ESP32 Easy short tutorial

Introduction

My ESP32 is 32WROOM-32

• https://docs.cirkitdesigner.com/component/61475118-b098-4ce5-a041-f984abcb9607/esp32-wroom
• https://www.az-delivery.de/en/products/esp32-developmentboard
• (https://www.mouser.com/datasheet/2/891/esp-wroom-32_datasheet_en-1223836.pdf)

• 

  Front side

• 

  Back side and connections

• 

  Tx light blinks when serial connection transfers data

Leds:

• Tx led blinks when transmitting data.

Pull Up Resistors

Enable pull up:

pinMode(13, INPUT_PULLUP); // Enable built-in pullup on pin 13

Pull up resistors are between a digital input pin and the VCC. Two main purposes:

1. Avoids issues with floating inputs.
2. The default "ON" state for inputs like buttons and switches which actively pull the pin low. The pull up resistor keeps the circuit reading high until the button grounds the pin.

Some pins do not have pullup resistors:

• GPIO34
• GPIO35
• GPIO36
• GPIO39

Others do:

Pin Name	GPIO Number	Pull Up?
GPIO0	0	Yes
GPIO2	2	Yes
GPIO4	4	Yes
GPIO5	5	Yes
GPIO12	12	Yes
GPIO13	13	Yes
GPIO14	14	Yes
GPIO15	15	Yes
GPIO25	25	Yes
GPIO26	26	Yes
GPIO27	27	Yes
GPIO32	32	Yes
GPIO33	33	Yes

For pins without built-in pull ups, or in output applications needing precise levels, you can add external pull up resistors. See the references for more information.

References:

• https://thelinuxcode.com/esp32-pull-up-pins/

Serial and Tx blink

Check that ESP32 works

void setup() {
    Serial.begin(9600);
}

void loop() {
  Serial.println("luntti.net");
  delay(500); 
}

This should write a text to serial monitor every 0.5 secs and blink the Tx led at the same time.

Blink

Blink an internal led

No:(

Blink a led

• 

  Blinking led. It is connected to pin18 and GND. Note that the (current limiting) resistor resistor is missing.

void setup() {
pinMode(18, OUTPUT);
}

void loop() {
  digitalWrite(18, LOW);
  delay(1000);
  digitalWrite(18, HIGH);
  delay(1000); 
}

CANbus TJA1051 T/3

Adafruit T/3 should mean that it is 3.3V compatible. All TJA1051 variants are not.

Connections

Note that Rx pin need not to be connected while uploading programs into ESP32.

Pins

• Vcc: the same power as the logic level of your microcontroller (Arduino: 5V, ESP32 3.3V)
• GND - common ground for power and logic.
• RX - CAN receive/input. Connect to ESP32's RX. Do not connect when uploading.
• TX - CAN transmit/output. Despite sharing the 'RX' and 'TX' name with UART, they're not at all the same interface. Connect to ESP32's TX.
• CANh
• CANl

ESP32-TWAI-CAN library

Install the library using Arduino IDEs library tools.

https://github.com/handmade0octopus/ESP32-TWAI-CAN

References

References

• Adafruit https://learn.adafruit.com/adafruit-can-pal
• Datasheet https://www.nxp.com/docs/en/data-sheet/TJA1051.pdf

Linux tutorial

Great linux tutorial: https://curiousstuff.eu/post/how-to-blink-the-damn-esp32-built-in-led/