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Standard Pin Names

In general, platform code should be portable across different Mbed supported boards with the same hardware capabilities or interfaces. Towards that goal, this document provides general developer guidelines on pin names that should apply to all boards.

LEDs

Available onboard LEDs are defined as LEDx e.g. LED1, LED2, ...

The detection of available LEDs at application level can be done as follows:

#ifdef LED1
    DigitalOut myLED(LED1);
    myLED = 1;
#endif

Alternatively, if the usage of an LED is required, then the application can detect its availability and generate an error accordingly:

#ifndef LED1
    #error This application requires the availability of an LED
#endif

It's possible to define new names of LEDs related to its properties, like color or functionality. They can be defined as aliases at application level as shown below:

#define LED_RED    LED1
#define LED_STATUS LED2

However, these names do not apply to all boards and hence should not be used in official example applications.

Buttons

Buttons that are available on a board will be defined as BUTTONx e.g. BUTTON1, BUTTON2, ...

The detection of available buttons at application level can be done as follow:

#ifdef BUTTON1
    DigitalIn myBUTTON(BUTTON1);
    int input = myBUTTON.read();
#endif

Alternatively, if the usage of a button is required, then the application can detect its availability and generate an error accordingly:

#ifndef BUTTON1
    #error This application requires the availability of a button
#endif

It's possible to define new names of buttons related to its properties. It's recommended to add a comment with a description. They can be defined as aliases at application level as shown below:

#define PUSH_BUTTON BUTTON1 // Momentary push Button

However, these names do not apply to all boards and hence should not be used in official example applications.

UART

Every Mbed board includes a serial interface to the host PC, which allows the console to print useful information about the application.

The pins for the main serial interface are defined as CONSOLE_TX and CONSOLE_RX.