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The Hardware

The CPU card

There are two different ESP32 CPU cards available for the WeMos D1 mini bus. The first card is based on an ESP-wroom-32 CPU while the second one uses the ESP-wrover-b chip.

Both cards have

  • 2 low-powerXtensa®32-bitLX6microprocessors
  • 520 KB of on-chip SRAM for data and instructions
  • 4 MB of SPI flash
  • I2C, I2S, SPI interface
  • 3 UARTs, 12 bit ADC up to 18 channels, 8 bit DAC
The ESP-wrover-b additionally has 8 MBytes of external PSRAM (of which only 4MBytes are accessible at a given time)

Here are photos of the boards:

ESP-wroom-32 ESP-wrover-b
esp32V1.png wrover.png
For more details please read the data sheet:

https://afnog.iotworkshop.africa/pub/UCC_Course_2020/TheHardware/esp32-wroom-32_datasheet_en.pdf

https://afnog.iotworkshop.africa/pub/UCC_Course_2020/TheHardware/esp32-wrover-b_datasheet_en.pdf

For convenience, here is the pinout of the ESP32 CPU card:

wroverbPinout.jpg

!!! Attention !!!

While the ESP32-wroom-32 uses GPIO 2 for its on-board user LED the ESP32-wrover-b uses GPIO 19.

The ESP32-wrover-b has a design flaw: GPIO 16 connected to pin D3 and GPIO 17 connected to pin D4 cannot be used to control sensors because these GPIO lines are used to control the PSRAM. This means that the CPU is incompatible with any shield using pins D3 and D4. Other GPIO lines should have been made available instead.

Checking the hardware table below shows that only the push button shield (D3) and the DHT11 (D4) use the forbidden pins. I therefore made hardware patches to connect their forbidden pins to D1.

The patches pus button shield The patched DHT11 shield
pushbuttonMod.png dht11Mod.png

The Base Board

This board has no active elements but it connects sensor shields to the CPU board. Like this the necessary connections are made in a Lego based manner by just plugging modules together without any further cable connections or soldering.

tripleBase.png

Switches

Two different types of switches are available as shields: a mechanical push button switch and a PIR sensor.

mechanical switch PIR sensor
button.png pir.png

LEDs

On the CPU card there is a user programmable LED which is used in the exercise on LEDs. This is a simple, single color (blue) LED.
In the series of shields we can also find an LED chain with 7 addressable WS2812 RGB LEDs.

leds.png

Temperature and Humidity Sensors and Barometric Pressure Sensor

There are several different environmental sensors of which we will use the DHT11 and the SHT30 temperature and humidity sensors. We work with both sensors in different exercises because these shields use quite different communication protocols which we want to study.

In addition to the temperature and humidity sensors we have a barometric pressure sensor, (which also allows to measure ambient temperature) the BMP180. With these 3 sensors we can construct a simple weather station.

DHT11 temperature and humidity sensor SHT30 I2C temperature and humidity sensor BMP180 barometric pressure sensor
wemosDHT11.png sht30.png bmp180.png

Real Time Clock and Data Logging

In order to store data taken with the environmental sensors we us a micro SD card supplied with the Real Time Clock and Data Logger card. With the Real Time Clock we can get a time stamp telling us when the data have been taken.

rtc.png sd_card.png

Displays

Of course we can transfer the measurement data to a PC over the Internet and use the plotting facilities on the PC to graphically show the data but it may sometimes be interesting to show the data also on the micro-controller without the need of an Internet access. This can be done with TFT screen sensors. The one we will use has a resolution of 128*128 pixels and text as well as simple pixel based graphics is possible with these devices.

tftScreen.png

Motors

You can also control different types of motors with the ESP32. To demonstrate this we use the motor controller shield.

motorShieldFront.png motorShieldBack.png
Motor shield front view Motor shield back view
Please notice the 2 solder jumpers that must
be made
with 3 different types of motors:

DC motor servo motor stepping motor
dcMotor.png servo.png stepper.png
Here is an overview table showing the devices and their connections:

Module Connections GPIO on ESP8266 GPIO on ESP32 Functionality
PSRAM D3
D4
  GPIO 17
GPIO 16
used by PSRAM on WROVER
cannot be used by shields
1 button shield D3
patched to D1
GPIO 0
patched to GPIO 5
GPIO 17
patched to GPIO 22
on / off push button
WS2812B RGB shield D2 GPIO 4 GPIO 21 addressable rgb LED
WS2812B RGB ring D0 GPIO 16 GPIO 26 7 LED WS2812 ring

DS1307 RTC and data logger

D1
D2

D5
D6
D7
D8

GPIO 5 I2C SCL
GPIO 4 I2C SDA

GPIO 14 SPI Clock
GPIO 12 SPI MOSI
GPIO 13 SPI MISO
GPIO 15 SPI CS

GPIO 22 I2C SCL
GPIO 21 I2C SDA

GPIO 18 SPI clock
GPIO 19 SPI MOSI
GPIO 23 SPI MISO
GPIO 5 SPI CS

Real Time Clock

SD card interface

Buzzer shield D5
D6
D7
D8
GPIO 14 (default)
GPIO 12
GPIO 13
GPIO15
GPIO 18 (default)
GPIO 19
GPIO 23
GPIO 5
passive buzzer
BMP180 shield D1
D2
GPIO 5 I2C SCL
GPIO 4 I2C SDA
GPIO 22 I2C SCL
GPIO 21 I2C SDA
I2C barometric pressure sensor and
temperature sensor
DHT11 shield D4
patched to D1
GPIO 2
patched to GPIO 5
GPIO 16
patched to GPIO 22
temperature and humidity sensor
OLED shield D1
D2
GPIO 5 I2C SCL
GPIO 4 I2C SDA
GPIO 22 I2C SCL
GPIO 21 I2C SDA
64x48 pixel display with SSD1036 I2C controller
TFT shield D0
D8
GPIO 16 CS
GPIO 15 DC
GPIO 26 CS
GPIO 5 DC
128x128 pixel display with ST7735 SPI controller
DS18B20 shield D2 GPIO 4 GPIO 21 1-wire digital temperature sensor
SHT30 shield D1
D2
GPIO 5 I2C SCL
GPIO 4 I2C SDA
GPIO 22 I2C SCL
GPIO 21 I2C SDA
I2C temperature and humidity sensor
Motor shield D1
D2
GPIO 5 I2C SCL
GPIO 4 I2C SDA
GPIO 22 I2C SCL
GPIO 21 I2C SDA
Controlling DC Motors
Servo Motor D0 GPIO 16 GPIO 26 Signal pin of SG90 servo motor
LED Matrix shield D5 GPIO 14 CLK
D7 GPIO 13 Din
GPIO 14: CLK
GPIO 13: Din
GPIO 18: CLK
GPIO 23: Din
8x8 LED Matrix
PIR sensor D4 (default) GPIO 2 GPIO 16 Passive Infrared Switch
BH1750 sensor D1
D2
GPIO 5 I2C SCL
GPIO 4 I2C SDA
GPIO 22 I2C SCL
GPIO 21 I2C SDA
Ambient light sensor
Relay to be configured     Relay shield
IR receiver/transmitter to be configured     IR remote control
-- TWiki Admin User - 2020-04-25

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