Debugging Classic ATtinys and ATmegaX8 in the Arduino IDE 2: A Quickstart Guide

LED 5mm yellow

Breadboard 100x70

Arduino IDE

Arduino Uno Rev3

Laptop or computer

Resistor 220 ohm

10 jumper wires 150mm male

USB 2.0 Cable Type A/B

Capacitor 10 uF

Ceramic Capacitor 100nF

10k Resistor

LED 5mm red

ATtiny85

<html><body><h3>Step 1: Install Arduino IDE</h3>You probably already have installed the Arduino IDE 2. If not, download and install it from <a href="https://arduino.cc">https://arduino.cc </a>. Check: Start IDE and check the <code class="code">About Arduino </code>entry under the <code class="code">Arduino </code>or <code class="code">Help </code>menu for the version number. It should be 2.3.4 or later. <h3>Step 2: Install new board definition files</h3>Open the <code class="code">Preference </code>dialog of the Arduino IDE and paste the following two <code class="code">Board Manager URLs </code>into the list: <pre>https://felias-fogg.github.io/ATTinyCore/package_drazzy.com_ATTinyCore_plus_Debug_index.json </pre><pre>https://felias-fogg.github.io/MiniCore/package_MCUdude_MiniCore_plus_Debug_index.json </pre>Close the <code class="code">Preference </code>dialog with <code class="code">OK </code>. Now we want to install the two cores <code class="code">ATTinyCore </code>and <code class="code">MiniCore </code>: <ol><li>Select <code class="code">Tools </code>-&gt; <code class="code">Board </code>-&gt; <code class="code">Board Managers </code><code class="code">... </code>. This will open the <code class="code">Boards Manager </code>dialog. </li><li>In the search field, type first <code class="code">MiniCore </code>and install the most recent version (or upgrade to the most recent one) with a <code class="code">+debug-2.X </code>suffix. </li><li>Afterwards, do the same with <code class="code">ATTinyCore </code>. </li></ol>Check : Select <code class="code">Tools </code>-&gt; <code class="code">Board </code>-&gt; <code class="code">ATTinyCore </code>-&gt; <code class="code">Attiny25/45/85 (no bootloader) </code>. Then check whether there is an entry <code class="code">Debug Compile Flags: "No Debug" </code>when you click on <code class="code">Tools </code>again. Check that also for <code class="code">Tools </code>-&gt; <code class="code">Board </code>-&gt; <code class="code">MiniCore </code>-&gt; <code class="code">Atmega328 </code>. <h3>Step 3: Install dw-link firmware</h3>Download the dw-link firmware into a place inside the Arduino sketchbook . This means, you should <ol><li>open the webpage <a href="https://github.com/felias-fogg/dw-link">https://github.com/felias-fogg/dw-link </a>, </li><li>click on <code class="code">Latest </code>in the field Releases </li><li>choose either <code class="code">zip </code>or <code class="code">tar.gz </code>, </li><li>download and copy the archive to a place in the sketchbook, </li><li>extract the firmware using <code class="code">unzip </code>or <code class="code">tar -xvzf </code>. </li></ol>In order to install the firmware, <ol><li>first connect the Arduino UNO to your computer with a USB cable. </li><li>Now open the Arduino IDE and select <code class="code">Arduino UNO </code>under <code class="code">Tools </code>as the destination <code class="code">Board </code>. </li><li>Perhaps, you have to select the right <code class="code">Port </code>in the <code class="code">Tools </code>menu as well. </li><li>Now load the dw-link sketch into the IDE, which is located at <code class="code">dw-link-x.y.z/dw-link/dw.link.ino </code>. </li><li>Finally, compile and download the sketch to the UNO by either pressing the right arrow button, or by typing <code class="code">CTRL-U </code>or <code class="code">⌘U </code>. The UNO acts now a hardware debugger (but needs a bit of additional hardware). </li></ol>Check : Open the <code class="code">Serial Monitor </code>(under <code class="code">Tools </code>menu), choose <code class="code">115200 baud </code>, type <code class="code">- </code>(minus sign) into the upper line, and send it. The hardware debugger should respond with <code class="code">$#00 </code>. <h3>Step 4: Hardware setup</h3>This description is for debugging an ATtiny85. However, almost any other classic ATtiny or ATmegaX8 would do. Just be aware that when trying to debug an Arduino UNO board, you need to physically alter the board (cut a solder bridge). How to set up an UNO is described in Section 4.5.2 of the <a href="https://github.com/felias-fogg/dw-link/blob/master/docs/manual.pdf">dw-link manual </a>. <figure><img src="https://projects.arduinocontent.cc/055e3d83-a957-4c16-bebc-fc2cbcfcba4d.png"/><figcaption>Hardware setup as Fritzing sketch</figcaption></figure>Note that the notch or dot on the ATtiny is oriented towards the left. Here is a table of all the connections so that you can check that you have made all the connections. <figure><img src="https://projects.arduinocontent.cc/f2161765-689c-4110-8e5e-f5b3542c884e.png"/><figcaption>Connections</figcaption></figure>The (yellow) system LED gives you information about the internal state of the debugger: 1. not connected (LED is off), 2. waiting for power-cycling the target (LED flashes every second for 0.1 sec), 3. target is connected (LED is on), 4. ISP programming (LED is blinking slowly), 5. error state, i.e., not possible to connect to target or internal error (LED blinks furiously every 0.1 sec). Note that state 2 (power-cycling) will be skipped in our configuration, where the debugger provides the power supply to the target via a GPIO line and does the power-cycling for you. Check: Go through the table above and check every connection. Wrong wiring can often cause hours of useless software debugging! <h3>Step 5: Debugging</h3>Now, we