OrgZephyr/zephyr
OrgZephyr
/
zephyr
mirror of https://github.com/zephyrproject-rtos/zephyr.git
1
0
Fork 0
Code Issues Releases Wiki Activity
zephyr/drivers/led_strip/Kconfig.ws2812

100 lines
3.2 KiB
Plaintext
Raw Normal View History

drivers: led_strip: add WS2812-ish driver The WS2812 LED driver IC has a one-wire interface which encodes bit values as pulse widths. The ICs themselves are basically shift registers. Roughly speaking, a "short" pulse shifts in a zero bit, a "long" pulse shifts in a one bit, and an inter-pulse gap exceeding a reset time threshold causes a pixel to latch the shifted-in color values. Each chip has an output pin for daisy chaining. Refer to the chip datsheets and comments in Kconfig.ws2812 for more details. To meet timing without hogging the core, this driver generates pulses using SPI. To work, this requires the MOSI line to stay low between SPI frames, and for inter-frame delays to be less than the reset pulse time. There are other ways do it (PWM + DMA on some SoCs, GPIO bit-banging if no other tasks need the core), but this is a reasonably general-purpose implementation. Signed-off-by: Marti Bolivar <marti.bolivar@linaro.org>
2017-10-17 11:28:15 +08:00
# Copyright (c) 2017 Linaro Limited
# SPDX-License-Identifier: Apache-2.0
# The following blog post is an excellent resource about pulse timing:
#
# https://wp.josh.com/2014/05/13/ws2812-neopixels-are-not-so-finicky-once-you-get-to-know-them/
menuconfig WS2812_STRIP
bool "Enable WS2812 (and compatible) LED strip driver"
depends on SPI
help
kconfig: Global whitespace/consistency cleanup Clean up space errors and use a consistent style throughout the Kconfig files. This makes reading the Kconfig files more distraction-free, helps with grepping, and encourages the same style getting copied around everywhere (meaning another pass hopefully won't be needed). Go for the most common style: - Indent properties with a single tab, including for choices. Properties on choices work exactly the same syntactically as properties on symbols, so not sure how the no-indentation thing happened. - Indent help texts with a tab followed by two spaces - Put a space between 'config' and the symbol name, not a tab. This also helps when grepping for definitions. - Do '# A comment' instead of '#A comment' I tweaked Kconfiglib a bit to find most of the stuff. Some help texts were reflowed to 79 columns with 'gq' in Vim as well, though not all, because I was afraid I'd accidentally mess up formatting. Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>
2019-11-01 17:24:07 +08:00
Enable LED strip driver for daisy chains of WS2812-ish
(or WS2812B, WS2813, SK6812, or compatible) devices.
These devices have a one-wire communications interface
which encodes bits using pulses. Short pulses indicate
zero bits, and long pulses indicate ones; refer to the
chip datasheets for precise specifications. To implement
this in a multitasking operating system, this driver
generates the pulses using a SPI peripheral.
drivers: led_strip: add WS2812-ish driver The WS2812 LED driver IC has a one-wire interface which encodes bit values as pulse widths. The ICs themselves are basically shift registers. Roughly speaking, a "short" pulse shifts in a zero bit, a "long" pulse shifts in a one bit, and an inter-pulse gap exceeding a reset time threshold causes a pixel to latch the shifted-in color values. Each chip has an output pin for daisy chaining. Refer to the chip datsheets and comments in Kconfig.ws2812 for more details. To meet timing without hogging the core, this driver generates pulses using SPI. To work, this requires the MOSI line to stay low between SPI frames, and for inter-frame delays to be less than the reset pulse time. There are other ways do it (PWM + DMA on some SoCs, GPIO bit-banging if no other tasks need the core), but this is a reasonably general-purpose implementation. Signed-off-by: Marti Bolivar <marti.bolivar@linaro.org>
2017-10-17 11:28:15 +08:00
if WS2812_STRIP
