raspberry GPIO 低权限寄存器访问函数简介

bcm2835   1.25

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Functions

Low level register access

Functions
uint32_t	bcm2835_peri_read (volatile uint32_t *paddr)
uint32_t	bcm2835_peri_read_nb (volatile uint32_t *paddr)
void	bcm2835_peri_write (volatile uint32_t *paddr, uint32_t value)
void	bcm2835_peri_write_nb (volatile uint32_t *paddr, uint32_t value)
void	bcm2835_peri_set_bits (volatile uint32_t *paddr, uint32_t value, uint32_t mask)

Detailed Description

These functions provide low level register access, and should not generally need to be used

Function Documentation

uint32_t bcm2835_peri_read

(

volatile uint32_t *

paddr

)

Reads 32 bit value from a peripheral address The read is done twice, and is therefore always safe in terms of manual section 1.3 Peripheral access precautions for correct memory ordering

Parameters:

[in]

paddr

Physical address to read from. See BCM2835_GPIO_BASE etc.

Returns:

the value read from the 32 bit register

See also:

Physical Addresses

uint32_t bcm2835_peri_read_nb

(

volatile uint32_t *

paddr

)

Reads 32 bit value from a peripheral address without the read barrier You should only use this when your code has previously called bcm2835_peri_read() within the same peripheral, and no other peripheral access has occurred since.

Parameters:

[in]

paddr

Physical address to read from. See BCM2835_GPIO_BASE etc.

Returns:

the value read from the 32 bit register

See also:

Physical Addresses

void bcm2835_peri_set_bits	(	volatile uint32_t *	paddr,
		uint32_t	value,
		uint32_t	mask
	)

Alters a number of bits in a 32 peripheral regsiter. It reads the current valu and then alters the bits deines as 1 in mask, according to the bit value in value. All other bits that are 0 in the mask are unaffected. Use this to alter a subset of the bits in a register. The write is done twice, and is therefore always safe in terms of manual section 1.3 Peripheral access precautions for correct memory ordering

Parameters:

[in]	paddr	Physical address to read from. See BCM2835_GPIO_BASE etc.
[in]	value	The 32 bit value to write, masked in by mask.
[in]	mask	Bitmask that defines the bits that will be altered in the register.

See also:

Physical Addresses

void bcm2835_peri_write	(	volatile uint32_t *	paddr,
		uint32_t	value
	)

Writes 32 bit value from a peripheral address The write is done twice, and is therefore always safe in terms of manual section 1.3 Peripheral access precautions for correct memory ordering

Parameters:

[in]	paddr	Physical address to read from. See BCM2835_GPIO_BASE etc.
[in]	value	The 32 bit value to write

See also:

Physical Addresses

void bcm2835_peri_write_nb	(	volatile uint32_t *	paddr,
		uint32_t	value
	)

Writes 32 bit value from a peripheral address without the write barrier You should only use this when your code has previously called bcm2835_peri_write() within the same peripheral, and no other peripheral access has occurred since.

Parameters:

[in]	paddr	Physical address to read from. See BCM2835_GPIO_BASE etc.
[in]	value	The 32 bit value to write

See also:

Physical Addresses