm-door-lock-lp/gerber.zip
diff --git a/_site/log/fpm-door-lock-lp/index.html b/_site/log/fpm-door-lock-lp/index.html
new file mode 100644
index 0000000..76715d7
--- /dev/null
+++ b/_site/log/fpm-door-lock-lp/index.html
@@ -0,0 +1,115 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8">
+    <title>Fingerprint door lock (LP)</title>
+
+    <head>
+  <meta charset="utf-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+  <title>Fingerprint door lock (LP)</title>
+  <link rel="stylesheet" href="/assets/css/main.css">
+  <link rel="stylesheet" href="/assets/css/skeleton.css">
+</head>
+
+
+
+  </head>
+  <body>
+
+    <div id="nav-container" class="container">
+  <ul id="navlist" class="left">
+    
+    <li >
+      <a href="/" class="link-decor-none">hme</a>
+    </li>
+    <li class="active">
+      <a href="/log/" class="link-decor-none">log</a>
+    </li>
+    <li >
+      <a href="/projects/" class="link-decor-none">poc</a>
+    </li>
+    <li >
+      <a href="/about/" class="link-decor-none">abt</a>
+    </li>
+    <li><a href="/feed.xml" class="link-decor-none">rss</a></li>
+  </ul>
+</div>
+
+
+
+    <main>
+      <div class="container">
+        <div class="container-2">
+          <h2 class="center" id="title">FINGERPRINT DOOR LOCK (LP)</h2>
+          <h6 class="center">18 AUGUST 2025</h5>
+          <br>
+          <div class="twocol justify"><p>Second iteration of the <a href="../fpm-door-lock-rf">RF door lock</a>. Old version worked
+but drew too much quiescent current. Sensor and servo pulled 13.8mA and 4.6mA
+idle. Linear regulators were a disaster. Battery didn’t last 24 hours.</p>
+
+<video style="max-width:100%;" controls="" poster="pcb.jpg">
+  <source src="video.mp4" type="video/mp4" />
+</video>
+
+<p>Redesigned the PCB completely. Tossed the RF modules and the second MCU.
+Connected R503 sensor directly to the ATmega328P. Sensor now mounts on door
+exterior, servo attaches to interior knob, MCU stays on the back to prevent
+tampering.</p>
+
+<table style="border: none; width: 100%">
+  <tr style="border: none;">
+    <td style="border: none; width: 49.9%; background-color: transparent; text-align: center;">
+      <img src="breadboard.jpg" alt="PCB" style="width: 100%" />
+    </td>
+    <td style="border: none; background-color: transparent; text-align: center;">
+      <img src="pcb1.jpg" alt="Design" style="width: 100%" />
+    </td>
+  </tr>
+  <tr style="border: none;">
+    <td colspan="2" style="border: none; background-color: transparent; text-align: center;">
+      <img src="footprint.png" alt="PCB footprint" style="width: 100%" />
+    </td>
+  </tr>
+</table>
+
+<p>PCB specs: 2-layer, 1oz copper, 0.3mm traces (1mm for power and servo). Ground
+plane on bottom layer.</p>
+
+<p>Solved idle power draw with MOSFETs. 2N7000 and NDP6020P cut power to sensor
+and servo before deep sleep. Through-hole MOSFETs that switch at 3.3V are
+getting harder to find. NDP6020P already obsolete.</p>
+
+<p>Replaced linear regulators with MP1584EN DC-DC buck converters. No RF, noise
+isn’t a big concern. Buck’s pin breakout not great–wouldn’t fit most
+commercial dev boards.</p>
+
+<p>Squeezed more power savings from the MCU by running it at 3.3V/8MHz. Combined
+with buck converters: 56% total power savings.</p>
+
+<p>Wake sequence: MCU activates sensor MOSFET, unlocks sensor over UART, scans and
