Hi,

 

a few months ago I have build a USB to UART "multiplexer" device, to monitor my multiple Orange Pi PC's using only one USB connection to a separate Host [1].

 

You can connect up to 8 hosts to the device simultaneous. And you can switch between the different inputs.

Only one USB connection is needed to your host you want to use as master.

A commandline tool is available to control the device.

 

Its also possible to send data through the device to the connected hosts. It works like a normal USB to serial adapter.

It is not possible to read the incoming data from all connected hosts simultaneous.

 

I am use it to log the boot process of my cluster nodes [2].

 

Maybe someone is interested. It is OpenSource and OpenHardware [3].

 

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[1] The device: https://klautesblog.blogspot.de/2016/09/usb-serial-multiplexer-usb2serialmux.html

[2] My cluster: https://klautesblog.blogspot.de/search/label/ChinaCluster

[3] Git project: https://git.okoyono.de/klaute/USB2SerialMux

Can you please estimate the costs of a fully equipped USB2SerialMux unit?

 

BTW: From time to time I think also about clusters made of cheap Allwinner devices (but still miss the use case to be honest) and based on wasted space for cabling I came up with a test setup a few weeks ago: Use one GbE equipped H3 device (OPi Plus 2E in my case) as 'cascading host' to interconnect 3 smaller H3 devices. All H3 devices we support can use their Micro USB port also as 'Ethernet connection' (g_ether module, slightly faster than Fast Ethernet).

 

Test setup was: OPi Plus 2E powering each NanoPi NEO through a dedicated USB port while also building the br0 device out of eth0, usb0, usb1 and usb2 network devices. Only connection to each NEO was just a short Micro USB cable and for those devices it didn't felt differently compared to be connected to a switch through Ethernet (since OPi Plus 2E bridged all interfaces). Unfortunately this won't work in a cluster setup since then consumption of the cluster nodes is too high.

 

But using eg. one Marvell ESPRESSOBin as master, connecting to 3 Orange Pi PC 2 (H5 based, GbE Ethernet and I believe exposing 3 UARTs on the 40 pin header each) which each connects 3 NanoPi NEO w/o Ethernet jack populated one would get a cluster setup with 12 Cortex-A53 cores (not counting those of the Marvell master) and 36 Cortex-A7 cores with minimal space and cabling requirements. The 9 NanoPi can be powered through jumper wires, same with the 3 OPi PC 2 and for interconnection no Ethernet switch is needed (just 9 short Micro USB and 3 short Cat-5e cables and an USB-to-Ethernet adapter plugged into the Marvell to get external connectivity for the whole cluster).

 

Not even SD cards would be needed in case one follows the 'cascading scheme' a little more and implements FEL/network boot (first the H5 devices would be booted by the ESPRESSOBin and then they would FEL boot the H3 devices, all the rootfs remaining on fast SSD storage on the ESPRESSOBin)

The costs of a fully equipped device is about 10$ (exclude the shipping).

 

Order your PCB from oshpark cost 13$ because you have to order at least 3 pieces.