50.1.20.31
dsl_modem----switchA------------router------lan---wifi-----pi4 RasPiOS workstation
               |         gateway.zefox.net  |           | 
               |                            |           |---Mac workstation
               |                            |
               |                            |------printer
  |------------|			    |-------Win10 laptop
  |
  |-50.1.20.29 ns1.zefox.net Pi3 14.0 aarch64 ftdi usb-serial----50.1.20.25
  |-50.1.20.30 ns2.zefox.net Pi2 12.3 armv7 2303 usb-serial----50.1.20.29
  |-50.1.20.27 www.zefox.net Pi2 12.3 armv7 2303 usb-serial----50.1.20.26
  |-50.1.20.24 pelorus.zefox.org Pi3 14.0 arm64  ftdi usb-serial---50.1.20.28
  |---50.1.20.28 www.zefox.org Pi3 arm64 current ftdi usb-serial--50.1.20.27
 switchB
  |---50.1.20.25 nemesis.zefox.com Pi4 arm64 current ftdi usb-serial--50.1.20.30
  |---50.1.20.26 www.zefox.com Pi2 armv7 releng/14 ftdi usb-serial--50.1.20.24

Each host acts as a terminal server with the serial end connected 
to the GPIO serial console of another host in the group. So long as 
the network and any one host come up it's possible to work around 
the ring putting other hosts back on the network. If the network
does not come up it's possible to "tipfrog" from one host to the
next, but gets very confusing very fast.

Normal practice is to keep an lxterminal window on pi4 workstation 
whenever it's up containing a separate tab for ssh connection to
each terminal server.

A tip session on each terminal server host connects to the gpio console pins
of the corresponding host to monitor its console output.

While possible to "tipfrog" from one host to the next (for example, 
if the network is down) it's extremely confusing. BTDT 8-)


Here are config.txt of each host. 

	50.1.20.30 ns2.zefox.net Pi2 v1.1
bob@ns1:~ % cat /boot/msdos/config.txt
init_uart_clock=3000000
enable_uart=1
kernel=u-boot.bin
kernel7=u-boot.bin
dtoverlay=mmc
bob@ns1:~ % 

	50.1.20.29 ns1.zefox.net Pi2 v1.1
bob@ns2:~ % cat /boot/msdos/config.txt
init_uart_clock=3000000
enable_uart=1
kernel=u-boot.bin
kernel7=u-boot.bin
dtoverlay=mmc
bob@ns2:~ % 

	50.1.20.27 www.zefox.net Pi2 v1.1
bob@www:~ % cat /boot/msdos/config.txt
init_uart_clock=3000000
enable_uart=1
kernel=u-boot.bin
kernel7=u-boot.bin
dtoverlay=mmc
bob@www:~ 

	50.1.20.24 pelorus.zefox.org Pi3
bob@pelorus:~ % cat /boot/efi/config.txt
[all]
arm_64bit=1
dtparam=audio=on,i2c_arm=on,spi=on
dtoverlay=mmc
dtoverlay=disable-bt
device_tree_address=0x4000
kernel=u-boot.bin

[pi4]
hdmi_safe=1
armstub=armstub8-gic.bin
bob@pelorus:~ % 

	50.1.20.25 nemesis.zefox.com Pi4
bob@nemesis:~ % cat /boot/msdos/config.txt
[all]
arm_64bit=1
dtparam=audio=on,i2c_arm=on,spi=on
dtoverlay=mmc
dtoverlay=disable-bt
device_tree_address=0x4000
kernel=u-boot.bin

[pi4]
#hdmi_safe=1
armstub=armstub8-gic.bin
gpio=2,3=a0
bob@nemesis:~ % 

	50.1.20.26 www.zefox.com Pi2 v1.1
bob@www:~ % cat /boot/msdos/config.txt
init_uart_clock=3000000
enable_uart=1
kernel=u-boot.bin
kernel7=u-boot.bin
dtoverlay=mmc
bob@www:~ % 

	50.1.20.28 www.zefox.org Pi3
bob@www:~ % cat /boot/msdos/config.txt
[all]
arm_64bit=1
dtparam=audio=on,i2c_arm=on,spi=on
dtoverlay=mmc
dtoverlay=disable-bt
device_tree_address=0x4000
kernel=u-boot.bin

[pi4]
hdmi_safe=1
armstub=armstub8-gic.bin

# Local addition:
[all]
force_mac_address=b8:27:eb:71:46:4f
bob@www:~ % 

20240113