+matches fingerprint. Match triggers blue LED, servo MOSFET, PWM signal to
+unlock. No match triggers red LED. MOSFETs off, back to sleep.</p>
+
+<p>Total power savings: 99.9% (30.6mA → 2.9μA). Verdict: Fixed.</p>
+
+<p>Commit:
+<a href="https://git.asciimx.com/fpm-door-lock/commit/?id=75290945b2fd84b3bc108fd46419ee478eaac3ca">7529094</a>
+| Gerber: <a href="gerber.zip">gerber.zip</a></p>
+</div>
+          <p class="post-author right">by W. D. Sadeep Madurange</p>
+        </div>
+      </div>
+    </main>
+
+    <div class="footer">
+  <div class="container">
+    <div class="twelve columns right container-2">
+      <p id="footer-text">&copy; ASCIIMX - 2025</p>
+    </div>
+  </div>
+</div>
+
+
+  </body>
+</html>
diff --git a/_site/log/fpm-door-lock/pcb.jpg b/_site/log/fpm-door-lock-lp/pcb.jpg
index fbd800b..fbd800b 100644
--- a/_site/log/fpm-door-lock/pcb.jpg
+++ b/_site/log/fpm-door-lock-lp/pcb.jpg
diff --git a/_site/log/fpm-door-lock/pcb1.jpg b/_site/log/fpm-door-lock-lp/pcb1.jpg
index 367187d..367187d 100644
--- a/_site/log/fpm-door-lock/pcb1.jpg
+++ b/_site/log/fpm-door-lock-lp/pcb1.jpg
diff --git a/_site/log/fpm-door-lock/source.tar.gz b/_site/log/fpm-door-lock-lp/source.tar.gz
index ef23422..ef23422 100644
--- a/_site/log/fpm-door-lock/source.tar.gz
+++ b/_site/log/fpm-door-lock-lp/source.tar.gz
diff --git a/_site/log/fpm-door-lock/thumb_sm.jpg b/_site/log/fpm-door-lock-lp/thumb_sm.jpg
index a8fa534..a8fa534 100644
--- a/_site/log/fpm-door-lock/thumb_sm.jpg
+++ b/_site/log/fpm-door-lock-lp/thumb_sm.jpg
diff --git a/_site/log/fpm-door-lock/video.mp4 b/_site/log/fpm-door-lock-lp/video.mp4
index a907a9b..a907a9b 100644
--- a/_site/log/fpm-door-lock/video.mp4
+++ b/_site/log/fpm-door-lock-lp/video.mp4
diff --git a/_site/log/my-first-pcb/back.jpeg b/_site/log/fpm-door-lock-rf/back.jpeg
index f458e69..f458e69 100644
--- a/_site/log/my-first-pcb/back.jpeg
+++ b/_site/log/fpm-door-lock-rf/back.jpeg
diff --git a/_site/log/my-first-pcb/back_design.jpeg b/_site/log/fpm-door-lock-rf/back_design.jpeg
index b6c0f5d..b6c0f5d 100644
--- a/_site/log/my-first-pcb/back_design.jpeg
+++ b/_site/log/fpm-door-lock-rf/back_design.jpeg
diff --git a/_site/log/my-first-pcb/front.jpeg b/_site/log/fpm-door-lock-rf/front.jpeg
index 2b2931f..2b2931f 100644
--- a/_site/log/my-first-pcb/front.jpeg
+++ b/_site/log/fpm-door-lock-rf/front.jpeg
diff --git a/_site/log/my-first-pcb/front_design.jpeg b/_site/log/fpm-door-lock-rf/front_design.jpeg
index f81f09c..f81f09c 100644
--- a/_site/log/my-first-pcb/front_design.jpeg
+++ b/_site/log/fpm-door-lock-rf/front_design.jpeg
diff --git a/_site/log/my-first-pcb/gerber_back.zip b/_site/log/fpm-door-lock-rf/gerber_back.zip
index 26659ad..26659ad 100644
--- a/_site/log/my-first-pcb/gerber_back.zip
+++ b/_site/log/fpm-door-lock-rf/gerber_back.zip
diff --git a/_site/log/my-first-pcb/gerber_front.zip b/_site/log/fpm-door-lock-rf/gerber_front.zip
index 864334e..864334e 100644
--- a/_site/log/my-first-pcb/gerber_front.zip
+++ b/_site/log/fpm-door-lock-rf/gerber_front.zip
diff --git a/_site/log/my-first-pcb/index.html b/_site/log/fpm-door-lock-rf/index.html
index 735a1da..c12d808 100644
--- a/_site/log/my-first-pcb/index.html
+++ b/_site/log/fpm-door-lock-rf/index.html
@@ -2,12 +2,12 @@
 <html>
   <head>
     <meta charset="utf-8">
-    <title>My first PCB</title>
+    <title>Fingerprint door lock (RF)</title>
 
