The Hardware

The CPU card

The ESP8266 CPU card has the following pinouts:

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\xAE32-bitLX6 microprocessors
• 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 datasheet:

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

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

The circuit diagram of the LiyGo T7 V1.4 and 1.5 can be found at https://github.com/LilyGO/TTGO-T7-Demo

!!! 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. According to the LilyGo (provider of the CPU board) engineer GPIO 25 can be jumpered to D3 (GPIO 16) and GPIO 4 can be jumpered to D4 (GPIO 16). Doing this will allow to use the bus lines on the new GPIO connections.

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. Having had the LilyGo information before I could have left the boards unchanged and added jumpers to the CPU board.

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. The 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, 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 environmental sensors of which we will use the DHT11 and the SHT30 temperature and humidity sensors. We work with both sensors in the 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 present the data but it may sometimes be interesting to show the data also on the micro-controller, without the need of Internet access. This is possible with TFT screens. The screeen we will use has a resolution of 128*128 pixels and text as well as simple pixel-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: (see also the wemos.cc documentation)

Module	Connections	GPIO on ESP8266	GPIO on ESP32	Functionality
WROVER CPU board	D3 D4		GPIO 17 GPIO 16	used by PSRAM on WROVER cannot be used by shields
Re-use pins D3 and D4 on WROVER CPU board:	D3 D4		GPIO 27 connected to GPIO 17 GPIO 25 connected to GPIO 16	then use GPIO 25 and GPIO 27
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
SD card shield	D5 D6 D7 D8		GPIO 18 SPI clock GPIO 19 SPI MISO GPIO 23 SPI MOSI GPIO 15 CS
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 MISO GPIO 13 SPI MOSI GPIO 15 SPI CS	GPIO 22 I2C SCL GPIO 21 I2C SDA GPIO 18 SPI clock GPIO 19 SPI MISO GPIO 23 SPI MOSI 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
64x48 pixel 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
128x128 pixel TFT shield	D0 D8	GPIO 16 CS GPIO 15 DC	GPIO 26 CS GPIO 5 DC	128x128 pixel display with ST7735 SPI controller
320 x 240 pixel TFT screen and touch screen	D8 D7 D6 D5 D0 D3		GPIO 5 (TFT_DC) GPIO 23 (MOSI) GPIO 19 (MISO) GPIO 18 (SCK) GPIO 26 (TFT_CS) GPIO 25 (TS_CS)	320x240 pixel display with ili9341 controller and xpt2046 touch screen controller GPIO 25 must be jumpered to GPIO 17 on the WROVER board
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	D1 (default)	GPIO 5	GPIO 22	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	D0	GPIO 16	GPIO 26	Relay shield
IR receiver IR transmitter	D2 D1		GPIO 21 GPIO 22

Here is a correspondence table between the Dx pin nomination and the ESP8266 and ESP32 GPIO pin numbers:

Dx	GPIO ESP8266	GPIO ESP32 WROOM	GPIO ESP32 WROVER	ESP32S3 Mini
A0	ADC 0	36	36	2
D0	16	26	26	4
D1 I2C SCL	5	22	22	36 I2C SCL
D2 I2C SDA	4	21	21	35 I2C SDA
D3	0	17	patched to 27	18
D4	18	16	patched to 25	16
D5 SPI clock	14	18	18	12 SPI clock
D6 SPI MISO	12	19	19	13 MISO
D7 SPI MOSI	13	23	23	11 MOSI
D8 SPI CS	15	5	5	10

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