FA 8 - Embedded Programing

Fab Academy 8

Embeded Programing

Node MCU - ESP8266

Mobirise

For this project I´m using a NodeMCU development boardwith an integrated ESP8266 chip that comes with integrated WIFi and Bluethoot module antena. From the datasheet, I will highlight some things that I find usefull to me (or that I understand).

• Integrated TCP/IP protocol stack

• Supports antenna diversity

• WiFi 2.4 GHz, support WPA/WPA2

• Support STA/AP/STA+AP operation modes

• Support Smart Link Function for both Android and iOS devices

• Operating temperature range -40C ~ 125C

Input only pins
GPIOs 34 to 39 are GPIs – input only pins. These pins don’t have internal pull-ups or pull-down resistors. They can’t be used as outputs, so use these pins only as inputs:

GPIO 34
GPIO 35
GPIO 36
GPIO 39

SPI flash integrated on the ESP-WROOM-32
GPIO 6 to GPIO 11 are exposed in some ESP32 development boards. However, these pins are connected to the integrated SPI flash on the ESP-WROOM-32 chip and are not recommended for other uses. So, don’t use these pins in your projects!

GPIO 6 (SCK/CLK)
GPIO 7 (SDO/SD0)
GPIO 8 (SDI/SD1)
GPIO 9 (SHD/SD2)
GPIO 10 (SWP/SD3)
GPIO 11 (CSC/CMD)

Capacitive touch GPIOs
The ESP32 has 10 internal capacitive touch sensors. These can sense variations in anything that holds an electrical charge, like the human skin. So they can detect variations induced when touching the GPIOs with a finger. These pins can be easily integrated into capacitive pads, and replace mechanical buttons. The capacitive touch pins can also be used to wake up the ESP32 from deep sleep.

Those internal touch sensors are connected to these GPIO’s.

T0 (GPIO 4)
T1 (GPIO 0)
T2 (GPIO 2)
T3 (GPIO 15)
T4 (GPIO 13)
T5 (GPIO 12)
T6 (GPIO 14)
T7 (GPIO 27)
T8 (GPIO 33)
T9 (GPIO 32)

Analog to Digital Converter (ADC)
The ESP32 has 18 x 12 bits ADC input channels (while the ESP8266 only has 1x 10 bits ADC). These are the GPIOs that can be used as ADC and respective channels.

ADC1_CH0 (GPIO 36)
ADC1_CH1 (GPIO 37)
ADC1_CH2 (GPIO 38)
ADC1_CH3 (GPIO 39)
ADC1_CH4 (GPIO 32)
ADC1_CH5 (GPIO 33)
ADC1_CH6 (GPIO 34)
ADC1_CH7 (GPIO 35)
ADC2_CH0 (GPIO 4)
ADC2_CH1 (GPIO 0)
ADC2_CH2 (GPIO 2)
ADC2_CH3 (GPIO 15)
ADC2_CH4 (GPIO 13)
ADC2_CH5 (GPIO 12)
ADC2_CH6 (GPIO 14)
ADC2_CH7 (GPIO 27)
ADC2_CH8 (GPIO 25)
ADC2_CH9 (GPIO 26)

How to use the ESP32 ADC pins
Note: ADC2 pins cannot be used when Wi-Fi is used. So, if you’re using Wi-Fi and you’re having trouble getting the value from an ADC2 GPIO, you may consider using an ADC1 GPIO instead, that should solve your problem.

The ADC input channels have a 12 bit resolution.
This means that you can get analog readings ranging from 0 to 4095, in which 0 corresponds to 0V and 4095 to 3.3V. You also have the ability to set the resolution of your channels on the code, as well as the ADC range.

The ESP32 ADC pins don’t have a linear behavior.
You’ll probably won’t be able to distinguish between 0 and 0.1V, or between 3.2 and 3.3V. You need to keep that in mind when using the ADC pins.

Digital to Analog Converter (DAC)
There are 2 x 8 bits DAC channels on the ESP32 to convert digital signals into analog voltage signal outputs. These are the DAC channels.

DAC1 (GPIO25)
DAC2 (GPIO26)
RTC GPIOs

There is RTC GPIO support on the ESP32.
The GPIOs routed to the RTC low-power subsystem can be used when the ESP32 is in deep sleep. These RTC GPIOs can be used to wake up the ESP32 from deep sleep when the Ultra Low Power (ULP) co-processor is running. The following GPIOs can be used as an external wake up source.

RTC_GPIO0 (GPIO36)
RTC_GPIO3 (GPIO39)
RTC_GPIO4 (GPIO34)
RTC_GPIO5 (GPIO35)
RTC_GPIO6 (GPIO25)
RTC_GPIO7 (GPIO26)
RTC_GPIO8 (GPIO33)
RTC_GPIO9 (GPIO32)
RTC_GPIO10 (GPIO4)
RTC_GPIO11 (GPIO0)
RTC_GPIO12 (GPIO2)
RTC_GPIO13 (GPIO15)
RTC_GPIO14 (GPIO13)
RTC_GPIO15 (GPIO12)
RTC_GPIO16 (GPIO14)
RTC_GPIO17 (GPIO27)

PWM
The ESP32 LED PWM controller has 16 independent channels that can be configured to generate PWM signals with different properties. All pins that can act as outputs can be used as PWM pins (GPIOs 34 to 39 can’t generate PWM).

To set a PWM signal, you need to define these parameters in the code:

Signal’s frequency;
Duty cycle;
PWM channel;
GPIO where you want to output the signal.
I2C
The ESP32 has two I2C channels and any pin can be set as SDA or SCL.

