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Getting Started

While exploring my local network, I stumbled upon several devices named espressif, and after some searching online I found the ESP32 was the likely culprit. I've always been interested in hardware and have experience working with electrical circuits from 120-480 volts, but I have never identified a resistor or even considered purchasing a breadboard.

So, I bought a board on Amazon because it was fast shipping and I had a long weekend coming up. I won't share an Amazon link here for several reasons, but the exact model that I purchased was the ESP32-DevKitC V4 which comes with the ESP32-WROOM chip soldered on.

I love smart devices. In fact, that's exactly how the ESP32 ended up on my local network. I tracked the espressif devices down to my cat's water and food bowls from Petlibro. So it's only natural that I'd like to use the ESP32 for some wifi controlled 'smart' task.

When the board first arrived, I tried out the Arduino IDE. It was fine for learning purposes, but it felt like the IDE was doing a lot for me without having the chance to really understand everything going on behind the scenes. Personally I (barely) prefer CLion, and I wanted to get back to the IDE that was familiar to me. More importantly, I wanted to work on the ESP32 without tethering myself to any IDE. I wanted the project to be completely stand-alone, and to document and install any dependencies manually. Using Sketches in the Arduino IDE wasn't going to get me there.

Enter the Espressif IoT Development Framework, or the ESP-IDF for short. This looks slightly intimidating at first, but if you're at all familiar with C programming you'll get along fine. Before we dive into the ESP-IDF, lets take a step back and gain our bearings.

Ecosystems

Typically the ESP32 examples recommended for beginners will be using the arduino-esp32 APIs - Espressif provides one such example called WiFiClient. These examples are also made available in the Arduino IDE's menus where you can create a new project (sketch) based on this WiFiClient example. This example uses higher level C++ APIs than what you'll find in the ESP-IDF examples.

But why would Espressif, creators of the ESP32 and not the Arduino, want to support Arduino APIs? Simply because they are a popular point of entry for learning programming on microcontrollers, and supporting these APIs lowers the barrier of entry for ESP32 devices.

The ESP-IDF build system supports using those same Arduino APIs via an IDF component configuration marking arduino-esp32 as a dependency. See the Espressif GitHub example here, paired with the IDF component documentation from espressif.

Feel

ESP-IDF

free

In tothe sections below, we will use thesethe simpler arduino-esp32 APIs and examples to get familiar with deploying to the ESP32 using the ESP-IDFIDF. beforeThis jumpingexample intoisn't going to do very much interesting other than validate our build system. If we are successful, it will simply write some output to the serial monitor. No lights, buttons, sensors, wifi, etc.

In a future post, I'll look at drawing to an LCD display using the I2C communication protocol with the lower-level ESP APIs.APIs instead, and drop the dependency for arduino-esp32 entirely.

ESP-IDF

Installing

First we need to install the ESP-IDF following GitHub instructions on ubuntu 24.04

WARNING: If you are using arduino-esp32 APIs mentioned above, pay attention to arduino-esp32 releases for the latest supported ESP-IDF version. The latest ESP-IDF version is likely not currently supported by arduino-esp32. At the time of this writing, the latest arduino-esp32 release is based on ESP-IDF 5.3.2, so below we checkout the v5.3.2 branch of github.com/espressif/esp-idf.git.

Install the prerequisites required for the ESP-IDF

sudo apt-get install -y git wget flex bison gperf python3 python3-pip python3-venv cmake ninja-build ccache libffi-dev libssl-dev dfu-util libusb-1.0-0

Clone the ESP-IDF using the v5.3.2 branch and install. There will be a lot of output produced from these commands that is not shown below.

git clone -b v5.3.2 git@github.com:espressif/esp-idf.git
cd esp-idf
./install.sh
. ./export.sh

Switching Versions

To switch versions after previously installing the ESP-IDF

cd /path/to/esp-idf
git checkout v5.3.2
git submodule update --init --recursive
./install.sh
. ./export.sh

If everything worked correctly, you should end up with this final output in your terminal -

Done! You can now compile ESP-IDF projects.
Go to the project directory and run:

  idf.py build

Project Example

First set up your environment to use ESP-IDF tools and to have the correct exports required for building with CMake. Unfortunately the way this is done is by sourcing a script in the ESP-IDF repository, after you've installed the ESP-IDf.

source /home/shaun/Code/Clones/esp-idf/export.sh

You should now have the idf.py tool available in your shell. This helper I am honestly not so fond of, but we will have to use it for some things and that's fine.

idf.py

Usage: idf.py [OPTIONS] COMMAND1 [ARGS]... [COMMAND2 [ARGS]...]...

