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diff --git a/_site/archive/arduino-due/index.html b/_site/archive/arduino-due/index.html index 13e006e..86f4fb0 100644 --- a/_site/archive/arduino-due/index.html +++ b/_site/archive/arduino-due/index.html @@ -2,12 +2,12 @@ <html> <head> <meta charset="utf-8"> - <title>Bare-metal ARM Cortex M3 chips</title> + <title>Bare-metal ATSAM3X8E chips</title> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1"> - <title>Bare-metal ARM Cortex M3 chips</title> + <title>Bare-metal ATSAM3X8E chips</title> <link rel="stylesheet" href="/assets/css/main.css"> <link rel="stylesheet" href="/assets/css/skeleton.css"> </head> @@ -40,34 +40,38 @@ <main> <div class="container"> - <h2 class="center" id="title">BARE-METAL ARM CORTEX M3 CHIPS</h2> + <h2 class="center" id="title">BARE-METAL ATSAM3X8E CHIPS</h2> <h6 class="center">05 OCTOBER 2024</h5> <br> - <div class="twocol justify"><p>This post is about programming bare metal SAM3X8E Arm Cortex M3 chips found on -Arduino Due boards. I had to learn how to do this because none of the -high-level tools for programming Arduino Dues are available for OpenBSD, which -I use for much of my personal computing.</p> + <div class="twocol justify"><p>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.</p> <h2 id="toolchain">Toolchain</h2> -<p>Since we will not be using pre-packaged development tools, we need to assemble -our own toolchain. As usual, we need a compiler toolchain to build programs for -the target chip. As we will be bypassing the embedded bootloader, we will also -need a hardware programmer and an on-chip debugger to flash programs to the -chip. I used the following toolchain.</p> +<p>To interact directly with a bare-metal ATSAM3X8E chips, we must bypass the +embedded bootloader. To do that, we need a hardware programmer capable of +communicating with the chip over the Serial Wire Debug (SWD) protocol. Since +the workstation we upload the program from presumably doesn’t speak SWD, the +hardware programmer acts as a SWD-USB adapter. The <a href="https://www.st.com/en/development-tools/st-link-v2.html" class="external" target="_blank" rel="noopener noreferrer">ST-LINK/V2</a> programmer fits this +bill.</p> -<ul> - <li><a href="https://developer.arm.com/Tools%20and%20Software/GNU%20Toolchain" class="external" target="_blank" rel="noopener noreferrer">Arm GNU compiler -toolchain</a>.</li> - <li><a href="https://openocd.org/" class="external" target="_blank" rel="noopener noreferrer">OpenOCD</a> on-chip debugger.</li> - <li><a href="https://www.st.com/en/development-tools/st-link-v2.html" class="external" target="_blank" rel="noopener noreferrer">ST-LINK/V2</a> -programmer.</li> -</ul> +<p>The <a href="https://openocd.org/" class="external" target="_blank" rel="noopener noreferrer">OpenOCD</a> on-chip debugger software supports +ATSAM3X8E chips. OpenOCD, on startup, runs a telnet server that we can connect to +to issue commands to the ATSAM3X8E chip. OpenOCD translates plain-text commands +into the binary sequences the chip understands, and sends them over the wire.</p> + +<p>Finally, we need the <a href="https://developer.arm.com/Tools%20and%20Software/GNU%20Toolchain" class="external" target="_blank" rel="noopener noreferrer">ARM GNU Compiler +Toolchain</a> to compile C programs for the chip. The ARM GNU compiler +toolchain and OpenOCD, as a consequence of being free software, are available +on every conceivable platform, including OpenBSD.</p> <h2 id="electrical-connections">Electrical connections</h2> -<p>The following diagram outlines the electrical connections between the different -components necessary to move a compiled program from a PC to the MCU.</p> +<p>The following photos illustrate the electrical connections between the Arduino +Due, PC, and the ST-LINK/V2 programmer required to transfer a compiled program +from a PC to the MCU.</p> <table style="border: none; width: 100%;"> <tr style="border: none;"> @@ -82,69 +86,70 @@ components necessary to move a compiled program from a PC to the MCU.</p> </tr> </table> -<p>Arduino Due exposes the SAM3X8E’s Serial Wire Debug (SWD) interface via its -DEBUG port. The ST-LINK/v2 programmer uses the SWD protocol to communicate with -the chip.</p> +<p>Arduino Due exposes the ATSAM3X8E’s SWD interface via its DEBUG port. The +ST-LINK/v2 programmer connects to that to communicate with the chip.