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stm32/uart: Support low baudrates on LPUART1. 

By selecting a larger prescaler when needed.

Signed-off-by: Damien George <damien@micropython.org>
This commit is contained in:
Damien George 2021-07-26 13:21:30 +10:00
parent fef2114404
commit aa0cf873bf
2 changed files with 22 additions and 1 deletions
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22
ports/stm32/uart.c
View File

@ -488,7 +488,7 @@ bool uart_init(pyb_uart_obj_t *uart_obj,
uart_obj->uartx = UARTx;
// init UARTx
// Set the initialisation parameters for the UART.
UART_HandleTypeDef huart;
memset(&huart, 0, sizeof(huart));
huart.Instance = UARTx;
@ -499,6 +499,26 @@ bool uart_init(pyb_uart_obj_t *uart_obj,
huart.Init.Mode = UART_MODE_TX_RX;
huart.Init.HwFlowCtl = flow;
huart.Init.OverSampling = UART_OVERSAMPLING_16;
#if !defined(STM32F4)
huart.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
#endif
#if defined(STM32H7) || defined(STM32WB)
// Compute the smallest prescaler that will allow the given baudrate.
uint32_t presc = UART_PRESCALER_DIV1;
if (uart_obj->uart_id == PYB_LPUART_1) {
uint32_t source_clk = uart_get_source_freq(uart_obj);
for (; presc < UART_PRESCALER_DIV256; ++presc) {
uint32_t brr = UART_DIV_LPUART(source_clk, baudrate, presc);
if (brr <= LPUART_BRR_MASK) {
break;
}
}
}
huart.Init.ClockPrescaler = presc;
#endif
// Initialise the UART hardware.
HAL_UART_Init(&huart);
// Disable all individual UART IRQs, but enable the global handler

1
ports/stm32/uart.h
View File

@ -88,6 +88,7 @@ void uart_deinit(pyb_uart_obj_t *uart_obj);
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_source_freq(pyb_uart_obj_t *self);
uint32_t uart_get_baudrate(pyb_uart_obj_t *self);
void uart_set_baudrate(pyb_uart_obj_t *self, uint32_t baudrate);