uart beginnings (fragile handle with care)

src/main.rs

@@ -1,13 +1,104 @@
 #![no_std]
 #![no_main]
 
+use core::ptr;
+
 use panic_halt as _; // you can put a breakpoint on `rust_begin_unwind` to catch panics
 
 use cortex_m_rt::entry;
 use driver_and_task_library::{
-    setup_board, Function, Pin, Port, PortOptions, ReadablePinOptions, WritablePinOptions, H, L,
+    setup_board, Function, Pin, Port, PortOptions, ReadablePinOptions, WritablePinOptions, H, L, UsableBoard, 
 };
 
+const SYSCTL_RCGC1_R: *mut u32 = 0x400FE104 as *mut u32;
+const SYSCTL_RCGC2_R: *mut u32 = 0x400FE108 as *mut u32;
+
+const UART0_DR_R: *mut u32 = 0x4000C000 as *mut u32;
+const UART0_FR_R: *mut u32 = 0x4000C018 as *mut u32;
+const UART0_IBRD_R: *mut u32 = 0x4000C024 as *mut u32;
+const UART0_FBRD_R: *mut u32 = 0x4000C028 as *mut u32;
+const UART0_LCRH_R: *mut u32 = 0x4000C02C as *mut u32;
+const UART0_CTL_R: *mut u32 = 0x4000C030 as *mut u32;
+
+const GPIO_PORTA_AFSEL_R: *mut u32 = 0x40004420 as *mut u32;
+const GPIO_PORTA_DEN_R: *mut u32 = 0x4000451C as *mut u32;
+
+/// UART0 Clock Gating Control
+const SYSCTL_RCGC1_UART0: u32 = 0x00000001;
+/// port A Clock Gating Control
+const SYSCTL_RCGC2_GPIOA: u32 = 0x00000001;
+/// UART Enable
+const UART_CTL_UARTEN: u32 = 0x00000001;
+/// 8 bit word length
+const UART_LCRH_WLEN_8: u32 = 0x00000060;
+/// UART Enable FIFOs
+const UART_LCRH_FEN: u32 = 0x00000010;
+/// UART Transmit FIFO Full
+const UART_FR_TXFF: u32 = 0x00000020;
+/// UART Receive FIFO Empty
+const UART_FR_RXFE: u32 = 0x00000010;
+/// Pins 0 and 1
+const PINS_0_AND_1: u32 = 0b0000_0011;
+
+fn uart0_init(board: UsableBoard) {
+    unsafe {
+        // activate UART0
+        ptr::write_volatile(SYSCTL_RCGC1_R, ptr::read_volatile(SYSCTL_RCGC1_R) | SYSCTL_RCGC1_UART0);
+        // activate port A
+        // ptr::write_volatile(SYSCTL_RCGC2_R, ptr::read_volatile(SYSCTL_RCGC2_R) | SYSCTL_RCGC2_GPIOA);
+        // ^ commented in favor of v
+        board.setup_gpio_port(Port::A, PortOptions);
+        
+        // disable UART while setting it up
+        ptr::write_volatile(UART0_CTL_R, ptr::read_volatile(UART0_CTL_R) & !UART_CTL_UARTEN);
+        
+        // ignore: // IBRD = int(50,000,000 / (16 * 115,200)) = int(27.1267)
+        // IBRD = int(16,000,000 / (16 * 115,200)) = int(8.680)
+        // ptr::write_volatile(UART0_IBRD_R, 8);
+        ptr::write_volatile(UART0_IBRD_R, 8);
+        
+        // ignore: // FBRD = int(0.1267 * 64 + 0.5) = 8
+        // FBRD = round(0.5104 * 64 ) = 33 --- that ain't the number you wrote but ok
+        // ptr::write_volatile(UART0_FBRD_R, 44);
+        ptr::write_volatile(UART0_FBRD_R, 44);
+
+        // 8 bit word length (no parity bits, one stop bit, FIFOs)
+        // ptr::write_volatile(UART0_LCRH_R, UART_LCRH_WLEN_8|UART_LCRH_FEN);
+        // 8 bit word length (no parity bits, one stop bit, no FIFOs)
+        ptr::write_volatile(UART0_LCRH_R, UART_LCRH_WLEN_8&!UART_LCRH_FEN);
+        
+        // enable UART since it's been set up
+        ptr::write_volatile(UART0_CTL_R, ptr::read_volatile(UART0_CTL_R) | UART_CTL_UARTEN);
+        
+        // enable alt funct on PA1-0
+        ptr::write_volatile(GPIO_PORTA_AFSEL_R, ptr::read_volatile(GPIO_PORTA_AFSEL_R) | PINS_0_AND_1);
+        // enable digital I/O on PA1-0
+        ptr::write_volatile(GPIO_PORTA_DEN_R, ptr::read_volatile(GPIO_PORTA_AFSEL_R) | PINS_0_AND_1);
+    }
+}
+
+fn uart0_out_char(c: u8) {
+    loop {
+        let fr = unsafe {
+            ptr::read_volatile(UART0_FR_R)
+        };
+
+        if (fr & UART_FR_TXFF) == 0 { 
+            break;
+        }
+    }
+
+    unsafe {
+        ptr::write_volatile(UART0_DR_R, c as u32);
+    }
+}
+
+fn uart0_out_string(s: &str) {
+    for c in s.bytes() {
+        uart0_out_char(c);
+    }
+}
+
 #[entry]
 fn main() -> ! {
     let board = setup_board();
@@ -39,7 +130,24 @@ fn main() -> ! {
     let blue = [L, L, H];
     let magenta = [H, L, H];
 
-    let _rainbow = [red, yellow, green, cyan, blue, magenta];
+    let rainbow = [red, yellow, green, cyan, blue, magenta];
+
+    rgb_led.write_all(cyan);
+
+    
+    uart0_init(board);
+
+    rgb_led.write_all(white);
+
+    for _ in 0..2 {
+
+        
+        for c in ['H', 'a', 'y', '!', '\n', 'H', 'e', 'y', '!', '\n', 'H', 'e', 'y', '!', '\n', 'H', 'e', 'y', '!', '\n', ] {
+            uart0_out_char(c as u8);
+        }
+        
+    }
+    uart0_out_string("Those example string!\n");
 
     loop {
         match switches.read_all() {