Category Archives: Tutorial

Automated unit testing in the metal

Unit testing your code is peace of mind. It has two main direct benefits that impact on your confidence about the code you are writing:

  • Testing expected behaviors
  • Avoiding regressions (i.e. breaking something that was working fine before)

Unit testing embedded systems is a bit more involved since there is the additional constraint of the hardware itself, sometimes more than one device or even different platforms. Quitting (or not even thinking about it) is the easy answer to the problem. All of us have debugged expected behaviors with inline prints. But automating some of these tasks have a huge benefit on the code quality and development speed.
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RAK833 meets Raspberry Pi

You might have heard about The Things Network (TTN from now on) here or somewhere else. If you have not, then it’s a good opportunity to visit the project and check if there is a community of users around you. I have been a core member of the TTN Catalunya community for over 2 years now. This year we are working hard deploying several new gateways in Barcelona and doing workshops and hackathons with the main goal of helping individuals and social entities to carry out projects around a LoRaWan open, libre (free as in freedom) and neutral telemetry network.

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EEPROM Rotation for ESP8266 and ESP32

The Arduino Core for ESP8266 and ESP32 uses one SPI flash memory sector to emulate an EEPROM. When you initialize the EEPROM object (calling begin) it reads the contents of the sector into a memory buffer. Reading a writing is done over that in-memory buffer. Whenever you call commit it write the contents back to the flash sector.

Due to the nature of this flash memory (NOR) a full sector erase must be done prior to write any new data. If a power failure (intended or not) happens during this process the sector data is lost.

Also, writing data to a NOR memory can be done byte by byte but only to change a 1 to a 0. The only way to turn 0s to 1s is to perform a sector erase which turns all memory positions in that sector to 1. But sector erasing must be done in full sectors, thus wearing out the flash memory faster.

How can we overcome these problems?

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Using Google Assistant to control your ESP8266 devices

In my last post I tried to explain how to access your IoT devices at home from the Internet in a secure way using a reverse proxy. Truth is that I had it running since maybe 6 months ago without giving it too much use until recently. Reason? My Nexus 5 had been having serious problems (battery not charging, screen broken, earpiece not working,…) and I decided to replace it with a new mobile phone and the new one has Google Assistant built in.

So one of the first things I have tried is to make Google Assistant toggle my smart switches flashed with ESPurna. Nad as it turns out it’s not hard to do but -at the moment- you have to relay on a cloud service like IFTTT (IF This Then That). This is a key difference with Amazon Alexa services you have to be aware. It has some benefits but also some drawbacks.

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Secure remote access to your IoT devices

When you are hacking with IoT devices at home you get to face the challenge of accessing remotely to them, that is from outside your home network. I’m not saying your home network is a safe place, beware. But that thing outside, you know, “the Internet”, it’s so scary… Unfortunately, most IoT devices are just not ready for the jungle. Neither the commercial ones, nor the hacked ones you might have. I wouldn’t dare to open a port in my router to anything inside unless it’s encrypted. So what should we do?

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