The default I2C pins are:
GPIO 21 (SDA)
GPIO 22 (SCL)

SPI
By default, the pin mapping for SPI is:

SPI MOSI MISO CLK CS
VSPI GPIO 23 GPIO 19 GPIO 18 GPIO 5
HSPI GPIO 13 GPIO 12 GPIO 14 GPIO 15

Interrupts
All GPIOs can be configured as interrupts.

Strapping Pins
The ESP32 chip has the following strapping pins:

GPIO 0
GPIO 2
GPIO 4
GPIO 5 (must be HIGH during boot)
GPIO 12 (must be LOW during boot)
GPIO 15 (must be HIGH during boot)
These are used to put the ESP32 into bootloader or flashing mode. On most development boards with built-in USB/Serial, you don’t need to worry about the state of these pins. The board puts the pins in the right state for flashing or boot mode.

However, if you have peripherals connected to those pins, you may have trouble trying to upload new code, flashing the ESP32 with new firmware or resetting the board. If you have some peripherals connected to the strapping pins and you are getting trouble uploading code or flashing the ESP32, it may be because those peripherals are preventing the ESP32 to enter the right mode. After resetting, flashing, or booting, those pins work as expected.

Pins HIGH at Boot
Some GPIO’s change its state to HIGH or output PWM signals at boot or reset. This means that if you have outputs connected to these GPIOs you may get unexpected results when the ESP32 resets or boots.

GPIO 1
GPIO 3
GPIO 5
GPIO 6 to GPIO 11 (connected to the ESP32 integrated SPI flash memory – not recommended to use).
GPIO 14
GPIO 15

Flash (program memory): 16384 bytes
EEPROM: 256 bytes
RAM: 2048 bytes
General-purpose I/O Pins: 12 (11 usable)
Digital pins: 2
ADC pins: 9 usable pins (pins marked with green color except for pin PA0). These pins must be used to read analog sensors.
PWM pins: 5 pins (pins marked with orange color and a ~ sign). These pins must be used to write PWM signals.
DAC: Yes
Serial communication: UART, SPI, I2C
Programming: UPDI
Working voltage: 1.8 - 5.5V

In order to access the I/O pins and their various functions from within our code, we need to read from/write to I/O registers of the chip. The programmer uses I/O registers to provide interfaces to the I/O peripherals of the micro-controller. Generally, registers are pins, and for each pin, there is a Data register (PORTx), a Data direction register (DDRx), and a Port input register (PINn). DDRx registers configure pins as INPUT (0) or OUTPUT (1). PINx registers store a value that can be read from the register in case it is defined as INPUT. PORTx registers write the value to pins as HIGH (1) or LOW (0). Each I/O register has a name (used by high-level language/C programmer); I/O address and an SRAM address (used in low-level assembly language).

A summary of ATtiny1614's I/O pins and how to use them:

GND: ground
VCC: power supply
PA0 - UDPI/RESET: programming (UPDI interface) & reset pin
PA6 - DAC: digital to analog converter
PA5 - VREF: the voltage reference pin used to enhance the accuracy of analog reading/writing. This pin acts as a very precise analog 'meter stick' against which the incoming analog signal is compared (as in an ADC) or the outgoing analog signal is generated (DAC).

PA1, PA2, PA3, PA4 - MOSI, MISO, SCK, SS: Master Out Slave In, Master In Slave Out, Serial Clock and Slave Select logic signals in SPI serial communication.

PB0, PB1 - SCL, SDA: Serial Clock and Serial Data lines in I2C serial communication. PA1 and PA2 can also be used for the same purpose.

PB2, PB3 - RXD, TXD: Receive and Transmit functions in UART serial communication. PA1 and PA2 can also be used for the same purpose.
In the case of ATtiny1614, pin names are of type Pxn, with x being the PORT instance (A, B) and n the pin number. Notation for signals is PORTx, DDRx, and PINn. The numbers 0-10 (marked with orange and blue colors) can also be used while programming in order to indicate the pins we want to refer to.

To make the LED BREATH assignment, I followed some of the instructions of the Jled Library from the GitLab repo, and after trying the different combinations (Candle, Blink, Static, Breath, Fade, etc). The ones I liked most where the ones with multiple leds, so I keept my conection with 3 leds, and used the multiles.ino code and modified it a bit. This one mixes the Breath, Fade and Blink codes in one. It also uses the internal led as a fourth led.

ADDING THE LIBRARY:
Since we are using a library that is not part of the arduino, we need to add jled to our library dependencies in our platformio.ini project file like this:

      [env:nodemcuv2]
        platform = espressif8266
        board = nodemcuv2
        framework = arduino
        lib_deps = jled

This is needed for the líbrary to load when you call it in your CCP code file.

PMW PINS:
Another important thing I realized, is that the breath effect and others, only work in PWM (Pulse Width Modulation) pins, which in case of the NodeMCU are D2, D5, D6 and D8. I have read that through software, you can also convert all the digital pins into PWM, but I´m not sure how to do it yet. This was interesting to me, because I have never understood what that really means untill now, and I also discovered that in the pinnout graphics they usually paint it with an ondulated line. I also dicovered that the UNO has painted lines near the numers in the PWM pins. I´m going to copy the Wikipedia description, just to remind in the future what they are.

        Pulse-width modulation:
        Pulse width modulation, or pulse-duration modulation, is a method of         reducing the average         power delivered by an electrical signal, by         effectively chopping it up into discrete parts. The         average value of         voltage fed to the load is controlled by turning the switch between supply         and load on and off at a fast rate.

This JLED Library was really usefull to do nicer things with less code, I could even do the same I did with the blinks, but with much less code.

INITIAL CODE:     JLED Library

MY CODE:     3 Led Breathe_Blink_Fade.cpp

Voltio