LEDAndNeopixels < IoT_Course

Tags: view all tags
---+ %SLIDESHOWSTART%
<h2 align="center">Lecture 2: LEDs and NeoPixel <br /><br /></h2> <h2 align="center">CSC 321: Embedded Sysytem</h2> <h2 align="center">First Semester 2020/2021</h2>

---+ The ESP32-WROVER-B MCU

| <img alt="esp32board.jpg" height="500" src="%ATTACHURL%/esp32board.jpg" title="esp32board.jpg" width="500" /> | <img alt="esp32boardlab.jpeg" height="474" src="%ATTACHURL%/esp32boardlab.jpeg" title="esp32boardlab.jpeg" width="474" /> |

---++ 
---+ CPU Pinout

<img alt="esp32board.png" height="454" src="%ATTACHURL%/esp32board.png" title="esp32board.png" width="700" />

Please note: The pin numbers IOxx on the ESP32 correspond to the GPIO pin numbers

[[https://www.espressif.com/sites/default/files/documentation/esp32-wrover-b_datasheet_en.pdf][Datasheet: ]] [[https://www.espressif.com/sites/default/files/documentation/esp32-wrover-b_datasheet_en.pdf][https://]] [[https://www.espressif.com/sites/default/files/documentation/esp32-wrover-b_datasheet_en.pdf][www.espressif.com]] [[https://www.espressif.com/sites/default/files/documentation/esp32-wrover-b_datasheet_en.pdf][/sites/default/files/documentation/esp32-wrover-b_datasheet_en.pdf]]
---++ 
---+ Meaning of pins on ESP32

| <img alt="pinout.jpg" height="354" src="%ATTACHURL%/pinout.jpg" title="pinout.jpg" width="500" /> | <img alt="pinout3.png" height="460" src="%ATTACHURL%/pinout3.png" title="pinout3.png" width="400" /> |
---++ <br /><br />

---+ How to program the processor

| <img alt="connect.png" src="%ATTACHURL%/connect.png" title="connect.png" width="400" /> | Several development tools are available:<br /> <ul> <li>ESP_IDF: The official Espressif development tool.<br />Includes a gcc compiler for the ESP8266 and the ESP32</li> </ul><p>Please see:<br /> https://docs.espressif.com/projects/esp-idf/en/latest <br /><br /></p> <ul> <li>The Arduino IDE<br />Needs extensions for these processors<br />and the different CPU boards</li> </ul><p>see:</p> <p>https://docs.espressif.com/projects/esp-idf/en/latest</p> <ul> <li>MicroPython</li> </ul><p>see:<br /> https://micropython-docs-esp32.readthedocs.io/en/esp32_doc</p> |

---++ 
---+ Flashing the code

<img alt="esptool.png" height="474" src="%ATTACHURL%/esptool.png" title="esptool.png" width="800" />
---++ 
---+ esptool
   * esptool is called from the Makefiles in ESP-IDF
   * esptool is used when we upload code from the Arduino IDE to the processor flash
   * esptool is used with Micropython IDE on uPyCraft/Thonny<br /><br />installs Micropython onto the processor flash
In the above cases the use of esptool is hidden to us.

We can however also execute esptool directly.

---++ 
---+ How to write a Micropython program?

First we need a Micropython interpreter!

You find the sources here:

https://github.com/micropython/micropython/

In the repository you find ports for the ESP8266 and the ESP32.

In order to compile the code you need the ESP-IDF and its cross compilers

The code compiles into a binary file (firmware-combined.bin) which contains a boot loader and the interpreter.

This binary must be uploaded and flashed.

For documentation of the ESP32port of Micropython look at

http://docs.micropython.org/en/latest/esp32/tutorial/intro.html

---++ 
---+ How to communicate with the Micropython interpreter?

We use a serial connection passing through the micro USB connection.

As soon as we connect the processor card to the PC we see the serial port to connect for communication

<img alt="interpret.png" height="329" src="%ATTACHURL%/interpret.png" title="interpret.png" width="500" />

---++ 
---+ What is REPL?

---++ 

<img alt="repl.png" height="270" src="%PUBURL%/AFNOG/HardwareAccessAndMicropython/repl.png" title="repl.png" width="683" />

---++ 
---+ The communication tools: minicom

<img alt="minicom.png" height="231" src="%PUBURL%/AFNOG/HardwareAccessAndMicropython/minicom.png" title="minicom.png" width="379" />

You see the command prompt and you can interact with Micropython.

But … how to upload scripts?

---++ 
---+ The command line tool ampy

<img alt="MPY1.png" height="585" src="%ATTACHURL%/MPY1.png" title="MPY1.png" width="700" />
---++ 
---+ IDE for Micropython: uPyCraft

<img alt="uPyCraft.png" height="830" src="%PUBURL%/AFNOG/HardwareAccessAndMicropython/uPyCraft.png" title="uPyCraft.png" width="1200" />

---++ 
---+ 
---+ Thonny

<img alt="thonny.png" src="%PUBURL%/AFNOG/HardwareAccessAndMicropython/thonny.png" title="thonny.png" />

---+ Thonny

Thonny is a complete Integrate Development Environment (IDE)

which lets you<br /><br />
   * Access the REPL<br /><br />
   * Create directories on the Micropython file system<br /><br />
   * Upload scripts<br /><br />
   * Syntax check scripts<br /><br />
   * Run scripts<br /><br />
   * Install Micropython on your processor board
---++ 
---+ Thonny

Thonny is an IDE for Python which has provisions for Micropython.<br /><br />Under Tools &rarr; Options button you can select the type of

Python interpreter you intend to use.

<img alt="interpret.png" height="329" src="%ATTACHURL%/interpret.png" title="interpret.png" width="500" />
---++ 
---+ Flashing Micropython

Compiling a new version of Micropython is substantially much easier with Thonny.

