README

This repo contains the source code for a system of MQTT networked ESP32 based devices used to demonstrate various RTOS concepts for a local Nashville TN microcontroller meetup. The original event details are here: https://www.meetup.com/NashMicro/events/236602045/

Additionally, it was fun to play around and learn more about the ESP32 and MQTT.

Features:

• A handful of fun LED Strip patterns
• Builds including an Accelerometer will issue an MQTT event when tapped/bumped and also light up the LED Strip.
• All builds subscribe to a Pattern MQTT event, enabling the ability to remotely change the LED Strip lighting pattern.
• Builds without an accelerometer subscribe to an Accelerometer topic, and will light up their LED Strip when that topic is hit.
• Some code modules written specifically to demonstrate various FreeRTOS concepts. Listed later in this readme document.

Target Hardware

Components

• Sparkfun ESP32 Thing
• Adafruit NeoPixel Digital RGB LED Strip - Black 60 LED
• Code as published assumes 60 LEDs per device, but is easy to change.
• ADXL345 Accelerometer
• Build supports with or without accelerometer, using "make menuconfig" to change.

Wiring / GPIO usage

• GPIO 5: LED and crude CPU usage monitor
• GPIO 21: LED Strip data connection
• GPIO 16: I2C-SDA for ADXL345
• GPIO 17: I2C-SCL for ADXL345

It is assumed (and recommended) that the LED Strip itself is externally powered, due to heavy peak current demands with some LED patterns.

Setup

Minimum Requirements

• ESP-IDF installed correctly on the development system. This code was tested against the latest IDF as of end of December 2016. NOTE: The ESP-IDF is a rapidly moving target. Your mileage may vary.
• FWIW, development for this project was performed using Mac OSX, and using Eclipse for editing
• I used the ESP32 Thing's built in serial bootloader to download new application code builds using the IDF's "make flash" feature. For faster downloads, I highly suggest using "make menuconfig" to increase the bootloader's serial bit rate AND use compression.

Configuration

Accelerometer

• Use "make menuconfig" to enable or disable the accelerometer option. See "Component Config -> EshThing" options.

Wifi and MQTT

• The wifi setup may be updated via "make menuconfig". See "Component Config"->"EshThing" to update SSID and password.
• The target MQTT server may be updated via "make menuconfig". See "Component Config"->"EshThing" to update the target MQTT server.
• The MQTT clientID may be updated via "make menuconfig". See "Component Config"->"EshThing" to update the MQTT ClientId.

MQTT Topics

• "/EshThings/Events/Pattern"
  • All builds subscribe to this topic. A simple string/number is expected:
  • '0' none. Pattern is off.
  • '1' Hann Window pulse. Single pulse and then off.
  • '2' Hann Window repeating pulse
  • '3' Random noise using ESP32 random generator source
  • '4' SOS Morse Code pattern pulse. Single pulse and then off.
  • '5' Same as '1', but scaled by 0.5
  • '6' Same as '2', but scaled by 0.5
  • '7' Knight Rider
• "/EshThings/Events/Accelerometer"
  • Builds WITHOUT a physical accelerometer will subscribe to this topic. Any event will trigger LED behavior.
  • Builds WITH a physical accelerometer will publish to this topic when a threshold of accelerometer data is crossed. The published data includes the magnitude information.

Teaching Demo

The purpose of this repository is to present various FreeRTOS concepts at a microcontroller meetup in Nashville TN. The concepts and their locations:

• Semaphores: led_strip (third party)
• Mutex: led_strip (third party as modified by Matthew)
• Queues: ColorMappedDataVisualizer (original to this code)
• Timers: PatternGenerator (original to this code)
• Polling Thread: AccelReader (original to this code)

Third Party

Third party code and modules required or included directly in this project:

• ESP-IDF
• ESP32_LED_STRIP aka led_strip
• esp32-i2c-adxl345
• esp32-mqtt

Other resources:

• Code - heatmaps and color gradients

Who do I talk to?

• Feel free to contact Matthew Eshleman if any interest or issues with this code.
• Reach out to the ESP32 community for ESP32 or ESP32-IDF specific issues.