</p> <h2 id="uploading-the-program">Uploading the program</h2> -<p>Follow the steps below to upload a program to the SAM3X8E chip. The -source.tar.gz tarball at the end of the page contains a sample program with a -OpenOCD config file and a linker script.</p> - -<ol> - <li>Start OpenOCD: - <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>$ openocd -f openocd-due.cfg -</code></pre></div> </div> - </li> - <li>Open a telnet session and set the GPNVM1 bit to 1: - <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>$ telnet localhost 4444 +<p>The source.tar.gz tarball at the end of this page contains a sample C program +(the classic LED blink program) with OpenOCD configuration and linker scripts. +First, use the following command to build it:</p> + +<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>$ arm-none-eabi-gcc -mcpu=cortex-m3 -mthumb -T script.ld \ + -nostartfiles \ + -nostdlib \ + -o a.elf main.c +</code></pre></div></div> + +<p>Then, open a telnet session with OpenOCD and issue the following sequence of +commands to configure the chip and upload the compiled program to it:</p> + +<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>$ openocd -f openocd-due.cfg +$ telnet localhost 4444 > halt > at91sam3 gpnvm show > at91sam3 gpnvm set 1 > at91sam3 gpnvm show -</code></pre></div> </div> - </li> - <li>Build the program using the custom linker script. - <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>$ arm-none-eabi-gcc -mcpu=cortex-m3 -mthumb -T script.ld \ - -nostartfiles \ - -nostdlib \ - -o a.elf main.c -</code></pre></div> </div> - </li> - <li>Upload the program using OpenOCD: - <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>$ openocd -f openocd-due.cfg -c "program a.elf verify reset exit" -</code></pre></div> </div> - </li> -</ol> +$ openocd -f openocd-due.cfg -c "program a.elf verify reset exit" +</code></pre></div></div> -<p>Refer to the OpenOCD manual (AT91SAM3 flash driver section) for a complete list -of commands supported for the ATSAM3X8E.</p> +<p>The first of the above commands starts OpenOCD. In the telnet session, the +first command halts the chip in preparation for receiving commands. Next, we +inspect the current GPNVM bit setting (more on this later). If the bit is unset +(the gpnvm show command returns 0), we set it to 1 and verify the update.</p> -<h2 id="gpnvm-bits-and-the-linker-script">GPNVM bits and the linker script</h2> +<p>The final command, issued from outside the telnet session, uploads the program +to the chip. Those are the bare minimum set of commands required to program the +chip. The AT91SAM3 flash driver section of the OpenOCD manual lists all +available commands for the ATSAM3X8E chip.</p> + +<h2 id="gpnvm-bits">GPNVM bits</h2> <p>By design, ARM chips boot into address 0x00000. ATSAM3X8E’s memory consists of a ROM and a dual-banked flash (flash0 and flash1), residing in different -locations of the chip’s address space.</p> - -<p>The GPNVM bits control which of them maps to 0x00000. When GPNVM1 is cleared -(default), the chip boots from the ROM, which contains Atmel’s SAM-BA -bootloader. So, the chip runs the embedded bootloader instead of our program.</p> - -<p>When the GPNVM1 bit is 1 (and the GPNVM2 bit is 0), flash0 at address 0x80000 -maps to 0x00000. When both GPNVM bits are 0, flash1 maps to 0x00000. Since we -place our program in flash0 using the linker script, we set the GPNVM1 bit and -leave the GPNVM2 bit as it is.</p> - -<p>The linker script places the vector table at the first address of the flash. -ARM chips expect this unless we relocate the vector table using the VTOR -register. The first entry of the vector table must be the stack pointer, and -the second must be the reset vector.</p> - -<p>Finally, the ATSAM3X8E uses a descending stack. So, in the linker script, we -initialize the stack pointer to the highest memory location available. In the -reset vector, we zero out memory, initialize registers, and perform other tasks -before passing control to the main program.</p> +locations of the chip’s address space. The GPNVM bits control which of them +maps to 0x00000. When GPNVM1 is cleared (the default), the chip boots from the ROM, +which contains Atmel’s SAM-BA bootloader.