Another thing you can do later is use the serial port. It only requires three (dupont) connectors between a pair of rpi. Making it work first time though is typically problematic. You'd need to prefix "console=serial0,115200" into /boot/firmware/cmdline.txt (assuming bookworm) of the rpi you want to see the output from (rasp-config can do this iirc) and *not* do that for the rpi on which you want to see the output (the one you install minicom onto) then invoke 'sudo minicom -D /dev/serial0'
An overview. pi04 is the rpi I want to interrogate. pi03 is the one I run 'minicom' on..Now it should be simple..I've used 'ssh' to get into pi04..Now you'll see pi04 serial outpu flying by on the pi03 minicom terminal..You can log in via the serial console also. Note also option 'L' (capture) which you can enable/disable then look through "mincom.cap" so you can see all the output....pi04 is a waste of space to post here as it's headless eg:..is the only mention of hdmi when pi04 boots.
Thus, should it turn out your rpi has developed a broken display, you could use it as a serial device for other rpi. Both the above are headless - all done via 'ssh' on my linux PC.
Another esoteric point to bear in mind. One of my TV's has a moody hdmi port. First port works fine. Use the second hdmi tv input and tv outright lies to the connected device: that was nice (ahem, not) to discover one time while failing to get my first ever rpi5 to display correctly!
An overview. pi04 is the rpi I want to interrogate. pi03 is the one I run 'minicom' on..
Code:
foo@pi04:~ $ cat /boot/firmware/cmdline.txt console=serial0,115200 console=tty1 root=PARTUUID=ab9d44c3-02 rootfstype=ext4 fsck.repair=yes rootwaitfoo@pi03:~ $ cat /boot/firmware/cmdline.txtconsole=tty1 root=PARTUUID=97d75629-02 rootfstype=ext4 fsck.repair=yes rootwaitfoo@pi03:~ $ sudo minicom -D /dev/serial0Welcome to minicom 2.8OPTIONS: I18n Port /dev/serial0, 19:13:31Press CTRL-A Z for help on special keys#[hit CR]pi04 login: #[hit ctrl-a z] | Minicom Command Summary |OPTIO| |Port | Commands can be called by CTRL-A <key> | | |Press| Main Functions Other Functions | | | | Dialing directory..D run script (Go)....G | Clear Screen.......C |pi04 | Send files.........S Receive files......R | cOnfigure Minicom..O | | comm Parameters....P Add linefeed.......A | Suspend minicom....J | | Capture on/off.....L Hangup.............H | eXit and reset.....X | | send break.........F initialize Modem...M | Quit with no reset.Q | | Terminal settings..T run Kermit.........K | Cursor key mode....I | | lineWrap on/off....W local Echo on/off..E | Help screen........Z | | Paste file.........Y Timestamp toggle...N | scroll Back........B | | Add Carriage Ret...U | | | | Select function or press Enter for none. #[hit o] | Filenames and paths | | File transfer protocols | | Serial port setup | | Modem and dialing | | Screen and keyboard | | Save setup as dfl | | Save setup as.. | | Exit^^^select "Serial port setup"OPTI+-----------------------------------------------------------------------+Port| A - Serial Device : /dev/serial0 | | B - Lockfile Location : /var/lock |Pres| C - Callin Program : | | D - Callout Program : | | E - Bps/Par/Bits : 115200 8N1 |pi04| F - Hardware Flow Control : Yes |Pass| G - Software Flow Control : No | | H - RS485 Enable : No |Logi| I - RS485 Rts On Send : No |pi04| J - RS485 Rts After Send : No |Logi| K - RS485 Rx During Tx : No |Rasp| L - RS485 Terminate Bus : No | | M - RS485 Delay Rts Before: 0 |pi04| N - RS485 Delay Rts After : 0 | | | | Change which setting? | +-----------------------------------------------------------------------+^^^check options A,E are correct (likely are).#[hit ESC until all options have gone away..]#[hit ctrl-a x to quit minicom]Code:
foo@pi03:~ $ sudo minicom -D /dev/serial0#[hit CR]Welcome to minicom 2.8OPTIONS: I18n Port /dev/serial0, 19:20:24Press CTRL-A Z for help on special keyspi04 login: Code:
foo@sdu:~$ ssh foo@pi04foo@pi04:~ $ df -hPFilesystem Size Used Avail Use% Mounted onudev 80M 0 80M 0% /devtmpfs 43M 976K 42M 3% /run/dev/mmcblk0p2 14G 2.5G 11G 19% /tmpfs 214M 0 214M 0% /dev/shmtmpfs 5.0M 12K 5.0M 1% /run/lock/dev/mmcblk0p1 510M 109M 402M 22% /boot/firmwaretmpfs 43M 0 43M 0% /run/user/1000foo@pi04:~ $ sudo rebootSorry, user foo is not allowed to execute '/usr/sbin/reboot' as root on pi04.^^^oopsfoo@pi04:~ $ sudo su -root@pi04:~# root@pi04:~# rebootCode:
pi04 login: [ 996.540216] watchdog: watchdog0: watchdog did not stop![snip][ 23.375802] systemd[1]: Finished modprobe@drm.service - Load Kernel Module d.[ 23.463398] systemd[1]: modprobe@efi_pstore.service: Deactivated successfull.[ 23.515743] systemd[1]: Finished modprobe@efi_pstore.service - Load Kernel M.[ 23.623500] systemd[1]: modprobe@fuse.service: Deactivated successfully. [ 23.675718] systemd[1]: Finished modprobe@fuse.service - Load Kernel Module .[ 23.763185] systemd[1]: modprobe@loop.service: Deactivated successfully. [ 23.823632] systemd[1]: Finished modprobe@loop.service - Load Kernel Module .[ 23.913391] systemd[1]: Finished systemd-modules-load.service - Load Kernel .[ 23.977940] systemd[1]: Finished keyboard-setup.service - Set the console ke.[ 24.040103] systemd[1]: Started systemd-journald.service - Journal Service. [ 24.914758] systemd-journald[192]: Received client request to flush runtime .[ 25.083736] systemd-journald[192]: File /var/log/journal/6b2c82362486457f99c. Raspbian GNU/Linux 12 pi04 ttyAMA0 pi04 login:[hit ctl-a x to exit minicom]Code:
foo@pi03:~ $ less minicom.capCode:
foo@pi03:~ $ egrep -i hdmi minicom.cap [ 0.000000] Kernel command line: coherent_pool=1M snd_bcm2835.enable_headphones=0 snd_bcm2835.enable_headphones=1 snd_bcm2835.enable_hdmi=1 snd_bcm2835.enable_hdmi=0 vc_mem.mem_base=0x1ec00000 vc_mem.mem_size=0x20000000 console=ttyAMA0,115200 console=tty1 root=PARTUUID=ab9d44c3-02 rootfstype=ext4 fsck.repair=yes rootwaitThus, should it turn out your rpi has developed a broken display, you could use it as a serial device for other rpi. Both the above are headless - all done via 'ssh' on my linux PC.
Another esoteric point to bear in mind. One of my TV's has a moody hdmi port. First port works fine. Use the second hdmi tv input and tv outright lies to the connected device: that was nice (ahem, not) to discover one time while failing to get my first ever rpi5 to display correctly!
Statistics: Posted by swampdog — Sun Jul 28, 2024 6:58 pm