led_strip: ws2812: HACK: memory-hungry pulse timing bugfix At least on nRF52 devices, we are taking too much time between pixels dealing with overhead inside the SPI driver transceive calls. This is leading to dropped frames, because the dead time between frames is long enough (5000ns+) to look like a reset pulse to the LED strip. Given this SPI driver limitation, it seems this LED driver's design decision to rely on SPI peripherals as efficient pulse generators doesn't work well in practice. The right way to handle this is probably to switch from SPI to efficient inline assembly which bit-bangs the pulses with interrupts disabled. This is what other efficient libraries do to drive this type of LED (e.g. FastLED uses C++ templates that expand into such assembly). The Zephyr GPIO API doesn't support doing that in a portable fashion, unfortunately. For now, we'll cheat by pre-allocating enough buffer space to send the entire strip's worth of data. This is preposterously inefficient (8x memory overhead since there's one byte to make a SPI frame for each bit of color), but makes the driver work correctly. (Note that using timer peripherals as pulse generators, when combined with DMA for efficiency, would also lead to similar levels of overhead.) Signed-off-by: Marti Bolivar <marti@opensourcefoundries.com>
2018-05-25 01:03:57 +08:00
config WS2812_STRIP_MAX_PIXELS
int "Maximum number of pixels in a strip"
default 12
help
kconfig: Global whitespace/consistency cleanup Clean up space errors and use a consistent style throughout the Kconfig files. This makes reading the Kconfig files more distraction-free, helps with grepping, and encourages the same style getting copied around everywhere (meaning another pass hopefully won't be needed). Go for the most common style: - Indent properties with a single tab, including for choices. Properties on choices work exactly the same syntactically as properties on symbols, so not sure how the no-indentation thing happened. - Indent help texts with a tab followed by two spaces - Put a space between 'config' and the symbol name, not a tab. This also helps when grepping for definitions. - Do '# A comment' instead of '#A comment' I tweaked Kconfiglib a bit to find most of the stuff. Some help texts were reflowed to 79 columns with 'gq' in Vim as well, though not all, because I was afraid I'd accidentally mess up formatting. Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>
2019-11-01 17:24:07 +08:00
Set this to the maximum number of pixels you need
to control at once. There is an 8x memory penalty associated
with each increment of this value, so it's worth optimizing.
led_strip: ws2812: HACK: memory-hungry pulse timing bugfix At least on nRF52 devices, we are taking too much time between pixels dealing with overhead inside the SPI driver transceive calls. This is leading to dropped frames, because the dead time between frames is long enough (5000ns+) to look like a reset pulse to the LED strip. Given this SPI driver limitation, it seems this LED driver's design decision to rely on SPI peripherals as efficient pulse generators doesn't work well in practice. The right way to handle this is probably to switch from SPI to efficient inline assembly which bit-bangs the pulses with interrupts disabled. This is what other efficient libraries do to drive this type of LED (e.g. FastLED uses C++ templates that expand into such assembly). The Zephyr GPIO API doesn't support doing that in a portable fashion, unfortunately. For now, we'll cheat by pre-allocating enough buffer space to send the entire strip's worth of data. This is preposterously inefficient (8x memory overhead since there's one byte to make a SPI frame for each bit of color), but makes the driver work correctly. (Note that using timer peripherals as pulse generators, when combined with DMA for efficiency, would also lead to similar levels of overhead.) Signed-off-by: Marti Bolivar <marti@opensourcefoundries.com>
2018-05-25 01:03:57 +08:00
drivers: led_strip: add WS2812-ish driver The WS2812 LED driver IC has a one-wire interface which encodes bit values as pulse widths. The ICs themselves are basically shift registers. Roughly speaking, a "short" pulse shifts in a zero bit, a "long" pulse shifts in a one bit, and an inter-pulse gap exceeding a reset time threshold causes a pixel to latch the shifted-in color values. Each chip has an output pin for daisy chaining. Refer to the chip datsheets and comments in Kconfig.ws2812 for more details. To meet timing without hogging the core, this driver generates pulses using SPI. To work, this requires the MOSI line to stay low between SPI frames, and for inter-frame delays to be less than the reset pulse time. There are other ways do it (PWM + DMA on some SoCs, GPIO bit-banging if no other tasks need the core), but this is a reasonably general-purpose implementation. Signed-off-by: Marti Bolivar <marti.bolivar@linaro.org>
2017-10-17 11:28:15 +08:00
config WS2812_STRIP_ONE_FRAME
hex "SPI frame to shift out to signal a one bit"
drivers: led_strip: guard SPI defaults on stm32f4x kconfig The given defaults were chosen for 96b_carbon, which is an STM32F4X board that supports the specified WS2812_STRIP_SPI_BAUD_RATE exactly. Rather than assume the rest of the world works that way, guard the Kconfig options accordingly. This is preparation work for adding configuration for other hardware. Signed-off-by: Marti Bolivar <marti@opensourcefoundries.com>
