# robot.drivers.apa102 源代码

    """
    from https://github.com/tinue/APA102_Pi
    This is the main driver module for APA102 LEDs
    """
    import spidev
    from math import ceil

    RGB_MAP = { 'rgb': [3, 2, 1], 'rbg': [3, 1, 2], 'grb': [2, 3, 1],
                'gbr': [2, 1, 3], 'brg': [1, 3, 2], 'bgr': [1, 2, 3] }

    class APA102:
        """
        Driver for APA102 LEDS (aka "DotStar").

        (c) Martin Erzberger 2016-2017

        My very first Python code, so I am sure there is a lot to be optimized ;)

        Public methods are:
         - set_pixel
         - set_pixel_rgb
         - show
         - clear_strip
         - cleanup

        Helper methods for color manipulation are:
         - combine_color
         - wheel

        The rest of the methods are used internally and should not be used by the
        user of the library.

        Very brief overview of APA102: An APA102 LED is addressed with SPI. The bits
        are shifted in one by one, starting with the least significant bit.

        An LED usually just forwards everything that is sent to its data-in to
        data-out. While doing this, it remembers its own color and keeps glowing
        with that color as long as there is power.

        An LED can be switched to not forward the data, but instead use the data
        to change it's own color. This is done by sending (at least) 32 bits of
        zeroes to data-in. The LED then accepts the next correct 32 bit LED
        frame (with color information) as its new color setting.

        After having received the 32 bit color frame, the LED changes color,
        and then resumes to just copying data-in to data-out.

        The really clever bit is this: While receiving the 32 bit LED frame,
        the LED sends zeroes on its data-out line. Because a color frame is
        32 bits, the LED sends 32 bits of zeroes to the next LED.
        As we have seen above, this means that the next LED is now ready
        to accept a color frame and update its color.

        So that's really the entire protocol:
        - Start by sending 32 bits of zeroes. This prepares LED 1 to update
          its color.
        - Send color information one by one, starting with the color for LED 1,
          then LED 2 etc.
        - Finish off by cycling the clock line a few times to get all data
          to the very last LED on the strip

        The last step is necessary, because each LED delays forwarding the data
        a bit. Imagine ten people in a row. When you yell the last color
        information, i.e. the one for person ten, to the first person in
        the line, then you are not finished yet. Person one has to turn around
        and yell it to person 2, and so on. So it takes ten additional "dummy"
        cycles until person ten knows the color. When you look closer,
        you will see that not even person 9 knows its own color yet. This
        information is still with person 2. Essentially the driver sends additional
        zeroes to LED 1 as long as it takes for the last color frame to make it
        down the line to the last LED.
        """
        # Constants
        MAX_BRIGHTNESS = 31 # Safeguard: Set to a value appropriate for your setup
        LED_START = 0b11100000 # Three "1" bits, followed by 5 brightness bits

        def __init__(self, num_led, global_brightness=MAX_BRIGHTNESS,
                     order='rgb', bus=0, device=1, max_speed_hz=8000000):
            self.num_led = num_led  # The number of LEDs in the Strip
            order = order.lower()
            self.rgb = RGB_MAP.get(order, RGB_MAP['rgb'])
            # Limit the brightness to the maximum if it's set higher
            if global_brightness > self.MAX_BRIGHTNESS:
                self.global_brightness = self.MAX_BRIGHTNESS
            else:
                self.global_brightness = global_brightness

            self.leds = [self.LED_START,0,0,0] * self.num_led # Pixel buffer
            self.spi = spidev.SpiDev()  # Init the SPI device
            self.spi.open(bus, device)  # Open SPI port 0, slave device (CS) 1
            # Up the speed a bit, so that the LEDs are painted faster
            if max_speed_hz:
                self.spi.max_speed_hz = max_speed_hz

        def clock_start_frame(self):
            """Sends a start frame to the LED strip.

            This method clocks out a start frame, telling the receiving LED
            that it must update its own color now.
            """
            self.spi.xfer2([0] * 4)  # Start frame, 32 zero bits

        def clock_end_frame(self):
            """Sends an end frame to the LED strip.

            As explained above, dummy data must be sent after the last real colour
            information so that all of the data can reach its destination down the line.
            The delay is not as bad as with the human example above.
            It is only 1/2 bit per LED. This is because the SPI clock line
            needs to be inverted.

            Say a bit is ready on the SPI data line. The sender communicates
            this by toggling the clock line. The bit is read by the LED
            and immediately forwarded to the output data line. When the clock goes
            down again on the input side, the LED will toggle the clock up
            on the output to tell the next LED that the bit is ready.

