The LPC1XXX HAL provides a number of macros to support the encoding
of GPIO pin identity and configuration into a single 32 bit
descriptor. This is useful to drivers and other packages that need
to configure and use different lines for different devices.
A descriptor is created with CYGHWR_HAL_LPC1XXX_GPIO(port,
bit, mode) which takes the following arguments:
port
This identifies the GPIO port to which the pin is
attached. Ports are identified numerically between 0 and 4.
bit
This gives the bit or pin number within the port. These are
numbered from 0 to 31.
mode
This defines the mode in which the pin is to be used. The following values are currently defined:
IN_PULLUP defines the pin as a GPIO input with a pull up resistor,
IN_PULLDOWN defines the pin as a GPIO input with a pull down resistor,
OUT_OPENDRAIN defines the pin as a GPIO output with an open drain,
OUT_PULLUP defines the pin as a GPIO out with a pull up resistor,
OUT_PULLDOWN defines the pin as a GPIO output with a pull down resistor,
ALT1, ALT2, ALT3
define the pin as a line under the control of a peripheral.
This set may be extended as further requirements emerge, so
check the sources for new definitions.
The following examples show how this macro may be used:
// Define port 0 pin 2 as a peripheral pin for alternate peripheral 1
#define CYGHWR_HAL_LPC1XXX_UART0_TX CYGHWR_HAL_LPC1XXX_GPIO( 0, 2, ALT1 )
// Define port 0 pin 16 as a GPIO output pin with a pull up resistor
#define CYGHWR_HAL_LPC1XXX_SPI_CS0 CYGHWR_HAL_LPC1XXX_GPIO(0, 16, OUT_PULLUP)
Additionally, the macro
CYGHWR_HAL_LPC1XXX_GPIO_NONE may be used in place
of a pin descriptor and has a value that no valid descriptor can
take. It may therefore be used as a placeholder where no GPIO pin
is present or to be used.
The remaining macros all take a GPIO pin descriptor as an
argument. CYGHWR_HAL_LPC1XXX_GPIO_SET
configures the pin according to the descriptor and must be called
before any other
macros. CYGHWR_HAL_LPC1XXX_GPIO_OUT sets the
output to the value of the least significant bit of the
val argument. The
val argument of
CYGHWR_HAL_LPC1XXX_GPIO_IN should be a pointer
to an int, which will be set to 0 if the pin input is
zero, and 1 otherwise.
