Update some readmes

06_drivers_gpio_uart/README.md

@@ -275,7 +275,7 @@ diff -uNr 05_safe_globals/src/bsp/device_driver/bcm/bcm2xxx_gpio.rs 06_drivers_g
 diff -uNr 05_safe_globals/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs 06_drivers_gpio_uart/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs
 --- 05_safe_globals/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs
 +++ 06_drivers_gpio_uart/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs
-@@ -0,0 +1,307 @@
+@@ -0,0 +1,311 @@
 +// SPDX-License-Identifier: MIT OR Apache-2.0
 +//
 +// Copyright (c) 2018-2020 Andre Richter <andre.o.richter@gmail.com>
@@ -452,8 +452,12 @@ diff -uNr 05_safe_globals/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs 06_dri
 +
 +    /// Set up baud rate and characteristics.
 +    ///
-+    /// Results in 8N1 and 230400 baud (if the clk has been previously set to 48 MHz by the
-+    /// firmware).
++    /// The calculation for the BRD given a target rate of 2300400 and a clock set to 48 MHz is:
++    /// `(48_000_000/16)/230400 = 13,02083`. `13` goes to the `IBRD` (integer field). The `FBRD`
++    /// (fractional field) is only 6 bits so `0,0208*64 = 1,3312 rounded to 1` will give the best
++    /// approximation we can get. A 5 modulo error margin is acceptable for UART and we're now at 0,01 modulo.
++    ///
++    /// This results in 8N1 and 230400 baud (we set the clock to 48 MHz in config.txt).
 +    pub fn init(&mut self) {
 +        // Turn it off temporarily.
 +        self.registers.CR.set(0);

07_uart_chainloader/README.md

@@ -197,7 +197,7 @@ diff -uNr 06_drivers_gpio_uart/src/_arch/aarch64/cpu.rs 07_uart_chainloader/src/
 diff -uNr 06_drivers_gpio_uart/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs 07_uart_chainloader/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs
 --- 06_drivers_gpio_uart/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs
 +++ 07_uart_chainloader/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs
-@@ -267,6 +267,16 @@
+@@ -271,6 +271,16 @@
          let mut r = &self.inner;
          r.lock(|inner| fmt::Write::write_fmt(inner, args))
      }
@@ -214,7 +214,7 @@ diff -uNr 06_drivers_gpio_uart/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs 0
  }
 
  impl console::interface::Read for PL011Uart {
-@@ -278,18 +288,21 @@
+@@ -282,18 +292,21 @@
                  cpu::nop();
              }
 

08_timestamps/README.md

@@ -227,7 +227,7 @@ diff -uNr 07_uart_chainloader/src/_arch/aarch64/time.rs 08_timestamps/src/_arch/
 diff -uNr 07_uart_chainloader/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs 08_timestamps/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs
 --- 07_uart_chainloader/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs
 +++ 08_timestamps/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs
-@@ -288,11 +288,18 @@
+@@ -292,11 +292,18 @@
                  cpu::nop();
              }
 

14_exceptions_part2_peripheral_IRQs/README.md

@@ -1893,7 +1893,7 @@ diff -uNr 13_integrated_testing/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs
  }
 
  //--------------------------------------------------------------------------------------------------
-@@ -186,6 +238,10 @@
+@@ -190,6 +242,10 @@
          self.registers
              .LCRH
              .write(LCRH::WLEN::EightBit + LCRH::FEN::FifosEnabled); // 8N1 + Fifo on
@@ -1904,7 +1904,7 @@ diff -uNr 13_integrated_testing/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs
          self.registers
              .CR
              .write(CR::UARTEN::Enabled + CR::TXE::Enabled + CR::RXE::Enabled);
-@@ -203,6 +259,35 @@
+@@ -207,6 +263,35 @@
 
          self.chars_written += 1;
      }
@@ -1940,7 +1940,7 @@ diff -uNr 13_integrated_testing/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs
  }
 
  /// Implementing `core::fmt::Write` enables usage of the `format_args!` macros, which in turn are
-@@ -228,9 +313,10 @@
+@@ -232,9 +317,10 @@
      /// # Safety
      ///
      /// - The user must ensure to provide the correct `base_addr`.
@@ -1953,7 +1953,7 @@ diff -uNr 13_integrated_testing/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs
          }
      }
  }
-@@ -251,6 +337,21 @@
+@@ -255,6 +341,21 @@
 
          Ok(())
      }
@@ -1975,7 +1975,7 @@ diff -uNr 13_integrated_testing/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs
  }
 
  impl console::interface::Write for PL011Uart {
-@@ -282,25 +383,7 @@
+@@ -286,25 +387,7 @@
  impl console::interface::Read for PL011Uart {
      fn read_char(&self) -> char {
          let mut r = &self.inner;
@@ -2002,7 +2002,7 @@ diff -uNr 13_integrated_testing/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs
      }
 
      fn clear(&self) {
-@@ -325,3 +408,25 @@
+@@ -329,3 +412,25 @@
          r.lock(|inner| inner.chars_read)
      }
  }