</p> + +<p>Conversely, when the GPNVM1 bit is 1 (and the GPNVM2 bit is 0), flash0 at +address 0x80000 maps to 0x00000. When both GPNVM bits are 0, flash1 maps to +0x00000. Since we place our program in flash0 in the linker script, we set the +GPNVM1 bit and leave the GPNVM2 bit unchanged to ensure the chip +executes our program instead of the embedded bootloader at startup.</p> + +<h2 id="linker-script">Linker script</h2> + +<p>At a minimum, the linker script must place the vector table at the first +address of the flash. This is mandatory for ARM chips unless we relocate the +vector table using the VTOR register.</p> + +<p>The first entry of the vector table must be the stack pointer. The stack +pointer must be initializes to the highest memory location available to +accommodate the ATSAM3X8E’s descending stack.</p> + +<p>The second entry of the vector table must be the reset vector. In the reset +vector, we can perform tasks such as zeroing out memory and initializing +registers before passing control to the main program.</p> <p>Files: <a href="source.tar.gz">source.tar.gz</a></p> </div> diff --git a/_site/archive/arduino-uno/index.html b/_site/archive/arduino-uno/index.html index 7509267..3b0234d 100644 --- a/_site/archive/arduino-uno/index.html +++ b/_site/archive/arduino-uno/index.html @@ -2,12 +2,12 @@ <html> <head> <meta charset="utf-8"> - <title>Programming ATmega328P chips</title> + <title>ATmega328P chips</title> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1"> - <title>Programming ATmega328P chips</title> + <title>ATmega328P chips</title> <link rel="stylesheet" href="/assets/css/main.css"> <link rel="stylesheet" href="/assets/css/skeleton.css"> </head> @@ -40,15 +40,15 @@ <main> <div class="container"> - <h2 class="center" id="title">PROGRAMMING ATMEGA328P CHIPS</h2> + <h2 class="center" id="title">ATMEGA328P CHIPS</h2> <h6 class="center">10 APRIL 2025</h5> <br> - <div class="twocol justify"><p>This post is a step-by-step guide for wiring up ATmega328P ICs to run at 5V -with a 16MHz crystal and 3.3V with an 8MHz crystal. While the 5V -configuration is common, the 3.3V configuration can be advantageous in -low-power applications and when interfacing with parts that run at 3.3V.</p> - -<h2 id="5v-16mhz-configuration">5V-16MHz configuration</h2> + <div class="twocol justify"><p>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.</p> <p>The steps that follow refer to the following pinout.</p> @@ -65,6 +65,8 @@ low-power applications and when interfacing with parts that run at 3.3V.</p> </tr> </table> +<h2 id="5v-16mhz-configuration">5V-16MHz configuration</h2> + <ol> <li>Connect pin 1 to 5V via a 10kΩ resistor.</li> <li>Connect a 16MHz crystal oscillator across pins 9 and 10.</li> @@ -73,23 +75,30 @@ low-power applications and when interfacing with parts that run at 3.3V.</p> <li>Connect pins 8 and 22 to ground.</li> </ol> -<p>In addition to the connections described above, it’s a good idea to add 0.1μF +<p>In addition to the the connections above, it’s a good idea to add 0.1μF decoupling capacitors between pins 7, 20, and 21 and ground. <a href="Makefile">Here’s</a> a sample Makefile for avr-gcc and avrdude.</p> <h2 id="33v-8mhz-configuration">3.3V-8MHz configuration</h2> -<p>The following steps use Arduino Uno as an ISP and Arduino utilities to program -ATmega328P’s bootloader and the fuses (e.g., BOD level) for a 3.3V supply.</p> +<p>Standard ATmega328P chips are preconfigured to run at 5V. To run one at 3.3V, +we must first modify its fuses (e.g., BOD level). If the chip contains a +pre-installed bootloader that expects a 16MHz clock (such as the Arduino Uno +bootloader), it must be replaced with one that is more amenable to an 8MHz +clock.</p> + +<p>In the following steps, we use an Arduino Uno as an in-system programmer to +replace the embedded bootloader and modify the appropriate fuses.</p> <ol> - <li>Upload the ‘ArduinoISP’ sketch to the Uno.</li> - <li>Wire up the ATmega328P as described in the previous section. Replace the 5V -supply with a 3.3V supply and use an 8MHz crystal instead of the 16MHz + <li>Upload the ‘ArduinoISP’ sketch to the Arduino Uno.</li> + <li>Wire up the ATmega328P IC as described in the previous section, while +replacing the 5V supply with a 3.3V supply and 16MHz crystal with an 8MHz crystal.</li> <li>Connect the SPI ports (SCK, MISO, and MOSI) of the two MCUs.</li> - <li>Connect Uno’s SS pin to the IC’s pin 1 (RESET).</li> - <li>The IC can be powered by the Arduino Uno’s 5V pin.