Use ws2812 leds on imxrt1062 boards

• For usage with smart-leds
• Implements the SmartLedsWrite trait

WARNING

WS2812s operate at 5v. IMXRT1062 pads operate at 3v and are not 5v tolerant. You will need a logic-level converter and some care in wiring.

Why?

Because I'm apparently too stupid to get a periodic timer working with ws2812-timer-delay.

How?

This library uses a simple nop loop in assembly to wait.

WS2812s read inputs with cycles about 333ns long. Write 3 bytes (GRB | Green, Red, Blue) per LED, then "latch" (set low) for 6us to 250us depending on your model. Writing a single bit entails a three-bit message that looks like [1, x, 0], where x is the bit you want to write. That all is to say, to write a bit of 1 to an LED you must send [1, 1, 0], waiting 333ns between each bit.

Despite WS2812 cycles allegedly being 333ns, some of the time constraints are very tight, and others are very loose.

Find out more about the timing constraints of WS2812s.

P.S. I have the latch hard coded to 6us. If you need 250us shoot me an email or clone the project.

Example using teensy4-bsp

#[cortex_m_rt::entry]
fn main() -> ! {
    ...

    let mut data: [RGB8; 3] = [RGB8::default(); 3];
    let empty: [RGB8; 3] = [RGB8::default(); 3];

    data[0] = RGB8 {
        r: 0x10,
        g: 0x00,
        b: 0x00,
    };
    data[1] = RGB8 {
        r: 0x00,
        g: 0x10,
        b: 0x00,
    };
    data[2] = RGB8 {
        r: 0x00,
        g: 0x00,
        b: 0x10,
    };

    configure(&mut pins.p2,{
        Config::zero()
            .set_drive_strength(DriveStrength::R0_7)
            .set_speed(Speed::Max)
            .set_slew_rate(SlewRate::Fast)
    });
    let pin = GPIO::new(pins.p2).output();

    let mut ws = ws2812_nop_imxrt1062::Ws2812::new(pin, 600.0);

    loop {
        ws.write(data.iter().cloned()).unwrap();
        systick.delay_ms(500);

        ws.write(empty.iter().cloned()).unwrap();
        systick.delay_ms(500);
    }
}