Configuration

Name

Configuration -- Platform-specific Configuration Options

Overview

The ea_lpc2468 platform HAL package is loaded automatically when eCos is configured for an ea_lpc2468_16 or ea_lpc2468_16 target. It should never be necessary to load this package explicitly. Unloading the package should only happen as a side effect of switching target hardware.

Startup

The ea_lpc2468 platform HAL package supports two separate startup types:

RAM

This is the startup type which is normally used during application development. The board has RedBoot programmed into flash at location 0x0 in internal on-chip Flash and boots from that location. arm-eabi-gdb is then used to load a RAM startup application into memory and debug it. It is assumed that the hardware has already been initialized by RedBoot. By default the application will use the eCos virtual vectors mechanism to obtain certain services from RedBoot, including diagnostic output.

ROM

This startup type can be used for finished applications which will be programmed into internal flash at location 0x0. The application will be self-contained with no dependencies on services provided by other software. eCos startup code will perform all necessary hardware initialization.

RedBoot and Virtual Vectors

If the application is intended to act as a ROM monitor, providing services for other applications, then the configuration option CYGSEM_HAL_ROM_MONITOR should be set. Typically this option is set only when building RedBoot.

If the application is supposed to make use of services provided by a ROM monitor, via the eCos virtual vector mechanism, then the configuration option CYGSEM_HAL_USE_ROM_MONITOR should be set. By default this option is enabled when building for a RAM startup, disabled otherwise. It can be manually disabled for a RAM startup, making the application self-contained, or as a testing step before switching to ROM startup.

If the application does not rely on a ROM monitor for diagnostic services then serial port UART0 will be claimed for HAL diagnostics.

Flash Driver

The LPC2468 OEM board contains an SST 39VF3201 NOR flash device. The CYGPKG_DEVS_FLASH_SST_39VFXXX_V2 package contains all the code necessary to support this part and the platform HAL package contains definitions that customize the driver to the Embedded Artists LPC2468 OEM board.

Ethernet Driver

The LPC2468 contains an ethernet MAC device. The CYGPKG_DEVS_ETH_ARM_LPC2XXX package contains all the code necessary to support this device and the platform HAL package contains definitions that customize the driver to the LPC2468 OEM board.

System Clock

By default, the system clock interrupts once every 10ms, corresponding to a 100Hz clock. This can be changed by the configuration option CYGNUM_HAL_RTC_DENOMINATOR which corresponds to the clock frequency. Other clock-related settings are recalculated automatically if the denominator is changed. The PLL multipliers and dividers may be configured to allow a core clock (CCLK) speed of up to 72MHz. However, the platform HAL currently sets the clock to 48MHz, duplicating the configuration in the supplied example code as a consequence of CPU errata affecting various revisions of the LPC2468. Setting the CPU revision with the CYGHWR_HAL_ARM_LPC2XXX_EA_LPC2468_CPU_REVISION configuration option can be used to provide default clock settings appropriate to the CPU revision in use. If the CPU revision cannot be guaranteed it should be left as "Initial". The description of the clock-related CDL options may be found in the LPC2xxx variant HAL documentation.

I²C Bus Configuration

The on-chip I²C devices are supported by a driver in the variant HAL package. Each bus for this driver needs to be configured in the platform HAL with the following options:

CYGPKG_HAL_ARM_LPC2XXX_I2CX

This is the master component, enabling this activates all the other configuration options and causes the driver to create the data structures to access this bus.

CYGPKG_HAL_ARM_LPC2XXX_I2CX_CLOCK

Bus clock speed in Hz. Usually frequencies of either 100kHz or 400kHz are chosen, the latter sometimes known as fast mode.

CYGPKG_HAL_ARM_LPC2XXX_I2CX_SDA

This option describes the pin used for SDA on this bus. This takes the form of an invocation of the macro __LPC2XXX_PINSEL_FUNC. Parameters are the port number, pin within that port, and the alternate select function for the pin. See the LPC2468 user manual for details of which pins may be used by each bus.

CYGPKG_HAL_ARM_LPC2XXX_I2CX_SCL

This option describes the pin used for SCL on this bus. Like SDA this takes the form of a call to __LPC2XXX_PINSEL_FUNC.

Note that "I2CX" is a placeholder for a given bus instance: "I2C0", "I2C1" or "I2C2". By default the platform HAL only enables I²C bus 0 in order to access the PCA9532 LED controller on the base board.