are ready to debug the sketch on the target chip. Check that the host , the computer you are sitting at, is connected to the hardware debugger , the UNO, with a USB cable. The hardware debugger should in turn be connected to the target chip, the ATtiny85, by 6 flying wires as we have prepared it in step 4. <ol><li>Load the sketch you want to debug into the IDE by choosing <code class="code">Open... </code>in the <code class="code">File </code>menu. </li><li>Select <code class="code">ATtiny25/45/85 (no bootloader) </code>as the board under <code class="code">Tools -&gt; Board -&gt; ATTinyCore </code>. </li><li>In the <code class="code">Tools </code>menu, choose <code class="code">1 MHz (internal) </code>as the <code class="code">Clock Source </code>(assuming that the ATtiny is as it comes from the factory and no fuse has been changed). </li></ol><ol><li>In the <code class="code">Sketch </code>menu, select <code class="code">Optimize for Debugging </code>. </li></ol><ol><li>Compile the code by clicking the <code class="code">Verify </code>button in the upper-left corner. </li><li>Open the debug panes by clicking the debug symbol (bug with the triangle) in the left sidebar. </li><li>Click the debug symbol in the top row to start debugging. This will start the debugger and the debug server. The activities are logged in the <code class="code">Debug Console </code>and the <code class="code">gdb-server console </code>in the bottom right part of the window. </li><li>After the debugger and debug-server have been started, the debugger will start executing the program on the target. Execution will stop at the first line of the <code class="code">setup </code>function. </li><li>Now, you are in business and can set breakpoints, continue executing, stop the program asynchronously, inspect and change values, and examine different stack frames. To terminate your debugging session, click the red box in the debug row. Check out the <a href="https://docs.arduino.cc/software/ide-v2/tutorials/ide-v2-debugger/">debugging tutorial </a>on the Arduino website </li></ol><h3>What can go wrong?</h3>First, you might be unable to start debugging because the debug button is greyed out. This happens for all MCUs that the IDE cannot debug. If you think that this is an error, you might need to install the correct board definition files or choose the <code class="code">Reload Board Data </code>entry in the <code class="code">Tools </code>menu. Second, the debug-server might terminate early. In this case, you should see an error message in the <code class="code">gdb-server </code>console. If something does not work as advertised, it is very often a simple wiring problem. The next possible sources of errors are installation errors, i.e., that a program is not installed at the right place, does not have the right permissions, the <code class="code">PATH </code>variable is not right, or one has installed the wrong board manager files. When some strange error messages show up, it may also be an indication that some component has not been installed. Google for the error message! Often there are hints how to mitigate the problem. Finally, there is also a troubleshooting section in the <a href="https://github.com/felias-fogg/dw-link/blob/master/docs/manual.pdf">dw-link manual </a>, which may be helpful. The most annoying problem is that after a debugging session, an MCU might not be responsive anymore. The reason can be that the RESET line, which during debugging is used as a communication line, has not been reenabled. While a regular exit of the debugger restores the RESET line, it can happen that the debugger is terminated without restoring the RESET line. An easy cure is to enter the debugger again and leave it regularly (after connecting to the target chip) with the command <code class="code">quit </code>. If you think that you have found a bug, please consider posting it on <a href="https://github.com/felias-fogg/dw-link/issues">issues </a>and consider filling out the <a href="https://github.com/felias-fogg/dw-link/blob/master/docs/issue_form.md">issue form </a>before. <h3>After debugging has finished</h3>So what do you do with your newly built hardware debugger after everything has been debugged? You don't have to throw it away. It is also an ISP programmer (STK500 v1). In the Arduino IDE, such a programmer is called <code class="code">AVR ISP </code>or <code class="code">Arduino as ISP </code>. You may also consider to give the hardware debugger a more durable shape. This is all covered in the <a href="https://github.com/felias-fogg/dw-link/blob/master/docs/manual.pdf">dw-link manual </a>. Acknowledgements I put a lot of effort in building dw-link, but it is not all my own doing. I made heavy use of other people's open source software, ideas, and publications. Many thanks to them for sharing their ideas: <ol><li>RiskusW's <a href="http://www.ruemohr.org/docs/debugwire.html">reverse engineering of debugWIRE </a>, </li><li>Jon Dolany's <a href="https://github.com/jdolinay/avr_debug">avr_gdb </a>project that provides a gdb-stub for ATmega328 and other ATmegas, </li><li>David C W Brown's debgWIRE debugger <a href="https://github.com/dcwbrown/dwire-debug">dwire-debug </a>, </li><li>Wayne Holder's <a href="https://github.com/wholder/DebugWireDebuggerProgrammer">DebugWireDebuggerProgrammer </a>, and </li><li>ccrause's <a href="https://github.com/ccrause/debugwire-gdb-bridge">debugwire-gdb-bridge </a>. </li></ol> </body></html>

dw-link

Debugging Classic ATtinys and ATmegaX8 in the Arduino IDE 2: A Quickstart Guide

Turn your Arduino UNO into a hardware debugger that can be used for embedded debugging of classic AVR chips in 5 easy steps. Takes less than one hour.