Configuration — Platform-specific Configuration Options
The AT91SAM9G20-EK platform HAL package is loaded automatically when eCos is
configured for the
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.
The platform HAL package supports two separate startup types:
- 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. 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.
- This startup type can be used for finished applications which will be programmed into DataFlash. The application will be self-contained with no dependencies on services provided by other software. eCos startup code will perform all necessary hardware initialization.
- This is the startup type which can be used during application development via a JTAG device such as the PEEDI. arm-eabi-gdb is used to load a JTAG startup application into memory and debug it. Hardware setup is divided between the initialization section of the PEEDI configuration file and software in the loaded application.
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
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.
The AT91SAM9G20-EK board contains an 8Mbyte Atmel AT45DB DataFlash
CYGPKG_DEVS_FLASH_ATMEL_DATAFLASH package contains all the
code necessary to support this part and the platform HAL package contains
definitions that customize the driver to the AT91SAM9G20-EK board. This driver is
not active until the generic Flash support package,
CYGPKG_IO_FLASH, is included in the configuration.
The AT91SAM9G20-EK board uses the AT91SAM9G20's internal EMAC ethernet device
attached to an external Davicom DM9161A PHY. The
CYGPKG_DEVS_ETH_ARM_AT91 package contains all the
code necessary to support this device and the platform HAL package contains
definitions that customize the driver to the AT91SAM9G20-EK board.
This driver is not active until the generic Ethernet support package,
CYGPKG_IO_ETH_DRIVERS, is included in the configuration.
The AT91SAM9G20-EK board uses the AT91SAM9G20's internal RTTC support. The
CYGPKG_DEVICES_WALLCLOCK_ARM_AT91RTTC package contains all the
code necessary to support this device. This driver is not active until the
generic wallclock device support package,
CYGPKG_IO_WALLCLOCK, is included in the configuration.
The AT91SAM9G20-EK board uses the AT91SAM9G20's internal watchdog support. The
CYGPKG_DEVICES_WATCHDOG_ARM_AT91WDTC package contains all the
code necessary to support this device. Within that package the
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.
The ATSAM926x processor will boot with watchdog support enabled, and the watchdog configuration is write-once. That is, if it is disabled, it cannot be re-enabled. Due to its nature, RedBoot disables the watchdog when it starts so any eCos applications with watchdog support enabled that are run by RedBoot will not function correctly.
USART Serial Driver
The AT91SAM9G20-EK board uses the AT91SAM9G20's internal USART serial
support as described in the SAM9 processor HAL
documentation. Three serial ports are available: the serial debug port
which is mapped to virtual vector channel 0 in the HAL diagnostic
driver or "
/dev/dbg" in the interrupt-driven
driver; USART 0 which is mapped to virtual vector channel 1 and
/dev/ser0"; and USART 1 which is mapped to
virtual vector channel 2 and "
USART 0 supports full modem control signals but USART 1 supports
As the SAM MCI driver is included in the hardware-specific
configuration for this target, nothing is
required to load it. Similarly the MMC/SD bus driver layer
CYGPKG_DEVS_DISK_MMC) is automatically included as part
of the hardware-specific configuration for this target. All that is required
to enable the support is to include the generic disk I/O infrastructure
CYGPKG_IO_DISK), along with the intended
filesystem, typically, the FAT filesystem (
and any of its package dependencies (including
CYGPKG_LINUX_COMPAT for FAT).
If the generic disk I/O infrastructure is needed for some
other reason, and you do not wish to also include the MCI driver,
then the configuration option within this platform HAL
CYGPKG_HAL_ARM_ARM9_SAM9G20EK_MMCSD can be
used to forcibly disable it.
Various options can be used to control specifics of the SAM MCI driver. Consult the SAM MCI driver documentation for information on its configuration.
On this target, it is not possible to detect from the MMC/SD socket whether cards have been inserted or removed. Thus the disk I/O layer's removeable media support will not detect when cards have been inserted or removed, and therefore the only way to detect if a card has been inserted is to attempt mounts.
The MMC/SD socket also does not permit detection of the write-protect (or "lock") switch present on SD cards. "Locked" cards will therefore not be detected which means that despite the switch position, it is still possible to write to them since the lock switch does not physically enforce write protection.
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:
The arm-eabi-gcc compiler supports many
variants of the ARM architecture.
-moption should be used to select the specific variant in use, and with current tools
-mcpu=arm9is the correct option for the ARM926EJ CPU in the AT91SAM9G20.
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
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
The HAL port includes a low-level driver to access the on-board Samsung K9F2G08U08 NAND
flash memory chip. To enable the driver, activate the CDL option
CYGPKG_HAL_SAM9G20EK_NAND and ensure that the
CYGPKG_DEVS_NAND_SAMSUNG_K9 package is present in your eCos
If set, this option configures the driver to wait for NAND operations to complete by waiting for the chip to deassert its Busy line. This is the default behaviour and is recommended, but may be disabled if you need to use the line (PIO C13) for some other purpose. (If disabled, the memory controller is configured to stall NAND accesses until they complete, which will interfere with multi-threading.)
The number of microseconds delay in the polling loops which wait for NAND operations 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
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, for example to read a Linux-style
partition table from the chip. To do so you will have to add
appropriate code to
|2019-03-19||eCosPro Non-Commercial Public License|