Seichy's Missing Bit

Project Log: MidiFaders - ESP-32 MIDI-BLE Faders

Sat, 04 Feb 2023 00:00:00 +0000

A while back I built a BLE MIDI controller. I was never too happy with it and had been meaning to take another stab at it.

My plan is pretty simple, I want a 4 or 5 faders in a small battery-powered box. I recently came across a TTGO display board. It brings most of what I need onboard, bluetooth, a screen, a couple of buttons, battery management and, best of all, a usb-c port.

I knew exactly what I wanted, so I went to my parts cabinet and grabbed some faders, and measured how many I could fit easily on that board.

Electrical Design

The electronics were pretty straightforward. I just needed all of my faders to be connected:

I rapidly routed a board, and proceeded to mill it.

Milling a PCB

I have a small desktop CNC I use for milling PCBs at home. I don’t use it nearly as often as I’d like but I love having it available. It’s much better than protoboard and way more fun.

I had a lot of issues milling this PCB though. It turns out most of the software I am used to using in Ubuntu flat out doesn’t work on a Mac M1. So I had to find solutions to some of those issues.

The biggest problem was FlatCam. FlatCam is awesome and I love it but it seems barely maintained and running it is getting harder every day. I decided to try out alternatives. It turns out there really aren’t any.

I ended up settling with Copper. This is a website provided by carbide3d that allows you to upload your layers and get a set of gcode files. You only get minimal options so I don’t think I’d use it for anything but a one-sided PCB but it seemed acceptable.

With my set of gcode files I felt ready to mill my PCB. Thankfully bCNC still runs flawlessly on a Pi so that part of my workflow remained intact. Here’s a quick rundown on how I usually do it (I’ll probably write a separate post to go into it in more detail).

I start by prepping a PCB blank. I clean it will alcohol and a scotch pad and set it on the bed using double-sided tape.

Next, I probe the PCB and set my working space.

I the autolevel but don’t click autolevel. If you’ve used bCNC before you know this breaks stuff.

After cleaning it up, we can do soldering. This is generally the easy part. I leave as much space as possible around my traces, as much as 1mm if there’s space. Soldering comes down to a lot of flux and as much solder as it takes. I’ll usually coat parts of the PCB with the excess solder, this is probably useless but I feel like it makes for a better connection on these homemade PCBs.

I’ll do a quick fit check with all parts and then start soldering.

It ended up looking pretty good.

Firmware~

So the firmware for these things is usually the hard part. My idea was extremely simple. Each fader should send, via bluetooth midi, a cc on a channel. These should be modifiable from within the device. The UI would have to be something I came up with as I went. I used the excellent arduino_midi_library with a bluetooth transport and everything went surprisingly smoothly.

In a couple of days I had implemented all menus, battery management, bluetooth and settings. Of the features I wanted to add, I am only missing presets and a web app to load these in. Overall I am extremely happy with how performant and easy to use it is.

Case

The case took a couple of iterations to get right. I hadn’t done any 3d printing in a while so I was a bit rusty.

After shifting around the design a bit I came up with something that was both easy to print and very functional.

The End ~

I am very happy with the final result. It came out really clean, easy to use and highly functional. Setting up new devices is fast and easy and since it’s compliant it connects seamlessly with other MIDI-BLE devices, like the widi masters.

Making Softcases for Small Electronics and Cables

Sun, 29 Jan 2023 00:00:00 +0000

Wraps are my favorite way of storing small electronics. Whenever I get a new one I’ll probably make one really quickly to store it and it’s accessories.

It’s a fairly straightforward process. Start with a piece of cloth. I really like this one, where it’s like felt on one side and like linen on the other. It makes it so the interior is really nice and soft.

I’ll start by measuring the device I’ll be wrapping. Once I’ve got the measurements I’ll lay my cloth on the floor and draw a rough rectangle. It’ll be a bit wider than needed and about four times the length of the device. This will let me wrap it comfortably a couple of times.

