README: add setup instructions (#136)

* README: add setup instructions

inspired by https://github.com/stm32-rs/stm32f1xx-hal/blob/master/README.md

Co-authored-by: Daniel Egger <daniel@eggers-club.de>

Author: marcoieni

README.md

@@ -45,6 +45,39 @@ crate by Jorge Aparicio.
 [stm32f103xx-hal]: https://github.com/japaric/stm32f103xx-hal
 [embedded-hal]: https://github.com/rust-embedded/embedded-hal
 
+Setting up your project
+-------
+
+Check if the BSP for your board exists in the
+[stm32-rs](https://github.com/stm32-rs) page.
+If it exists, the `stm32f4xx-hal` crate should be already included, so you can
+use the bsp as BSP for your project.
+
+Otherwise, create a new Rust project as you usually do with `cargo init`. The
+"hello world" of embedded development is usually to blink a LED. The code to do
+so is available in [examples/delay-blinky.rs](examples/delay-blinky.rs).
+Copy that file to the `main.rs` of your project.
+
+You also need to add some dependencies to your `Cargo.toml`:
+
+```toml
+[dependencies]
+embedded-hal = "0.2.3"
+nb = "0.1.2"
+cortex-m = "0.6.2"
+cortex-m-rt = "0.6.11"
+# Panic behaviour, see https://crates.io/keywords/panic-impl for alternatives
+panic-halt = "0.2.0"
+
+[dependencies.stm32f4xx-hal]
+version = "0.7"
+features = ["rt", "stm32f407"] # replace the model of your microcontroller here
+```
+
+We also need to tell Rust how to link our executable and how to lay out the
+result in memory. To accomplish all this, copy [.cargo/config](.cargo/config)
+and [memory.x](memory.x) from the `stm32f4xx-hal` repository to your project and make sure the sizes match up with the datasheet. Also note that there might be different kinds of memory which are not equal; to be on the safe side only specify the size of the first block at the specified address.
+
 License
 -------