update UART clock config, bugfix

tools/uart-clock-calc/src/main.rs

@@ -0,0 +1,50 @@
+use arbitrary_int::{u6, u18};
+
+#[derive(Debug, Copy, Clone)]
+pub struct ClockConfig {
+    pub frac: u6,
+    pub int: u18,
+}
+
+#[derive(Debug, Copy, Clone)]
+pub enum BaudMultiplier {
+    _8 = 8,
+    _16 = 16,
+}
+
+pub fn uart_clock_calc(ref_clk: u32, baudrate: u32, baud_mult: BaudMultiplier) -> ClockConfig {
+    // This is the calculation: (64.0 * (x - integer_part as f32) + 0.5) as u32 without floating
+    // point calculations.
+    let multiplier = baud_mult as u32;
+    let frac = ((ref_clk % (baudrate * multiplier)) * 64 + (baudrate * (multiplier / 2)))
+        / (baudrate * multiplier);
+    // Calculations here are derived from chapter 4.8.5 (p.79) of the datasheet.
+    let integer_part = ref_clk / (baudrate * multiplier);
+    ClockConfig {
+        frac: u6::new(frac as u8),
+        int: u18::new(integer_part),
+    }
+}
+
+const SYS_CLK_50_MHZ: u32 = 50_000_000;
+
+fn main() {
+    println!("UART Clock Configuration App");
+    let clock_config = uart_clock_calc(SYS_CLK_50_MHZ, 38400, BaudMultiplier::_16);
+    println!(
+        "For a reference clock of {} Hz and baud rate of {} bps with multiplier {}, the clock configuration is: {:?}",
+        SYS_CLK_50_MHZ,
+        38400,
+        BaudMultiplier::_16 as u32,
+        clock_config
+    );
+    let clock_config = uart_clock_calc(SYS_CLK_50_MHZ, 38400, BaudMultiplier::_8);
+    println!(
+        "For a reference clock of {} Hz and baud rate of {} bps with multiplier {}, the clock configuration is: {:?}",
+        SYS_CLK_50_MHZ,
+        38400,
+        BaudMultiplier::_8 as u32,
+        clock_config
+    );
+    ()
+}