I’ll then cut this rectangle off.

I’ll then fold a third of this cloth on top of itself and sew it. I got a free sewing machine a while back (all it took was a couple of 3d printed replacement parts to get it working but that’s a story for another day) which I use for this.

Once that’s done I’ll flip it inside-out and sew any open borders to give it a cleaner look.

I’ll also sew a elastic on the open side so I can close it up.

I am not great a sewing.

I’ll then place the device inside, wrap it up and figure out where to put a button so that it closes up cleanly.

Buttons are hard. I’ll do as many passes as possible because I really suck at place them. Just doing a lot of passes will usually yield a nice looking result.

It’s all about confidence. Once it’s all done, you can insert the device in and wrap it, using the elastic as a latch.

DIY Midi Cable for the OP-Z and ZM-1

Sun, 15 Jan 2023 00:00:00 +0000

I’ve been using an old Rockband Keytar as a midi controller for the longest time. I usually take advantage of the OP-Z’s ability to be a MIDI host to use the keytar via a midi to usb adapter. This is fairly cumbersome as I have to use big cables and a USB-A to USB-C adapter.

Last year I got myself a ZM-1 module for the OP-Z which allows me to connect MIDI devices via a 3.5mm jack. These are fairly easy to put together and I had all the spare parts I needed hanging around already so I decided to make a couple.

All you need is a MIDI jack, and 3.5mm jack and some cable. I used a midi jack that already had it’s cable attached. I took this from a previous midi project so that cut the soldering in half.

I couldn’t find documentation stating weather this cable is meant to be type a or b or something else. So I tried wiring it as a type-A (a being the “standard” from what I know). This didn’t work, it turns out is actually type-B. Here’s the diagram:

Some soldering later and the cable is mostly ready:

I used some heatshrink as strain-relief. I was also lacking the piece of plastic that screws to the 3.5mm jack so I wrapped it in some extra heatshrink to give it some strength. Here’s the final cable:

Here’s what my keytar setup looks like now:

It works flawlessly and makes for a fun little weekend project.

Project Log: Some Sort of Guitar

Mon, 02 Jan 2023 00:00:00 +0000

I was lucky enough to be gifted an old, broken guitar.

It was in pretty rough shape. The bridge had been bolted to the body so when it started lifting it broke through the top.

I felt that it wasn’t really worth restoring it and that I’d rather try building something new on top of it. I was thinking that just adding a pickup would make it a bit more interesting.

I started by removing half of the top. Since I don’t care too much about the quality, I was able to remove the lower half quite easily with a utility knife.

I used this lower half to create a template to create a new lower half.

I used this template to cut a thin sheet of plywood to replace that piece. It’s a bit oversized but I will be sanding it down to size.

The new plywood was a bit thicker than the rest of the top so I had to plane the outer wall down so that both parts would be somewhat flush together.

January 22nd

Here’s the not-so-fun part. I started prepping the guitar for painting. I am thinking I want to paint the entire thing in a solid color, a dark one should make the entire thing easier to match.

I started with the body. I needed to make sure all edges were as neat as possible. There’s an upper bound to how good I think I can get it to look so I am trying to cover the basics at least.

I didn’t have a chisel on hand so I had to use a utility knife. It made the process rather slow but I got it done.

After cleaning the edges, I sanded the body.

Next I had to do the neck and fittings. I started by removing the old fittings, I don’t intend to buy new ones so I’ll have to clean these.

Luckily disassembly is pretty straightforward.

Next I prepped the neck. Some light sanding…

and some light scrapping…

and it was ready to be painted.

We applied a primer, to hopefully even everything out a bit.

Now it only needs a second coat of primer and we’ll apply it’s final color.

January 24

In the meantime, I’ve gone ahead and cleaned up it’s original hardware. I left it all submerged in a cup with 1 part of distilled white vinegar and 1 part water overnight.

The next day I had a go at it with a scotch pad and some steel wool under running water.

