Tag: linux

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Raspberry Pi Setup

A few notes on how I set up new raspi systems, of which I am using quite a few for random home automation or toy things.

This is for the old version based on Debian Buster. For Debian Bullseye based OS just use the ‘advanced’ menu in the imager tool.

Prepping the SD card

  • Install “Lite” version of Raspberry Pi OS
  • This should have created one FAT formatted partition that Windows/Mac can access, this is the boot partition
  • Create file “ssh.txt” on boot partition to enable ssh right away, otherwise need to attach a screen for first login
  • If newer raspi and wifi should be used, create file “wpa_supplicant.conf” on boot partition (docs)
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1
country=<Insert 2 letter ISO 3166-1 country code here>

network={
 ssid="<Name of your wireless LAN>"
 psk="<Password for your wireless LAN>"
}

Initial Setup

  • Startup raspi, find IP in DHCP server or try direct ssh to host “raspberrypi” and cross fingers that something somewhere worked right (I think Unifi DHCP server automatically using DHCP provided hostname for DNS? Or is this some MDNS magic? No idea, never looked into it.)
  • Log in with username “pi”, default password “raspberry”
  • sudo raspi-config
    • set system-> hostname
    • set localization -> timezone
    • exit without reboot, it’s not necessary now
  • sudo su -
    • adduser kapet
    • adduser kapet adm
    • adduser kapet sudo
      • and more groups as necessary: dialout, cdrom, audio, video, plugdev, games, input, netdev, spi, i2c, gpio
    • Copy /etc/sudoers.d/010_pi-nopasswd for kapet and update it accordingly
    • reboot
  • Log in as “kapet”
  • sudo su -
    • disable login to the pi account: usermod -e1 -L pi
    • enable longrunning and at-boot started scripts for kapet: loginctl enable-linger kapet
    • apt update
    • apt dist-upgrade
    • apt install lsof tcpdump vim-nox
    • set the NTP server in /etc/systemd/timesyncd.conf
    • reboot

Other Potential Setup

  • set up basic X11: apt install raspberrypi-ui-mods
  • disable bluetooth on pi3: add dtoverlay=pi3-disable-bt to /boot/config.txt
  • when using any GPU to framebuffer magic like raspi2fb for a local LCD display remember to give the GPU enough memory through raspi-config, the minimum amount is not sufficient
  • setup Watterott display: docs

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A Surprisingly Useful Tool

20x magnifying stereo microscope, with a common ruler in its fangs.

Based on a recommendation from a coworker I bought a simple stereo microscope for around 30 Euro a while ago. I believe the manufacturers idea is that kids look at insects or little rocks with this (it actually comes with a few tiny splinters of different rocks), but this thing turned out to be extremely useful for several of the electronics stuff I’ve done lately.

For example I’ve used it to check my work after etching a PCB or soldering it. The magnification of 20x turned out to be perfect – it’s significantly better than my eyes but still “real” enough that I can interact with the object using small tools or a soldering bit.

I found having two occulars is not magically improving what I can see, but it certainly makes it less stressful to look through it for a long time. The magnified image shows about 8mm of object width.

In a recent case I was struggling with an Arduino Nano, which was connected to a Raspberry Pi, and just did not want to work if the host rebooted while it was plugged in the USB port. All I got were errors like this in the logfile:

May 23 20:32:28 raspberrypi kernel: [    3.707998] usb 1-1.3: new full-speed USB device number 4 using dwc_otg
May 23 20:32:28 raspberrypi kernel: [    3.807985] usb 1-1.3: device descriptor read/64, error -32
May 23 20:32:28 raspberrypi kernel: [    4.028021] usb 1-1.3: device descriptor read/64, error -32
May 23 20:32:28 raspberrypi kernel: [    4.257989] usb 1-1.3: new full-speed USB device number 5 using dwc_otg         
May 23 20:32:28 raspberrypi kernel: [    4.357989] usb 1-1.3: device descriptor read/64, error -32
May 23 20:32:28 raspberrypi kernel: [    4.577988] usb 1-1.3: device descriptor read/64, error -32
May 23 20:32:28 raspberrypi kernel: [    4.698153] usb 1-1-port3: attempt power cycle
May 23 20:32:28 raspberrypi kernel: [    5.358060] usb 1-1.3: new full-speed USB device number 6 using dwc_otg
May 23 20:32:28 raspberrypi kernel: [    5.818026] usb 1-1.3: device not accepting address 6, error -32
May 23 20:32:28 raspberrypi kernel: [    5.918003] usb 1-1.3: new full-speed USB device number 7 using dwc_otg
May 23 20:32:28 raspberrypi kernel: [    6.357982] usb 1-1.3: device not accepting address 7, error -32
May 23 20:32:28 raspberrypi kernel: [    6.358192] usb 1-1-port3: unable to enumerate USB device

Turns out the problem is not with the USB driver in the Linux kernel, but instead it’s a hardware bug in the Nano: The FTDI serial chip’s “TEST” pin was left unconnected. This way it “floats” after a power cycle and reliably prevented prober USB device enumerating. Ugh. I realized this is the problem after a lengthy search and finally stumbling over this issue in the FHEM wiki.

So here it goes, on the bottom side of the Arduino Nano I need to connect two freaking small SMD pins with each other, so TEST is reliably pulled to ground. I can hardly see those pins properly!

Perfect situation to use the microscope: Put a tiny blob of solder on the very tip of the soldering iron, veeeery slowly direct it to the right pins, and done!

With this the Nano gets connected properly whenever then Raspberry Pi reboots. 🙂

Microscope set up to allow viewing the bottom side of the Arduino Nano.
Solder blob connecting TEST and AGND pins.