diff --git a/src/protocol.rs b/src/protocol.rs
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+++ b/src/protocol.rs
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+//! Protocol used to update the badge
+
+use std::num::TryFromIntError;
+
+#[cfg(feature = "embedded-graphics")]
+use embedded_graphics::{
+    draw_target::DrawTarget,
+    geometry::{Dimensions, Point, Size},
+    pixelcolor::BinaryColor,
+    prelude::Pixel,
+    primitives::Rectangle,
+    Drawable,
+};
+use time::OffsetDateTime;
+use zerocopy::{BigEndian, FromBytes, Immutable, IntoBytes, KnownLayout, U16};
+
+/// Message style configuration
+/// ```
+/// use badgemagic::protocol::{Mode, Style};
+/// # (
+/// Style::default().blink().border().mode(Mode::Center)
+/// # );
+/// ```
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[cfg_attr(feature = "serde", serde(deny_unknown_fields))]
+#[must_use]
+pub struct Style {
+    #[cfg_attr(feature = "serde", serde(default))]
+    blink: bool,
+
+    #[cfg_attr(feature = "serde", serde(default))]
+    border: bool,
+
+    #[cfg_attr(feature = "serde", serde(default))]
+    speed: Speed,
+
+    #[cfg_attr(feature = "serde", serde(default))]
+    mode: Mode,
+}
+
+impl Style {
+    /// Enable blink mode
+    ///
+    /// The message will blink.
+    /// ```
+    /// use badgemagic::protocol::Style;
+    /// # (
+    /// Style::default().blink()
+    /// # );
+    /// ```
+    pub fn blink(mut self) -> Self {
+        self.blink = true;
+        self
+    }
+
+    /// Show a dotted border around the display.
+    /// ```
+    /// use badgemagic::protocol::Style;
+    /// # (
+    /// Style::default().blink()
+    /// # );
+    /// ```
+    pub fn border(mut self) -> Self {
+        self.border = true;
+        self
+    }
+
+    /// Set the update speed of the animations.
+    ///
+    /// The animation will jump to the next pixel at the specified frame rate.
+    /// ```
+    /// use badgemagic::protocol::{Speed, Style};
+    /// # (
+    /// Style::default().speed(Speed::Fps1_2)
+    /// # );
+    /// ```
+    pub fn speed(mut self, speed: Speed) -> Self {
+        self.speed = speed;
+        self
+    }
+
+    /// Set the display animation.
+    /// ```
+    /// use badgemagic::protocol::{Mode, Style};
+    /// # (
+    /// Style::default().mode(Mode::Curtain)
+    /// # );
+    /// ```
+    ///
+    /// Show text centered, without an animation:
+    /// ```
+    /// use badgemagic::protocol::{Mode, Style};
+    /// # (
+    /// Style::default().mode(Mode::Center)
+    /// # );
+    /// ```
+    pub fn mode(mut self, mode: Mode) -> Self {
+        self.mode = mode;
+        self
+    }
+}
+
+/// Animation update speed
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[cfg_attr(feature = "serde", serde(try_from = "u8", into = "u8"))]
+pub enum Speed {
+    /// 1.2 FPS
+    Fps1_2,
+
+    /// 1.3 FPS
+    Fps1_3,
+
+    /// 2 FPS
+    Fps2,
+
+    /// 2.4 FPS
+    Fps2_4,
+
+    /// 2.8 FPS
+    #[default]
+    Fps2_8,
+
+    /// 4.5 FPS
+    Fps4_5,
+
+    /// 7.5 FPS
+    Fps7_5,
+
+    /// 15 FPS
+    Fps15,
+}
+
+impl From<Speed> for u8 {
+    fn from(value: Speed) -> Self {
+        value as u8
+    }
+}
+
+impl TryFrom<u8> for Speed {
+    type Error = TryFromIntError;
+
+    fn try_from(value: u8) -> Result<Self, Self::Error> {
+        Ok(match value {
+            0 => Self::Fps1_2,
+            1 => Self::Fps1_3,
+            2 => Self::Fps2,
+            3 => Self::Fps2_4,
+            4 => Self::Fps2_8,
+            5 => Self::Fps4_5,
+            6 => Self::Fps7_5,
+            7 => Self::Fps15,
+            _ => return Err(u8::try_from(-1).unwrap_err()),
+        })
+    }
+}
+
+/// Message display mode
