Revision as of 02:20, 17 November 2016

Introduction

The Lightrouter

Up to now, the Lightrouter was our preferred workhorse for collecting and transmitting Lightmeter data. It's low-cost and low-power design allowed for continuous nightsky measurements, automatic data transmission and even - to some extent -  remote maintenance.

But, over time several issues surfaced: 

• The hardware version 2 of the WR1043ND rendered our firmware image obsolete, leading to a more manual setup routine.
• Future hardware versions will come with a locked firmware, preventing the use of OpenWRT (due to a new FCC rule).
• In offline-scenarios (no NTP, and no GPS) the internal clock performed terrible, exhibiting nonlinear, irregular drifts.
• The internal flash memory is not large enough to hold the entire setup, leading to the need of an overlay filesystem, creating a high dependency on the presence of the USB stick.
• Due to ill-defined brown-out behaviour of the router, the filesystem of several USB sticks got corrupted, leaving the stations paralyzed.
• Our central server died (summer 2016), leaving the reverse-SSH-tunnels dangling in mid-air, and thus preventing remote connections and data collection.
• Power consumption with up to 18W is too much for solar powered off-grid stations.
• Some gerneral reliability issues.

The LightPi

To combat all these shortcomings, the LightPi is under development. Based on a Raspberry Pi, extended by a realtime module, the LightPi will be easier to set up and to maintain, without increasing the price tag.

Some of it's main features are:

• High and reliable hardware availability, good inter-generation compatibility.
• Higher computing power and full debian-based operating system.
• Lower power consumption (2-4W [Model 3 B], 0.5-1.2W [Model A+]). * 
• 4 USB ports (Model B+ upwards), eliminating the USB hub.
• SD-card instead of small onboard flash - no more overlay filesystems.
• Highly accurate DS3231 RTC module (+/-3.5ppm).
• Simple plug-and-play with any FAT32 formatted USB stick for data storage.
• As inexpensive as the Lightrouter.

*...based on interpolation of various internet sources.

As the LightPi platform ist still under active development, several features are not yet implemented:

• Remote shell access (partly implemented).
• Data transmission/collection (planned).
• NTP synchronsiation (planned).
• GPS synchronisation (planned).
• On-site network service for data access (planned).
• Independence of a central server infrastructure (design guideline).

Current state

The LightPi project's current state is  developing / testing .

All the key networking capabilities have yet to be implemented, but the offline version is already up and running. First long-term reliability tests are currently in their starting phase.

Setup

Preparation

Hardware for the LightPi:

• Raspberry Pi (any model)
• DS3231 RTC module
• MicroSD / SD card (dep. on RasPi model) with 4+GB
• Power supply (5V, micro USB)
• USB stick (FAT32 formatted)
• For model A/A+/Zero USB hub
• For model Zero: USB-OTG adapter
• Optional, but recommended: A case for the RasPi

For the setup process you need:

• Your computer
• SD/MicroSD card reader
• HDMI capable monitor
• HDMI cable
• USB mouse
• USB keyboard

(The USB/HDMI items may be borrowed from your computer - no need for a second set.)

Optional, but highly recommended for the setup process:

• Internet connection via WiFi
• USB WiFi adapter (for all models except 3 B)

or:

• Internet connection via Ethernet
• USB Ethernet adapter (for models A/A+/Zero)

Configuration

LightPi RTC-Module.jpg

Raspberry Pi Model 3 B (left) and Model A+ (right), outfitted with a DS3231 RTC module (a third one on the bottom right).

...

--Nero2401 (talk) 00:43, 17 November 2016 (CET)