  ESP-IDF CLI build management tool. For commands that are not known to idf.py an attempt to execute
  it as a build system target will be made. Selected target: None

To make this simpler I threw an alias in my .bash_aliases file. I prefix all my alias commands with a comma. It looks strange, but it clearly separates an alias from a typical command.command and I think that's pretty cool.

echo "alias ,esp='source $HOME/Code/Clones/esp-idf/export.sh'" >> ~/.bash_aliases

So next time when I want to work on ESP things I can just run ,esp in a terminal to initialize my environment. From here we can use CMake to create an ESP-IDF project, and even flash to our device or open a serial monitor.

BuildingNew Project

Now that we canhave the tools to configure and build ESP-IDF projects with cmake, we can look at creating our first project. The example code that I'm going to build here is available at git.shaunreed.com/shaunrd0/klips. The commands below will not clone this repository, but instead set up the project as I did when creating it.

First set the build target to the ESP32 device. This tells the ESP-IDF which microcontroller we are working with.

TODO File tree before (set up the tree with main/ directory first)

#mkdir My example project directory04_esp-idf-arduino
cd ~/Code/klips/esp/cpp/04_esp-idf-arduino
idf.py set-target esp32
#

Next we need to add a dependency for the arduino-esp32 APIs. These simpler APIs will be a nice way to test our build system and get familiar with the tools.

IMPORTANT: We set the 3.1.1 version because the release is compatible with esp-idfESP-IDF v5.3.2 we installed in the first stepstep.

# https://github.com/espressif/arduino-esp32/releases/tag/3.1.1
idf.py add-dependency "espressif/arduino-esp32^3.1.1"
#
Autostart

TODO File tree before and after project setup

Now we need to automatically start Arduino forunder the ESP-IDF so that we can make use of `the Arduino loop()` and `setup()` functions #in our example. You can also use the esp-idf `app_main()` function if preferredpreferred, # https://docs.espressif.com/projects/arduino-esp32/en/latest/esp-idf_component.html#configuration # You can alternatively do this insee the GUIexamples toolbelow `idf.pyfor menuconfig`differences echo "CONFIG_AUTOSTART_ARDUINO=y" >> sdkconfig sed -i -e 's/CONFIG_FREERTOS_HZ=100/CONFIG_FREERTOS_HZ=1000/' sdkconfig # Buildbetween the project idf.py build two.

ESP-IDF example using app_main()
ESP-IDF example using Arduino loop() and setup()

You can alternatively do this in the TUI tool idf.py menuconfig, but here is a bash command to append the same configuration to the sdkconfig in your project directory that was generated by the ESP-IDF.

TODO: We also faced an error that required updating the CONFIG_FREERTOS_HZ value from 100 to 1000, as the error states.

echo "CONFIG_AUTOSTART_ARDUINO=y" >> sdkconfig
sed -i -e 's/CONFIG_FREERTOS_HZ=100/CONFIG_FREERTOS_HZ=1000/' sdkconfig

CMake

Setting up the project in CMake is fairly simple. For more information about build system see ESP-IDF - Build System

cmake_minimum_required(VERSION 3.26)

include($ENV{IDF_PATH}/tools/cmake/project.cmake)

project(
    #[[NAME]]   esp-idf-arduino
    VERSION     0.1
    DESCRIPTION "Example ESP-IDF cmake project"
    LANGUAGES   CXX
)

# For writing pure cmake components, see the documentation
# https://docs.espressif.com/projects/esp-idf/en/stable/esp32/api-guides/build-system.html#writing-pure-cmake-components
idf_build_set_property(COMPILE_OPTIONS "-Wno-error" APPEND)

And within our main/ directory we basically have a one liner CMakeLists.txt

idf_component_register(
    SRCS "main.cpp"
    INCLUDE_DIRS "."
)

TODO configure commands

Application Code

Now we write the source code for our application. I hope you're prepared, because it's a lot.