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[cfg_attr(feature = "serde", serde(rename_all = "snake_case"))]
+pub enum Mode {
+    /// Scroll through the message from left to right
+    #[default]
+    Left,
+
+    /// Scroll through the message from right to left
+    Right,
+
+    /// Enter from the bottom, move up
+    Up,
+
+    /// Enter from the top, move down
+    Down,
+
+    /// Center the text, no animation
+    Center,
+
+    /// Fast mode for animations
+    ///
+    /// Will leave a 4 pixel gap between screens:
+    /// Place a 44x11 pixel screen every 48 pixels
+    Fast,
+
+    /// Drop rows of pixels from the top
+    Drop,
+
+    /// Open a curtain and reveal the message
+    Curtain,
+
+    /// A laser will reveal the message from left to right
+    Laser,
+}
+
+/// Display Brightness
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[cfg_attr(feature = "serde", serde(rename_all = "snake_case"))]
+pub enum Brightness {
+    #[default]
+    Full = 0x00,
+    ThreeQuarters = 0x10,
+    Half = 0x20,
+    OneQuarter = 0x30,
+}
+
+impl From<Brightness> for u8 {
+    fn from(value: Brightness) -> Self {
+        value as u8
+    }
+}
+
+impl TryFrom<u8> for Brightness {
+    type Error = TryFromIntError;
+
+    fn try_from(value: u8) -> Result<Self, Self::Error> {
+        Ok(match value {
+            0x00 => Self::Full,
+            0x10 => Self::ThreeQuarters,
+            0x20 => Self::Half,
+            0x30 => Self::OneQuarter,
+            _ => return Err(u8::try_from(-1).unwrap_err()),
+        })
+    }
+}
+
+const MSG_PADDING_ALIGN: usize = 64;
+
+const MAGIC: [u8; 5] = *b"wang\0";
+
+#[derive(FromBytes, IntoBytes, Immutable, KnownLayout)]
+#[repr(C)]
+struct Header {
+    magic: [u8; 5],
+    brightness: u8,
+    blink: u8,
+    border: u8,
+    speed_and_mode: [u8; 8],
+    message_length: [U16<BigEndian>; 8],
+    _padding_1: [u8; 6],
+    timestamp: Timestamp,
+    _padding_2: [u8; 20],
+}
+
+#[derive(FromBytes, IntoBytes, Immutable, KnownLayout)]
+#[repr(C)]
+struct Timestamp {
+    year: u8,
+    month: u8,
+    day: u8,
+    hour: u8,
+    minute: u8,
+    second: u8,
+}
+
+impl Timestamp {
+    fn new(ts: OffsetDateTime) -> Self {
+        Self {
+            #[allow(clippy::cast_possible_truncation)] // clippy does not understand `rem_euclid(100) <= 100`
+            year: ts.year().rem_euclid(100) as u8,
+            month: ts.month() as u8,
+            day: ts.day(),
+            hour: ts.hour(),
+            minute: ts.minute(),
+            second: ts.second(),
+        }
+    }
+
+    fn now() -> Self {
+        Self::new(OffsetDateTime::now_utc())
+    }
+}
+
+/// Buffer to create a payload
+///
+/// A payload consists of up to 8 messages
+/// ```
+/// # #[cfg(feature = "embedded-graphics")]
+/// # fn main() {
+/// # use badgemagic::protocol::{PayloadBuffer, Style};
+/// use badgemagic::embedded_graphics::{
+///     geometry::{Point, Size},
+///     pixelcolor::BinaryColor,
+///     primitives::{PrimitiveStyle, Rectangle, Styled},
+/// };
+///
+/// let mut buffer = PayloadBuffer;
+/// buffer.add_message_drawable(
+///     Style::default(),
+///     &Styled::new(
+///         Rectangle::new(Point::new(2, 2), Size::new(4, 7)),
+///         PrimitiveStyle::with_fill(BinaryColor::On),
+///     ),
+/// );
+/// # }
+/// # #[cfg(not(feature = "embedded-graphics"))]
+/// # fn main() {}
+/// ```
+pub struct PayloadBuffer {
+    num_messages: u8,
+    data: Vec<u8>,
+}
+
+impl Default for PayloadBuffer {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl PayloadBuffer {
+    /// Create a new empty buffer
+    #[must_use]
+    pub fn new() -> Self {
+        Self {
+            num_messages: 0,