SPI Bus Configuration

The on-chip SSP SPI devices (not the Legacy SPI device) are supported by the NXPSSP driver package, CYGPKG_DEVS_SPI_ARM_NXPSSP. This needs some configuration in the platform HAL:

CYGPKG_HAL_ARM_LPC2XXX_SPI

This is the master component, enabling this activates all the other configuration options. It also causes ea_lpc2468_spi.c to be compiled, which contains descriptions of the devices on the SPI buses.

CYGPKG_HAL_ARM_LPC2XXX_SPIX

This is the master component for each bus. Enabling this activates the other configuration options for this bus, and causes the driver to support this bus.

CYGPKG_HAL_ARM_LPC2XXX_SPIX_SCLK

This option describes the pin used for SCLK on SPIX. It takes the form of an invocation of __LPC2XXX_PINSEL_FUNC. The parameters are the port number, pin within that port, and the alternate select function for the pin. See the LPC2468 user manual for details."

CYGPKG_HAL_ARM_LPC2XXX_SPIX_MISO

This option describes the pin used for MISO on SPIX. Like SCLK it takes the form of a call to __LPC2XXX_PINSEL_FUNC.

CYGPKG_HAL_ARM_LPC2XXX_SPIX_MOSI

This option describes the pin used for MOSI on SPIX. Like SCLK it takes the form of a call to __LPC2XXX_PINSEL_FUNC.

CYGPKG_HAL_ARM_LPC2XXX_SPIX_CS_PINS

This defines the pins to be uses as chip selects for this bus. It is a comma separated list of GPIO pin names, the first for device 0, the second for device 1, and so on. Pin names are defined in the var_io.h header in the LPC2xxx variant HAL.

Note that "SPIX" is a placeholder for a given bus instance: "SPI0" or "SPI1". By default the platform HAL only enables SPI0, for testing only.

MCI peripheral configuration

The on-chip Multimedia Card Interface (MCI) is supported to allow access to Multimedia Cards (MMC) or Secure Digital (SD) cards using the socket on the OEM board. This support is provided in conjunction with the generic MMC/SD driver package (CYGPKG_DEVS_DISK_MMC), the Primecell MCI driver package (CYGPKG_DEVS_MMCSD_ARM_PRIMECELL_MCI) and the LPC2xxx variant HAL in order to provide some elements of the DMA support. Documentation and configuration options within those packages should also be consulted. Note that the miniSD socket on the CPU board is not supported.

In order to configure the hardware for access to the socket, Jumper J47 on the base board must be set with pins 2-3 connected (P0.22 selected for MCIDAT0), and Jumper J27 must be set with MCIPWR active low.

The following CDL configuration options are used to control the behaviour of the MMC/SD card support:

MMC/SD card support (CYGPKG_HAL_ARM_LPC2XXX_EA_LPC2468_MCI)

This option allows the MMC/SD card support as a whole to be enabled or disabled, although the generic disk device driver package (CYGPKG_IO_DISK) must be loaded in order to enable the MMC/SD support.

Use on-chip USB memory for DMA (CYGSEM_HAL_ARM_LPC2XXX_EA_LPC2468_MCI_USE_USB_MEM_FOR_DMA

The LPC2468 cannot always keep up with the data transfer requirements, especially at slower CPU clock speeds. This is because the DMA controller runs at the speed of the CPU clock (CCLK) along with the fact that some LPC2468 have errata which decreases their achievable CPU clock frequency.

Using on-chip memory dedicated to USB helps reduce or remove these problems, depending on CPU frequency. Clearly this option must be disabled if the on-chip USB peripheral is to be used. It is also desirable to disable this option if the CPU frequency is high enough, in order to remove an extra copy on every data transfer, thus improving performance. The USB memory used is 512 bytes at the start of the USB memory space (0x7FD00000).

If this option is disabled and the DMA is not able to proceed quickly enough, this will be visible in the form of I/O errors. In that case, if it is not possible to enable this option it is recommended to adjust the CYGDAT_HAL_ARM_LPC2XXX_EA_LPC2468_MCI_BUS_SPEED_LIMIT configuration option.

Lock AHB bus during DMA transfer (CYGSEM_HAL_ARM_LPC2XXX_EA_LPC2468_MCI_DMA_LOCKS_AHB)

The AMBA Hardware Bus (AHB) is used to connect AMBA peripherals within the LPC2468, including the ARM core, DMA controller and memory controllers. When this option is enabled, the AHB is locked for the duration of MCI DMA transfer bursts. If another AMBA host needs to make a transfer it may be delayed as a result, which may not be desirable.

