# Zephyr RTOS - Hello World Application

[TOC]

## References

First step is to go through [*Getting Started Guide*](https://docs.zephyrproject.org/latest/develop/getting_started/index.html#select-and-update-os) in Zephyr official doc, wich is what [Let's run Zephyr OS on Raspberry Pi Pico. Ep.1](https://youtu.be/OyMyY4IwsJE) does. This is rather straight forward. Copy-pasting commands listed on the doc should just work.

Note that in the [Build the Blinky Sample](https://docs.zephyrproject.org/latest/develop/getting_started/index.html#build-the-blinky-sample) step, you can build target that runs on QEMU in stead of a real board. To do this, choose a "board" (or compilation target rather) in [Supported Boards](https://docs.zephyrproject.org/latest/boards/index.html#boards) that runs on QEMU as `<your-board-name>`. For example you can choose `qemu_riscv64`:

$ west build -p auto -b qemu_riscv64 samples/philosophers 

and then run it with:

$ west build -t run

You can then see the example running:

Philosopher 0 [P: 3]  THINKING [  300 ms ] 
Philosopher 1 [P: 2]  THINKING [  425 ms ] 
Philosopher 2 [P: 1]  HOLDING ONE FORK   
Philosopher 3 [P: 0]  EATING   [  625 ms ] 
Philosopher 4 [C:-1]  STARVING       
Philosopher 5 [C:-2]  EATING   [  75 ms  ]  


Demo Description
----------------
An implementation of a solution to the Dining Philosophers
problem (a classic multi-thread synchronization problem).
This particular implementation demonstrates the usage of multiple
preemptible and cooperative threads of differing priorities, as
well as dynamic mutexes and thread sleeping.

Do note that there are ways other than `west flash` to update Zephyr binaries on a MCU. For example, if you have [Simple Management Protocol (SMP)](https://docs.zephyrproject.org/latest/samples/subsys/mgmt/mcumgr/smp_svr/README.html#smp-svr-sample-build) enabled on Zephry, then it is possible to upload binary to MCU with [`mcumgr`](https://docs.zephyrproject.org/latest/services/device_mgmt/mcumgr.html) at run time.

### [Let's run Zephyr OS on Raspberry Pi Pico. Ep.1](https://youtu.be/OyMyY4IwsJE)

{%youtube OyMyY4IwsJE %}