CrcLib: How to access IO pins

Owned by David Martin (Unlicensed)
Last updated: Oct 04, 2024 by CRC Volunteer
3 min read

This page presents how to access the CrcDuino IO pins using CrcLib.

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Pins

Physical pins of the CrcDuino are accessible using the following symbolic constants (aliases/names, familiarly called defines). They are already defined by CrcLib using a #define preprocessor directive, which allow programmers to give meaningful names to parts of their code.

For more information about the hardware aspect of the I/O pins, refer to the CrcDuino Hardware Details page.

We encourage programmers to use their own #define preprocessor directive at the top of their .ino file to give pins a name in their program that reflects its effective use (instead of the generic CRC_xxx_x), for example:

#define RIGHT_FEEDER_MOTOR CRC_PWM_5

#define ARM_EXTENDED_LIMIT_SWITCH CRC_DIG_1

In these cases, whenever the compiler stumbles upon the text string “RIGHT_FEEDER_MOTOR”, it will be replaced in the code by “CRC_PWM_5”. Whenever it reads “ARM_EXTENDED_LIMIT_SWITCH”, it will be replaced by “CRC_DIG_1”.

Digital Pins

These pins read or outputs digital signals.

  • CRC_DIG_1

  • CRC_DIG_2

  • CRC_DIG_3

  • CRC_DIG_4

  • CRC_DIG_5

  • CRC_DIG_6

  • CRC_DIG_7

  • CRC_DIG_8

  • CRC_DIG_9

  • CRC_DIG_10

  • CRC_DIG_11

  • CRC_DIG_12

The numbers for the pins match the one written on the board.

These pins are used with the SetDigitalPinMode(), GetDigitalInput() or SetDigitalOutput() CrcLib function.

PWM Pins

These pins output Servo type PWM signals.

  • CRC_PWM_1

  • CRC_PWM_2

  • CRC_PWM_3

  • CRC_PWM_4

  • CRC_PWM_5

  • CRC_PWM_6

  • CRC_PWM_7

  • CRC_PWM_8

  • CRC_PWM_9

  • CRC_PWM_10

  • CRC_PWM_11

  • CRC_PWM_12

The numbers for the pins match the one written on the board.

These pins are used with the InitializePwmOutput(), SetPwmOutput(), MoveTank(), MoveArcade() or MoveHolomonic() CrcLib function.

Analog Pins

These pins read and quantify analog voltage signals.

  • CRC_ANA_1

  • CRC_ANA_2

  • CRC_ANA_3

  • CRC_ANA_4

The numbers for the pins match the one written on the board.

These pins are used with the GetAnalogInput()CrcLib function.

Communication Pins

These pins are used to communicate with the outside world using various communication protocols.

SPI Port

  • CRC_SPI_MISO

  • CRC_SPI_MOSI

  • CRC_SPI_SCK

  • CRC_SPI_SS

These pins can be used with the Arduino standard SPI library.

I2C Port

  • CRC_I2C_SDA(physically aligned w/ the “MISO” mark)

  • CRC_I2C_SCL(physically aligned w/ the “MOSI” mark)

These pins can be used with the Arduino standard Wire library for I2C networking.

SERIAL Port

  • CRC_SERIAL_TXD1(physically aligned w/ the “MISO” mark)

  • CRC_SERIAL_RXD1(physically aligned w/ the “MOSI” mark)

These pins can be used with the native Arduino Serial communication functions.

Encoder Pins

These pins are meant to be used to read digital signals coming from a quadrature encoder.

ENCO Port

  • CRC_ENCO_A (physically aligned w/ the “MISO” mark)

  • CRC_ENCO_B (physically aligned w/ the “MOSI” mark)

Physically inaccessible pins

  • CRC_LM35D : Reserved for receiving temperature data from the board temperature sensor, if installed. Most CrcDuino boards don't have a LM35D temperature sensor installed. If there's no component soldered in the 3 holes right below the 0270 inscription next to the buzzer, it means your board is not equipped with a temperature sensor.

  • CRC_VBATT : Reserved for reading the board power source voltage. It's highly recommended to use the GetBatteryVoltage()  function instead of directly reading from this pin using the native Arduino function digitalRead().

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