Only enable usart tx/rx when needed

Author: david-sawatzke

src/serial.rs

@@ -198,7 +198,9 @@ macro_rules! usart {
                 pub fn $usart(usart: $USART, pins: (TXPIN, RXPIN), baud_rate: Bps, clocks: Clocks) -> Self
                 {
                     let mut serial = Serial { usart, pins };
-                    serial.enable(baud_rate, clocks);
+                    serial.configure(baud_rate, clocks);
+                    // Enable transmission and receiving
+                    serial.usart.cr1.modify(|_, w| w.te().set_bit().re().set_bit().ue().set_bit());
                     serial
                 }
             }
@@ -212,7 +214,9 @@ macro_rules! usart {
                 {
                     let rxpin = ();
                     let mut serial = Serial { usart, pins: (txpin, rxpin) };
-                    serial.enable(baud_rate, clocks);
+                    serial.configure(baud_rate, clocks);
+                    // Enable transmission
+                    serial.usart.cr1.modify(|_, w| w.te().set_bit().ue().set_bit());
                     serial
                 }
             }
@@ -226,13 +230,15 @@ macro_rules! usart {
                 {
                     let txpin = ();
                     let mut serial = Serial { usart, pins: (txpin, rxpin) };
-                    serial.enable(baud_rate, clocks);
+                    serial.configure(baud_rate, clocks);
+                    // Enable receiving
+                    serial.usart.cr1.modify(|_, w| w.re().set_bit().ue().set_bit());
                     serial
                 }
             }
 
             impl<TXPIN, RXPIN> Serial<$USART, TXPIN, RXPIN> {
-                fn enable(&mut self, baud_rate: Bps, clocks: Clocks) {
+                fn configure(&mut self, baud_rate: Bps, clocks: Clocks) {
                     // NOTE(unsafe) This executes only during initialisation
                     let rcc = unsafe { &(*crate::stm32::RCC::ptr()) };
 
@@ -246,9 +252,6 @@ macro_rules! usart {
                     // Reset other registers to disable advanced USART features
                     self.usart.cr2.reset();
                     self.usart.cr3.reset();
-
-                    // Enable transmission and receiving
-                    self.usart.cr1.modify(|_, w| w.te().set_bit().re().set_bit().ue().set_bit());
                 }
 
                 /// Starts listening for an interrupt event