</li> + <li>Connect the Arduino Uno’s SS pin to the IC’s RESET pin (pin 1).</li> + <li>Connect the IC’s V<sub>CC</sub> to a 5V supply (e.g., the Arduino Uno’s 5V +pin).</li> <li>Burn the bootloader to the ATmega328P: <ul> <li>Select ‘ATmega328P (3.3V, 8MHz)’ from Tools > Processor.</li> @@ -100,14 +109,14 @@ crystal.</li> </ol> <p>The ATmega328P is now ready to run at 8MHz with a 3.3V power supply. You can -upload programs to the ATmega328P as you usually would using avrdude. +upload programs to the ATmega328P as you normally would using avrdude. <a href="3v3.Makefile">Here’s</a> a sample Makefile with adjusted parameters (e.g., baud rate) for an 8MHz clock.</p> <p>In both configurations, if you intend to use the ATmega328P’s analog-to-digital converter with the internal 1.1V or AV<sub>cc</sub> voltage as reference, do -not connect AREF (pin 21) to V<sub>cc</sub>. Refer to section 23.5.2 ADC -Voltage Reference in the datasheet for more information.</p> +not connect AREF (pin 21) to V<sub>cc</sub>. Refer to section 23.5.2 in the +datasheet for more information.</p> </div> <p class="post-author right">by Wickramage Don Sadeep Madurange</p> diff --git a/_site/archive/awesome-books/index.html b/_site/archive/awesome-books/index.html index c9f1934..8f2f45e 100644 --- a/_site/archive/awesome-books/index.html +++ b/_site/archive/awesome-books/index.html @@ -43,65 +43,74 @@ <h2 class="center" id="title">AWESOME BOOKS</h2> <h6 class="center">20 APRIL 2025</h5> <br> - <div class="twocol justify"><p>This article contains a list of my favourite books.</p> - -<h2 id="cloud-atlas">Cloud Atlas</h2> + <div class="twocol justify"><h2 id="cloud-atlas">Cloud Atlas</h2> <p>This highly creative novel rekindled my love of fiction. Cloud Atlas is a -collection of six tales linked across time. As the novel unfolds, each story -riffles over the previous ones, like a pack of playing cards.</p> +collection of six tales linked across time. As the book unfolds, the stories +riffle over one another like a pack of cards. David Mitchell brings the Cloud +Atlas world and the characters in it to life with beautiful, vivid +descriptions. The novel explores themes ranging from social to spiritual, +including the struggle for freedom against oppression, interconnectedness, and +rebirth.</p> <h2 id="enders-game">Ender’s Game</h2> -<p>In this sci-fi novel, Andrew “Ender” Wiggin, a young boy, is drafted to lead a -squad of young children in an offensive against an alien race. It’s a complex -story that touches upon various political and philosophical issues. Those -perceived as gifted by others (and alienated for it) will likely connect with -Ender.</p> +<p>In this sci-fi novel, Andrew “Ender” Wiggin, an 11-year-old boy, is drafted to +lead a squad of young children in an offensive against an alien race. Ender’s +Game is a complex story that explores themes of war, leadership, and the +challenges gifted individuals must face as they navigate a lonely life marked +by envy, alienation, and, sometimes, much-needed friendship.</p> <h2 id="flowers-for-algernon">Flowers for Algernon</h2> -<p>This novel, written as a series of progress reports, tells the story of Charlie -Gordon, a developmentally disabled man who acquires superhuman cognitive -abilities through an experimental medical procedure. For some reason, I felt a -deep connection with Charlie. If I had to pick a favourite book on this list, -that would be this.</p> +<p>This novel, written as a series of progress reports, tells the tragic story of +Charlie Gordon, a developmentally disabled man who acquires superhuman +cognitive abilities through an experimental medical procedure. Charlie’s birth +family abandons him because he is not smart enough; his friends abandon him +because he is too smart. In the end, to spare everyone’s feelings, Charlie must +end up in the Warren Home.<sup><a href="#footnote-1">1</a></sup> This is my +favourite book in the list.</p> <h2 id="dead-souls">Dead Souls</h2> -<p>Nikolai Gogol is one of the most original authors I’ve read. Dead Souls is the -story of Ivanovich Chichikov, a traveling merchant who trades dead serfs. -Instead of simply describing them, Gogol develops realistic characters in -minute detail by employing theatrical clashes between them.