After letting it dry and having it reassembled, it all looked great.

Installing Gitea on Dokku

Sun, 07 Aug 2022 00:00:00 +0000

I’ve been meaning to backup my GitHub repos somewhere for a while. I recently discovered that Gitea can mirror them and will keep them updated. I am running Dokku on my dedicated server and pretty much run everything I can think of there. Gitea was a bit tricky to install so here are some notes.

You start by creating the app:

; dokku app:create gitea

Once that’s done, we can initialize it from the docker image:

; dokku git:from-image gitea gitea/gitea:latest

This is a good time to set the correct domain name and mount the Gitea directories.

; dokku domains:add gitea git.example.org
; dokku storage:ensure-directory gitea
; dokku storage:mount gitea /var/lib/dokku/data/storage/gitea:/data

We can rebuild the app now:

; dokku ps:rebuild gitea

Dokku will get some ports wrong sometimes, we should check those:

; dokku proxy:report gitea
=====> gitea proxy information
       Proxy enabled:                 true
       Proxy port map:                http:22:22 http:3000:3000
       Proxy type:                    nginx

Those look somewhat wrong, lets fix them:

; dokku proxy:ports-remove gitea http:3000:3000 http:22:22
; dokku proxy:ports-add gitea http:80:3000

We can enable LetsEncrypt now:

; dokku letsencrypt:enable gitea

That’s pretty much it! Seems a lot simpler once I’ve written it down. If you want to change the config file you can go ahead and edit it + restart the app:

; sudo vim /var/lib/dokku/data/storage/gitea/gitea/conf/app.ini
; dokku ps:restart gitea

Cheers!

The Pandemic

Fri, 05 Aug 2022 00:00:00 +0000

As the end¹ of the Pandemic approaches, I wanted to write a blog post to remind myself of these past 18 months and how we spent our time in exile. There isn’t really a point to this blog post in general it’s mostly a slice of my life and a lot of disconnected thoughts.

I originally started writing this post in August 8th, 2021. It took me a year to get around to finishing it but here it is. Better late than never I guess!

Before The Pandemic

My exile started a bit before the pandemic got to Honduras. Towards the end of the previous year (2019) I had a cancer scare. It turned out to be nothing but I developed a lot of anxiety around my health because of it. I had become overly weary of anything health related and hearing of this SARS-like disease that was showing up everywhere didn’t help. By that time everyone was a bit tired of my shenanigans and when I asked everyone around me to prepare for it I (understandably) was not taken very seriously.

Honduras is poor and I knew it wouldn’t take much for it’s system to collapse. If even rich countries seem to be struggling it wouldn’t really take much for the same to happen here. I told my mother that if she wanted to visit she’d have to do so before the first case was reported in Honduras. Once that happened I’d pretty much lock myself up and isolate for however long it took. She came to visit a couple of weeks before the first case, just in-case. It sounded like masks and hand sanitizer would be the first thing to fly off the shelves so I purchased some preemptively. I figured I was being overly dramatic but better safe than sorry. Having basic things I could hold to would make my anxiety easier to control I figured.

As the pandemic seemed to get closer I told everyone my plans of staying indoors until it was under control, that it might be a bit long but hopefully not more than a couple of months. The 8th of March, we had Arleth over for brunch, we talked about the upcoming pandemic over coffee.

On 10th of March, 2020 the first two cases of covid were reported in Honduras my lock down would begin two days later. The following day I dismissed the house staff, had them take the day off and go purchase groceries and supplies. I assured them that they would still receive their salaries and that they would have job once this was over.

The first month

Once the first cases were reported everything started moving too fast. By Sunday every supermarket was swamped with people and supplies started dwindling. I felt a bit validated knowing I had prepared myself with a couple months worth of food. That sense of validation didn’t really last long.

For the first couple of weeks everything was under strict lockdown and looked like Honduras wouldn’t spiral too bad. Wishful thinking.

