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diff --git a/_site/archive/arduino-due/index.html b/_site/archive/arduino-due/index.html deleted file mode 100644 index e146957..0000000 --- a/_site/archive/arduino-due/index.html +++ /dev/null @@ -1,172 +0,0 @@ -<!DOCTYPE html> -<html> - <head> - <meta charset="utf-8"> - <title>How to set up ATSAM3X8E microcontrollers for bare-metal programming in C</title> - - <head> - <meta charset="utf-8"> - <meta name="viewport" content="width=device-width, initial-scale=1"> - <title>How to set up ATSAM3X8E microcontrollers for bare-metal programming in C</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="/archive/" class="link-decor-none">blg</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">HOW TO SET UP ATSAM3X8E MICROCONTROLLERS FOR BARE-METAL PROGRAMMING IN C</h2> - <h6 class="center">05 OCTOBER 2024</h5> - <br> - <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>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> - -<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 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;"> - <td style="border: none; width: 50%; vertical-align: top; background-color: transparent;"> - <img src="schematic.png" alt="Pinout" style="width: 100%" /> - <p style="text-align: center;">Wiring</p> - </td> - <td style="border: none; width: 50%; vertical-align: top; background-color: transparent;"> - <img src="connections.jpeg" alt="Circuit" style="width: 100%" /> - <p style="text-align: center;">Arduino Due</p> - </td> - </tr> -</table> - -<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>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 -$ openocd -f openocd-due.cfg -c "program a.elf verify reset exit" -</code></pre></div></div> - -<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> - -<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. 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> - <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">© ASCIIMX - 2025</p> - </div> - </div> -</div> - - - </body> -</html> |