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u-boot/doc/README.LED
Peter Tyser ea0364f1bb Move lib_$ARCH directories to arch/$ARCH/lib
Also move lib_$ARCH/config.mk to arch/$ARCH/config.mk

This change is intended to clean up the top-level directory structure
and more closely mimic Linux's directory organization.

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
2010-04-13 09:13:03 +02:00

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Status LED
========================================
This README describes the status LED API.
The API is defined by the include file include/status_led.h
The first step is to define CONFIG_STATUS_LED in the board config file.
If the LED support is only for a single board, define CONFIG_BOARD_SPECIFIC_LED
in the board config file.
At a minimum, these macros must be defined at
STATUS_LED_BIT
STATUS_LED_STATE
STATUS_LED_PERIOD
If there are multiple status LED's define
STATUS_LED_BIT<n>
STATUS_LED_STATE<n>
STATUS_LED_PERIOD<n>
Where <n> can a integer 1 through 3.
STATUS_LED_BIT is passed into the __led_* functions to identify which LED is
being acted on. As such, the value choose must be unique with with respect to
the other STATUS_LED_BIT's. Mapping the value to a physical LED is the
reponsiblity of the __led_* function.
STATUS_LED_STATE is the initial state of the LED. It should be set to one of
these values: STATUS_LED_OFF or STATUS_LED_ON.
STATUS_LED_PERIOD is how long is the LED blink period. This usually set to
(CONFIG_SYS_HZ / <N>) where <N> is the frequency of the blink. Typical values
range from 2 to 10.
Some other LED macros
STATUS_LED_BOOT is the LED to light when the board is booting. This must be a
valid STATUS_LED_BIT value.
STATUS_LED_RED is the red LED. It is used signal errors. This must be a valid
STATUS_LED_BIT value. Other similar color LED's are STATUS_LED_YELLOW and
STATUS_LED_BLUE.
These board must define these functions
__led_init is called once to initialize the LED to STATUS_LED_STATE. One time
start up code should be placed here.
__led_set is called to change the state of the LED.
__led_toggle is called to toggle the current state of the LED.
Colour LED
========================================
Colour LED's are at present only used by ARM.
The functions names explain their purpose.
coloured_LED_init
red_LED_on
red_LED_off
green_LED_on
green_LED_off
yellow_LED_on
yellow_LED_off
blue_LED_on
blue_LED_off
These are weakly defined in arch/arm/lib/board.c to noops. Where applicable, define
these functions in the board specific source.
TBD : Describe older board dependent macros similar to what is done for
CONFIG_TQM8xxL.
TBD : Describe general support via asm/status_led.h