# NuttX RTOS — LVGL documentation

# NuttX RTOS

## What is NuttX?

NuttX is a mature and secure real-time operating system (RTOS) with an emphasis on technical standards compliance and small size. It is scalable from 8-bit to 64-bit microcontrollers and microprocessors and compliant with the Portable Operating System Interface (POSIX) and the American National Standards Institute (ANSI) standards and with many Linux-like subsystems. The best way to think about NuttX is to think of it as a small Unix/Linux for microcontrollers.

### Highlights of NuttX

- Small - Fits and runs in microcontrollers as small as 32 kB Flash and 8 kB of RAM.

- Compliant - Strives to be as compatible as possible with POSIX and Linux.

- Versatile - Supports many architectures (ARM, ARM Thumb, AVR, MIPS, OpenRISC, RISC-V 32-bit and 64-bit, RX65N, x86-64, Xtensa, Z80/Z180, etc.).

- Modular - Its modular design allows developers to select only what really matters and use modules to include new features.

- Popular - NuttX is used by many companies around the world. Probably you already used a product with NuttX without knowing it was running NuttX.

- Predictable - NuttX is a preemptible Realtime kernel, so you can use it to create predictable applications for realtime control.

## Why NuttX + LVGL?

Although NuttX has its own graphic library called NX, LVGL is a good alternative because users could find more eye-candy demos and they can reuse code from previous projects. LVGL is an Object-Oriented Component Based high-level GUI library, that could fit very well for a RTOS with advanced features like NuttX. LVGL is implemented in C and its APIs are in C.

### Here are some advantages of using LVGL in NuttX

- Develop GUI in Linux first and when it is done just compile it for NuttX. Nothing more, no wasting of time.

- Usually, GUI development for low level RTOS requires multiple iterations to get things right, where each iteration consists of ``Change code`` > ``Build`` > ``Flash`` > ``Run``. Using LVGL, Linux and NuttX you can reduce this process and just test everything on your computer and when it is done, compile it on NuttX and that is it.

### NuttX + LVGL could be used for

- GUI demos to demonstrate your board graphics capacities.

- Fast prototyping GUI for MVP (Minimum Viable Product) presentation.

- visualize sensor data directly and easily on the board without using a computer.

- Final products with a GUI without a touchscreen (i.e. 3D Printer Interface using Rotary Encoder to Input data).

- Final products with a touchscreen (and all sorts of bells and whistles).

## How to get started with NuttX and LVGL?

There are many boards in the NuttX mainline with support for LVGL. Let's use the STM32F429IDISCOVERY as an example because it is a very popular board.

### First you need to install the pre-requisites on your system

Let's use the Windows Subsystem for Linux

    $ sudo apt-get install automake bison build-essential flex gcc-arm-none-eabi gperf git libncurses5-dev libtool libusb-dev libusb-1.0.0-dev pkg-config kconfig-frontends openocd

### Now let's create a workspace to save our files

    $ mkdir ~/nuttxspace
    $ cd ~/nuttxspace

### Clone the NuttX and Apps repositories:

    $ git clone https://github.com/apache/incubator-nuttx nuttx
    $ git clone https://github.com/apache/incubator-nuttx-apps apps

### Configure NuttX to use the stm32f429i-disco board and the LVGL Demo

    $ ./tools/configure.sh stm32f429i-disco:lvgl
    $ make

If everything went fine you should have now the file `nuttx.bin` to flash on your board:

    $ ls -l nuttx.bin
    -rwxrwxr-x 1 alan alan 287144 Jun 27 09:26 nuttx.bin

### Flashing the firmware in the board using OpenOCD:

    $ sudo openocd -f interface/stlink-v2.cfg -f target/stm32f4x.cfg -c init -c "reset halt" -c "flash write_image erase nuttx.bin 0x08000000"

Reset the board and using the 'NSH>' terminal start the LVGL demo:

    nsh> lvgldemo

## Where can I find more information?

- This blog post: LVGL on LPCXpresso54628

- NuttX mailing list: Apache NuttX Mailing List