OpenBenches Train Sign

Displaying the most recent bench from https://openbenches.org/ on a 96ⅹ26 train sign.

There are three parts

• (transformer) a script to turn the OpenBenches RSS Feed into the text for the most recent bench
• (fetcher) an ESP8266 microcontroller to fetch the latest bench, and push it over I2C
• (controller) an Arduino to control the text on the sign, and listen on I2C for new text to display

Transformer

For this project, I only want "the inscription of the most recent bench". OpenBenches provides a geoJSON API, but I can't see a way to limit this to "most recent 1/5/10 benches" (see GitHub issue), so I use the RSS feed.

This bash CGI script parses the RSS feed and returns an HTTP request with the text of the most recently uploaded bench. It also includes the Last-Modified header using the RSS pubDate. It gets the description from the RSS description, and returns it, with newlines replaced with space " ", HTML entities decoded (i.e., ' & " → ' & "), and whitespace trimmed.

#!/bin/bash

feed=$(curl -s https://openbenches.org/feed)

echo "Content-type: text/plain"
echo "Last-Modified: " $(echo $feed | pcregrep -o1 '<pubDate>(.*?)</pubDate>' | head -n1)
echo ""

echo $feed | tr "\\n" " " | tr -d $'\r' | pcregrep -Mo1 '<description><!\[CDATA\[((\n|.)*?)<br>(\n|.)*?</description>' | perl -n -mHTML::Entities -e ' ; print HTML::Entities::decode_entities($_) ;' | sed 's/^\s*//' | sed 's/\s*$//' | head -n1

exit 0

This CGI script can be placed on an HTTP server by using this nginx config. When debugging SCRIPT_FILENAME, running sudo strace -f -e trace=file -p $(pidof fcgiwrap) will display all attempts to do things by fastcgi, which is very helpful.

server {
    ...
    location /bench {
        fastcgi_intercept_errors on;
        include fastcgi_params;
        fastcgi_param SCRIPT_FILENAME /var/www/localhost/bench.cgi;
        fastcgi_pass unix:/var/run/fcgiwrap.socket;
    }
    ...
}

For example, I have placed it on http://server.alifeee.co.uk/bench

IN MEMORY OF FRED KENYON 1927 TO 2012 Railwayman for over 40 years Love from all his Family

Fetcher

This is code to flash an ESP8266, in ./fetcher/.

To program the ESP, use Platform IO for VSCode or another method. To use PlatformIO, you must use VSCode.

Copy the example secrets file (./fetcher/src/secrets.example.h) and enter your Wi-Fi details, and the URL of the file to fetch (i.e., http://server.alifeee.co.uk/bench).

Controller

This is code to flash an Arduino Uno, in ./controller/.

It uses Serial communication to listen for messages, which are then displayed on the train sign.

For more information on this see the train sign repository.