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Description
NXP PCF857X I/O Expander Driver unit
The NXP PCF8574 is an 8 bit I/O expander that provides GPIO pin control functions over an I2C connection.
The device can be represented in Ultibo as a standard GPIO device which is accessible via the GPIO unit functions. Because the PCF857X is a chip that can be used and configured in multiple different scenarios this unit does not autocreate a GPIO device, instead you need to call the function PCF8574GPIOCreate and pass an I2C device and address. The function will create and return a GPIO device with the appropriate number of pins and other information for the specified chip, the returned devices will have been registered with the GPIO device unit and started ready for use.
Note: This unit does not currently implement the interrupt capabilities of the PCF857X chips however it could be expanded to allow the interrupt pin to be connected to a GPIO pin on the SoC and use a trigger event from that to enable GPIOInputWait/GPIOInputEvent functions for the PCF857X chips.
Constants
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PCF857X specific constants PCF8574_GPIO_*
PCF8574_GPIO_DESCRIPTION = 'NXP PCF8574 8-bit I/O Expander';
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Description of PCF8574 device
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PCF8574_GPIO_MIN_PIN = GPIO_PIN_0;
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PCF8574_GPIO_MAX_PIN = GPIO_PIN_7;
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PCF8574_GPIO_PIN_COUNT = 8;
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PCF857X_GPIO_MAX_LEVEL = GPIO_LEVEL_HIGH;
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PCF857X_GPIO_MAX_PULL = GPIO_PULL_UP;
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PCF857X_GPIO_MIN_FUNCTION = GPIO_FUNCTION_IN;
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PCF857X_GPIO_MAX_FUNCTION = GPIO_FUNCTION_OUT;
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PCF857X chip PCF857X_CHIP_*
PCF857X_CHIP_PCF8574 = 0;
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PCF857X I2C PCF8574_I2C_*
| Note: The PCF857X is a single register device and does not have any direction, pull or configuration registers
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PCF8574_I2C_RATE = 100000;
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Default I2C clock rate (Device supports 100KHz only)
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PCF8574_I2C_SIZE = 1;
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Number of bytes to read/write all pin values
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PCF857X_I2C_MAX_SIZE = 2;
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Maximum number of bytes to read/write all pin values
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Type definitions
PCF857X GPIO
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PPCF857XGPIO = ^TPCF857XGPIO;
TPCF857XGPIO = record
| GPIO Properties
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GPIO:TGPIODevice;
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| PCF857X Properties
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I2C:PI2CDevice;
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The I2C device this GPIO is connected to
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Address:Word;
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The I2C address of the device
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Chip:LongWord;
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The chip type (eg PCF857X_CHIP_PCF8574)
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Size:LongWord;
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Size of an I2C read/write for the device
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Rate:LongWord;
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Clock rate for this device
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GPIOValues:array[0..PCF857X_I2C_MAX_SIZE - 1] of Byte;
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Buffer for GPIO port values (Output only)
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GPPUValues:array[0..PCF857X_I2C_MAX_SIZE - 1] of Byte;
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Buffer for GPPU pull up values
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IODIRValues:array[0..PCF857X_I2C_MAX_SIZE - 1] of Byte;
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Buffer for IODIR I/O direction values
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Public variables
None defined
Function declarations
PCF857X functions
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function PCF8574GPIOCreate(I2C:PI2CDevice; Address:Word):PGPIODevice;
Description: Create, register and start a new PCF8574 GPIO device connected to the specified I2C device
| I2C
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The I2C device this PCF8574 is connected to
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| Address
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The I2C address for this PCF8574
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| Return
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Pointer to the new GPIO device or nil on failure
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function PCF857XGPIODestroy(GPIO:PGPIODevice):LongWord;
Description: Stop, deregister and destroy a PCF857X GPIO device created by this driver
| GPIO
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The GPIO device to destroy
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| Return
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ERROR_SUCCESS if completed or another error code on failure
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PCF857X GPIO functions
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function PCF857XGPIOStart(GPIO:PGPIODevice):LongWord;
Description: Implementation of GPIODeviceStart API for PCF857X
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Not intended to be called directly by applications, use GPIODeviceStart instead.
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function PCF857XGPIOStop(GPIO:PGPIODevice):LongWord;
Description: Implementation of GPIODeviceStop API for PCF857X
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Not intended to be called directly by applications, use GPIODeviceStop instead.
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function PCF857XGPIORead(GPIO:PGPIODevice; Reg:LongWord):LongWord;
Description: Implementation of GPIODeviceRead API for PCF857X
| Note
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Not intended to be called directly by applications, use GPIODeviceRead instead.
Will read only a single register byte.
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procedure PCF857XGPIOWrite(GPIO:PGPIODevice; Reg,Value:LongWord);
Description: Implementation of GPIODeviceWrite API for PCF857X
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Not intended to be called directly by applications, use GPIODeviceWrite instead.
Will write only a single register byte.
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function PCF857XGPIOInputGet(GPIO:PGPIODevice; Pin:LongWord):LongWord;
Description: Implementation of GPIODeviceInputGet API for PCF857X
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Not intended to be called directly by applications, use GPIODeviceInputGet instead.
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function PCF857XGPIOOutputSet(GPIO:PGPIODevice; Pin,Level:LongWord):LongWord;
Description: Implementation of GPIODeviceOutputSet API for PCF857X
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Not intended to be called directly by applications, use GPIODeviceOutputSet instead.
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function PCF857XGPIOPullGet(GPIO:PGPIODevice; Pin:LongWord):LongWord;
Description: Implementation of GPIODevicePullGet API for PCF857X
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Not intended to be called directly by applications, use GPIODevicePullGet instead.
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function PCF857XGPIOFunctionGet(GPIO:PGPIODevice; Pin:LongWord):LongWord;
Description: Implementation of GPIODeviceFunctionGet API for PCF857X
| Note
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Not intended to be called directly by applications, use GPIODeviceFunctionGet instead.
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function PCF857XGPIOFunctionSelect(GPIO:PGPIODevice; Pin,Mode:LongWord):LongWord;
Description: Implementation of GPIODeviceFunctionSelect API for PCF857X
| Note
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Not intended to be called directly by applications, use GPIODeviceFunctionSelect instead.
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