The 20th we had a nice break with the release of Animal Crossing: New Horizons. It came in at the best time, the boredom was settling in and everyone with a switch was playing it. It felt like a community event, everyone was alone, playing together. It carried us over a month or two.

By the end of march the food was a little less varied so it seemed like the right time to resupply. It looked like all supermarkets were booked for deliveries for a month or so in advanced so we had to get creative. For non-perishable we used a small supermarket that specialized in organic goods. It’s variety wasn’t great and it was really expensive but it allowed us to get some basics and some not-so-basics while the regular supermarkets got their act together.

Mid April everything got a lot better. We found a local catering company that being unable to cater, had started selling vegetables, dairy and eggs. Getting fresh vegetables for the first time after almost two months gave me back my will to live.

The following 4 months

As the pandemic raged on I realized I was not doing too great. I had become a bit of a hypochondriac and had developed some anxiety. I had been stuck in my apartment for a while now so it seemed justified. One day I decided I wanted to get into therapy. I found a nice Colombian psychologist that would treat me online. It worked out great and after a month or two I felt better and was told I could stop going.

Whenever I am bored I get started on new hobbies. I had a ton of paint around the apartment so I started painting. I would experiment quite a bit with acrylics, I didn’t like how glossy they were but it grew on me. I eventually started drawing over them with markers and developed a bit of a “style”. I would paint quite a bit over the next couple of months.

As the sense of normalcy grew and I had more time off I started playing Call of Duty with Carlos and Carla. It happened almost by accident but we started playing a couple of hours every day. It was great fun, they’ve been my best friends for the longest time and being able to spend time with them, even if only online, felt awesome.

Eventually I fell back to my oldest habit, overworking. I decided I wanted to be more productive and get more done. I had been toying with an idea to help local companies get their products online. Honduras is really far behind on this sort of thing and during the pandemic it really showed. I’ve had an Estonian e-residency for a while so I used that to incorporate a business and started working on the app. I would let it sit to focus on my day job soon after.

Up to this point we had been using a small refrigerator I bought back when I first moved in. It was fine at the beginning but since getting delivery was hard it made more sense to order more food and store it than try to order when needed. We got a new fridge which was a pretty large QOL upgrade at the time. Sounds weird but it really cheered us up.

At this point my anxiety had improved so I decided to let myself drink coffee again. It’s always been a large part of my life so it felt like that’d help me go back “normal”. I decided to make a hobby off it (it technically already was) and got myself a espresso machine. I named it Pino.

I eventually start working on my small side project, a site to simplify selling online, elmarket.

The rest of 2020

Very little happened the rest of the year:

We raised moths.

We would raise more moths the following year at around the same time of the year.

Customs eventually reopened so we bought some extra art supplies. I got a new camera (Which I called Prismo). I painted some more. My sister suggested we run a book club, we read one book, tiny fire everywhere, I hated it and decided to stop book clubbing.

I took a couple of weeks off in December to try to chill for a bit.

A New Year

On my first day back after the Christmas break we were told at Azlo that our CEO was leaving. The following day they announced we would be shutting down. Our parent company had been sold off and no one really wanted to keep operating Azlo.

Since I was still stuck home I immediately started interviewing and looking for a new gig. I found a really nice job at Blueonion Labs. They were doing really cool things that closely matched the reconciliation stuff I was doing at Azlo. I would start the week after my birthday. I decided to ignore it that year, it didn’t seem fair to count it.

We got a roomba shortly after, it was surprisingly helpful, we were spending quite a bit of time cleaning and just having it run everyday made it way easier.

I started working at Blueonion Labs.

We found Pitt, the chunkiest boy. We originally offered him to Edward for adoption but he didn’t want to adopt him. After a couple of days, even though we thought we had enough cats, we ended up falling in love with him.

We finally got our first vaccine shot in August. It was nice, it felt like maybe it was coming to an end.

A bit later my grandfather died from Covid. My uncle followed a couple of weeks later.

I left my job. I was feeling a bit burnt out and depressed.