You still need to install esptool first. You just select your port and firmware then install.

<img alt="flashing.png" height="325" src="%ATTACHURL%/flashing.png" title="flashing.png" width="500" />
---++ 
---+ !IoT Hello World program

A “Hello World” program, just printing “Hello World” on the screen

does not look very exciting.

However, this is generally used to verify that the infrastructure<br /><br />Compiler, linker, downloader, flash program<br /><br />are working correctly<br /><br />In embedded systems printing can be quite complex

and a blinking LED is used instead.

---++ 
---+ Switching on and off a LED

The ESP32-WROVER-B have a “user LED” connected to GPIO 19.

How do we control this LED?<br /><br />
   * Define that the LED is connected to GPIO 19<br /><br />
   * Program this pin as output<br /><br />
   * Write a logic 1 to the pin to switch it on<br /><br />
   * Write a logic 0 to the pin to switch it off<br /><br />
   * The logic state may be inverted if the LED is active low
---++ 
---+ Micropython hardware functions

<img alt="hardwareFunctions.png" src="%PUBURL%/AFNOG/HardwareAccessAndMicropython/hardwareFunctions.png" title="hardwareFunctions.png" />

---++ 
---+ The machine.Pin class

<img alt="pinClass.png" height="811" src="%PUBURL%/AFNOG/HardwareAccessAndMicropython/pinClass.png" title="pinClass.png" width="1228" />

---++ 
---+ Switch the LED on, version 1

<img alt="ledControl1.png" height="266" src="%PUBURL%/AFNOG/HardwareAccessAndMicropython/ledControl1.png" title="ledControl1.png" width="367" />

---++ 
---+ Switch the LED on, version 2

<img alt="ledControl2.png" height="256" src="%PUBURL%/AFNOG/HardwareAccessAndMicropython/ledControl2.png" title="ledControl2.png" width="349" />

---++ 
---+ The blinking LED

Now we put the code into a script and run it

<img alt="blinkingLed.png" height="590" src="%PUBURL%/AFNOG/HardwareAccessAndMicropython/blinkingLed.png" title="blinkingLed.png" width="800" />

---++ 
---+ Changing the light intensity

The LED is connected to a digital line which can only be set to 0 or Vcc.

How can we change the light intensity and dim the LED?

The light intensity depends on the average current flowing through the LED.

The answer is PWM: pulse width modulation.

<img alt="pwm.png" src="%PUBURL%/AFNOG/HardwareAccessAndMicropython/pwm.png" title="pwm.png" />

---++ 
---+ PWM in Micropython

<img alt="pwm_uP.png" height="383" src="%PUBURL%/AFNOG/HardwareAccessAndMicropython/pwm_uP.png" title="pwm_uP.png" width="766" />

---++ 
---+ Our PWM implementation

<img alt="pwmImpl.png" src="%PUBURL%/AFNOG/HardwareAccessAndMicropython/pwmImpl.png" title="pwmImpl.png" />

---++ 
---+ The !WS2812B LED

A more complex LED:<br /><br />
   * rgb LED used in LED chains.<br /><br />
   * each ws18b12 contains the 3 colored LEDs and a controller.<br /><br />
   * Can be cascaded and individually addressed, depending on its position in the chain<br /><br />
   * Needs precise timing<br /><br />
   * To use it we pass through the neopixel library built into micropython
---++ 
---+ !WS2812B timing

For all the details on the ws2812b look at<br /><br /> https://cdn-shop.adafruit.com/datasheets/WS2812B.pdf

24 bit of colour data puts 2e24 colours at your disposal

Coding of a single bit

<img alt="ws2812Bits.png" height="273" src="%PUBURL%/AFNOG/HardwareAccessAndMicropython/ws2812Bits.png" title="ws2812Bits.png" width="481" />

The control word:

<img alt="ws2812ControlWord.png" height="76" src="%PUBURL%/AFNOG/HardwareAccessAndMicropython/ws2812ControlWord.png" title="ws2812ControlWord.png" width="924" />

---++ 
---+ Cascading the !WS2812B

---++ 

<img alt="ws2812Chain.png" height="579" src="%PUBURL%/AFNOG/HardwareAccessAndMicropython/ws2812Chain.png" title="ws2812Chain.png" width="397" />

---++ 
---+ Using the neopixel library

<img alt="neopixel.png" src="%PUBURL%/AFNOG/HardwareAccessAndMicropython/neopixel.png" title="neopixel.png" />

---++ 
---+ … and our code

We have a single neopixel connected to

GPIO pin 4 (ESP8266)

or

GPIO pin 21 (ESP32)

This code works on both CPUs!

<img alt="neopixelCode.png" height="549" src="%PUBURL%/AFNOG/HardwareAccessAndMicropython/neopixelCode.png" title="neopixelCode.png" width="679" />

---++ 

%SLIDESHOWEND%

-- %USERSIG{IsaacArmahMensah - 2021-02-28}%

---++ Comments

<br />%COMMENT%
Attachments
Topic attachments
I	Attachment	History	Action	Size	Date	Who
png	MPY1.png	r1	manage	423.0 K	2021-03-02 - 08:20	IsaacArmahMensah
jpg	esp32board.jpg	r1	manage	279.8 K	2021-03-02 - 00:20	IsaacArmahMensah
png	esp32board.png	r1	manage	2095.9 K	2021-02-28 - 01:28	IsaacArmahMensah
png	esptool.png	r2 r1	manage	385.0 K	2021-02-28 - 16:01	IsaacArmahMensah
png	interpret.png	r1	manage	105.0 K	2021-03-02 - 00:42	IsaacArmahMensah
Topic revision: r7 - 2021-03-09 - UliRaich