16c550

Simple 16C550 UART chip driver. More...

Collaboration diagram for 16c550:

Topics
	UartRegs
	16C550 UART registers
	UartOuts
	Output pins controlled by the MCR UART register.
	UartIns
	Input pins readed in the MSR UART register.
	mw_ctrl_pins
	Pins used to control WiFi module.

Classes
struct	UartShadow
	Structure with the shadow registers. More...

Macros
#define	UART_BASE   0xA130C1
	16C550 UART base address
#define	UART_CLK   24000000LU
	Clock applied to 16C550 chip. Currently using 24 MHz crystal.
#define	UART_BR   1500000LU
#define	UART_TX_FIFO_LEN   16
	Length of the TX FIFO in bytes.
#define	UART_BUFLEN   1460
#define	DivWithRounding(dividend, divisor)
	Division with one bit rounding, useful for divisor calculations.
#define	UART_DLM_VAL   (DivWithRounding(UART_CLK, 16 * UART_BR)>>8)
	Value to load on the UART divisor, high byte.
#define	UART_DLL_VAL   (DivWithRounding(UART_CLK, 16 * UART_BR) & 0xFF)
	Value to load on the UART divisor, low byte.
#define	uart_set(reg, val)
	Sets a value in IER, FCR, LCR or MCR register.
#define	uart_get(reg)
	Gets value of IER, FCR, LCR or MCR register.
#define	uart_set_bits(reg, val)
	Sets bits in IER, FCR, LCR or MCR register.
#define	uart_clr_bits(reg, val)
	Clears bits in IER, FCR, LCR or MCR register.
#define	uart_test(reg, val)
	Test Connection with registers.

Functions
void	uart_init (void)
	Initializes the driver. The baud rate is set to UART_BR, and the UART FIFOs are enabled. This function must be called before using any other API call.
bool	uart_is_present (void)
	Check if uart is present.
bool	uart_tx_ready ()
	Checks if UART transmit register/FIFO is ready. In FIFO mode, up to 16 characters can be loaded each time transmitter is ready.
bool	uart_rx_ready ()
	Checks if UART receive register/FIFO has data available.
void	uart_putc (u8 c)
	Sends a character. Please make sure there is room in the transmit register/FIFO by calling uart_rx_ready() before using this function.
u8	uart_getc ()
	Returns a received character. Please make sure data is available by calling uart_rx_ready() before using this function.
void	uart_reset_fifos ()
	Reset TX and RX FIFOs.
void	uart_reset (void)
void	uart_start (void)
void	uart_line_sync (void)
	Sends syncrhonization frame.

Variables
UartShadow	sh
	Uart shadow registers. Do NOT access directly!

Detailed Description

Simple 16C550 UART chip driver.

Author

Jesus Alonso (doragasu)

Date

2016

Macro Definition Documentation

DivWithRounding

#define DivWithRounding	(		dividend,
			divisor )

Value:

((((dividend)*2/(divisor))+1)/2)

Division with one bit rounding, useful for divisor calculations.

UART_BR

#define UART_BR   1500000LU

Desired baud rate. Maximum achievable baudrate with 24 MHz crystal is 24000000/16 = 1.5 Mbps

uart_clr_bits

#define uart_clr_bits	(		reg,
			val )

Value:

do{sh.reg &= ~(val);                    \
UART_##reg = sh.reg;}while(0)

Clears bits in IER, FCR, LCR or MCR register.

Parameters

[in]	reg	Register to modify (IER, FCR, LCR or MCR).
[in]	val	Bits set in val, will be cleared in reg register.

uart_get

#define uart_get

(

reg

)

Value:

(sh.reg)

Gets value of IER, FCR, LCR or MCR register.

Parameters

[in]

reg

Register to read (IER, FCR, LCR or MCR).

Returns

The value of the requested register.

uart_set

#define uart_set	(		reg,
			val )

Value:

do{sh.reg = (val);UART_##reg = (val);}while(0)

Sets a value in IER, FCR, LCR or MCR register.

Parameters

[in]	reg	Register to modify (IER, FCR, LCR or MCR).
[in]	val	Value to set in IER, FCR, LCR or MCR register.

uart_set_bits

#define uart_set_bits	(		reg,
			val )

Value:

do{sh.reg |= (val);                     \
UART_##reg = sh.reg;}while(0)

Sets bits in IER, FCR, LCR or MCR register.

Parameters

[in]	reg	Register to modify (IER, FCR, LCR or MCR).
[in]	val	Bits set in val, will be set in reg register.

uart_test

#define uart_test	(		reg,
			val )

Value:

reg = val;

Test Connection with registers.

Parameters

[in]	reg	Register to modify
[in]	val	Bits set in val, will be readed from reg register.

Function Documentation

uart_getc()

u8 uart_getc

(

)

Returns a received character. Please make sure data is available by calling uart_rx_ready() before using this function.

Returns

Received character.

uart_line_sync()

void uart_line_sync

(

void

)

Sends syncrhonization frame.

This function sends a chunk of 0x55 bytes to help physical layer to synchronize. It is usually not necessary to use this function, but might help some UART chips to compute an accurate clock.

uart_putc()

void uart_putc

(

u8

c

)

Sends a character. Please make sure there is room in the transmit register/FIFO by calling uart_rx_ready() before using this function.

Returns

Received character.

uart_rx_ready()

bool uart_rx_ready

(

)

Checks if UART receive register/FIFO has data available.

Returns

TRUE if at least 1 byte is available, FALSE otherwise.

uart_tx_ready()

bool uart_tx_ready

(

)

Checks if UART transmit register/FIFO is ready. In FIFO mode, up to 16 characters can be loaded each time transmitter is ready.

Returns

TRUE if transmitter is ready, FALSE otherwise.