io_port

>= 20.39.0

A set of templates for building interface classes to memory mapped hardware ports.

They avoid the need to directly map carefully packed (and possibly non-portable) structures onto memory addresses.

Note: A read from a write-only, or write to a read-only port will result in a compile time error.

Defines classes for the following IO types:-

Read / Write.

Read only.

Write only.

Write only with shadow register.

With a shadow register, the value written is stored locally and may be read back.

The port may either have an address fixed at compile time or set at runtime. The compile time versions require no

extra overhead compared to a plain memory mapped structure.

Ports may be sent as parameters to algorithms that expect iterators, except the runtime address version of

io_port_wos, which must use the built-in iterator if the shadow value is to be correctly updated for writes.

All classes define the following typedefs.

T value_type

volatile T* pointer

volatile const T* const_pointer

volatile T& reference

volatile const T& const_reference

Compile time port addresses

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io_port_rw

Read/write port.

io_port_rw<typename T, uintptr_t Address>

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iterator

const_iterator

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operator T() const

Read the value. Conversion operator to T.

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iterator iter()

Get an iterator to this port.

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const_iterator iter() const

const_iterator citer() const

Get a const_iterator to this port.

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T read() const

Read the value.

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void write(T value)

Write the value.

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io_port_rw& operator =(T value)

Write the value.

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pointer get_address()

const_pointer get_address() const

Gets the address of the port.

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io_port_rw& operator |=(value_type value)

Or-Equals operator.

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io_port_rw& operator &=(value_type value)

And-Equals operator.

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io_port_rw& operator ^=(value_type value)

Exclusive-Or-Equals operator.

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io_port_rw& operator <<=(int shift)

Left-Shift-Equals operator.

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io_port_rw& operator >>=(int shift)

Right-Shift-Equals operator.

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value_type operator ~() const

Not operator.

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io_port_ro

Read only port.

io_port_ro<typename T, uintptr_t Address>

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const_iterator

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operator T() const

Read the value. Conversion operator to T.

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const_iterator iter() const

const_iterator citer() const

Get a const_iterator to this port.

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T read() const

Read the value.

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const_pointer get_address() const

Gets the address of the port.

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io_port_wo

Write only port.

io_port_wo<typename T, uintptr_t Address>

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iterator

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iterator iter()

Get an iterator to this port.

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void write(T value)

Write the value.

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io_port_wo& operator =(T value)

Write the value.

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pointer get_address()

Gets the address of the port.

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io_port_wos

Write only port, with shadow register for reading.

io_port_wos<typename T, uintptr_t Address>

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iterator

const_iterator

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operator T() const

Read the value. Conversion operator to T.

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iterator iter()

Get an iterator to this port.

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const_iterator iter() const

const_iterator citer() const

Get a const_iterator to this port.

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T read() const

Read the value.

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void write(T value)

Write the value.

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io_port_rw& operator =(T value)

Write the value.

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pointer get_address()

const_pointer get_address() const

Gets the address of the port.

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io_port_rw& operator |=(value_type value)

Or-Equals operator.

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io_port_rw& operator &=(value_type value)

And-Equals operator.

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io_port_rw& operator ^=(value_type value)

Exclusive-Or-Equals operator.

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io_port_rw& operator <<=(int shift)

Left-Shift-Equals operator.

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io_port_rw& operator >>=(int shift)

Right-Shift-Equals operator.

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value_type operator ~() const

Not operator.

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Example serial port

The example uses a port at a compile time address.

rxdata is an 8 bit read only port.

txdata is an 8 bit write only port.

control is a 16 bit write only port, with shadow register.

status is a 16 bit read only port. It shares an address with control.

option is an 8 bit read/write port.

template <uintptr_t Address>

struct serial_port

{

etl::io_port_ro<char, Address> rxdata; // Read only rx data register.

etl::io_port_wo<char, Address + 1> txdata; // Write only tx register.

etl::io_port_wos<uint16_t, Address + 2> control; // Write only, with shadow, control register.

etl::io_port_ro<uint16_t, Address + 2> status; // Read only status register.

etl::io_port_ro<char, Address> option; // Read/Write register.

};

serial_port<0x800> port; // A serial port at address 0x800

// Read Rx data

char data = port.rxdata;

// Write Tx data

port.txdata = 'A';

// Compile error! txdata is write only.

data = port.txdata;

// Write to the control register and read back what we wrote.

port.control = 0x1234;

uint16_t control = port.control;

// Flip bit 3 of the control register.

port.control ^= 0x0080;

// Read from the status register.

uint16_t status = port.status;

// Copy data from a buffer to the Tx data port.

std::copy(txBuffer.begin(), txBuffer.end(), serial_port.txdata.iter());

// Copy data from the Rx data port to a buffer.

std::copy_n(serial_port.rxdata, serial_port.status, std::back_inserter(rxBuffer));

io_port.h