Disabling this option allows the AHB arbiter to permit other AHB hosts to perform transfers. Of course this may mean the MCI DMA transfers can in turn themselves get delayed, risking data overruns or underruns in MCI transfers, resulting in I/O errors during block reads or writes. This is particularly likely on processors running at slower clock speeds where there may already be difficulties with the DMA servicing data transfers quickly enough.

MMC/SD bus frequency limit (CYGNUM_HAL_ARM_LPC2XXX_EA_LPC2468_MCI_BUS_SPEED_LIMIT)

The LPC2468 cannot always keep up with the data transfer requirements, especially at slower CPU clock speeds. This is because the DMA controller runs at the speed of the CPU clock (CCLK) along with the fact that some LPC2468 have errata which decreases their achievable CPU clock frequency. The adjacent options to use on-chip USB memory and to lock the AHB bus can help prevent this, but sometimes they are insufficient to prevent data overruns or underruns resulting in I/O errors during block reads or writes. In which case the only remaining recourse is to reduce the required data transfer rate between the MCI and the card.

This option can be used to impose an upper limit on the MMC/SD bus frequency. The value used in this option is measured in Hertz, and the use of 4-bit mode with SD cards is not a factor - this option provides the bus frequency, so a 4-bit bus will transfer four times the amount of data as a 1-bit bus in the same time period.

Note that this option provides a limit, and does not mean the card bus will operate at that frequency. The frequency is also governed by what the card will support, and the resolution of the clock used to derive the MMC/SD clock signal, and how it can be divided down.

Compiler Flags

The platform HAL defines the default compiler and linker flags for all packages, although it is possible to override these on a per-package basis. Most of the flags used are the same as for other architectures supported by eCos.

However there are two flags that are used if Thumb mode is to be supported:

-mthumb

The arm-eabi-gcc compiler will compile C and C++ files into the Thumb instruction set when this option is used.

-mthumb-interwork

This option allows programs to be created that mix ARM and Thumb instruction sets. Without this option, some memory can be saved. This option should be used if -mthumb is used.

Onboard NAND

The HAL port includes a low-level driver to access the on-board Samsung K9F1G08U08 NAND flash memory chip. To enable the driver, activate the CDL option CYGHWR_HAL_ARM_LPC2XXX_EA_LPC2468_NAND and ensure that the CYGPKG_DEVS_NAND_SAMSUNG_K9 package is present in your eCos configuration. The driver is capable of operating with or without the NAND_RDY line connected.

CYGHWR_HAL_ARM_LPC2XXX_EA_LPC2468_USE_NAND_RDY

The EA OEM Base Board provides a jumper which connects the ready line of the NAND chip (NAND_RDY) to pin P2.12 on the CPU. Setting this option indicates to the driver that that jumper, or similar layout with the same effect, is in place. This provides an improvement in efficiency, but must not be set if the jumper is not so connected.

CYGHWR_HAL_ARM_LPC2XXX_EA_LPC2468_NAND_RDY_USE_INTERRUPT

(Only active if CYGHWR_HAL_ARM_LPC2XXX_EA_LPC2468_USE_NAND_RDY is set.) If set, pin P2.12 (see above) is set up as an interrupt (EINT2). Setting this causes the thread invoking the driver to sleep when waiting for a program or erase operation to complete, as opposed to entering a polling loop. This potentially represents an efficiency gain if you have at least one other thread which can carry on performing useful work while the NAND chip works.

If this option is not set, the driver polls the ready line.

When this option is set, the driver automatically detects whether the eCos kernel scheduler is running; if it is not, interrupt mode cannot operate, and the driver falls back to polling the ready line.

Interrupt mode imposes its own overheads on the driver thread. Benchmarking chip program and erase operations alone will necessarily appear to show a slow-down in interrupt mode when the scheduler is running. This option can only improve efficiency on a holistic basis, and only then in the case where there are other threads which can continue to work while the driver is waiting for the NAND operation to complete.

Partitioning the NAND chip

The NAND chip must be partitioned before it can become available to applications.

A CDL script which allows the chip to be manually partitioned is provided (see CYGSEM_DEVS_NAND_EA_LPC2468_PARTITION_MANUAL_CONFIG); if you choose to use this, the relevant data structures will automatically be set up for you when the device is initialised. By default, the manual config CDL script sets up a single partition (number 0) encompassing the entire device.

It is possible to configure the partitions in some other way, should it be appropriate for your setup. To do so you will have to add appropriate code to ea_lpc2468_nand.c.

2017-02-09
Documentation license for this page: eCosPro License