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.
I came across a very useful post by Thomas Scherrer that describes how to read data from a Peacefair PZEM-021 energy meter by spying on the SPI bus with an Arduino. I decided to do the same thing with an ESP-12F WiFi module so that I could view the results remotely and plot graphs, etc. It took me a lot longer to get this working than I anticipated due to a few problems along the way.
The main hardware difference is the ESP8266 is a 3.3V device but the Arduino is 5V. The PZEM-021 is actually a mixture. The RN8208G metering chip is a 5V device. It is a SPI slave, the SPI master is an STM32 ARM processor that is 3.3V but with 5V tolerant inputs.
Rui Santos writes, “In this project, you’re going to learn how to control the ESP8266 or the ESP32 with voice commands using Alexa (Amazon Echo Dot). As an example, we’ll control two 12V lamps connected to a relay module. We’ll also add two 433 MHz RF wall panel switches to physically control the lamps.”
Rui Santos over at Random Nerd Tutorials posted a step by step guide on building an ESP8266 Wi-Fi button:
In this project you’re going to build an ESP8266 Wi-Fi Button that can trigger any home automation event. This is like a remote control that you can take in your pocket or place anywhere that when pressed sends out an email. It can also be called a DIY Amazon Dash Button clone.
For once, this project was not for me… it was for my wife !
Every morning she takes the bus then train to go to work. If she misses her train, she has to wait for more than 30 minutes for the next one. Not missing her bus is therefore quite important.
Where we live every bus station has a display letting you know in real time when the next bus will be there. My first thought was to reverse engineer its RF signal but something easier then came to mind.
In the very same bus stations, a small QR code brings you to a web page displaying the very same “minutes before bus arrival”… HTML parsing therefore made more sense given that I was fairly busy with other projects.
Like a million other people on the Internet, I’ve been experimenting with home weather logging. I roll my eyes at the phrase “Internet of Things”, but it’s hard to deny the potential of cheap networked sensors and switches, and a weather logging system is like this field’s Hello World application. Back in June I posted about my initial experiments in ESP8266 weather logging. Since then I’ve finalized the hardware setup, installed multiple nodes around the house, organized a nice web page to analyze all the data, and integrated everything with Amazon Alexa. Time for an update.
Rui Santos has written a great guide shows us what’s Deep Sleep and how to use it with the ESP8266 in the Arduino IDE.
With most of the ESP8266 modules, you can’t change the hardware to save power, but you can write software to do it. If you use the sleep functions with the ESP8266, it will draw less power and your batteries will last longer. In this guide, we’re going to talk about Deep Sleep with the ESP8266.
Using e-paper for a weather station is an ideal solution, as the data does not need to be updated often. By default, the station reaches out every 20 minutes for new data over WiFi and then updates the display. Daniel Eichhorn already has published kits for OLED (see “WiFi OLED Mini Weather Station with ESP8266“) and touch display (see “WiFi TFT Touch LCD Weather Station with ESP8266“). I like them both, but especially the TFT one is very power-hungry and not really designed to work from batteries. What I would like is a station which can run for weeks.
After the “WiFi OLED Mini Weather Station with ESP8266“, here is another one: this time with Touch LCD :-) In the previous article (“WiFi OLED Mini Weather Station with ESP8266“) I have used the OLED kit from blog.squix.org. And as promised, this time it is about the “ESP8266 WiFi Color Display Kit”
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