Towards the end of September we were fully immunized and decided it was time to start moving on. We started planning a trip, it’d be the third time leaving the house in 18 months. The other two were for vaccinations.

Shortly before leaving we found Gomita, the newest member of our family. We had no intentions of adopting another cat at the point but she needed a ton of help and it didn’t seem fair to pin her off on someone else. So we kept her. No regrets.

We left for Europe in October and spent a couple of weeks over there. I had to go to Estonia to open a bank account for the company I had founded the year before but we spent the rest of time relaxing and doing normally touristy stuff (mostly eating).

We are about 4 weeks away from being fully immunized which is as far as I know, the closest thing to an end there can be for the time being. ↩

Installing FlatCAM on Ubuntu

Fri, 22 Jan 2021 00:00:00 +0000

So FlatCAM is an essential part of my PCB milling workflow and has become increasingly difficult to install on the latest version of Ubuntu. Here’s a couple of notes on how I managed to get it running.

The first thing is to clone the repo:

git clone https://bitbucket.org/jpcgt/flatcam

Something I didn’t notice at first is that there’s a beta branch available, it uses newer versions of pyqt which makes everything way easier.

git checkout origin/Beta

If you are on Ubuntu you can run ubuntu_setup.sh and should install pretty much everything you need. I did hit a snag though, for whatever reason if I tried installing the requirements, gdal would not compile. Turns out it comes down to it not finding the correct headers. You can get around it by installing it manually like this:

sudo apt install libgdal-dev gdal-bin
pip install gdal==3.0.4 --global-option=build_ext --global-option="-I/usr/include/gdal/"

You should use whatever version gdal-config --version prints out. You should also update the requirements.txt so that the version of gdal is also the same so that the rest of the dependencies install.

Once that’s up you can run it with python FlatCAM.py.

Haproxy, Nginx and Dokku

Mon, 04 Jan 2021 00:00:00 +0000

I just finished setting up a wordpress site for my sister over the past weekend. I usually setup some plugins to automatically block bruteforce attempts on these since they are so common. Everything went smooth as usual until I checked in on it the next morning and found myself blocked. I checked the logs and it turns out it banned the reverse proxy’s ip.

I am using Haproxy as a reverse proxy / load balancer for the entire server but the ssl is handled by dokku which means Haproxy runs in tcp mode and doesn’t do much other than route the traffic. Dokku also has a reverse proxy which it uses to handle domains, it uses Nginx for this.

It turns out Haproxy can’t add requests to an https request that terminates on a different server. This makes sense but wasn’t obvious from the get go, the easy solution was to use the proxy protocol so that Haproxy and Nginx can agree on which ip is which.

Here’s how to do it:

First, we need to tell Haproxy to use the proxy protocol. All we have to do is add send-proxy to the server option. This will send over all of the info Nginx will need to find the correct ip.

backend web
        mode tcp
        server web-http dokku send-proxy

Next we need to tell Nginx to actually use that info. This is done by adding the proxy_protocol parameter to the listen option.

server {
  listen      443 ssl proxy_protocol http2;
  ...
}

Finally, we need to set the request’s X-Forwarded-For header to the real ip. We can achieve this by adding a new conf file in /etc/nginx/conf.d/set_real_ip.conf. You can name it whatever you want, it should look something like this:

set_real_ip_from  10.0.0.0/8;
set_real_ip_from  172.0.0.0/8;
real_ip_header proxy_protocol;

You should list off all of the proxies that are part of the chain here. proxy_protocol will take care to set the X-Forwarded-For ip to the correct value automatically.

KVM Backups, the easy way

Fri, 30 Oct 2020 00:00:00 +0000

I am now using a dedicated server to host all of my various projects. It turns out if you are willing to do a lot of the work yourself you can get quite a bit for you buck. Since I have to take care of backups myself now I had to rethink my general backup strategy.