2018-02-21 23:12:10 +08:00
default 0x7c if SOC_SERIES_STM32F4X
drivers: led_strip: add ws2812 defaults for nRF5 devices Define a SPI baud rate, as well as WS2812_STRIP_ONE_FRAME and WS2812_STRIP_ZERO_FRAME values, that work for nRF5 devices. Signed-off-by: Marti Bolivar <marti@opensourcefoundries.com>
2018-02-21 23:28:29 +08:00
default 0x70 if SOC_FAMILY_NRF
drivers: led_strip: add WS2812-ish driver The WS2812 LED driver IC has a one-wire interface which encodes bit values as pulse widths. The ICs themselves are basically shift registers. Roughly speaking, a "short" pulse shifts in a zero bit, a "long" pulse shifts in a one bit, and an inter-pulse gap exceeding a reset time threshold causes a pixel to latch the shifted-in color values. Each chip has an output pin for daisy chaining. Refer to the chip datsheets and comments in Kconfig.ws2812 for more details. To meet timing without hogging the core, this driver generates pulses using SPI. To work, this requires the MOSI line to stay low between SPI frames, and for inter-frame delays to be less than the reset pulse time. There are other ways do it (PWM + DMA on some SoCs, GPIO bit-banging if no other tasks need the core), but this is a reasonably general-purpose implementation. Signed-off-by: Marti Bolivar <marti.bolivar@linaro.org>
2017-10-17 11:28:15 +08:00
help
kconfig: Global whitespace/consistency cleanup Clean up space errors and use a consistent style throughout the Kconfig files. This makes reading the Kconfig files more distraction-free, helps with grepping, and encourages the same style getting copied around everywhere (meaning another pass hopefully won't be needed). Go for the most common style: - Indent properties with a single tab, including for choices. Properties on choices work exactly the same syntactically as properties on symbols, so not sure how the no-indentation thing happened. - Indent help texts with a tab followed by two spaces - Put a space between 'config' and the symbol name, not a tab. This also helps when grepping for definitions. - Do '# A comment' instead of '#A comment' I tweaked Kconfiglib a bit to find most of the stuff. Some help texts were reflowed to 79 columns with 'gq' in Vim as well, though not all, because I was afraid I'd accidentally mess up formatting. Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>
2019-11-01 17:24:07 +08:00
When shifted out at the configured clock frequency,
this must generate a pulse whose width fits within the chipset
specifications for T1H, and whose interpulse timing meets low
times. It is recommended that the first and last bits in the
frame be zero; this "encourages" SPI IPs to leave MOSI low
between frames.
drivers: led_strip: add WS2812-ish driver The WS2812 LED driver IC has a one-wire interface which encodes bit values as pulse widths. The ICs themselves are basically shift registers. Roughly speaking, a "short" pulse shifts in a zero bit, a "long" pulse shifts in a one bit, and an inter-pulse gap exceeding a reset time threshold causes a pixel to latch the shifted-in color values. Each chip has an output pin for daisy chaining. Refer to the chip datsheets and comments in Kconfig.ws2812 for more details. To meet timing without hogging the core, this driver generates pulses using SPI. To work, this requires the MOSI line to stay low between SPI frames, and for inter-frame delays to be less than the reset pulse time. There are other ways do it (PWM + DMA on some SoCs, GPIO bit-banging if no other tasks need the core), but this is a reasonably general-purpose implementation. Signed-off-by: Marti Bolivar <marti.bolivar@linaro.org>
2017-10-17 11:28:15 +08:00
config WS2812_STRIP_ZERO_FRAME
hex "SPI frame to shift out to signal a zero bit"
drivers: led_strip: guard SPI defaults on stm32f4x kconfig The given defaults were chosen for 96b_carbon, which is an STM32F4X board that supports the specified WS2812_STRIP_SPI_BAUD_RATE exactly. Rather than assume the rest of the world works that way, guard the Kconfig options accordingly. This is preparation work for adding configuration for other hardware. Signed-off-by: Marti Bolivar <marti@opensourcefoundries.com>
2018-02-21 23:12:10 +08:00
default 0x60 if SOC_SERIES_STM32F4X
drivers: led_strip: add ws2812 defaults for nRF5 devices Define a SPI baud rate, as well as WS2812_STRIP_ONE_FRAME and WS2812_STRIP_ZERO_FRAME values, that work for nRF5 devices. Signed-off-by: Marti Bolivar <marti@opensourcefoundries.com>
2018-02-21 23:28:29 +08:00