// main/main.cpp
#include "Arduino.h"

void setup() {
  Serial.begin(115200);
}

void loop() {
  Serial.println("Hello world!");
  delay(1000);
}

Finally, we can build the project

idf.py build

If everything completed normally, the build output will end with

Project build complete. To flash, run:
 idf.py flash
or
 idf.py -p PORT flash
or
 python -m esptool --chip esp32 -b 460800 --before default_reset --after hard_reset write_flash --flash_mode dio --flash_size 2MB --flash_freq 40m 0x1000 build/bootloader/bootloader.bin 0x8000 build/partition_table/partition-table.bin 0x10000 build/main.bin
or from the "/home/shaun/Code/klips/esp/cpp/04_esp-idf-arduino/build" directory
 python -m esptool --chip esp32 -b 460800 --before default_reset --after hard_reset write_flash "@flash_args"

Flashing

Find the device for the ESP32. Mine is /dev/ttyUSB0 in the output below.

$ ls /dev/tty*
/dev/tty    /dev/tty16  /dev/tty24  /dev/tty32  /dev/tty40  /dev/tty49  /dev/tty57  /dev/tty8       /dev/ttyS14  /dev/ttyS22  /dev/ttyS30
/dev/tty0   /dev/tty17  /dev/tty25  /dev/tty33  /dev/tty41  /dev/tty5   /dev/tty58  /dev/tty9       /dev/ttyS15  /dev/ttyS23  /dev/ttyS31
/dev/tty1   /dev/tty18  /dev/tty26  /dev/tty34  /dev/tty42  /dev/tty50  /dev/tty59  /dev/ttyprintk  /dev/ttyS16  /dev/ttyS24  /dev/ttyS4
/dev/tty10  /dev/tty19  /dev/tty27  /dev/tty35  /dev/tty43  /dev/tty51  /dev/tty6   /dev/ttyS0      /dev/ttyS17  /dev/ttyS25  /dev/ttyS5
/dev/tty11  /dev/tty2   /dev/tty28  /dev/tty36  /dev/tty44  /dev/tty52  /dev/tty60  /dev/ttyS1      /dev/ttyS18  /dev/ttyS26  /dev/ttyS6
/dev/tty12  /dev/tty20  /dev/tty29  /dev/tty37  /dev/tty45  /dev/tty53  /dev/tty61  /dev/ttyS10     /dev/ttyS19  /dev/ttyS27  /dev/ttyS7
/dev/tty13  /dev/tty21  /dev/tty3   /dev/tty38  /dev/tty46  /dev/tty54  /dev/tty62  /dev/ttyS11     /dev/ttyS2   /dev/ttyS28  /dev/ttyS8
/dev/tty14  /dev/tty22  /dev/tty30  /dev/tty39  /dev/tty47  /dev/tty55  /dev/tty63  /dev/ttyS12     /dev/ttyS20  /dev/ttyS29  /dev/ttyS9
/dev/tty15  /dev/tty23  /dev/tty31  /dev/tty4   /dev/tty48  /dev/tty56  /dev/tty7   /dev/ttyS13     /dev/ttyS21  /dev/ttyS3   /dev/ttyUSB0

To flash run the following commands.

# Manually selecting port with above output
# Baud rate matters: https://docs.espressif.com/projects/esp-idf/en/stable/esp32/get-started/establish-serial-connection.html#connect-esp32-to-pc
idf.py -p /dev/ttyUSB0 -b 115200 flash

# Let esp-idf automatically detect port and baud rate
idf.py flash

To open serial monitor with esp-idf via the commandline -

idf.py monitor -b 115200

Or in CLion the Serial Monitor extension works well.

Personal notes

this board on Amazon

Tutorials specific to this board are here.

Some other tutorials / refrences I collected going down this rabbit hole -

Development Methods

There are different ways to organize ESP32 projects, below is a brief on formats I've explored.

Arduino IDE

The Arduino IDE can be used to load sketches easily and flash to your ESP32.

This is easiest for a beginner, but you will have to use the Arudino IDE.

Download Arduino IDE here

unzip arduino-ide_2.3.4_Linux_64bit.zip -d ./arduino-ide_2.3.4
cd arduino-ide_2.3.4/
sudo chown root:root /home/shaun/Downloads/arduino-ide_2.3.4/chrome-sandbox
# Maybe
sudo chmod 4755 /home/shaun/Downloads/arduino-ide_2.3.4/chrome-sandbox

# For permissions to access USB devices
newgrp uucp
newgrp dialout

# Start IDE
./arduino-ide

ESP-IDF (CMake / CLion)

This is recommended for advanced setups only. If just getting started I would recommend the section above on Arduino IDE.

github.com/espressif/esp-idf

The ESP-IDF supports using arduino APIs via an IDF component configuration. See the official GitHub example here, paired with the official documentation from espressif.

Official Arduino documentation for using Arduino as an ESP-IDF component.

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