     <head>
   <meta charset="utf-8">
   <meta name="viewport" content="width=device-width, initial-scale=1">
-  <title>My first PCB</title>
+  <title>Fingerprint door lock (RF)</title>
   <link rel="stylesheet" href="/assets/css/main.css">
   <link rel="stylesheet" href="/assets/css/skeleton.css">
 </head>
@@ -41,7 +41,7 @@
     <main>
       <div class="container">
         <div class="container-2">
-          <h2 class="center" id="title">MY FIRST PCB</h2>
+          <h2 class="center" id="title">FINGERPRINT DOOR LOCK (RF)</h2>
           <h6 class="center">26 APRIL 2025</h5>
           <br>
           <div class="twocol justify"><p>In 2023, I started tinkering with DIY electronics as a hobby. Until now, I’ve
diff --git a/_site/log/my-first-pcb/source.tar.gz b/_site/log/fpm-door-lock-rf/source.tar.gz
index c31aa22..c31aa22 100644
--- a/_site/log/my-first-pcb/source.tar.gz
+++ b/_site/log/fpm-door-lock-rf/source.tar.gz
diff --git a/_site/log/my-first-pcb/thumb_sm.jpeg b/_site/log/fpm-door-lock-rf/thumb_sm.jpeg
index c275b12..c275b12 100644
--- a/_site/log/my-first-pcb/thumb_sm.jpeg
+++ b/_site/log/fpm-door-lock-rf/thumb_sm.jpeg
diff --git a/_site/log/fpm-door-lock/index.html b/_site/log/fpm-door-lock/index.html
deleted file mode 100644
index 1460053..0000000
--- a/_site/log/fpm-door-lock/index.html
+++ /dev/null
@@ -1,168 +0,0 @@
-<!DOCTYPE html>
-<html>
-  <head>
-    <meta charset="utf-8">
-    <title>Fingerprint door lock</title>
-
-    <head>
-  <meta charset="utf-8">
-  <meta name="viewport" content="width=device-width, initial-scale=1">
-  <title>Fingerprint door lock</title>
-  <link rel="stylesheet" href="/assets/css/main.css">
-  <link rel="stylesheet" href="/assets/css/skeleton.css">
-</head>
-
-
-
-  </head>
-  <body>
-
-    <div id="nav-container" class="container">
-  <ul id="navlist" class="left">
-    
-    <li >
-      <a href="/" class="link-decor-none">hme</a>
-    </li>
-    <li class="active">
-      <a href="/log/" class="link-decor-none">log</a>
-    </li>
-    <li >
-      <a href="/projects/" class="link-decor-none">poc</a>
-    </li>
-    <li >
-      <a href="/about/" class="link-decor-none">abt</a>
-    </li>
-    <li><a href="/feed.xml" class="link-decor-none">rss</a></li>
-  </ul>
-</div>
-
-
-
-    <main>
-      <div class="container">
-        <div class="container-2">
-          <h2 class="center" id="title">FINGERPRINT DOOR LOCK</h2>
-          <h6 class="center">18 AUGUST 2025</h5>
-          <br>
-          <div class="twocol justify"><p>This project features a fingerprint door lock powered by an ATmega328P
-microcontroller.</p>
-
-<video style="max-width:100%;" controls="" poster="pcb.jpg">
-  <source src="video.mp4" type="video/mp4" />
-</video>
-
-<h2 id="overview">Overview</h2>
-
-<p>The lock comprises three subsystems: the ATmega328P microcontroller, an R503
-fingerprint sensor, and an FS5106B high-torque servo. The sensor mounted on the
-front surface of the door enables users to unlock it from the outside. The
-servo is 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 13.8mA 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
-2.9μA 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>
