From 9ea07b3d30e9405cd51a48e5af4e40ae27b17ca6 Mon Sep 17 00:00:00 2001
From: Tilman Sauerbeck <tilman@code-monkey.de>
Date: Sat, 28 Dec 2019 19:54:46 +0100
Subject: [PATCH] common: Add the uart module.

---
 SConscript.libcommon |   1 +
 src/common/lib.rs    |   1 +
 src/common/uart.rs   | 134 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 136 insertions(+)
 create mode 100644 src/common/uart.rs

diff --git a/SConscript.libcommon b/SConscript.libcommon
index d353e61..e1d378c 100644
--- a/SConscript.libcommon
+++ b/SConscript.libcommon
@@ -10,6 +10,7 @@ source_files_rs = [
     'src/common/port.rs',
     'src/common/gpio.rs',
     'src/common/i2c.rs',
+    'src/common/uart.rs',
     'src/common/watchdog.rs',
     'src/common/crc32.rs',
     'src/common/buffer.rs',
diff --git a/src/common/lib.rs b/src/common/lib.rs
index b6a08c7..61d8f79 100644
--- a/src/common/lib.rs
+++ b/src/common/lib.rs
@@ -32,6 +32,7 @@ pub mod systick;
 pub mod port;
 pub mod gpio;
 pub mod i2c;
+pub mod uart;
 pub mod watchdog;
 pub mod crc32;
 pub mod buffer;
diff --git a/src/common/uart.rs b/src/common/uart.rs
new file mode 100644
index 0000000..98a0c51
--- /dev/null
+++ b/src/common/uart.rs
@@ -0,0 +1,134 @@
+/*
+ * Copyright (c) 2019 Tilman Sauerbeck (tilman at code-monkey de)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+use register;
+
+type Reg8 = register::Register<u8>;
+type Reg32 = register::Register<u32>;
+
+const UART_BASE: u32 = 0x4006a000;
+
+pub const UART0: u32 = UART_BASE + 0x0000;
+pub const UART1: u32 = UART_BASE + 0x1000;
+pub const UART2: u32 = UART_BASE + 0x2000;
+
+const SIM_BASE : u32 = 0x40047000;
+
+const SIM_SOPT2: u32 = SIM_BASE + 0x1004;
+const SIM_SCGC4: u32 = SIM_BASE + 0x1034;
+
+const SIM_SOPT2_UART0SRC_SHIFT: u32 = 26;
+
+const SIM_SCGC4_UART0: u32 = 1 << 10;
+const SIM_SCGC4_UART1: u32 = 1 << 11;
+const SIM_SCGC4_UART2: u32 = 1 << 12;
+
+const UART_BDH: u32 = 0x00;
+const UART_BDL: u32 = 0x01;
+const UART_C2 : u32 = 0x03;
+const UART_S1 : u32 = 0x04;
+const UART_D  : u32 = 0x07;
+const UART_C4 : u32 = 0x0a;
+const UART_C5 : u32 = 0x0b;
+
+const UART_S1_RDRF: u8 = 1 << 5;
+
+const UART_C2_RE  : u8 = 1 << 2;
+const UART_C2_TE  : u8 = 1 << 3;
+const UART_C2_RIE : u8 = 1 << 5;
+
+const UART_C4_OSR_SHIFT: u32 = 0;
+const UART_C4_OSR_MASK : u8 = 0xf << UART_C4_OSR_SHIFT;
+
+const UART_C5_BOTHEDGE : u8 = 1 << 1;
+
+pub fn configure(uart: u32) {
+    Reg32::new(SIM_SOPT2).modify(|v| {
+        let mut m = v;
+
+        m &= !(3 << SIM_SOPT2_UART0SRC_SHIFT);
+        m |= 2 << SIM_SOPT2_UART0SRC_SHIFT;
+
+        m
+    });
+
+    Reg32::new(SIM_SCGC4).modify(|v| {
+        if uart == UART0 {
+            v | SIM_SCGC4_UART0
+        } else if uart == UART1 {
+            v | SIM_SCGC4_UART1
+        } else if uart == UART2 {
+            v | SIM_SCGC4_UART2
+        } else {
+            v
+        }
+    });
+
+    // Before we may mess with the baud rate, we need to disable
+    // both the receiver and the transmitter.
+    Reg8::new(uart + UART_C2).modify(|v| v & !(UART_C2_RE | UART_C2_TE));
+
+    // Set baud rate.
+    Reg8::new(uart + UART_BDH).write(0x0);
+    Reg8::new(uart + UART_BDL).write(0x34);
+
+    // Configure minimum oversampling ratio.
+    Reg8::new(uart + UART_C4).modify(|v| {
+        let mut m = v;
+
+        m &= !UART_C4_OSR_MASK;
+        m |= 3 << UART_C4_OSR_SHIFT;
+
+        m
+    });
+
+    Reg8::new(uart + UART_C5).modify(|v| v | UART_C5_BOTHEDGE);
+
+    // Enable receiver only (including interrupt).
+    Reg8::new(uart + UART_C2).write(UART_C2_RE | UART_C2_RIE);
+
+    // XXX:
+    // Is this needed?
+    Reg8::new(uart + UART_S1).write(0xf); // Clear errors.
+}
+
+pub fn try_read(uart: u32) -> Option<u8> {
+    let mut uart_s1 = Reg8::new(uart + UART_S1);
+
+    let s1 = uart_s1.read();
+
+    let result = if (s1 & UART_S1_RDRF) == 0 {
+        None
+    } else {
+        Some(Reg8::new(uart + UART_D).read())
+    };
+
+    let set_error_flags = s1 & 0x1f;
+
+    // Acknowledge errors.
+    if set_error_flags != 0 {
+        uart_s1.write(set_error_flags);
+    }
+
+    result
+}
-- 
2.30.2