ESP8266/Arduino: processing huge JSON objects directly on the ESP

For a while now I wanted to improve my weather station project by adding more sources of information that can be displayed. But these sources I had in mind either used SSL (https) or delivered huge JSON responses. SSL is not yet supported on the ESP8266/Arduino platform (and from what I hear also broken on Nodemcu/Lua). Big JSON objects are a problem because all the existing libraries I tried are DOM based which consumes a lot of memory since.....

ESP8266/Arduino: Playing around with the upcoming filesystem feature

I recently stumbled on a feature that hopefully soon will be integrated into the stable release of the ESP8266/Arduino environment: a file system interface. Low-Level: EEPROM Up until now and currently your best bet for data persistence in the stable release you could use the EEPROM interface to write and read your data so it would be available between reboots of the device. This persistence interface is pretty lo.....

ESP8266/Arduino: MAX7219 8×8 Led Matrix Library

Twice a year the company I work for (Netcetera) organizes a retreat for programmers, usually in the mountains. In the Spring issue this year we went to a resort in a beautiful mountain region. Inspired by the wonderful landscape I managed to write a library for the recently published Arduino IDE for ESP8266 which allows you to manipulate pixels and write animated.....

ESP8266: Using a seeeduino to talk to the ESP8266 module directly

I recently received two of these shiny new Wifi modules from China and had to test them out. In many posts around the web they say you should use a serial-to-usb adapter to send some AT commands to the module and set it up with your local access point. My problem was: I didn’t have such an adapter, or so I thought. It turns out you can use some types of Arduino’s for the job just fine. I had a Seeeduino V3.0 laying around and that.....

DevDuino Sensor Node – Part 1 – Programming the DevDuino

It took me far too long to get this working, but I finally did it: a small Arduino compatible board called “DevDuino” running on a CR2032 cell battery is sending temperature and battery voltage over the air to another Arduino board which records it. Sounds easy, doesn’t it? Well, it depends…: which Arduino are you using? how good is the documentation of the DevDuino?.....

Turn on/off USB Power on TL-MR3020 running OpenWrt to restart Arduino

In a later blog post I will describe how I am using a TL-MR3020 router as low-cost wifi shield for my Arduino to transmit sensor data over wifi. In this post I just want to show how you can script a restart of the arduino by powering off the USB port that the Arduino is connected to. In need this because sometimes the arduino does not send anymore data to the ttyUSB0 device. So as a workaround I’m restarting the Arduino from time to tim.....