stm32/uart: Add uart_set_baudrate function.

This allows changing the baudrate of the UART without reinitialising it
(reinitialising can lead to spurious characters sent on the TX line).
Signed-off-by: Damien George <damien@micropython.org>

ports/stm32/boards/stm32f0xx_hal_conf_base.h

@@ -49,6 +49,7 @@
 #include "stm32f0xx_hal_wwdg.h"
 #include "stm32f0xx_ll_adc.h"
 #include "stm32f0xx_ll_rtc.h"
+#include "stm32f0xx_ll_usart.h"
 
 // Enable various HAL modules
 #define HAL_MODULE_ENABLED

ports/stm32/boards/stm32f4xx_hal_conf_base.h

@@ -56,6 +56,7 @@
 #include "stm32f4xx_ll_adc.h"
 #include "stm32f4xx_ll_pwr.h"
 #include "stm32f4xx_ll_rtc.h"
+#include "stm32f4xx_ll_usart.h"
 
 // Enable various HAL modules
 #define HAL_ADC_MODULE_ENABLED

ports/stm32/boards/stm32f7xx_hal_conf_base.h

@@ -56,6 +56,7 @@
 #include "stm32f7xx_ll_adc.h"
 #include "stm32f7xx_ll_pwr.h"
 #include "stm32f7xx_ll_rtc.h"
+#include "stm32f7xx_ll_usart.h"
 
 // Enable various HAL modules
 #define HAL_ADC_MODULE_ENABLED

ports/stm32/boards/stm32h7xx_hal_conf_base.h

@@ -56,6 +56,7 @@
 #include "stm32h7xx_ll_adc.h"
 #include "stm32h7xx_ll_pwr.h"
 #include "stm32h7xx_ll_rtc.h"
+#include "stm32h7xx_ll_usart.h"
 
 // Enable various HAL modules
 #define HAL_ADC_MODULE_ENABLED

ports/stm32/boards/stm32l0xx_hal_conf_base.h

@@ -48,6 +48,7 @@
 #include "stm32l0xx_hal_wwdg.h"
 #include "stm32l0xx_ll_adc.h"
 #include "stm32l0xx_ll_rtc.h"
+#include "stm32l0xx_ll_usart.h"
 
 // Enable various HAL modules
 #define HAL_MODULE_ENABLED

ports/stm32/boards/stm32l4xx_hal_conf_base.h

@@ -52,6 +52,7 @@
 #include "stm32l4xx_hal_wwdg.h"
 #include "stm32l4xx_ll_adc.h"
 #include "stm32l4xx_ll_rtc.h"
+#include "stm32l4xx_ll_usart.h"
 
 // Enable various HAL modules
 #define HAL_MODULE_ENABLED

ports/stm32/boards/stm32wbxx_hal_conf_base.h

@@ -43,6 +43,7 @@
 #include "stm32wbxx_hal_usart.h"
 #include "stm32wbxx_ll_adc.h"
 #include "stm32wbxx_ll_rtc.h"
+#include "stm32wbxx_ll_usart.h"
 
 // Enable various HAL modules
 #define HAL_MODULE_ENABLED

ports/stm32/uart.c

@@ -603,7 +603,7 @@ void uart_attach_to_repl(pyb_uart_obj_t *self, bool attached) {
     self->attached_to_repl = attached;
 }
 
-uint32_t uart_get_baudrate(pyb_uart_obj_t *self) {
+uint32_t uart_get_source_freq(pyb_uart_obj_t *self) {
     uint32_t uart_clk = 0;
 
     #if defined(STM32F0)
@@ -672,10 +672,20 @@ uint32_t uart_get_baudrate(pyb_uart_obj_t *self) {
     }
     #endif
 
+    return uart_clk;
+}
+
+uint32_t uart_get_baudrate(pyb_uart_obj_t *self) {
     // This formula assumes UART_OVERSAMPLING_16
-    uint32_t baudrate = uart_clk / self->uartx->BRR;
+    return uart_get_source_freq(self) / self->uartx->BRR;
+}
 
-    return baudrate;
+void uart_set_baudrate(pyb_uart_obj_t *self, uint32_t baudrate) {
+    LL_USART_SetBaudRate(self->uartx, uart_get_source_freq(self),
+        #if defined(STM32H7) || defined(STM32WB)
+        LL_USART_PRESCALER_DIV1,
+        #endif
+        LL_USART_OVERSAMPLING_16, baudrate);
 }
 
 mp_uint_t uart_rx_any(pyb_uart_obj_t *self) {

ports/stm32/uart.h

@@ -86,6 +86,8 @@ void uart_irq_handler(mp_uint_t uart_id);
 
 void uart_attach_to_repl(pyb_uart_obj_t *self, bool attached);
 uint32_t uart_get_baudrate(pyb_uart_obj_t *self);
+void uart_set_baudrate(pyb_uart_obj_t *self, uint32_t baudrate);
+
 mp_uint_t uart_rx_any(pyb_uart_obj_t *uart_obj);
 bool uart_rx_wait(pyb_uart_obj_t *self, uint32_t timeout);
 int uart_rx_char(pyb_uart_obj_t *uart_obj);