ESP-01, MQTT and an OLED (SSD1306)

OLED ScreenIt took me about a week to get this going. There are still a few kinks that need to be ironed out, or worked around. But I wanted to get this out there before I forgot about it. I could not find a sketch for using an Arduino or ESP with an OLED and MQTT. Not one that didn’t just display data from a connected sensor., that is not what I wanted. I wanted to be able to send messages to the OLED screen via MQTT. I spent quite a while looking for it and I couldn’t find anything. About a week or two ago I finally broke the wall that was keeping me from sending and receiving MQTT message on an ESP. So I took that code and the working code from the Adafruit OLED sketch and made a baby.

I was able to produce a sketch that will simply display any text received via MQTT. Perfect. I plan on using this cobbled together with Node-Red. That way I can have one screen and send multiple sensor readings to it with minimal coding and parts. There are a few things I still need to figure out. For example I can’t get the screen to clear. Perhaps thats what the OLED reset pin was for? But my OLED only has four pins; SDA, SCL, Vcc and Ground. No reset. What to do? I think that is actually the only thing I need to work out. The Adafruit code will wrap your text to new lines, so make a note of that. I have gotten around clearing the screen by injecting spaces via MQTT. Its a little more effort in Node-Red for now until I get that down. But it works. It doesn’t matter how you get there as long as you get there right?

I Program the ESP via the Arduino IDE, if you don’t know how to set that up take a stroll down Google lane. Tons of help there on that topic. As it stands in the code below, once powered up the OLED should flash the Adafruit logo until a message is received then it will display the message until a new one is received. Simple. The default topic is “inTopic”, and the default OLED font size is 1. I have tried a font size of 2 but no higher. I also stumbled upon this library here. Much smaller and designed just for text. May try that in the future, but if it ain’t broke don’t fix it.

Items Required:
(1) ESP-01 (mine is a standard ESP-01 from eBay)
(1) OLED I2C Screen (I used a 0.96″ 4pin OLED also off eBay)

IDE Library Requirements:
Adafruit GFX
Adafruit SSD1306

Some places that helped

This was the tutorial that helped me get what I have going. I couldn’t get the OLED to work quite right until I came across this post. I used it as the base for what I have.

This page helped but not until I specified the SDA, SCL pins for the ESP. I couldn’t get the display to work properly and do what I wanted.

And the code (below): [See the comments for updated code]
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MPU6050 on an ESP8266-01 via MQTT

Update 3/16/17: I added code at the end of the post for dual MPU6050s
Update 2/2/18: Added images of possible wiring examples for ESP-01 and NodeMCU

Another milestone for me. I’m on a fucking roll! I found an Arduino sketch that takes an MPU6050 on an ESP8266-01  and spits it out data via MQTT. I have been looking for this and trying to accomplish this for months. My end goal is a clothes washer and dryer monitor for the family. There are sketches out there for laundry monitors but they don’t have what I need, mainly multiple users…I digress. So I found the script and it works, but some of it was it Italian which made it confusing for me and it did clumped all the sensor data into just two categories; accelerometer or gyroscope. I need more detailed information so I hacked it up a bit and it works!!

I commented out some stuff that was not needed (it all works for me YMMV), and I split all of the sensor data up into their own MQTT topic. So you get topics for AcX, AcY, AcZ and GyX, GyY, GyZ. This allows me to just use the sensor that works for the washer or dryer. Made it really easy once I plotted the data to a line graph.

Code below:
Originally taken from here

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I2C Scanner for ESP8266-01

I2CI am semi new to programming electronics. Straight amateur thats for sure, but I know enough to be dangerous. I have been trying to figure out how to get my MPU6050 sensor to work with the ESP-01. I couldn’t figure it out for the life of me. I have tried all kinds of things. I started this endeavor back when there was no Arduino IDE support for the ESP (a while ago). It was AT commands or LUA. Now that the Arduino IDE can be used it makes things much easier (I initially had issues getting it to work on my Mac). But sometimes there is a catch. I have noticed that most of the Arduino sketches will work but with a small minor tweak here or there. For example most tutorials I have found people are using the ESP8266-12. The model 12 has multiple pins available for TX & RX, the 01 model does not. The 01 model is the cheapest and happens to be what I have.

I found out it was pretty easy to change the sketch to get it working, most of the time. In the case of say I2C you have to specify the pins used for communication. The 01 only has two free pins, GPIO0 and GPIO2. Those can be used as inputs/outputs for a relay or say an LED. Or, you can use them for I2C communication. You need to specify the pins used in the sketch though. I am pretty sure this is beginner stuff, but hey I just figured it out.

Load up the default I2C scanner sketch and where you see Wire.being()  change that to Wire.being(0,2)  and you are now good to go. That should get you going on almost any I2C based sketch for Arduinos. You wont be able to use the pins for input/outputs (as far as I know) but now you have I2C.