All LPCOPen code includes the sys_config.h file. The sys_config.h is used to setup definitions for how the code builds for a specific platform such as crystal frequency, debug support, and chip variants. It is recommended to use the sys_config.h file for definitions instead of the compiler argument list for static configuration definitions, as this file is shared across all files - even across multiple projects.

To add a definition in sys_config.h, just add the definition with or without a value in the file. Note that some definitions, such as CORE_M0 must be defined in the compiler's definition list.

CHIP: LPC8xx Chip driver build time options
CHIP: LPC11xx Chip driver build time options
CHIP: LPC13xx Chip driver build time options
CHIP: LPC17xx/40xx Chip driver build time options
CHIP: LPC18xx/43xx Chip driver build time options

Common build definitions on all platforms

Example:

/* Build for 407x/8x chip family */
#define CHIP_LPC407X_8X

/* Build for RMII interface */
#define USE_RMII

/* Un-comment DEBUG_ENABLE for IO support via the UART */
#define DEBUG_ENABLE

/* Board UART used for debug output */
#define DEBUG_UART LPC_UART0

/* Crystal frequency into device */
#define CRYSTAL_MAIN_FREQ_IN (12000000)

/* Crystal frequency into device for RTC/32K input */
#define CRYSTAL_32K_FREQ_IN (32768)

/* Enable DMA in SDC driver */
#define SDC_DMA_ENABLE

Definitions can also be added to the compiler definition list instead of being in sys_config.h
Adding platform definitions using the compiler