default 0x40 if SOC_FAMILY_NRF
drivers: led_strip: add WS2812-ish driver The WS2812 LED driver IC has a one-wire interface which encodes bit values as pulse widths. The ICs themselves are basically shift registers. Roughly speaking, a "short" pulse shifts in a zero bit, a "long" pulse shifts in a one bit, and an inter-pulse gap exceeding a reset time threshold causes a pixel to latch the shifted-in color values. Each chip has an output pin for daisy chaining. Refer to the chip datsheets and comments in Kconfig.ws2812 for more details. To meet timing without hogging the core, this driver generates pulses using SPI. To work, this requires the MOSI line to stay low between SPI frames, and for inter-frame delays to be less than the reset pulse time. There are other ways do it (PWM + DMA on some SoCs, GPIO bit-banging if no other tasks need the core), but this is a reasonably general-purpose implementation. Signed-off-by: Marti Bolivar <marti.bolivar@linaro.org>
2017-10-17 11:28:15 +08:00
help
kconfig: Global whitespace/consistency cleanup Clean up space errors and use a consistent style throughout the Kconfig files. This makes reading the Kconfig files more distraction-free, helps with grepping, and encourages the same style getting copied around everywhere (meaning another pass hopefully won't be needed). Go for the most common style: - Indent properties with a single tab, including for choices. Properties on choices work exactly the same syntactically as properties on symbols, so not sure how the no-indentation thing happened. - Indent help texts with a tab followed by two spaces - Put a space between 'config' and the symbol name, not a tab. This also helps when grepping for definitions. - Do '# A comment' instead of '#A comment' I tweaked Kconfiglib a bit to find most of the stuff. Some help texts were reflowed to 79 columns with 'gq' in Vim as well, though not all, because I was afraid I'd accidentally mess up formatting. Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>
2019-11-01 17:24:07 +08:00
When shifted out at the configured clock frequency,
this must generate a pulse whose width fits within the chipset
specifications for T0H, and whose interpulse timing meets low
times. It is recommended that the first and last bits in the
frame be zero; this "encourages" SPI IPs to leave MOSI low
between frames.
drivers: led_strip: add WS2812-ish driver The WS2812 LED driver IC has a one-wire interface which encodes bit values as pulse widths. The ICs themselves are basically shift registers. Roughly speaking, a "short" pulse shifts in a zero bit, a "long" pulse shifts in a one bit, and an inter-pulse gap exceeding a reset time threshold causes a pixel to latch the shifted-in color values. Each chip has an output pin for daisy chaining. Refer to the chip datsheets and comments in Kconfig.ws2812 for more details. To meet timing without hogging the core, this driver generates pulses using SPI. To work, this requires the MOSI line to stay low between SPI frames, and for inter-frame delays to be less than the reset pulse time. There are other ways do it (PWM + DMA on some SoCs, GPIO bit-banging if no other tasks need the core), but this is a reasonably general-purpose implementation. Signed-off-by: Marti Bolivar <marti.bolivar@linaro.org>
2017-10-17 11:28:15 +08:00
# By default, we use GRBW [sic] (and ignore W).
comment "The following options determine channel data order on the wire."
config WS2812_RED_ORDER
int "Order in which a red pixel should be shifted out"
default 1
range 0 3
help
kconfig: Global whitespace/consistency cleanup Clean up space errors and use a consistent style throughout the Kconfig files. This makes reading the Kconfig files more distraction-free, helps with grepping, and encourages the same style getting copied around everywhere (meaning another pass hopefully won't be needed). Go for the most common style: - Indent properties with a single tab, including for choices. Properties on choices work exactly the same syntactically as properties on symbols, so not sure how the no-indentation thing happened. - Indent help texts with a tab followed by two spaces - Put a space between 'config' and the symbol name, not a tab. This also helps when grepping for definitions. - Do '# A comment' instead of '#A comment' I tweaked Kconfiglib a bit to find most of the stuff. Some help texts were reflowed to 79 columns with 'gq' in Vim as well, though not all, because I was afraid I'd accidentally mess up formatting. Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>
2019-11-01 17:24:07 +08:00
If the red channel is shifted out first, specify 0.
