Twopercent Blog

DJ on a Bike

2025-06-07T00:00:00-05:00

Music on the Move

Backgrond

Inspired by this video of a person playing the piano on the back of a cargo bike, I have wanted to add music to our Spicy Curry since we bought it. No one in my family plays piano and even a novice DJ can play coherent music so I decided on a DJ setup.

Parts

Raspberry Pi 5
10" touchscreen display (touchscreen isn't necessary but it helps with adjusting mixxx settings)
DJ Controller
Bike with passenger seating
Batter pack
Portable speaker
Cables

DJ Software

I used fayaaz's mixx-pi-gen fork because it handled a lot of the installation and configuration of mixxx. The controller I am using, a Pioneer DDJ-SB3, had a mapping already built-in to mixxx so no additional configuration was needed. The DDJ-SB3 also has a build in audio card so I connected it to the portalble speaker with a 2-channel RCA <-> 3.5mm cable. The controller is connected (and gets its power) from the RPI with a USB Type-A <-> USB Type-B cable. I suspect that connecting the RPI to the speaker with bluetooth would insert so much lag that mixxing would be near impossible.

Speaker

I found a ION Sport Go portable speaker for cheap. I replaced the battery and it is good to go. I looked for RCA inputs on the speaker as I thought they would be a little sturdier on bumpy paths. The the ION was the right price as well as weather resistant. Make sure the speaker fits in the front basket of your bike without hindering the handelbars. A few pool noodles on the bottom and sides of the bread basket (yuba's term for the front basket) offer a softer ride for the speaker.

Power

During initial tests the RPI would power cycle as soon as the controller was plugged in. My assumption was that the controller was drawing too much current for the 3 amp chunky I was using. I read that the RPI 5 can handle up to 5 amps at 5 volts so I ordered a semi-official 5.1 volt 5 amp chunky. Using this wall plug, it worked properly. There were no 5V5A power banks that I could find so we experimented with some USB-PD voltage selectors and a buck converter to request 9V from a USB-PD battery pack and convert to 5V with the buck converter. If we can draw 9V3A we should get close to 5V5A after conversion. This solution also didn't work. We later disovered that power on the RPI 5 USB ports is limited to 600mA unless the official power supply is used. Here is a good reddit thread on the topic. You can add a line to your /boot/config.txt file to enable up to 1.6 amps on the USB ports even with other power supply's

usb_max_current_enable=1

I considered powering the 10" display from an alternate source but the mouse touches are handled throught same USB interface and the touchscreen is handy. You can use a wide variety of portable batttery packs to power the RPI now. I found a reasonable priced 20,000 mAh Anker battery pack (A1383) on eBay that works well.

Orientation

The hdmi and usb connectors on the 10" display are on the bottom left side of the screen. Construction of the screen holder proved easier of the display was upside down and the ports were at the top left. Many resources suggest adding lcd_rotate=2 to /boot/config.txt but this only works with official RPI display. Another suggested route is within the display settings of the Raspberry PI OS GUI. Since mixxx-pi-gen uses a stripped down OS and the sway window manager, there is no GUI configuration. After figuring out the name of my display, I added the following to ~/.config/sway/config

output HDMI-A-1 transform 180
input type:touch calibration matrix "-1.0" 0.0 1.0 0.0 "-1.0" 1.0

The first line rotates the display and the second transforms the mouse clicks to match the rotated display.

Construction

Brother Joe helped with the design and building of the wood table to hold the controller and batter pack. Some small wood segments hold the controller centered. A velcro strap holds the battery in place. Two 2x4's with a slot routered in them hold the touchscreen. The RPI is attached to the back of the touchscreen.

We raised the monkey bars to accomodate a rider with longer legs. We added a small section (~17 cm) of 2x4 in between the monkey bar and the bike frame. A longer 5mm x 60mm screw is needed.

The first ride was challending because we hadn't figured out the screen rotation yet so the display was upside down. But we still had fun!

RAID 1 with LVM

2024-12-18T00:00:00-06:00

Convert an existing linear logical volume to a raid1 or mirror

Backgrond

I have a server running on a single disk. I now find myself relying on it more and want redundant storage. The server installer created a single volume group on a single physical volume.

I have added a second disk to the system. I will duplicate the paritioning of the original drive, create a physical volume on it, and convert the existing volume group into a raid1 or mirror across both physical volumes.

