eCos Support for the Atmel AT91SAM7A3-EK — Overview


This document covers the configuration and usage of eCos and GDB Stubs on the Atmel AT91SAM7A3-EK Evaluation Kit. The AT91SAM7A3-EK Evaluation Kit contains the AT91SAM7A3 processor, external connections for one serial channel, USB host/device, MMC card. eCos support for the devices and peripherals on the AT91SAM7A3 is described below.

Application development on this board can take one of several approaches. Applications may be loaded into RAM via a JTAG device; however, the application size is limited by the amount of on-chip RAM: 32KiB. Applications may also be loaded into the on-chip flash memory where the RAM limit will only apply to the data portion of the application. Finally, it is possible to program a GDB debugging stub into flash which will then allow applications to be loaded into RAM via the serial port. This allows development to proceed without needing to use a JTAG device, although one will be required to program the debugging stub in the first place, and application size is limited to just 28KiB, since the GDB stub uses the least significant 4KiB.

This documentation is expected to be read in conjunction with the AT91 processor HAL and AT91SAM7 variant HAL documentation and further device support and subsystems are described and documented there.

Supported Hardware

The on-chip NOR flash is organized into 1024 pages of 256 bytes each.

There is a serial driver CYGPKG_IO_SERIAL_ARM_AT91 which supports the Debug Unit and USART serial devices. The debug serial port at J2 can be used for communication. If the GDB stub ROM is installed, it uses the Debug Unit serial device. The serial driver package is loaded automatically when configuring for the AT91SAM7A3-EK target.

There is a watchdog driver CYGPKG_DEVICES_WATCHDOG_ARM_AT91WDTC. This driver is also loaded automatically when configuring for the AT91SAM7A3-EK target.

In general, devices (PIO, UARTs, etc.) are initialized only as far as is necessary for eCos to run. Other devices (RTC, I²C, SPI etc.) are not touched unless the appropriate driver is loaded, although in some cases, the HAL boot sequence will set up the appropriate PIO configuration.


The AT91SAM7A3-EK support is intended to work with GNU tools configured for an arm-elf target. The original port was undertaken using arm-elf-gcc version 3.4.4, arm-elf-gdb version 6.3, and binutils version 2.15.