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