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

For more details please read the data sheet:

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

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

!!! 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

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.

Switches

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

mechanical switch	PIR sensor

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.

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

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.

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.

Motors

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

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

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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