-
-<p>If the fingerprint matches an enrolled fingerprint, the MCU activates the blue
-LED on the sensor, turns on the MOSFET connected to the servo, and sends a PWM
-signal to the servo to unlock the door. Otherwise, the MCU activates the red
-LED on the sensor. Finally, the MCU deactivates the MOSFETS and goes back to
-sleep.</p>
-
-<h2 id="embedded-software">Embedded software</h2>
-
-<p>The embedded software, written in C, includes a driver for the sensor, servo
-control routines, and a battery monitoring system.</p>
-
-<p>In addition to controlling the sensor and the servo, the program strives to
-maintain precise control over the microcontroller’s sleep modes, as well as
-when the peripherals are activated and for how long they remain active. I
-thoroughly enjoyed writing the embedded software. There’s something magical
-about being able to alter the physical world around you by uttering a few lines
-of C code.</p>
-
-<p>The source code of the project, which includes a driver for the R503
-fingerprint sensor module, is enclosed in the tarball linked at the end of the
-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 primarily concerned with optimizing power
-consumption and extending battery life.</p>
-
-<table style="border: none; width: 100%">
-  <tr style="border: none;">
-    <td style="border: none; width: 49.9%; background-color: transparent; text-align: center;">
-      <img src="breadboard.jpg" alt="PCB" style="width: 100%" />
-    </td>
-    <td style="border: none; background-color: transparent; text-align: center;">
-      <img src="pcb1.jpg" alt="Design" style="width: 100%" />
-    </td>
-  </tr>
-  <tr style="border: none;">
-    <td colspan="2" style="border: none; background-color: transparent; text-align: center;">
-      <img src="footprint.png" alt="PCB footprint" style="width: 100%" />
-    </td>
-  </tr>
-</table>
-
-<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 5V with a 16MHz crystal oscillator. To
-further reduce power consumption, I modified the ATmega328P’s fuses to run at
-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 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 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
-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,
-designed my first PCB, and developed drivers from scratch. The project was far
-from a smooth sail. Bad electrical connections, soldering and desoldering, and
-the heartache of purchasing the wrong parts were routine. It was a long but
-rewarding journey from the messy breadboard to the shiny PCB.</p>
-
-<p>Files: <a href="source.tar.gz">source.tar.gz</a>, <a href="gerber.zip">gerber.zip</a></p>
-</div>
-          <p class="post-author right">by W. D. Sadeep Madurange</p>
-        </div>
-      </div>
-    </main>
-
-    <div class="footer">
-  <div class="container">
-    <div class="twelve columns right container-2">
-      <p id="footer-text">&copy; ASCIIMX - 2025</p>
-    </div>
-  </div>
-</div>
-
-
-  </body>
-</html>
diff --git a/_site/log/index.html b/_site/log/index.html
index 8074ae3..bcc001e 100644
--- a/_site/log/index.html
+++ b/_site/log/index.html
@@ -59,7 +59,7 @@
   
