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Description
Raspberry Pi Firmware GPIO Expander Driver
As of February 2017 the Raspberry Pi firmware contains a mailbox interface to allow control of the GPIO expander on the Raspberry Pi 3 and Compute Module 3.
Unlike the earlier virtual GPIO interface this mailbox service now supports most GPIO functionality including getting and setting a pin value, getting and changing the pin function and getting or changing the pull up/down options.
This driver implements most of the functionality available in the new mailbox service as a standard Ultibo GPIO device and also provides direct mailbox calls to allow access to any additional options not covered by the GPIO device API.
When included in a project this driver replaces the Virtual GPIO functions provided by the PlatformRPi2 and PlatformRPi3 units.
According to /arch/arm/boot/dts/bcm2710-rpi-3-b.dts the following pin assignments are known:
- GPIO_PIN_2 = Activity LED
- GPIO_PIN_4 = HDMI Detect (Input / Active Low)
- GPIO_PIN_7 = Power LED (Input / Active Low)
For the Raspberry Pi 3B+ the assignments show in /arch/arm/boot/dts/bcm2710-rpi-3-b.dts have changed as follows:
- GPIO_PIN_2 = Power LED (Active Low)
- GPIO_PIN_4 = HDMI Detect (Input / Active Low)
Note that this driver requires the most recent firmware (later than February 2017) and has been tested successfully with the firmware release from 17 March 2018.
The latest version of the firmware is available from https://github.com/raspberrypi/firmware
Constants
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RPiGPIO expander specific constants RPIGPIOEXP_GPIO_*
RPIGPIOEXP_GPIO_DESCRIPTION = 'Raspberry Pi Firmware GPIO Expander';
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Description of RPiGPIO Expander device
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RPIGPIOEXP_GPIO_MIN_PIN = GPIO_PIN_0;
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RPIGPIOEXP_GPIO_MAX_PIN = GPIO_PIN_7;
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RPIGPIOEXP_GPIO_PIN_COUNT = 8;
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RPIGPIOEXP_GPIO_PIN_OFFSET = 128;
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RPIGPIOEXP_GPIO_MAX_LEVEL = GPIO_LEVEL_HIGH;
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RPIGPIOEXP_GPIO_MAX_PULL = GPIO_PULL_DOWN;
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RPIGPIOEXP_GPIO_MIN_FUNCTION = GPIO_FUNCTION_IN;
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RPIGPIOEXP_GPIO_MAX_FUNCTION = GPIO_FUNCTION_OUT;
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Type definitions
RPiGPIO expander specific types
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PRPiGPIOExpander = ^TRPiGPIOExpander;
TRPiGPIOExpander = record
| GPIO Properties
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GPIO:TGPIODevice;
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| RPiGPIO Expander Properties
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Public variables
None defined
Function declarations
Initialization functions
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procedure RPiGPIOExpanderInit;
Description: Initialize the RPiGPIO Expander unit and create, register and start the device
| Note
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Called only during system startup
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RPiGPIO expander GPIO functions
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function RPiGPIOExpanderStart(GPIO:PGPIODevice):LongWord;
Description: Implementation of GPIODeviceStart API for RPiGPIO Expander
| Note
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Not intended to be called directly by applications, use GPIODeviceStart instead
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function RPiGPIOExpanderStop(GPIO:PGPIODevice):LongWord;
Description: Implementation of GPIODeviceStop API for RPiGPIO Expander
| Note
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Not intended to be called directly by applications, use GPIODeviceStop instead
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function RPiGPIOExpanderInputGet(GPIO:PGPIODevice; Pin:LongWord):LongWord;
Description: Implementation of GPIODeviceInputGet API for RPiGPIO Expander
| Note
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Not intended to be called directly by applications, use GPIODeviceInputGet instead
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function RPiGPIOExpanderOutputSet(GPIO:PGPIODevice; Pin,Level:LongWord):LongWord;
Description: Implementation of GPIODeviceOutputSet API for RPiGPIO Expander
| Note
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Not intended to be called directly by applications, use GPIODeviceOutputSet instead
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function RPiGPIOExpanderPullGet(GPIO:PGPIODevice; Pin:LongWord):LongWord;
Description: Implementation of GPIODevicePullGet API for RPiGPIO Expander
| Note
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Not intended to be called directly by applications, use GPIODevicePullGet instead
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function RPiGPIOExpanderPullSelect(GPIO:PGPIODevice; Pin,Mode:LongWord):LongWord;
Description: Implementation of GPIODevicePullSelect API for RPiGPIO Expander
| Note
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Not intended to be called directly by applications, use GPIODevicePullSelect instead
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function RPiGPIOExpanderFunctionGet(GPIO:PGPIODevice; Pin:LongWord):LongWord;
Description: Implementation of GPIODeviceFunctionGet API for RPiGPIO Expander
| Note
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Not intended to be called directly by applications, use GPIODeviceFunctionGet instead
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function RPiGPIOExpanderFunctionSelect(GPIO:PGPIODevice; Pin,Mode:LongWord):LongWord;
Description: Implementation of GPIODeviceFunctionSelect API for RPiGPIO Expander
| Note
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Not intended to be called directly by applications, use GPIODeviceFunctionSelect instead
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RTL virtual GPIO functions
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function SysVirtualGPIOInputGet(Pin:LongWord):LongWord;
Description: Get the current state of a virtual GPIO input pin
| Pin
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The pin to get the state for (eg VIRTUAL_GPIO_PIN_1)
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| Return
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The current state (eg GPIO_LEVEL_HIGH) or GPIO_LEVEL_UNKNOWN on failure
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function SysVirtualGPIOOutputSet(Pin,Level:LongWord):LongWord;
Description: Set the state of a virtual GPIO output pin
| Pin
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The pin to set the state for (eg GPIO_PIN_1)
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| Level
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The state to set the pin to (eg GPIO_LEVEL_HIGH)
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| Return
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ERROR_SUCCESS if completed successfully or another error code on failure
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function SysVirtualGPIOFunctionGet(Pin:LongWord):LongWord;
Description: Get the current function of a virtual GPIO pin
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The pin to get the function for (eg GPIO_PIN_1)
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| Return
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The current function of the pin (eg GPIO_FUNCTION_IN) or GPIO_FUNCTION_UNKNOWN on failure
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[Expand]
function SysVirtualGPIOFunctionSelect(Pin,Mode:LongWord):LongWord;
Description: Change the function of a virtual GPIO pin
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The pin to change the function for (eg GPIO_PIN_1)
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| Mode
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The function to set for the pin (eg GPIO_FUNCTION_OUT)
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| Return
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ERROR_SUCCESS if completed successfully or another error code on failure
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RPiGPIO expander helper functions
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function RPiGPIOExpanderGetState(GPIO:LongWord; var State:LongWord):LongWord;
Description: Raspberry Pi Firmware Mailbox call for Get GPIO State
[Expand]
function RPiGPIOExpanderSetState(GPIO,State:LongWord):LongWord;
Description: Raspberry Pi Firmware Mailbox call for Set GPIO State
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function RPiGPIOExpanderGetConfig(GPIO:LongWord; var Direction,Polarity,Terminator,PullUp:LongWord):LongWord;
Description: Raspberry Pi Firmware Mailbox call for Get GPIO Config
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function RPiGPIOExpanderSetConfig(GPIO,Direction,Polarity,Terminator,PullUp,State:LongWord):LongWord;
Description: Raspberry Pi Firmware Mailbox call for Set GPIO Config
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