Tools

sudo apt install lvm2

Examine disks:

lsblk

Examine physical volumes:

pvscan
pvs
pvdisplay

Examine volume groups:

vgscan
vgs
vgdisplay

Examine logical volumes:

lvscan
lvs
lvdisplay

Prepare the new disk

The new disk is identical in size to the original. Use sfdisk to dump the partition table from the original disk and apply it to the new one. THIS WILL DESTROY ALL THE DATA ON /dev/sdb.

sudo sfdisk --dump /dev/sda > part_table
sudo sfdisk /dev/sdb < part_table

I have two additional partitions (EFI and boot) that I will attempt to manually sync at a later time. For now, create a new lvm physical volume on the new disk.

sudo pvcreate /dev/sdb3

And add it to the existing volume group.

sudo vgextend <vg_name> /dev/sdb3

And finally:

lvconvert --type raid1 --mirrors 1 <vg_name>/<lv_name>

Raspberry Jira

2024-02-09T00:00:00-06:00

Raspberry Pi with an e-ink display to show the status of a Jira board

Parts

Setup

I used rpi-imager to flash Raspberry Pi OS Lite (64-bit) onto a 4GB SD card. Since we don't require a desktop, we can use the smaller "Lite" image which will fit onto a 4GB card.

Configure a user name and password on first boot. Then set localisation and network settings with sudo raspi-config You can get the latest packages with raspi-config as well

Follow the Waveshare wiki to enable the SPI interface:

Use raspi-config tool. SPI is enabled in Interfacing Options -> SPI

Skip the C section in the wiki and proceed with the Python installation. Skip python2 packages (we'll use python3) as well as pip. All of the python requirements can be installed with the Debian package manager apt. In Debian Bookworm and later, the python3 interpreter is marked externally-managed. This means pip will not work unless extra steps are taken. Read more about it here

sudo apt update
sudo apt install git python3-pil python3-numpy python3-rpi.gpio python3-spidev python3-dotenv

Review the demo code from Waveshare or

Pandoc 3 breaks Pandoc Resume

2023-12-26T00:00:00-06:00

I've been using Mark Szepieniec's Markdown Resume but recently noticed a degradation in the styling.

Original version of the resume:	Current version of the resume:

The tool relies on pandoc and context

pandoc --version and context --version reveal:

pandoc 3.0.1
mtx-context     | ConTeXt Process Management 1.04

Pandoc was just updated to major release 3 in Debian Trixie (testing) and could be causing the issue.

This issue in the pandoc_resume github repo also suggests updated pandoc is the cause.

Use sudo apt-cache policy pandoc to see if a previous version is still available.

None were available so I added (uncommented) the stable release in my /etc/apt/sources.list file.

Then sudo apt update, check the policy again and I can see pandoc 2.17.1.1-2~deb12u1 is available.

Remove pandoc 3 as well as the pandoc-data depencancy:

sudo apt remove pandoc
sudo apt autoremove

Finally install pandoc 2:

sudo apt install pandoc=2.17.1.1-2~deb12u1 pandoc-data=2.17.1.1-2~deb12u1

Hold the pandoc 2 package:

sudo apt-mark hold pandoc

Alternatively, use the included docker-compose.yml file to build your resume with a docker container that contains a pandoc 2

docker-compose up -d

Update

I asked claude how to fix the regression introduced with pandoc 3. There is a one line fix to add --top-level-division=section \ after line 14 in the Makefile.

I added claude's full response to the github issue linked above.

TimeFlip2 and Harvest

2023-01-26T00:00:00-06:00

We use Harvest timetracking at work. I have a TimeFlip 2

It would really be great if I could use my timeflip with harvest.

Lodestar on Ubuntu

2022-02-10T00:00:00-06:00

In order to create a robust decentralized blockchain, Ethereum 2 will require a diverse set of clients. Prysm and Lighthouse are currently dominating. I will install Lodestar, a Eth2 implementation written in Typescript maintained by ChainSafe Systems via npm

Lodestar Documentation

Install Ubuntu

Install the latest Ubuntu LTS release (currently Ubuntu 20.04.3 LTS Focal Fossa)

Ubuntu desktop and server are the same but offer different default packages. I started with server because we don't need a desktop environment, office suite, web browser...

We will need make. This is achieved with:

sudo apt install build-essential

Lodestar requirements

The nodejs package in Ubuntu repositories is crusty. Install nvm (node version manager) Check their Github page for the latest version of the install script. Update your environment variables after running the script.

curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.1/install.sh | bash

source .bashrc

Now install node Long Term Support and yarn

nvm install --lts

nvm use --lts

npm install -g yarn

Install lodestar

npm install -g @chainsafe/lodestar-cli

Run

lodestar --help

If you get a -bash: /home/USER/.nvm/versions/node/v16.14.0/bin/lodestar: Permission denied error, run:

chmod +x ~/.nvm/versions/node/v16.14.0/lib/node_modules/@chainsafe/lodestar-cli/lib/index.js

Ansible for Windows

2016-05-31T16:24:00-05:00

A co-worker of mine is using Ansible to manage some windows hosts. I set up my own environment to do some testing for him. Recently released Ansible 2.1 has some new features for Windows management so I installed this from epel-testing. sshpass is also required.