If second, specify 1, and so on.
drivers: led_strip: add WS2812-ish driver The WS2812 LED driver IC has a one-wire interface which encodes bit values as pulse widths. The ICs themselves are basically shift registers. Roughly speaking, a "short" pulse shifts in a zero bit, a "long" pulse shifts in a one bit, and an inter-pulse gap exceeding a reset time threshold causes a pixel to latch the shifted-in color values. Each chip has an output pin for daisy chaining. Refer to the chip datsheets and comments in Kconfig.ws2812 for more details. To meet timing without hogging the core, this driver generates pulses using SPI. To work, this requires the MOSI line to stay low between SPI frames, and for inter-frame delays to be less than the reset pulse time. There are other ways do it (PWM + DMA on some SoCs, GPIO bit-banging if no other tasks need the core), but this is a reasonably general-purpose implementation. Signed-off-by: Marti Bolivar <marti.bolivar@linaro.org>
2017-10-17 11:28:15 +08:00
config WS2812_GRN_ORDER
int "Order in which a green pixel should be shifted out"
default 0
range 0 3
help
kconfig: Global whitespace/consistency cleanup Clean up space errors and use a consistent style throughout the Kconfig files. This makes reading the Kconfig files more distraction-free, helps with grepping, and encourages the same style getting copied around everywhere (meaning another pass hopefully won't be needed). Go for the most common style: - Indent properties with a single tab, including for choices. Properties on choices work exactly the same syntactically as properties on symbols, so not sure how the no-indentation thing happened. - Indent help texts with a tab followed by two spaces - Put a space between 'config' and the symbol name, not a tab. This also helps when grepping for definitions. - Do '# A comment' instead of '#A comment' I tweaked Kconfiglib a bit to find most of the stuff. Some help texts were reflowed to 79 columns with 'gq' in Vim as well, though not all, because I was afraid I'd accidentally mess up formatting. Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>
2019-11-01 17:24:07 +08:00
If the green channel is shifted out first, specify 0.
If second, specify 1, and so on.
drivers: led_strip: add WS2812-ish driver The WS2812 LED driver IC has a one-wire interface which encodes bit values as pulse widths. The ICs themselves are basically shift registers. Roughly speaking, a "short" pulse shifts in a zero bit, a "long" pulse shifts in a one bit, and an inter-pulse gap exceeding a reset time threshold causes a pixel to latch the shifted-in color values. Each chip has an output pin for daisy chaining. Refer to the chip datsheets and comments in Kconfig.ws2812 for more details. To meet timing without hogging the core, this driver generates pulses using SPI. To work, this requires the MOSI line to stay low between SPI frames, and for inter-frame delays to be less than the reset pulse time. There are other ways do it (PWM + DMA on some SoCs, GPIO bit-banging if no other tasks need the core), but this is a reasonably general-purpose implementation. Signed-off-by: Marti Bolivar <marti.bolivar@linaro.org>
2017-10-17 11:28:15 +08:00
config WS2812_BLU_ORDER
int "Order in which a blue pixel should be shifted out"
default 2
range 0 3
help
kconfig: Global whitespace/consistency cleanup Clean up space errors and use a consistent style throughout the Kconfig files. This makes reading the Kconfig files more distraction-free, helps with grepping, and encourages the same style getting copied around everywhere (meaning another pass hopefully won't be needed). Go for the most common style: - Indent properties with a single tab, including for choices. Properties on choices work exactly the same syntactically as properties on symbols, so not sure how the no-indentation thing happened. - Indent help texts with a tab followed by two spaces - Put a space between 'config' and the symbol name, not a tab. This also helps when grepping for definitions. - Do '# A comment' instead of '#A comment' I tweaked Kconfiglib a bit to find most of the stuff. Some help texts were reflowed to 79 columns with 'gq' in Vim as well, though not all, because I was afraid I'd accidentally mess up formatting. Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>
2019-11-01 17:24:07 +08:00
If the blue channel is shifted out first, specify 0.
