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Use the PortOut interface to define which pins of a hardware GPIO port are set as an output and to write those pins. The port name is device specific and defined in the device's PortNames.h file in the mbed-os/targets folder.

A bit mask defines which pins of the GPIO port are set as an output (1b = include, 0b = ignore). The default mask value is 0xFFFFFFFF which sets all pins as an output.

The device-specific PinNames.h and the respective datasheet or reference manual define the pins associated with a GPIO port.

Note: You can combine pins from different GPIO ports using the BusOut interface. Use PortIn to define which GPIO pins are to be used as digital input.

PortOut class reference

Public Member Functions
 PortOut (PortName port, int mask=0xFFFFFFFF)
 Create a PortOut, connected to the specified port. More...
void write (int value)
 Write the value to the output port. More...
int read ()
 Read the value currently output on the port. More...
PortOutoperator= (int value)
 A shorthand for write() More...
PortOutoperator= (PortOut &rhs)
 A shorthand for read() More...
 operator int ()
 A shorthand for read() More...

PortOut hello, world

/* mbed Example Program
 * Copyright (c) 2006-2014 ARM Limited
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *     http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the License for the specific language governing permissions and
 * limitations under the License.

// Toggle all four LEDs
#include "mbed.h"
// LED1 = P1.18  LED2 = P1.20  LED3 = P1.21  LED4 = P1.23
#define LED_MASK 0x00B40000
PortOut ledport(Port1, LED_MASK);
int main() {
    while(1) {
        ledport = LED_MASK;
        ledport = 0;
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