            After one LED the clock is inverted, and after two LEDs it is in sync
            again, but one cycle behind. Therefore, for every two LEDs, one bit
            of delay gets accumulated. For 300 LEDs, 150 additional bits must be fed to
            the input of LED one so that the data can reach the last LED.

            Ultimately, we need to send additional numLEDs/2 arbitrary data bits,
            in order to trigger numLEDs/2 additional clock changes. This driver
            sends zeroes, which has the benefit of getting LED one partially or
            fully ready for the next update to the strip. An optimized version
            of the driver could omit the "clockStartFrame" method if enough zeroes have
            been sent as part of "clockEndFrame".
            """
            # Round up num_led/2 bits (or num_led/16 bytes)
            for _ in range((self.num_led + 15) // 16):
                self.spi.xfer2([0x00])

        def clear_strip(self):
            """ Turns off the strip and shows the result right away."""

            for led in range(self.num_led):
                self.set_pixel(led, 0, 0, 0)
            self.show()

        def set_pixel(self, led_num, red, green, blue, bright_percent=100):
            """Sets the color of one pixel in the LED stripe.

            The changed pixel is not shown yet on the Stripe, it is only
            written to the pixel buffer. Colors are passed individually.
            If brightness is not set the global brightness setting is used.
            """
            if led_num < 0:
                return  # Pixel is invisible, so ignore
            if led_num >= self.num_led:
                return  # again, invisible

            # Calculate pixel brightness as a percentage of the
            # defined global_brightness. Round up to nearest integer
            # as we expect some brightness unless set to 0
            brightness = ceil(bright_percent*self.global_brightness/100.0)
            brightness = int(brightness)

            # LED startframe is three "1" bits, followed by 5 brightness bits
            ledstart = (brightness & 0b00011111) | self.LED_START

            start_index = 4 * led_num
            self.leds[start_index] = ledstart
            self.leds[start_index + self.rgb[0]] = red
            self.leds[start_index + self.rgb[1]] = green
            self.leds[start_index + self.rgb[2]] = blue

        def set_pixel_rgb(self, led_num, rgb_color, bright_percent=100):
            """Sets the color of one pixel in the LED stripe.

            The changed pixel is not shown yet on the Stripe, it is only
            written to the pixel buffer.
            Colors are passed combined (3 bytes concatenated)
            If brightness is not set the global brightness setting is used.
            """
            self.set_pixel(led_num, (rgb_color & 0xFF0000) >> 16,
                           (rgb_color & 0x00FF00) >> 8, rgb_color & 0x0000FF,
                            bright_percent)

        def rotate(self, positions=1):
            """ Rotate the LEDs by the specified number of positions.

            Treating the internal LED array as a circular buffer, rotate it by
            the specified number of positions. The number could be negative,
            which means rotating in the opposite direction.
            """
            cutoff = 4 * (positions % self.num_led)
            self.leds = self.leds[cutoff:] + self.leds[:cutoff]

        def show(self):
            """Sends the content of the pixel buffer to the strip.

            Todo: More than 1024 LEDs requires more than one xfer operation.
            """
            self.clock_start_frame()
            # xfer2 kills the list, unfortunately. So it must be copied first
            # SPI takes up to 4096 Integers. So we are fine for up to 1024 LEDs.
            self.spi.xfer2(list(self.leds))
            self.clock_end_frame()

        def cleanup(self):
            """Release the SPI device; Call this method at the end"""

            self.spi.close()  # Close SPI port

        @staticmethod
        def combine_color(red, green, blue):
            """Make one 3*8 byte color value."""

            return (red << 16) + (green << 8) + blue

        def wheel(self, wheel_pos):
            """Get a color from a color wheel; Green -> Red -> Blue -> Green"""

            if wheel_pos > 255:
                wheel_pos = 255 # Safeguard
            if wheel_pos < 85:  # Green -> Red
                return self.combine_color(wheel_pos * 3, 255 - wheel_pos * 3, 0)
            if wheel_pos < 170:  # Red -> Blue
                wheel_pos -= 85
                return self.combine_color(255 - wheel_pos * 3, 0, wheel_pos * 3)
            # Blue -> Green
            wheel_pos -= 170
            return self.combine_color(0, wheel_pos * 3, 255 - wheel_pos * 3)

        def dump_array(self):
            """For debug purposes: Dump the LED array onto the console."""

            print(self.leds)