If second, specify 1, and so on.
drivers: led_strip: add WS2812-ish driver The WS2812 LED driver IC has a one-wire interface which encodes bit values as pulse widths. The ICs themselves are basically shift registers. Roughly speaking, a "short" pulse shifts in a zero bit, a "long" pulse shifts in a one bit, and an inter-pulse gap exceeding a reset time threshold causes a pixel to latch the shifted-in color values. Each chip has an output pin for daisy chaining. Refer to the chip datsheets and comments in Kconfig.ws2812 for more details. To meet timing without hogging the core, this driver generates pulses using SPI. To work, this requires the MOSI line to stay low between SPI frames, and for inter-frame delays to be less than the reset pulse time. There are other ways do it (PWM + DMA on some SoCs, GPIO bit-banging if no other tasks need the core), but this is a reasonably general-purpose implementation. Signed-off-by: Marti Bolivar <marti.bolivar@linaro.org>
2017-10-17 11:28:15 +08:00
config WS2812_HAS_WHITE_CHANNEL
bool "Does the chip have a white channel on wire?"
default y
help
kconfig: Global whitespace/consistency cleanup Clean up space errors and use a consistent style throughout the Kconfig files. This makes reading the Kconfig files more distraction-free, helps with grepping, and encourages the same style getting copied around everywhere (meaning another pass hopefully won't be needed). Go for the most common style: - Indent properties with a single tab, including for choices. Properties on choices work exactly the same syntactically as properties on symbols, so not sure how the no-indentation thing happened. - Indent help texts with a tab followed by two spaces - Put a space between 'config' and the symbol name, not a tab. This also helps when grepping for definitions. - Do '# A comment' instead of '#A comment' I tweaked Kconfiglib a bit to find most of the stuff. Some help texts were reflowed to 79 columns with 'gq' in Vim as well, though not all, because I was afraid I'd accidentally mess up formatting. Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>
2019-11-01 17:24:07 +08:00
If the chipset has a white channel, say y. White channels
are not used by the driver, but must be declared if expected
by the chip.
drivers: led_strip: add WS2812-ish driver The WS2812 LED driver IC has a one-wire interface which encodes bit values as pulse widths. The ICs themselves are basically shift registers. Roughly speaking, a "short" pulse shifts in a zero bit, a "long" pulse shifts in a one bit, and an inter-pulse gap exceeding a reset time threshold causes a pixel to latch the shifted-in color values. Each chip has an output pin for daisy chaining. Refer to the chip datsheets and comments in Kconfig.ws2812 for more details. To meet timing without hogging the core, this driver generates pulses using SPI. To work, this requires the MOSI line to stay low between SPI frames, and for inter-frame delays to be less than the reset pulse time. There are other ways do it (PWM + DMA on some SoCs, GPIO bit-banging if no other tasks need the core), but this is a reasonably general-purpose implementation. Signed-off-by: Marti Bolivar <marti.bolivar@linaro.org>
2017-10-17 11:28:15 +08:00
config WS2812_WHT_ORDER
int "Order in which a white pixel should be shifted out"
default 3
range 0 3
depends on WS2812_HAS_WHITE_CHANNEL
help
kconfig: Global whitespace/consistency cleanup Clean up space errors and use a consistent style throughout the Kconfig files. This makes reading the Kconfig files more distraction-free, helps with grepping, and encourages the same style getting copied around everywhere (meaning another pass hopefully won't be needed). Go for the most common style: - Indent properties with a single tab, including for choices. Properties on choices work exactly the same syntactically as properties on symbols, so not sure how the no-indentation thing happened. - Indent help texts with a tab followed by two spaces - Put a space between 'config' and the symbol name, not a tab. This also helps when grepping for definitions. - Do '# A comment' instead of '#A comment' I tweaked Kconfiglib a bit to find most of the stuff. Some help texts were reflowed to 79 columns with 'gq' in Vim as well, though not all, because I was afraid I'd accidentally mess up formatting. Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>
2019-11-01 17:24:07 +08:00
If the blue channel is shifted out first, specify 0.
If second, specify 1, and so on.
drivers: led_strip: add WS2812-ish driver The WS2812 LED driver IC has a one-wire interface which encodes bit values as pulse widths. The ICs themselves are basically shift registers. Roughly speaking, a "short" pulse shifts in a zero bit, a "long" pulse shifts in a one bit, and an inter-pulse gap exceeding a reset time threshold causes a pixel to latch the shifted-in color values. Each chip has an output pin for daisy chaining. Refer to the chip datsheets and comments in Kconfig.ws2812 for more details. To meet timing without hogging the core, this driver generates pulses using SPI. To work, this requires the MOSI line to stay low between SPI frames, and for inter-frame delays to be less than the reset pulse time. There are other ways do it (PWM + DMA on some SoCs, GPIO bit-banging if no other tasks need the core), but this is a reasonably general-purpose implementation. Signed-off-by: Marti Bolivar <marti.bolivar@linaro.org>
2017-10-17 11:28:15 +08:00
endif # WS2812_STRIP