This is the second of three posts about using gdb and simavr to debug AVR code. The complete series is:

• Part 1: Using GDB

  A walkthrough of using GDB to manually inspect the behavior of our code.

• Part 2: Automating GDB with scripts

  Creating GDB scripts to automatically test the behavior of our code.

• Part 3: Tracing with simavr

  Using simavr to collect information about the state of microcontroller pins while our code is running.

This is the third of three posts about using gdb and simavr to debug AVR code. The complete series is:

• Part 1: Using GDB

  A walkthrough of using GDB to manually inspect the behavior of our code.

• Part 2: Automating GDB with scripts

  Creating GDB scripts to automatically test the behavior of our code.

• Part 3: Tracing with simavr

  Using simavr to collect information about the state of microcontroller pins while our code is running.

I have a Raspberry Pi running RetroPie hooked up to a television. It’s powered from a USB port on the TV, which is convenient, but it means that whenever we shut off the TV we’re pulling the plug on the Pi. While there haven’t been any problems so far, this is a classic recipe for filesystem problems or data loss at some point. I started looking into UPS options to alleviate this issue. I wanted something with the following features:

Bitwarden is a password management service (like LastPass or 1Password). It’s unique in that it is built entirely on open source software. In addition to the the web UI and mobile apps that you would expect, Bitwarden also provides a command-line tool for interacting with the your password store.

At $WORK(-ish) we’re looking into Bitwarden because we want a password sharing and management solution that was better than dropping files into directories on remote hosts or sharing things over Slack. At the same time, we are also thinking about bringing more automation to our operational environment, possibly by making more extensive use of Ansible. It looked like all the pieces were available to use Bitwarden as a credential storage mechanism for Ansible playbooks, so I set out to write a lookup plugin to implement the integration…

The Pi Zero (and Zero W) have support for acting as a USB gadget: that means that they can be configured to act as a USB device – like a serial port, an ethernet interface, a mass storage device, etc.

There are two different ways of configuring this support. The first only allows you to configure a single type of gadget at a time, and boils down to:

1. Enable the dwc2 overlay in /boot/config.txt
2. Reboot.
3. modprobe g_serial

This process is more fully documented here.

Recent releases of Raspbian have adopted the use of dhcpcd to manage both dynamic and static interface configuration. If you would prefer to use the traditional /etc/network/interfaces mechanism instead, follow these steps.

1. First, disable dhcpcd and wpa_supplicant.

    systemctl disable --now dhdpcd wpa_supplicant
   

2. You will need a wpa_supplicant configuration for wlan0 in /etc/wpa_supplicant/wpa_supplicant-wlan0.conf.

   If you already have an appropriate configuration in /etc/wpa_supplicant/wpa_supplicant.conf, you can just symlink the file:

     cd /etc/wpa_supplicant
     ln -s wpa_supplicant.conf wpa_supplicant-wlan0.conf
   

3. Enable the wpa_supplicant service for wlan0:

CircuitPython is “an education friendly open source derivative of MicroPython”. MicroPython is a port of Python to microcontroller environments; it can run on boards with very few resources such as the ESP8266. I’ve recently started experimenting with CircuitPython on a Wemos D1 mini, which is a small form-factor ESP8266 board.

I had previously been using Mike Causer’s micropython-tm1637 for MicroPython to drive a 4 digit LED display. I was hoping to get the same code working under CircuitPython, but when I tried to build an image that included the tm1637 module I ran into:

The DS18B20 is a popular temperature sensor that uses the 1-Wire protocol for communication. Recent versions of the Linux kernel include a kernel driver for this protocol, making it relatively convenient to connect one or more of these devices to a Raspberry Pi or similar device. 1-Wire devices can be daisy chained, so it is possible to connect several devices to your Pi using only a single GPIO pin, and you’ll find many articles out there that describe how to do so.

A question that crops up regularly on #docker is “How do I attach a container directly to my local network?” One possible answer to that question is the macvlan network type, which lets you create “clones” of a physical interface on your host and use that to attach containers directly to your local network. For the most part it works great, but it does come with some minor caveats and limitations. I would like to explore those here.

On IRC – and other online communities – it is common to use a “pastebin” service to share snippets of code, logs, and other material, rather than pasting them directly into a conversation. These services will typically return a URL that you can share with others so that they can see the content in their browser.

One of my favorite pastebin services is termbin.com, because it works from the command line using tools you probably already have installed. Termbin runs the fiche service, which listens for TCP connections on port 9999, reads any content that you provide, and then returns a URL. For example, if I wanted to share my iptables configuration with someone I could just run: