747e902761
We now have the same API for MMIO and CPU registers. Makes the code more concise, inntuitive, and improves readability. https://crates.io/crates/register
1.4 KiB
Tutorial 03 - UART1, Auxilary mini UART
It is time for the famous Hello World example. We're going to write on the UART1 first, as it's easier to program as it has a fixed clocked frequency.
NOTE: qemu does not redirect UART1 to terminal by default, only UART0!
gpio.rs
We have a new file that defines the GPIO controller addresses. It is going to be very popular, as many device will need it in the future.
We are using the register crate to modify MMIO addresses, because it allows easy wrapping of addresses to volatile types. It will also be used for UART registers.
uart.rs
A very minimal implementation.
MiniUart::init(&self) initializes the device and maps it to the GPIO ports.
MiniUart::send(&self, c: char) sends a character over the serial line.
MiniUart::getc(&self) receives a character. The carrige return character (13)
will be converted into a newline character (10).
MiniUart::puts(&self, string: &str) prints out a string. On newline, a carrige
return character will also be sent (13 + 10).
main.rs
First we have to call the uart initialization code. Then we wait for the first
keypress from the user before we say "Hello Rustacean!". If you've purchased an
USB serial cable, you should see it on screen's screen. After that, every
character typed in screen will be echoed back. If you haven't turned off local
echo, that means you'll see every pressed key twice.