Zoom on a Pi 4 (4GB)

It works using chromium not the Zoom app (which only runs on x86, not ARM). I tested it with a two-person, two-video stream call. You need a screen (I happened to have a spare 7″ touchscreen). You also need a keyboard for the initial setup, and a mouse if you don’t have a touchscreen.

The really nice thing is that Video4Linux (bcm2835-v4l2) support has improved so it works with both v1 and v2 raspi cameras, and no need for options bcm2835-v4l2 gst_v4l2src_is_broken=1 🎉🎉

IMG_4695

So:

  • Install Raspian Buster
  • Connect the screen keyboard, mouse, camera and speaker/mic. I used a Sennheiser usb speaker / mic, and a standard 2.1 Raspberry pi camera.
  • Boot up. I had to add lcd_rotate=2 in /boot/config.txt for my screen to rotate it 180 degrees.
  • Don’t forget to enable the camera in raspi-config
  • Enable bcm2835-v4l2 – add it to sudo nano /etc/modules
  • I increased swapsize using sudo nano /etc/dphys-swapfile -> CONF_SWAPSIZE=2000 -> sudo /etc/init.d/dphys-swapfile restart
  • I increased GPU memory using sudo nano /boot/config.txt -> gpu_mem=512

You’ll need to set up Zoom and pass capchas using the keyboard and mouse. Once you have logged into Zoom you can often ssh in and start it remotely like this:

export DISPLAY=:0.0
/usr/bin/chromium-browser --kiosk --disable-infobars --disable-session-crashed-bubble --no-first-run https://zoom.us/wc/XXXXXXXXXX/join/

Note the url format – this is what you get when you click “join from my browser”. If you use the standard Zoom url you’ll need to click this url yourself, ignoring the Open xdg-open prompts.

IMG_4699

You’ll still need to select the audio and start the video, including allowing it in the browser. You might need to select the correct audio and video, but I didn’t need to.

I experimented a bit with an ancient logitech webcam-speaker-mic and the speaker-mic part worked and video started but stalled – which made me think that a better / more recent webcam might just work.

Removing rivets

I wanted to stay away from the computer during a week off work so I had a plan to fix up some garden chairs whose wooden slats had gone rotten:

IMG_4610

Looking more closely I realised the slats were riveted on. How do you get rivets off? I asked my hackspace buddies and Barney suggested drilling them out. They have an indentation in the back and you don’t have to drill very far to get them out.

The first chair took me two hours to drill out 15 rivets, and was a frustrating and sweaty experience. I checked YouTube to make sure I wasn’t doing anything stupid and tried a few different drill bits. My last chair today took 15 minutes, so! My amateurish top tips / reminder for me next time:

  1. Find a drill bit the same size as the hole that the rivet’s gone though
  2. Make sure it’s a tough drill bit, and not too pointy. You are trying to pop off the bottom end of the rivet – it comes off like a ring – and not drill a hole into the rivet itself.
  3. Wear eye protection – there’s the potential for little bits of sharp metal to be flying around
  4. Give it some welly – I found it was really fast once I started to put some pressure on the drill
  5. Get the angle right – it seemed to work best when I was drilling exactly vertically down into to the rivet, and not at a slight angle.
  6. Once drilled, you might need to pop them out with a screwdriver or something of the right width plus a hammer

IMG_4616

More about rivets.

Pi / openCV / Tensorflow again

Cat detector code updated for Raspian Buster. I used lite. A few things have changed since the last time. The code is here.

Download Raspian

I got Raspbian Buster Lite (from https://www.raspberrypi.org/downloads/raspbian/ )

Burn it onto a SD card.

touch /boot/ssh
Add the wifi
nano /boot/wpa_supplicant.conf

The file should containing something like:

country=GB
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1
network={
   ssid="foo"
   psk="bar"
}

then eject the card and put it in the pi.

ssh into it from your laptop

pi@raspberrypi.local
password: raspberry
sudo nano /etc/hosts
sudo nano /etc/hostname

Reboot

sudo reboot

Set up a virtualenv for python

ssh in again, then:

sudo apt update
sudo apt-get install python3-pip
sudo pip3 install virtualenv -p
python3 env
source env/bin/activate
(env) pi@birdbot:~ $ python --version

Enable the camera

sudo raspi-config # and enable camera under 'interfacing'; reboot

Install Tensorflow

Increase the swap size:

sudo nano /etc/dphys-swapfile

The default value in Raspbian is:

CONF_SWAPSIZE=100

We will need to change this to:

CONF_SWAPSIZE=1024

Restart the service that manages the swapfile own Raspbian:

sudo /etc/init.d/dphys-swapfile restart

Install tensorflow dependencies

sudo apt-get install libatlas-base-dev
sudo apt-get install git
pip install --upgrade tensorflow

(this takes a few minutes)

Test that tensorflow installed ok:

python -c "import tensorflow as tf; tf.enable_eager_execution(); print(tf.reduce_sum(tf.random_normal([1000, 1000])))"

You may see an error about hadoop –

HadoopFileSystem load error: libhdfs.so: cannot open shared object file: No such file or directory.

See also tensorflow/tensorflow#36141 and tensorflow/tensorflow#36141. That doesn’t seem to matter.

You could try some user built tensorflow binaries – I tried this one, which seemed to corrupt my SD card, but not tried this one. Tensorflow 2 would be better to learn (the apis all changed between 1.4 and 2).

Install OpenCV

sudo apt-get install libjasper-dev
sudo apt-get install libqtgui4
sudo apt install libqt4-test

pip install opencv-contrib-python==3.4.3.18 #(see this)

test

python -c 'import cv2; print(cv2.__version__)'

Install camera dependencies

sudo apt-get install imutils picamera

Install speaking dependencies

sudo apt-get install espeak-ng

Finally:

git clone https://github.com/libbymiller/cat_loving_robot
cd cat_loving_robot
python classify_image.py

If you want to add the servos and so on for cat detecting and running towards cats, there’s more info in github.