       <tr>
         <td class="posts-td posts-td-link">
-          <a href="/log/fpm-door-lock/" class="link-decor-none">Fingerprint door lock</a>
+          <a href="/log/fpm-door-lock-lp/" class="link-decor-none">Fingerprint door lock (LP)</a>
         </td>
         <td class="posts-td posts-td-time">
           <span class="post-meta">
@@ -98,7 +98,7 @@
   
       <tr>
         <td class="posts-td posts-td-link">
-          <a href="/log/my-first-pcb/" class="link-decor-none">My first PCB</a>
+          <a href="/log/fpm-door-lock-rf/" class="link-decor-none">Fingerprint door lock (RF)</a>
         </td>
         <td class="posts-td posts-td-time">
           <span class="post-meta">
diff --git a/_site/log/matrix-digital-rain/index.html b/_site/log/matrix-digital-rain/index.html
index f254ed2..8383776 100644
--- a/_site/log/matrix-digital-rain/index.html
+++ b/_site/log/matrix-digital-rain/index.html
@@ -54,45 +54,48 @@ than it needed to be.</p>
 </video>
 
 <p>Moved phosphor decay into the 4th byte of the RGB union–should’ve done this 
-in 2022. What was I thinking.</p>
+in 2022; What was I thinking.</p>
 
 <p>Keeping the RGB union despite portability concerns. All my systems are
 little-endian and the code is cleaner this way.</p>
 
 <p>Fixed Unicode by introducing a charset array. UNICODE(min, max) packs Unicode
-ranges into uint64–low four bytes for start, high four bytes for end.
+ranges into uint64: low four bytes for start, high four bytes for end.
 insert_code() unpacks a random block and picks a character from it:</p>
 
-<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>static uint64_t glyphs[] = {
+<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>#define UNICODE(min, max)  (((uint64_t)max &lt;&lt; 32) | min)
+
+static uint64_t glyphs[] = {
     UNICODE(0x0021, 0x007E), /* ASCII */
     UNICODE(0xFF65, 0xFF9F), /* Half-width Katakana */
 };
-</code></pre></div></div>
-
-<p>Full-width Katakana breaks column alignment. Stick to half-width
-(U+FF61-U+FF9F) range. Compile with -DNOKANA to disable Katakana altogether.</p>
 
-<p>blend() simulates phosphor decay by eroding RGB channels toward
-background color:</p>
-
-<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>static inline void blend(matrix *mat, size_t row, size_t col)
+static inline void insert_code(matrix *mat,
+    size_t row, size_t col) 
 {
-    unsigned char *color = mat-&gt;rgb[index(mat, row, col)].color;
-    color[R] = color[R] - (color[R] - RGB_BG_RED) / DECAY_MPLIER;
-    color[G] = color[G] - (color[G] - RGB_BG_GRN) / DECAY_MPLIER;
-    color[B] = color[B] - (color[B] - RGB_BG_BLU) / DECAY_MPLIER;
+    uint64_t blk;
+    uint32_t min, max;
+
+    blk = glyphs[(rand() % glyphlen)];
+    min = (uint32_t)blk;
+    max = (uint32_t)(blk &gt;&gt; 32);
+    mat-&gt;code[index(mat, row, col)] = rand() % (max - min) + min;
 }
 </code></pre></div></div>
 
-<p>That’s still good. Leaving it alone.</p>
+<p>Full-width Katakana breaks column alignment. Stick to half-width
+(U+FF61-U+FF9F) range. Compile with -DNOKANA to disable Katakana altogether.</p>
+
+<p>blend() is still good. Leaving it alone.</p>
 
 <p>Tossed license and automake cruft. Just <code class="language-plaintext highlighter-rouge">cc -O3 main.c -o matrix</code> now. Don’t
 need the ceremony.</p>
 
-<p>Runs at 2-3% CPU on OpenBSD (T490). No regressions. Fans are quiet.</p>
+<p>Runs at 2-3% CPU on OpenBSD (T490). No cause to measure performance more
+precisely. No regressions. Fans are quiet.</p>
 
 <p>Commit:
-<a href="https://git.asciimx.com/matrix-digital-rain/commit/?id=03f8d87ba7c2e46bd3f3cc4c772fb3a2ac740c92">03f8d87</a></p>
+<a href="https://git.asciimx.com/matrix-digital-rain/commit/main.c?id=69a888a5b0bc4ef4bce4f86c1556a06f0f131fda">69a888a</a></p>
 </div>
           <p class="post-author right">by W. D. Sadeep Madurange</p>
         </div>
author	Sadeep Madurange <sadeep@asciimx.com>	2025-12-26 16:53:45 +0800
committer	Sadeep Madurange <sadeep@asciimx.com>	2025-12-26 21:43:43 +0800
commit	e04ce2ab6ca82d0014bec8b217215f35b436ff25 (patch)
tree	4fdc82fb2bf46de34213cf7b2d3f1a5abed0b7be /_site/log
parent	9b95f811472a15280e67f99c90c0013987b32ee2 (diff)
download	www-e04ce2ab6ca82d0014bec8b217215f35b436ff25.tar.gz