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drivers: serial: ra: reduce uart baud rate error

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Using the 8 base clock cycles per bit period setting (instead of 16)
reduces the uart baud rate error when using a 12MHz crystal (found on
many RA Microcontroller development kits boards). This setting also
slightly reduces the error when using the internal 48MHz oscillator,
used by the Arduino UNO R4 Minima board currently support by Zephyr.

Signed-off-by: Ian Morris <ian.d.morris@outlook.com>
This commit is contained in:
Ian Morris 2024-01-05 15:01:15 -08:00 • committed by David Leach
commit 826d67af91
1 changed files with 3 additions and 3 deletions
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6
drivers/serial/uart_renesas_ra.c
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@ -216,11 +216,11 @@ static void uart_ra_set_baudrate(const struct device *dev, uint32_t baud_rate)
uint8_t reg_val;
reg_val = uart_ra_read_8(dev, SEMR);
reg_val |= REG_MASK(SEMR_BGDM);
reg_val &= ~(REG_MASK(SEMR_BRME) | REG_MASK(SEMR_ABCSE) | REG_MASK(SEMR_ABCS));
reg_val |= (REG_MASK(SEMR_BGDM) | REG_MASK(SEMR_ABCS));
reg_val &= ~(REG_MASK(SEMR_BRME) | REG_MASK(SEMR_ABCSE));
uart_ra_write_8(dev, SEMR, reg_val);
reg_val = (data->clk_rate / (16 * data->current_config.baudrate)) - 1;
reg_val = (data->clk_rate / (8 * data->current_config.baudrate)) - 1;
uart_ra_write_8(dev, BRR, reg_val);
}