Installation

On CentOS 7:

sudo yum -y --enablerepo epel --enablerepo epel-testing install ansible sshpass

You will also need pywinrm as well:

sudo pip install pywinrm

Configure Windows Clients

I followed the Windows System Prep guide on docs.ansible.com. The first suggestion is to run a powershell script on each Windows host. I have no reason to believe Ansible would be mailicious but I don't like the idea of running this script without needing to. Getting started, we only need to verify that powershell 3.0.0 or later is installed and that the WinRM service is installed and running. Open powershell and run the following commands:

$PSVersionTable.PSVersion
Get-Service "WinRM"

If powershell is too old or the WinRM service is not installed or not running, remedy these before moving on.

Create a local administrator account for Ansible to use.

Configure Ansible

Change to /etc/ansible and modify the "hosts" file. Declare a [windows] group and list one or more Windows hosts.

[windows]
workPC.mydomain.com
homePC.mydonain.com

Create the /etc/ansible/group_vars directory and create a "windows.yml" file in it. This will describe the local account to use, password, and connection settings.

ansible_user: ansible
ansible_password: secret_password
ansible_port: 5985
ansible_connection: winrm

Port 5985 is the default http port for WS-Management. We can switch to 5986 after an SSL certificate is arranged and installed.

The Results

That should be all we need. On the control server issue the following command:

ansible windows -m win_ping

workPC.mydomain.com | SUCCESS => {
    "changed": false,
    "ping": "pong"
}
homePC.mydomain.com | SUCCESS => {
    "changed": false,
    "ping": "pong"
}

Metro Transit CLI Bus Locations Part 2

2015-10-20T16:37:00-05:00

Continuing with the mtcli package, I added busloc.py which will display the locations of vehicles on a specified route. There are two main functions, getLocations(busNum) and openMap(busLocations).

First the user is prompted for a bus number. A call is made to the metro transit API to return an array of arrays of information about all the vehicles currently active on that route. Two of the attributes of interest are the latitude and longitude. I build a GeoJSON MultiPoint array of the GPS coordinates of each vehicle. More info on the GeoJSON format can be foud here.

I was recommended to a great resource in GeoJSON.io to display the locations on map in a browser. You can upload data in many forms to geojson.io or point it to an online datasets. Since I wanted a fluid experience with my application I chose to encode the coordinate data into the URL used to request the site. I used the urllib.parse.quote module to replace special characters in the coordinate data using %xx escape format. Finally webbrowser.open_new_tab(url) is called to open geojson.org with the location data.

Metro Transit allows you to specity "0" as a route number and it will return data on all vehicles currently in operation.

I am thinking about ways to combine mtcli.py and busloc.py into a single application.

All Metro Transit vehicles in operation at 16:00 on a Tuesday

Metro Transit CLI Bus Locations

2015-09-22T16:37:00-05:00

Metro Transit is the main transit operator in the twin cities. They have a fine website but a little too much clicking is required to find out when the next bus is going to roll by. I found the Metro Transit Web Services page to be just what I needed.

I wrote three functions to request the applicable directions of a specific route, the time stops on a route, and the next arrivals at a time stop. There is also some logic to present the user with the results of each query and enter input to craft the next request. I used

urllib.request</code>

and

xml.etree.ElementTree

from the python 3.4 standard library.

First the user is prompted for a route number and a call is made to the API to return the directions, either North - South or East - West, of that route. The data is returned in XML format as an array of text value pairs, the direction and a direcion code. ElementTree is used to parse them. I load the data into a list of lists so that I can display the options with a <code>0.</code> and <code>1.</code> identifier. The users input is used to select the index of the parent list, taking the first index of the child list, which is the direction code.

The direction code is used alond with the bus number to craft the next API call. An array of pairs is again returned. Time stops and a four character stop code are returned in order of the direction that was specified. A list of lists is again created and the users is promtped for a seletion.

The final call combines the route number, the direction of travel and the time stop location. A collection of "NexTripDeparture" are returned which contain information about the next vehicles scheduled to stop at the requested location. I print the arrival time, bus number, route description, and a "BlockNumber" designator for the vehicle. (maybe a bus number)

The code is on GitHub

Use git clone to clone is locally:

git clone https://github.com/twopercent/mtcli

Some more work can be done to pull out the XML parsing from the API call functions as it is very simiar in all three.