stm32/usart: Implemented a function to get the current databits setting for a USART

include/libopencm3/stm32/common/usart_common_all.h

@@ -100,6 +100,7 @@ BEGIN_DECLS
 
 void usart_set_baudrate(uint32_t usart, uint32_t baud);
 void usart_set_databits(uint32_t usart, uint32_t bits);
+uint32_t usart_get_databits(uint32_t usart);
 void usart_set_stopbits(uint32_t usart, uint32_t stopbits);
 void usart_set_parity(uint32_t usart, uint32_t parity);
 void usart_set_mode(uint32_t usart, uint32_t mode);

lib/stm32/common/usart_common_all.c

@@ -95,6 +95,27 @@ void usart_set_databits(uint32_t usart, uint32_t bits)
 	}
 }
 
+/*---------------------------------------------------------------------------*/
+/** @brief USART Get Word Length.
+
+The word length is set to 8 or 9 bits. Note that the last bit will be a parity
+bit if parity is enabled, in which case the data length will be 7 or 8 bits
+respectively.
+
+@param[in] usart unsigned 32 bit. USART block register address base @ref
+usart_reg_base
+@returns unsigned 32 bit Word length in bits 8 or 9.
+*/
+
+uint32_t usart_get_databits(uint32_t usart)
+{
+	const uint32_t reg32 = USART_CR1(usart) & USART_CR1_M;
+	if (reg32)
+		return 9;
+	else
+		return 8;
+}
+
 /*---------------------------------------------------------------------------*/
 /** @brief USART Set Stop Bit(s).