{"id":181,"date":"2016-04-29T21:27:48","date_gmt":"2016-04-29T20:27:48","guid":{"rendered":"http:\/\/eoghan.me.uk\/notes\/?p=181"},"modified":"2017-12-01T18:28:24","modified_gmt":"2017-12-01T18:28:24","slug":"raspberry-pi-nfc","status":"publish","type":"post","link":"https:\/\/eoghan.me.uk\/notes\/2016\/04\/29\/raspberry-pi-nfc\/","title":{"rendered":"Raspberry Pi with NFC"},"content":{"rendered":"

Note<\/strong>: This NFC project uses a Raspberry Pi 2 Model B, and the proceedure may be different to connect RC522 RFID readers to older Raspberry Pis. This is also a work in progress, and these notes are not yet complete.<\/p>\n

A few friends from work and I are taking part in a sponsored climb<\/a>, six of us climbing the height of the U.K. three peaks (11,180ft) between us on an indoor climbing wall over six hours. One part of our preparation is working out how we’re going to keep track of the height we have climbed as we go up and down an 8m wall.<\/p>\n

What if each of us had an NFC tag on our wrists which we could tap on an NFC reader at the top of the wall? (Or might be safer to tap when we were safely back on the ground.) A slight complication is that there are two heights of wall we might climb, 8m and 6m – so we could have two NFC readers to tap, one for each wall height. This sounded like a nice Raspberry Pi project.<\/p>\n

\"The<\/a>
The two RC522 NFC readers wired up to the Raspberry Pi<\/figcaption><\/figure>\n
\"Attached<\/a>
The finished contraption duct taped to the climbing wall<\/figcaption><\/figure>\n

Looking on the Net, I first found an Attendance system using Raspberry Pi and NFC Tag reader by Yim<\/a> which seemed a good place to start.<\/p>\n

The plan<\/h2>\n

The plan would be something like this:<\/p>\n

    \n
  1. A Raspberry Pi with two NFC sensors would be set up at the bottom of the climbing walls (somehow safely out of the way of climbers and belayers). One sensor would have a notice on it saying “8m”, the other one saying “6m”<\/li>\n
  2. Each climber would have a wristband with an NFC tag attached to it.<\/li>\n
  3. After reaching the top of the wall, and abseiling back down, each climber would tap their wrist tag on the sensor for the height of the wall they had just climbed.<\/li>\n
  4. The Raspberry Pi would determine which sensor had been tapped by which tag (i.e. what height wall had been climbed by which climber).<\/li>\n
  5. The Pi would sound a buzzer and\/or light up an LED to indicate a successful read.<\/li>\n
  6. The Pi would then update a MySQL database on a web host with the wall height and climber ID.<\/li>\n
  7. A simple PHP script would read the MySQL database, and display a running total of the height left to climb, so people could follow us live online.<\/li>\n<\/ol>\n

    This application would only need to read the ID of the tags, so it wouldn’t read or write data to them – though that could be an idea for an improvement.<\/p>\n

    Bearing in Mind<\/h3>\n

    I expect I would need to wait a few seconds after a successful read before accepting another reading from the same tag\/climber, so we don’t accidentally record multiple ascents for the same climber if they leave their tag in contact with the reader for a couple of seconds.<\/p>\n

    Updated plan<\/h3>\n

    The original idea was to update a MySQL DB on an external webserver, so the data was safely off the Pi in case it crashed.<\/p>\n

    But my web server won’t allow an external device to write to its MySQL databases unless the external device’s IP address is registered (see Troubleshooting section below). However, running the Raspberry Pi off the eduroam WiFi network, we can’t get a static IP address for the Pi, nor can we be sure what the external IP address would be. So even if we did register the IP address it was using on eduroam, we couldn’t be sure the Pi would continue using that same IP address, and might find my web server blocks it from writing to its MySQL DBs.<\/p>\n

    So the new plan was to was to install Apache, PHP and MySQL on the Pi, and write to the Pi’s own DB.<\/p>\n

    But, because of the same problem knowing the Pi’s IP address on eduroam, our friends outside wouldn’t be able to connect to it to view our progress.<\/p>\n

    So the final plan was to write to the Pi’s own MySQL DB, use PHP on the Pi to build the web page (drawing on the info in the DB) – then copy that completed web page onto my web server.<\/p>\n

    This proved a good system, because the Pi periodically lost it’s WiFi connection, but the info was still being collected on the Pi, and could be uploaded to the web server when the WiFi connection picked up again.f<\/p>\n

    The parts<\/h2>\n