In the name of being as lazy as possible what I’ve been doing now is using libvirt to create individual VMs for every project. To back them up I can just copy off the entire disk somewhere else. Once compressed these are relatively small for what they are and are easy to move around into storage.

I am also using git underneath almost everything so that actual code and assets are also backed up locally and on github/gitea etc.

Anyways, here’s what I am using to back machines up:

DOMAIN="$1"

DISK="$(virsh domblklist $DOMAIN | tail -n +3 | awk '{print $2}' | tr -d '\n')";
TIME=$(date "+%Y-%m-%d--%H.%M.%S");

virsh snapshot-create-as --domain $DOMAIN "$DOMAIN-backup" \
        --diskspec vda,file=/var/lib/libvirt/images/$DOMAIN-backup.qcow2 \
        --disk-only --atomic --quiesce --no-metadata;

xz -k --verbose /var/lib/libvirt/images/$DOMAIN.qcow2;

curl --netrc -T /var/lib/libvirt/images/$DOMAIN.qcow2.xz ftp://ftp.example.org/$DOMAIN.$TIME.qcow2.xz;

virsh blockcommit $DOMAIN vda --active --verbose --pivot;
rm /var/lib/libvirt/images/$DOMAIN.qcow2.xz;
rm /var/lib/libvirt/images/$DOMAIN-backup.qcow2;

First I create a snapshot for the current machine I’ll be backing up, these machines are running the qemu agent so I get to use --quiesce to freeze the file system. If you don’t have the agent installed you’d probably have to make some small changes to the command.

virsh snapshot-create-as --domain $DOMAIN "$DOMAIN-backup" \
        --diskspec vda,file=/var/lib/libvirt/images/$DOMAIN-backup.qcow2 \
        --disk-only --atomic --quiesce --no-metadata;

Once that’s done I’ll compress it using xz. This will make the backup tiny but it takes a really long time, you could use zip, tar or nothing at all if you want the whole process to be faster.

xz -k --verbose /var/lib/libvirt/images/$DOMAIN.qcow2;

Now we can upload the compressed file to our backup location. I use curl to upload to a local network drive I have available. I also attach a timestamp to the file name as I do this.

curl --netrc -T /var/lib/libvirt/images/$DOMAIN.qcow2.xz ftp://ftp.example.org/$DOMAIN.$TIME.qcow2.xz;

Finally I will use blockcommit to pivot back to the original disk image, merging the contents of the backup and anything that’s happened since the snapshot was taken, and remove the unnecessary snapshot and compressed files.

virsh blockcommit $DOMAIN vda --active --verbose --pivot;
rm /var/lib/libvirt/images/$DOMAIN.qcow2.xz;
rm /var/lib/libvirt/images/$DOMAIN-backup.qcow2;

It took me a bit to figure out how to do this which is why I am documenting it here for myself. Most of this is based of off this wiki entry.

PocketChip in 2020

Sat, 24 Oct 2020 00:00:00 +0000

After many years of wanting one and then giving up on them when the company went under, I finally acquired a PocketChip. This thing is great. Not all around great but great in principle. It has a great form factor with a nice screen and great battery life. I quite like it. I’ve been using it to control my plotters wirelessly, for counting words on my typewriter and to backup my op-z. I’ve ran into a bunch of issues along the way so here are my notes on it, what’s worked and what hasn’t in case someone else wants to give it a go.

Apt Sources

The first thing you should do is change you apt sources. It turns out when the NextThingCo went under they took their mirrors with them (naturally). Luckily a valuable member of the community took the time to create a mirror for it we can all use here. That same member of the community also took the time to mirror all of NextThingCo’s repositories and other goodies: http://chip.jfpossibilities.com/ this is in general the single best resource of data and code available for the chip in 2020.

