Implement blinking LED

src/uart.rs

@@ -0,0 +1,86 @@
+const BAUD: u32 = 115200;
+const UART_CLK: u32 = 48_000_000;
+
+const UART0_DR: u32 = 0x3F20_1000;
+
+const UART0_FR: u32 = 0x3F20_1018;
+const UART0_FR_TXFF: u32 = 1 << 5;
+
+const UART0_IBRD: u32 = 0x3F20_1024;
+const UART0_FBRD: u32 = 0x3F20_1028;
+
+const UART0_CR: u32 = 0x3F20_1030;
+const UART0_CR_UARTEN: u32 = 1 << 0;
+const UART0_CR_TXE: u32 = 1 << 8;
+
+const UART0_LCRH: u32 = 0x3F20_102c;
+const UART0_LCRH_FEN: u32 = 1 << 4;
+
+pub fn print(s: &str) {
+    for byte in s.bytes() {
+        unsafe {
+            while core::ptr::read_volatile(UART0_FR as *const u32) & UART0_FR_TXFF != 0 {}
+            core::ptr::write_volatile(UART0_DR as *mut u32, byte as u32);
+        }
+    }
+}
+
+pub fn configure_uart() {
+    let baud_div_times_64 = (UART_CLK * 4) / BAUD;
+
+    let ibrd = baud_div_times_64 / 64;
+    let fbrd = baud_div_times_64 % 64;
+
+    unsafe {
+        uart_enable(false);
+        uart_fifo_enable(false);
+
+        core::ptr::write_volatile(UART0_IBRD as *mut u32, ibrd);
+        core::ptr::write_volatile(UART0_FBRD as *mut u32, fbrd);
+
+        uart_set_lcrh(0b11, true);
+
+        // Enable transmit and uart
+        let mut cr = core::ptr::read_volatile(UART0_CR as *mut u32);
+        cr |= UART0_CR_UARTEN | UART0_CR_TXE;
+        core::ptr::write_volatile(UART0_CR as *mut u32, cr);
+    }
+}
+
+fn uart_enable(enable: bool) {
+    unsafe {
+        let mut cr = core::ptr::read_volatile(UART0_CR as *mut u32);
+
+        if enable {
+            cr |= UART0_CR_UARTEN;
+        } else {
+            cr &= !UART0_CR_UARTEN;
+        }
+
+        core::ptr::write_volatile(UART0_CR as *mut u32, cr);
+    }
+}
+
+fn uart_fifo_enable(enable: bool) {
+    unsafe {
+        let mut lcrh = core::ptr::read_volatile(UART0_LCRH as *mut u32);
+
+        if enable {
+            lcrh |= UART0_LCRH_FEN;
+        } else {
+            lcrh &= !UART0_LCRH_FEN;
+        }
+
+        core::ptr::write_volatile(UART0_LCRH as *mut u32, lcrh);
+    }
+}
+
+fn uart_set_lcrh(wlen: u32, enable_fifo: bool) {
+    unsafe {
+        let mut value = (wlen & 0b11) << 5;
+        if enable_fifo {
+            value |= UART0_LCRH_FEN;
+        }
+        core::ptr::write_volatile(UART0_LCRH as *mut u32, value);
+    }
+}