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mimxrt/machine_uart: Support slow baud rates for UART. 

Down to 50 baud (in reverence to Jean-Maurice-Émile Baudot).  Implemented
for the MIMXRT10xx MCU's only.  The MIMXRT1176 runs down to 300 baud.

Signed-off-by: robert-hh <robert@hammelrath.com>
This commit is contained in:
robert-hh 2023-08-31 08:02:32 +02:00 committed by Damien George
parent c86b9ec8bd
commit 81c19d93bc
1 changed files with 12 additions and 1 deletions
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13
ports/mimxrt/machine_uart.c
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@ -288,7 +288,18 @@ STATIC mp_obj_t machine_uart_init_helper(machine_uart_obj_t *self, size_t n_args
self->timeout_char = min_timeout_char;
}
LPUART_Init(self->lpuart, &self->config, BOARD_BOOTCLOCKRUN_UART_CLK_ROOT);
#if defined(MIMXRT117x_SERIES)
// Use the Lpuart1 clock value, which is set for All UART devices.
LPUART_Init(self->lpuart, &self->config, CLOCK_GetRootClockFreq(kCLOCK_Root_Lpuart1));
#else
// For baud rates < 1000000 divide the clock by 10, supporting baud rates down to 50 baud.
if (self->config.baudRate_Bps > 1000000) {
CLOCK_SetDiv(kCLOCK_UartDiv, 0);
} else {
CLOCK_SetDiv(kCLOCK_UartDiv, 9);
}
LPUART_Init(self->lpuart, &self->config, CLOCK_GetClockRootFreq(kCLOCK_UartClkRoot));
#endif
LPUART_TransferCreateHandle(self->lpuart, &self->handle, LPUART_UserCallback, self);
uint8_t *buffer = m_new(uint8_t, rxbuf_len + 1);
LPUART_TransferStartRingBuffer(self->lpuart, &self->handle, buffer, rxbuf_len);