Merge pull request #409 from mas192/patch-1

Update teaching material duration for bare-metal Rust

Author: BartMassey

src/intro/index.md

@@ -60,7 +60,7 @@ If you are unfamiliar with anything mentioned above or if you want more informat
 | Rust, Embedded | [Embedded Rust Bookshelf](https://docs.rust-embedded.org) | Here you can find several other resources provided by Rust's Embedded Working Group. |
 | Rust, Embedded | [Embedonomicon](https://docs.rust-embedded.org/embedonomicon/) | The nitty gritty details when doing embedded programming in Rust. |
 | Rust, Embedded | [embedded FAQ](https://docs.rust-embedded.org/faq.html) | Frequently asked questions about Rust in an embedded context. |
-| Rust, Embedded | [Comprehensive Rust 🦀: Bare Metal](https://google.github.io/comprehensive-rust/bare-metal.html) | Teaching material for a 1-day class on bare-metal Rust development |
+| Rust, Embedded | [Comprehensive Rust 🦀: Bare Metal](https://google.github.io/comprehensive-rust/bare-metal.html) | Teaching material for a 4-day class on bare-metal Rust development |
 | Interrupts | [Interrupt](https://en.wikipedia.org/wiki/Interrupt) | - |
 | Memory-mapped IO/Peripherals | [Memory-mapped I/O](https://en.wikipedia.org/wiki/Memory-mapped_I/O) | - |
 | SPI, UART, RS232, USB, I2C, TTL | [Stack Exchange about SPI, UART, and other interfaces](https://electronics.stackexchange.com/questions/37814/usart-uart-rs232-usb-spi-i2c-ttl-etc-what-are-all-of-these-and-how-do-th) | - |