Add extensive explanation of the code.
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@ -1,14 +1,21 @@
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#![no_main]
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#![no_std]
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use embedded_hal::delay::DelayNs;
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use embedded_hal::spi::SpiBus;
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/// This application demonstrates using a Raspberry Pi Pico to control an individual SK9822 module.
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/// Keep in mind that the Pico, though it accepts 5V for power, it runs on 3.3V logic. The GPIO
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/// pins will emit only 3.3 volts, and the SK9822 needs 5V logic. So, make sure that the GPIO pins
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/// run through a transistor or a logic level lhifter to go from 3.3V logic to 5V logic.
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use embedded_hal::{delay::DelayNs, spi::SpiBus};
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use panic_halt as _;
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use rp_pico::{
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entry,
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hal::{
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clocks::init_clocks_and_plls,
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fugit::RateExtU32,
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gpio::{
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bank0::{Gpio10, Gpio11},
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FunctionSpi, Pin, PullDown,
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},
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spi::Spi,
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Clock, Sio, Timer, Watchdog,
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},
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@ -21,15 +28,28 @@ const XOSC_CRYSTAL_FREQ: u32 = 12_000_000; // MHz, https://forums.raspberrypi.co
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#[entry]
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unsafe fn main() -> ! {
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// rp_pico::pac::Peripherals is a reference to physical hardware defined on the Pico.
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let mut peripherals = pac::Peripherals::take().unwrap();
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// SIO inidcates "Single Cycle IO". I don't know what this means, but it could mean that this
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// is a class of IO operations that can be run in a single clock cycle, such as switching a
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// GPIO pin on or off.
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let sio = Sio::new(peripherals.SIO);
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// Many of the following systems require a watchdog. I do not know what this does, either, but
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// it may be some failsafe software that will reset operations if the watchdog detects a lack
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// of activity.
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let mut watchdog = Watchdog::new(peripherals.WATCHDOG);
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// Here we grab the GPIO pins in bank 0.
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let pins = Pins::new(
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peripherals.IO_BANK0,
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peripherals.PADS_BANK0,
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sio.gpio_bank0,
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&mut peripherals.RESETS,
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);
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// Initialize an abstraction of the clock system with a batch of standard hardware clocks.
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let clocks = init_clocks_and_plls(
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XOSC_CRYSTAL_FREQ,
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peripherals.XOSC,
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@ -42,15 +62,23 @@ unsafe fn main() -> ! {
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.ok()
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.unwrap();
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// An abstraction for a timer which we can use to delay the code.
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let mut timer = Timer::new(peripherals.TIMER, &mut peripherals.RESETS, &clocks);
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let spi_clk = pins.gpio10.into_function();
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let spi_sdo = pins.gpio11.into_function();
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let spi = Spi::<_, _, _, 8>::new(peripherals.SPI1, (spi_sdo, spi_clk));
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let mut spi = spi.init(
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// Grab the clock and data pins for SPI1. For Clock pins and for Data pins, there are only two
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// pins each on the Pico which can function for SPI1.
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let spi_clk: Pin<Gpio10, FunctionSpi, PullDown> = pins.gpio10.into_function();
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let spi_sdo: Pin<Gpio11, FunctionSpi, PullDown> = pins.gpio11.into_function();
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// Now, create the SPI function abstraction for SPI1 with spi_clk and spi_sdo.
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let mut spi = Spi::<_, _, _, 8>::new(peripherals.SPI1, (spi_sdo, spi_clk)).init(
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&mut peripherals.RESETS,
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// The SPI system uses the peripheral clock
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clocks.peripheral_clock.freq(),
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// Transmit data at a rate of 1Mbit.
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1_u32.MHz(),
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// Run with SPI Mode 1. This means that the clock line should start high and that data will
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// be sampled starting at the first falling edge.
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embedded_hal::spi::MODE_1,
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);
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@ -59,13 +87,27 @@ unsafe fn main() -> ! {
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// 4 for the end frame
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// = 20 bytes
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let mut lights: [u8; 12] = [0; 12];
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// We just skip the first four bytes, because the start frame is four bytes of 0.
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// Set the first byte of the one and only lamp. The first byte follows the pattern of three 1
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// bits followed by five additional bits that indicate an overall brightness level of the
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// pixel. The datasheet for the SK9822 doesn't specify the exact effect, but it does mean that
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// the higher this number is, the brighter 255 means for an given LED in the array. 1 is the
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// lowest brightness that emits light, and 31 is the highest supported brightness.
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lights[4] = 0xe0 + 1;
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// Set the Blue light of the dotstar to 255, assuming the dotstar frame format is RBG. Note
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// that the standard SK9822 datasheed indicates that the format is BGR. Your mileage may vary.
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lights[6] = 255;
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// The end frame is four bytes of 255.
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lights[8] = 0xff;
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lights[9] = 0xff;
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lights[10] = 0xff;
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lights[11] = 0xff;
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lights[4] = 0xe0 + 1;
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// The rest of this is just a stock pulsating animation which is slightly brightening and
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// dimming the *blue* LED (on my set of dotstars).
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let mut brightness = 1;
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let mut step = 1;
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loop {
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@ -75,8 +117,6 @@ unsafe fn main() -> ! {
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step = 1;
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};
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lights[5] = brightness as u8;
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lights[6] = 255;
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// lights[7] = brightness as u8;
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brightness = brightness + step;
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let _ = spi.write(lights.as_slice());
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