Mesh Station 24.01

Community Cluster compute station
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1. Raspberry Pi Zero W

Mesh Stations running the Raspberry Pi OS are called Raspberry Mesh Stations. Like other Mesh Stations they are ultra low cost and generally have less than 2GByte of random access memory (RAM).

The Raspberry Pi Zero W is the Reference Mesh Station for the Private Cyberspace 20.12 release.

Raspberry Pi Zero W measures only 65mm by 30mm, but has a lot of features.

rpi0wh_1
image source: micro robotics

As of September 2023, Raspberry Pi Zero W should be available cheaply in reasonable quantity worldwide.

1.1. Zero WH

A slightly more expensive version called "Raspberry Pi Zero WH" is just a "Raspberry Pi Zero W" but WITH headers soldered on (thus the extra H at the end of the name).

rpi0wh
rpi0wh3340×1174 565 KB

The above image shows a Raspberry Pi Zero W next to a Raspberry Pi Zero WH, both mounted according to our novel Spacer Wall design.

Although headers are NOT required in most use cases, when given a choice it is best to pick the Zero WH, so the 40 expansion pins can be used to attach peripherals instantly.

1.2. Zero 2 W

An improved Raspberry Pi Zero 2 W model has been released but it is in very short supply.

Similarities

  1. Memory size (512MB)
  2. Physical size (65mm x 30mm)
  3. WiFi Frequency (2.4GHz)
  4. Connectors (2 micro-USB, 1 mini-HDMI, 1 CSI-2)

Differences

  1. Zero 2 W has a 64-bit 4-core processor
    Zero W has a 32-bit 1-core processor

  2. Zero 2 W has Bluetooth 4.2
    Zero W has Bluetooth 4.1

  3. Zero 2 W has no microSD limit
    Zero W has 256GB microSD limit

  4. Zero 2 W produced until at least Jan-2028
    Zero W produced until at least Jan-2026

A more detailed comparison is available

Zero 2 W and its header version Zero 2 WH may be used as future Reference Mesh Stations but currently, only the Zero W and Zero WH models are being used as the 20.12 Reference Mesh Station.

1.3. Dimension

Raspberry Pi Zero W is light and small, besides the "standard" positioning on the window sill, it can be deployed almost anywhere e.g. stick on to the window glass with adhesive tape or throw into a backpack with a battery pack.

rpi0wh

1.1. Comparison with Other Mesh Stations

In order to deploy billions of Mesh Stations (e.g. having a Mesh Station sitting on the window sill of every room in the world) the Raspberry Mesh Station has been designed with extreme low cost in mind.

due to the scale of its deployment.

We are talking about tens of billions of devices , saving just 10 cents is a billion dollars.

1.2. Comparison with Mobile Station

2. Wireless Performance

Frequency Band

Rpi0w only has a 2.4GHz wifi radio that is NOT capable of running as a mesh

Antenna Pattern

Zero W uses a resonant cavity antenna design from Proant to reduce cost.

Raspberry Pi Foundation will not release the antenna pattern freely to the public (needs signing some documents), luckily Carl Turner has measured the antenna pattern and published it freely!

rpi0w

Note from the pattern that the radio signal on the header side is rather weak, which our

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1. Micro USB Ethernet Hub

An optional Micro-USB Ethernet Hub can be added to Mesh Stations to give them extra features. Typically these hubs expands the single micro-SD port on the Mesh Station into 3 x USB2 Type A female ports and also 1 x 100BaseTX ethernet port.

Although Multiple Transaction Translator (MTT) hubs have higher performances, these Micro-USB Ethernet Hubs are normally of the cheaper Single Transaction Translator (STT) type.

Troubleshooting

Some links to help you troubleshoot your Micro-USB Ethernet Hub:

2. CoreChips based Ethernet Hub

Micro-USB Ethernet Hubs built with Corechips components tends to be cheapest. Some of them will have problems with its ethernet driver (please see section below on "Fixing Linux Driver"), so do not expect the ethernet to work easily, but they are so CHEAP in Australia (less than AUD10 including tax and delivery) they are worth buying just for the 3 x USB2 ports alone and the whole device is packaged in such a small and convenient physical form factor.

2.1. Hardware Design

When we opened up some CoreChips based ethernet hubs, we discovered that the traditional transformers are replaced with capacitors by using capacitive coupling, we cannot find any documentation on using capacitors from CoreChips but there are plenty from others (e.g. Realtek, Texas Instruments etc.).

CoreChips_Ethernet

As an interesting aside, it is possible to have ethernet RJ45 connectors with integrated transformers hidden inside (so there is no need for any external transformer), like Raspberry Pi RJ45 connectors which has transformers.

Although using capacitive coupling can be considered low-end and are not suitable in all situations, they can be used in some limited situations after considering all the pros and cons e.g. using it only occasionally, always using less than one metre of Cat5e or better grade cables, connecting only to "compatible" ethernet devices that can tolerate others not having transformers, powering both devices from the same extension board etc.

2.2. CoreChips SL2.1A

CoreChips_SL2-1A.pdf (385.1 KB)

  • this is a Single Transaction Translator Hub

2.3. CoreChips SR7600

The ethernet chip is normally the CoreChips SR7600, which seems to be the same as the CoreChips RD9700 in almost every way:

Fixing Linux Driver

Some CoreChips SR9700 based Ethernet Hubs have USB Device ID that are DIFFERENT to the 0x9700 defined in the Linux driver:

https://github.com/torvalds/linux/blob/master/drivers/net/usb/sr9700.c

Instead of 0x9700, these Ethernet Hubs have numbers like 0x9702. For them to work properly under Linux, these extra Device IDs need to be added to the Linux driver.

3. Terminus Technology

Terminus has a number of USB Hubs.

3.1. Terminus FE1.1

Terminus_FE1-1S.pdf (409.2 KB)

  • this is a Single Transaction Translator Hub
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WiFi

The onboard wifi adapter can be made to work as BOTH an access point and a managed client.

4

Audio Peripheral

If possible add MEMS instead of ECM microphones to your Mesh Station.

USB Microphones

Header based Microphone and Speaker

HAT based Microphone and Speakers

5

Relay

Relay should be 3.3V instead 5V.

3V_relay

Notice "03VDC" printed on the blue relay box in the image above.