How to wake up the WiFi on a Zero 2W (it was working but has stopped)

Bring it in and put a terminal and keyboard on it so you can look at the logs.

I have a 30 metre pi Pico and it connects anywhere between -80dM and 'not at all' for no visible reason - maybe its leaves blowing in the wind. I dunno.

Right now its a happy little -84dBm. Its having a good day.

That's not very easy, it's a bit of a 'fixed' installation. It might be easier to move one of the routers nearer to it.

I just checked the WiFi signal strength using an Android tablet right next to the Pi Zero and the better of the two SSIDs is around -70dBM so it **should** be OK I would have thought.

I think I have discovered the problem, the SD card is faulty/wearing out. I just tried to boot the system with a display attached and it sits repeating an error message about "bcm2835 timeout waiting for hardware interrupt".

Putting the card in a reader in my desktop machine it gets read

I think a (some?) new SD card is on the agenda! :-)

Well keyboards are portable enough. HDMI screen - not so much.

I get up to 20dB variation. Try rebooting it and see if you can get it back on target

Somewhere in my documentation is what I did to my pi zero in order to avoid any SD card writes at all

Basically I created a ram disk and mounted it on /var/log. And disabled systemd as much as possible.

Then ensure the SD card is mounted with noatime etc.

If you replace /sbin/init (usually symlinked to /lib/systemd/systemd) with a bash script you get to run in a truly read-only environment (root filesystem still mounted ro). Of course nothing in userland works at that point, so your script has to do some initialisation - setting up a ramdisk for a copuple of directories, as you said, mounting procfs, creating some device nodes, configuring IP, loading kernel modules if you need them (e.g. for wifi). Useful for small applications (forget running a GUI, obv.).

Brutal, but effective. Here's an example:

---------------------------------------------------------------------------- # cat init-ro #!/bin/bash

clear echo "Running ${0}..."

# # Config... #

source /etc/ro-config

export OUR_BC="${OUR_IP%.*}.255" export OUR_GW="${OUR_IP%.*}.1"

# # Need to set these so we can prime PS1 for bash... # (see nonsense in /etc/bash.bashrc)... #

export SUDO_USER=0 export SUDO_PS1="-"

# # Mount tmpfs filesystems on /run and /tmp, # as these need to be rw... #

mount -t tmpfs -o size=256m tmpfs /run mount -t tmpfs -o size=10m tmpfs /tmp

mkdir /run/lock mkdir /run/log

# # Need /dev/pts for ssh... #

mkdir /dev/pts mount -t devpts devpts /dev/pts

# # Need loopback... #

ifconfig lo up

# # Need /proc... #

mount -t proc none /proc

# # Set host name and domain name... #

hostname "${OUR_HOSTNAME}" domainname "${OUR_HOSTNAME#*.}"

# # If wifi, set up the wireless interface... #

# # Wait for interface to appear before # configuring it... #

while [ ! -d "/proc/sys/net/ipv4/conf/${OUR_IF}/" ] do echo "Waiting for interface \"${OUR_IF}\"..." sleep 1 done

# # Bring the interface up... #

ip link set "${OUR_IF}" up

# # Check if the MAC address matches the config. If not, don't # bring up the network, just pop up a shell to allow the config # to be updated (allows cloning of the image)... #

real_eth="$(ip addr list ${OUR_IF} | awk '/link\/ether/ {print $2}')"

if [ "${real_eth^^}" != "${OUR_ETH^^}" ] then echo "This MAC address (${real_eth^^}) doesn't match config (${OUR_ETH^^})" echo "" echo "Please edit config and reboot..." echo ""

cd /ro mount -o remount,rw /dev/root /

PS1="RW-SHELL \h:\w# " /bin/bash

reboot -f fi

# # Set the IP address and default route... #

echo "Setting IP address for ${OUR_IF}: ${OUR_IP}/24, gw: ${OUR_GW}"

ip addr add "${OUR_IP}/24" brd "${OUR_BC}" dev "${OUR_IF}" ip route add 0/0 via "${OUR_GW}"

# # Wait for network, check by pinging our default gateway... #

while ! ping -c 1 -q -w 1 "${OUR_GW}" > /dev/null 2>&1 do echo "Waiting for network, ping gw (${OUR_GW})..." sleep 1 done

# # Start ntpd to get the time... #

echo "Starting ntpd..."

/usr/sbin/ntpd -g

echo "Waiting for time sync..." ntp-wait -n 30 -s 1 date

# # Start sshd #

echo "Starting sshd..."

mkdir /run/sshd /usr/sbin/sshd

# # Now start application screen sessions... #

echo "Starting applications..."

cd /ro

./start-screens

# # Shell for testing... #

while true do PS1="RO-SHELL \h:\w# " /bin/bash done

# # We can't exit from init (causes kernel panic), so force a reboot if we get here... #

reboot -f

----------------------------------------------------------------------------

Don’t you need udev on /dev, and sysfs on /sys, as well?

There is no "udev" filesystem, and I don't need udev.

devtmpfs is already mounted on /dev, providing basic devices built into the kernel.

Could mount sysfs on /sys if it's needed, so far it hasn't been.