+            data: Header {
+                magic: MAGIC,
+                brightness: Brightness::Full.into(),
+                blink: 0,
+                border: 0,
+                speed_and_mode: [0; 8],
+                message_length: [0.into(); 8],
+                _padding_1: [0; 6],
+                timestamp: Timestamp::now(),
+                _padding_2: [0; 20],
+            }
+            .as_bytes()
+            .into(),
+        }
+    }
+
+    fn header_mut(&mut self) -> &mut Header {
+        Header::mut_from_prefix(&mut self.data).unwrap().0
+    }
+
+    pub fn set_brightness(&mut self, brightness: Brightness) {
+        self.header_mut().brightness = brightness.into();
+    }
+
+    /// Return the current number of messages
+    pub fn num_messages(&mut self) -> usize {
+        self.num_messages as usize
+    }
+
+    /// Add a messages containing the specified `content`
+    ///
+    /// ## Panics
+    /// This method panics if it is unable to draw the content.
+    #[cfg(feature = "embedded-graphics")]
+    pub fn add_message_drawable<O>(
+        &mut self,
+        style: Style,
+        content: &(impl Drawable<Color = BinaryColor, Output = O> + Dimensions),
+    ) -> O {
+        #[allow(clippy::cast_possible_wrap)]
+        fn saturating_usize_to_isize(n: usize) -> isize {
+            usize::min(n, isize::MAX as usize) as isize
+        }
+
+        fn add(a: i32, b: u32) -> usize {
+            let result = a as isize + saturating_usize_to_isize(b as usize);
+            result.try_into().unwrap_or_default()
+        }
+
+        let bounds = content.bounding_box();
+        let width = add(bounds.top_left.x, bounds.size.width);
+        let mut message = self.add_message(style, width.div_ceil(8));
+        content.draw(&mut message).unwrap()
+    }
+
+    /// Add a message with `count * 8`  columns
+    ///
+    /// The returned `MessageBuffer` can be used as an `embedded_graphics::DrawTarget`
+    /// with the `embedded_graphics` feature.
+    ///
+    /// ## Panics
+    /// Panics if the supported number of messages is reached.
+    pub fn add_message(&mut self, style: Style, count: usize) -> MessageBuffer {
+        let index = self.num_messages as usize;
+        assert!(
+            index < 8,
+            "maximum number of supported messages reached: {index} messages",
+        );
+        self.num_messages += 1;
+
+        let header = self.header_mut();
+
+        if style.blink {
+            header.blink |= 1 << index;
+        }
+        if style.border {
+            header.border |= 1 << index;
+        }
+        header.speed_and_mode[index] = ((style.speed as u8) << 4) | style.mode as u8;
+        header.message_length[index] = count.try_into().unwrap();
+
+        let start = self.data.len();
+        self.data.resize(start + count * 11, 0);
+        MessageBuffer(FromBytes::mut_from_bytes(&mut self.data[start..]).unwrap())
+    }
+
+    /// Get the current payload as bytes (without padding)
+    #[must_use]
+    pub fn as_bytes(&self) -> &[u8] {
+        &self.data
+    }
+
+    /// Convert the payload buffer into bytes (with padding)
+    #[allow(clippy::missing_panics_doc)] // should never panic
+    #[must_use]
+    pub fn into_padded_bytes(self) -> impl AsRef<[u8]> {
+        let mut data = self.data;
+
+        let prev_len = data.len();
+
+        // pad msg to align to 64 bytes
+        data.resize(
+            (data.len() + (MSG_PADDING_ALIGN - 1)) & !(MSG_PADDING_ALIGN - 1),
+            0,
+        );
+
+        // validate alignment
+        assert_eq!(data.len() % 64, 0);
+        assert!(prev_len <= data.len());
+
+        data
+    }
+}
+
+/// A display buffer for a single message.