</p> +<p>Dead Souls is the story of Ivanovich Chichikov, a traveling merchant who trades +dead serfs. Gogol’s writing style is similar to Dostoyevsky’s. Considering how +Gogol’s work predates Dostoyevsky’s, Gogol is one of the most original authors +I’ve read. Instead of simply describing them, Gogol develops realistic +characters in minute detail by employing theatrical clashes between them.</p> <h2 id="the-overcoat">The Overcoat</h2> <p>Gogol’s The Overcoat is one of the finest short stories I’ve read. Akaky -Akakievich, an impoverished government clerk, must buy a new overcoat. I -recommend reading Gogol before Dostoyevsky. What Gogol invented, Dostoyevsky -perfected.</p> +Akakievich, an impoverished government clerk, buys a new overcoat. I recommend +reading Gogol before Dostoyevsky. What Gogol invented, Dostoyevsky perfected.</p> <h2 id="demons">Demons</h2> <p>After reading Demons, a story about an attempted revolution, I realized that -Dostoevsky’s reputation is well-deserved. Dostoyevsky was a great observer of -the human psyche. The depth with which he depicts his characters is -unparalleled. Demons is a book that anyone aspiring to bring about change -through revolution must read.</p> +Dostoyevsky’s reputation is well-deserved. Dostoyevsky was a great observer of +human nature. He depicts characters in profound detail. Dostoyevsky’s writing +can feel long and meandering at times. However, as character development goes, +Dostoyevsky wastes no stroke of the brush. Demons is a book that anyone +aspiring to bring about change through revolution, especially in the name of +someone else’s ideals, must read.</p> <h2 id="the-outsider">The Outsider</h2> -<p>Camus’s quote, “In our society, any man who doesn’t cry at his mother’s funeral -is liable to be condemned to death,” summarizes the book quite well. To -appreciate the philosophical elements of this absurdist novel, you may also -want to check out The Myth of Sisyphus.</p> +<p>Camus’s own quote, “In our society, any man who doesn’t cry at his mother’s +funeral is liable to be condemned to death,” summarizes the book quite well. +The book is about the philosophy of the absurd: the contention between our +propensity to seek meaning in a seemingly silent and indifferent universe. To +appreciate the philosophical elements of this novel, check out The Myth of +Sisyphus.</p> <h2 id="frankenstein">Frankenstein</h2> -<p>I’m not sure why I found this story so charming. Perhaps it’s a deep-felt -empathy for Victor Frankenstein. Maybe it’s the rustic descriptions of places -I’d never seen. After reading the book, I traveled Frankenstein’s trail from -Germany through Lucerne, Geneva, and Scotland.</p> +<p>I first got to know the Frankenstein story through its popular derivatives. The +book changed my impression of the story from one about a familiar monster to +one about a poignant genius deserving empathy. Mary Shelley’s intricate writing +style is singularly captivating. In this list, Frankenstein is the most +beautifully written book.</p> <h2 id="strange-case-of-dr-jekyll-and-mr-hyde">Strange Case of Dr Jekyll and Mr Hyde</h2> @@ -125,6 +134,15 @@ two books are more relevant today than they’ve ever been.</p> Aksenty Ivanovich’s diary, the story documents the government clerk’s descent into madness. His obsession with social status and self-aggrandizement leads him on a trajectory of envy, wounded pride, and outright insanity.</p> + +<div class="footnotes" role="doc-endnotes"> + <ol> + <li> + <a href="https://www.cliffsnotes.com/literature/f/flowers-for-algernon/about-flowers-for-algernon" class="external" target="_blank" rel="noopener noreferrer"> Cliff's Notes </a> + </li> + </ol> +</div> + </div> <p class="post-author right">by Wickramage Don Sadeep Madurange</p> </div> diff --git a/_site/archive/index.html b/_site/archive/index.html index 228167a..91a7361 100644 --- a/_site/archive/index.html +++ b/_site/archive/index.html @@ -85,7 +85,7 @@ <tr> <td class="posts-td posts-td-link"> - <a href="/archive/arduino-uno/" class="link-decor-none">Programming ATmega328P chips</a> + <a href="/archive/arduino-uno/" class="link-decor-none">ATmega328P chips</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="/archive/arduino-due/" class="link-decor-none">Bare-metal ARM Cortex M3 chips</a> + <a href="/archive/arduino-due/" class="link-decor-none">Bare-metal ATSAM3X8E chips</a> </td> <td class="posts-td posts-td-time"> <span class="post-meta"> |