I ran into an issue with Jessie backports, as the distribution is pretty old it’ll be necessary to update your apt sources to use the debian archive mirror:

deb http://security.debian.org/ jessie/updates main
deb-src http://security.debian.org/ jessie/updates main

deb http://archive.debian.org/debian/ jessie-backports main
deb-src http://archive.debian.org/debian/ jessie-backports main

deb http://archive.debian.org/debian/ jessie main contrib non-free
deb-src http://archive.debian.org/debian/ jessie main contrib non-free

Don’t forget to disable validity checks:

echo "Acquire::Check-Valid-Until false;" | sudo tee -a /etc/apt/apt.conf.d/10-nocheckvalid

SSH Access

The PocketChip doesn’t include an ssh server by default so I’d recommend installing one once you’ve gotten your apt updating and running:

sudo apt-get install openssh-server

Checking the Battery Level

There’s two magic files in the os that reflect your current battery state, you can use /usr/lib/pocketchip-batt/voltage to check how charged your PocketChip is and you can use /usr/lib/pocketchip-batt/charging to check if it’s charging or not. These are mostly useful for scripts and such.

The voltage range is from 3600 to 4200 from what I’ve seen.

Using UART

If you want to use the built-in UART you need to shutdown getty:

sudo systemctl stop serial-getty@ttyS0.service

You can then use /dev/ttyS0 as you normally would as a terminal or programmer and stty to check the config stty -F /dev/ttyS0 or change it stty -F /dev/ttyUSB0 9600.

A full desktop environment

If you want to have a full desktop environment running on your chip, you can use PocketDesk, which sets it up for you.

Using your GPIO Pins

This actually took a lot of tinkering and was going to be the original focus of this blog post.

PocketOS provides an easy way (once you figure it out) to enable or disable gpio pins. Under /sys/class/gpio there’s two sinks export and unexport. As root you can use export to enable a gpio pin by piping it the pin’s identifier:

echo 1015 > /sys/class/gpio/export

Apparently these identifiers changed depending on the OS version, on mine it starts with GPIO 1 as 1015 and follows with GPIO 2 on 1016 and so on. When you are done using a pin you should unexport it:

echo 1015 > /sys/class/gpio/unexport

While the pin is exported you can set three settings according to what you are trying to achieve:

Pin direction:

echo "in" > /sys/class/gpio/gpio1015/direction
echo "out" > /sys/class/gpio/gpio1015/direction

Active Low:

echo 1 > /sys/class/gpio/gpio1015/active_low
echo 0 > /sys/class/gpio/gpio1015/active_low

Edge detection:

echo "rising" > /sys/class/gpio/gpio1015/edge
echo "falling" > /sys/class/gpio/gpio1015/edge
echo "none" > /sys/class/gpio/gpio1015/edge

You can check the GPIO’s state by reading the value:

cat /sys/class/gpio/gpio1015/value
# Either 0 or 1 depending on the current state of the pin.

Since this behaves like a normal file and emits events you can use anything that uses inotify to watch it. For example, here’s how you’d monitor a button press using inotify-hookable:

cd /sys/class/gpio
echo 1015 > export
cd gpio1015

echo 0 > active_low
echo "in" > direction
echo "rising" > edge

inotify-hookable -f ./value -c "cat ./value"

There’s some extra information about the pins in the community wiki. The pin numbers seem wrong for the pocketchip but the rest of the information available seems solid.

Configure the app launcher

The default built-in launcher for the PocketChip, PocketHome, can be minimally configured by editing a json file /usr/share/pocket-home/config.json. You can change the apps and the icons from there among other small niceties.

I’d recommend changing the terminal to xfce-terminal, it comes pre-installed and seems to be better in general, I changed the terminal button to this:

{
  "name": "Terminal",
  "shell": "xfce-terminal --hide-borders --fullscreen --hide-menubar",
  "icon": "appIcons/terminal.png"
}

You need to restart the entire PocketChip for the changes to kick in.

Also, if you are ever using a keyboard, dmenu is installed and mapped to alt + space which is super nice for quickly switching apps.

And that’s it, I think, everything I’ve had to figure out about the PocketChip, distilled into one blog post. Let me know if there’s anything important you think I should know.