+///
+/// Can be used as an `embedded_graphics::DrawTarget`.
+pub struct MessageBuffer<'a>(&'a mut [[u8; 11]]);
+
+impl MessageBuffer<'_> {
+    /// Set the state of the pixel at point (`x`, `y`)
+    ///
+    /// Returns `None` if the pixel was out of bounds.
+    pub fn set(&mut self, (x, y): (usize, usize), state: State) -> Option<()> {
+        let byte = self.0.get_mut(x / 8)?.get_mut(y)?;
+        let bit = 0x80 >> (x % 8);
+        match state {
+            State::Off => {
+                *byte &= !bit;
+            }
+            State::On => {
+                *byte |= bit;
+            }
+        }
+        Some(())
+    }
+
+    #[cfg(feature = "embedded-graphics")]
+    fn set_embedded_graphics(&mut self, point: Point, color: BinaryColor) -> Option<()> {
+        let x = point.x.try_into().ok()?;
+        let y = point.y.try_into().ok()?;
+        self.set((x, y), color.into())
+    }
+}
+
+/// State of a pixel
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub enum State {
+    #[default]
+    Off,
+    On,
+}
+
+impl From<bool> for State {
+    fn from(value: bool) -> Self {
+        if value {
+            Self::On
+        } else {
+            Self::Off
+        }
+    }
+}
+
+#[cfg(feature = "embedded-graphics")]
+impl From<BinaryColor> for State {
+    fn from(value: BinaryColor) -> Self {
+        match value {
+            BinaryColor::Off => Self::Off,
+            BinaryColor::On => Self::On,
+        }
+    }
+}
+
+#[cfg(feature = "embedded-graphics")]
+impl Dimensions for MessageBuffer<'_> {
+    fn bounding_box(&self) -> embedded_graphics::primitives::Rectangle {
+        Rectangle::new(
+            Point::zero(),
+            Size::new((self.0.len() * 8).try_into().unwrap(), 11),
+        )
+    }
+}
+
+#[cfg(feature = "embedded-graphics")]
+impl DrawTarget for MessageBuffer<'_> {
+    type Color = BinaryColor;
+
+    type Error = std::convert::Infallible;
+
+    fn draw_iter<I>(&mut self, pixels: I) -> Result<(), Self::Error>
+    where
+        I: IntoIterator<Item = Pixel<Self::Color>>,
+    {
+        for Pixel(point, color) in pixels {
+            #[allow(clippy::manual_assert)]
+            if self.set_embedded_graphics(point, color).is_none() {
+                panic!(
+                    "tried to draw pixel outside the display area (x: {}, y: {})",
+                    point.x, point.y
+                );
+            }
+        }
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use std::ops::Range;
+
+    use super::{Brightness, Speed};
+
+    #[test]
+    fn speed_to_u8_and_back() {
+        const VALID_SPEED_VALUES: Range<u8> = 1..8;
+        for i in u8::MIN..u8::MAX {
+            if let Ok(speed) = Speed::try_from(i) {
+                assert_eq!(u8::from(speed), i);
+            } else {
+                assert!(!VALID_SPEED_VALUES.contains(&i));
+            }
+        }
+    }
+
+    #[test]
+    fn brightness_to_u8_and_back() {
+        const VALID_BRIGHTNESS_VALUES: [(Brightness, u8); 4] = [
+            (Brightness::Full, 0x00),
+            (Brightness::ThreeQuarters, 0x10),
+            (Brightness::Half, 0x20),
+            (Brightness::OneQuarter, 0x30),
+        ];
+
+        for (value, raw) in VALID_BRIGHTNESS_VALUES {
+            assert_eq!(u8::from(value), raw);
+            assert_eq!(Brightness::try_from(raw).unwrap(), value);
+        }
+    }
+
+}