Configuration

Name

Configuration -- Platform-specific Configuration Options

Overview

The MCIMX25X platform HAL package is loaded automatically when eCos is configured for the mcimx25x 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 platform HAL package supports three separate startup types:

RAM

This is the startup type which is normally used during application development. The board has RedBoot programmed into flash and boots into that initially. arm-eabi-gdb is then used to load a RAM startup application into memory and debug it. RAM applications can also be downloaded to the board, programmed into flash and then run from the RedBoot prompt. 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 Flash. The application will be self-contained with no dependencies on services provided by other software. An initialization table in the image header and eCos startup code will perform all necessary hardware initialization.

JTAG

This startup type can be used for finished applications which will be loaded via JTAG. The application will be self-contained with no dependencies on services provided by other software. The JTAG init file plus 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, as a testing step before switching to ROM startup.

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

Flash Driver

The board contains an 2Mbyte Macronix MX25L1605D SPI serial NOR flash device. The CYGPKG_DEVS_FLASH_SPI_M25PXX package contains all the code necessary to support this part and the platform HAL package contains definitions that customize the driver to the board. This driver is not active until the generic Flash support package, CYGPKG_IO_FLASH, is included in the configuration.

This driver is capable of supporting the JFFS2 filesystem. However, note that the SPI interface means that this file system has reduced bandwidth and increased latency compared with other implementations. All that is required to enable the support is to include the filesystem (CYGPKG_FS_JFFS2) and any of its package dependencies (including CYGPKG_IO_FILEIO and CYGPKG_LINUX_COMPAT) together with the flash infrastructure (CYGPKG_IO_FLASH).

Ethernet Driver

The board uses the internal FEC Ethernet device attached to an external Texas Instruments DP83640 PHY. The CYGPKG_DEVS_ETH_FREESCALE_ENET package contains all the code necessary to support this device and the platform HAL package contains definitions that customize the driver to the board. This driver is not active until the generic Ethernet support package, CYGPKG_IO_ETH_DRIVERS, is included in the configuration.

Watchdog Driver

The board uses the i.MXxx internal watchdog. The CYGPKG_DEVICES_WATCHDOG_ARM_IMX package contains all the code necessary to support this device. Within that package the CYGNUM_DEVS_WATCHDOG_ARM_IMX_DESIRED_TIMEOUT_MS configuration option controls the watchdog timeout, and by default will force a reset of the board upon timeout. This driver is not active until the generic watchdog device support package, CYGPKG_IO_WATCHDOG, is included in the configuration.

UART Serial Driver

The board uses the i.MXxx internal UART serial support as described in the i.MXxx processor HAL documentation. Only one serial connector is available on the board, which is connected to UART1. This connector has the RTS/CTS hardware flow control lines connected in addition to the data lines.

ADC Driver

ADC support is provided by the CYGPKG_DEVS_ADC_ARM_TSC package. Only ADC inputs INAUX0, INAUX1 and INAUX2 are supported at present. In addition to the TSC ADC device, this driver uses GPT1 to provide the sample rate clock. Application code should avoid using this timer if the ADC is to be used. This driver is only active if the generic ADC support package, CYGPKG_IO_ADC, is included in the configuration.

LCD Driver

LCD support is provided by the CYGPKG_DEVS_FRAMEBUF_ARM_IMX package. It supports a single frame buffer format, 640 by 480 pixels, 16 bits per pixel true colour. The frame buffer is placed at a fixed address in memory at 0x83F00000. This driver is only active if the generic framebuffer support package, CYGPKG_IO_FRAMEBUF, is included in the configuration.

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. There are just three flags specific to this port:

-mcpu=arm926ej-s

The arm-eabi-gcc compiler supports many variants of the ARM architecture. A -m option should be used to select the specific variant in use, and with current tools -mcpu=arm926ej-s is the correct option for the ARM926EJ-S CPU in the i.MX25.

-mthumb

The arm-eabi-gcc compiler will compile C and C++ files into the Thumb instruction set when this option is used. The best way to build eCos in Thumb mode is to enable the configuration option CYGHWR_THUMB.

-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. The best way to build eCos with Thumb interworking is to enable the configuration option CYGBLD_ARM_ENABLE_THUMB_INTERWORK.

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