serial: Add databits, use default config in examples

Author: maximeborges

examples/serial_delay.rs

@@ -39,11 +39,8 @@ fn main() -> ! {
         (tx, rx),
         &clocks,
         serial::Config {
-            baud_rate: 115_200.bps(),
-            oversampling: serial::Oversampling::By16,
-            character_match: None,
-            sysclock: false,
-            parity: serial::Parity::ParityNone,
+            // Default to 115_200 bauds
+            ..Default::default()
         },
     );
     let (mut tx, _) = serial.split();

examples/serial_dma.rs

@@ -47,11 +47,8 @@ fn main() -> ! {
         (tx, rx),
         &clocks,
         serial::Config {
-            baud_rate: 115_200.bps(),
-            oversampling: serial::Oversampling::By16,
-            character_match: None,
-            sysclock: false,
-            parity: serial::Parity::ParityNone,
+            // Default to 115_200 bauds
+            ..Default::default()
         },
     );
     let (mut tx, mut rx) = serial.split();

examples/serial_echo.rs

@@ -36,11 +36,8 @@ fn main() -> ! {
         (tx, rx),
         &clocks,
         serial::Config {
-            baud_rate: 115_200.bps(),
-            oversampling: serial::Oversampling::By16,
-            character_match: None,
-            sysclock: false,
-            parity: serial::Parity::ParityNone,
+            // Default to 115_200 bauds
+            ..Default::default()
         },
     );
 

examples/serial_parity.rs

@@ -15,7 +15,7 @@ use cortex_m_rt::entry;
 use stm32f7xx_hal::{
     pac,
     prelude::*,
-    serial::{self, Serial},
+    serial::{self, Serial, DataBits},
 };
 
 #[entry]
@@ -37,11 +37,11 @@ fn main() -> ! {
         (tx, rx),
         &clocks,
         serial::Config {
-            baud_rate: 56_700.bps(),
-            oversampling: serial::Oversampling::By16,
-            character_match: None,
-            sysclock: false,
-            parity: serial::Parity::ParityEven,
+            // Using 8 bits of data + 1 for even parity
+            data_bits: DataBits::Bits9,
+            parity: Parity::ParityEven,
+            // Default to 115_200 bauds
+            ..Default::default()
         },
     );
 

src/serial.rs

@@ -163,22 +163,28 @@ where
         let ch = config.character_match.unwrap_or(0);
         usart.cr2.write(|w| w.add().bits(ch));
 
-        // Enable tx / rx and configure parity
+        // Enable tx / rx, configure data bits and parity
         usart.cr1.modify(|_, w| {
-            w.te()
-                .enabled()
-                .re()
-                .enabled()
-                .ue()
-                .enabled()
-                .m1()
-                .m0()
-                .m0()
-                .bit(!matches!(config.parity, Parity::ParityNone))
-                .pce()
-                .bit(!matches!(config.parity, Parity::ParityNone))
-                .ps()
-                .bit(matches!(config.parity, Parity::ParityOdd))
+            w
+                .te().enabled()
+                .re().enabled()
+                .ue().enabled();
+
+            // M[1:0] are used to set data bits
+            // M[1:0] = 00: 1 Start bit, 8 data bits, n stop bits
+            // M[1:0] = 01: 1 Start bit, 9 data bits, n stop bits
+            // M[1:0] = 10: 1 Start bit, 7 data bits, n stop bits
+            match config.data_bits {
+                DataBits::Bits8 => w.m1().clear_bit().m0().bit8(),
+                DataBits::Bits9 => w.m1().clear_bit().m0().bit9(),
+                DataBits::Bits7 => w.m0().clear_bit().m1().bit7(),
+            };
+
+            match config.parity {
+                Parity::ParityEven => w.ps().even().pce().enabled(),
+                Parity::ParityOdd  => w.ps().odd().pce().enabled(),
+                Parity::ParityNone => w.pce().disabled(),
+            }
         });
 
         // Enable DMA
@@ -429,13 +435,25 @@ pub struct Config {
     pub character_match: Option<u8>,
     pub sysclock: bool,
     pub parity: Parity,
+    pub data_bits: DataBits,
+
 }
 
 pub enum Oversampling {
     By8,
     By16,
 }
 
+/// Number of data bits
+pub enum DataBits {
+    /// 8 bits of data
+    Bits8,
+    /// 9 bits of data
+    Bits9,
+    /// 7 bits of data
+    Bits7,
+}
+
 /// Parity generation and checking. If odd or even parity is selected, the
 /// underlying USART will be configured to send/receive the parity bit in
 /// addtion to the data bits.
@@ -458,6 +476,7 @@ impl Default for Config {
             character_match: None,
             sysclock: false,
             parity: Parity::ParityNone,
+            data_bits: DataBits::Bits8,
         }
     }
 }