Struct DmaFrameBuffer 

pub struct DmaFrameBuffer<const ROWS: usize, const COLS: usize, const NROWS: usize, const BITS: u8, const FRAME_COUNT: usize> { /* private fields */ }

DMA-compatible framebuffer for HUB75 LED panels.

This is a framebuffer implementation that:

• Manages multiple frames for Binary Code Modulation (BCM)
• Provides DMA-compatible memory layout
• Implements the embedded-graphics DrawTarget trait

Type Parameters

• ROWS: Total number of rows in the panel
• COLS: Number of columns in the panel
• NROWS: Number of rows per scan (typically half of ROWS)
• BITS: Color depth (1-8 bits)
• FRAME_COUNT: Number of frames used for Binary Code Modulation

Helper Functions

Use these functions to compute the correct values:

• esp_hub75::compute_frame_count(BITS): Computes the required number of frames
• esp_hub75::compute_rows(ROWS): Computes the number of rows per scan

Memory Layout

The buffer is aligned to ensure efficient DMA transfers and contains:

• A 64-bit alignment field
• An array of frames, each containing the full panel data

Implementations

impl<const ROWS: usize, const COLS: usize, const NROWS: usize, const BITS: u8, const FRAME_COUNT: usize> DmaFrameBuffer<ROWS, COLS, NROWS, BITS, FRAME_COUNT>

pub const fn new() -> Self

Create a new, ready-to-use framebuffer.

This creates a new framebuffer and automatically formats it with proper timing signals. The framebuffer is immediately ready for pixel operations and DMA transfers.

Panics

Panics if BITS is greater than 8, as only 1-8 bit color depths are supported. With the esp32-ordering feature, also panics if COLS is not even (the ESP32’s byte-order swap requires an even column count).

Example

use hub75_framebuffer::{Color,plain::DmaFrameBuffer,compute_rows,compute_frame_count};

const ROWS: usize = 32;
const COLS: usize = 64;
const BITS: u8 = 3; // Color depth (8 brightness levels, 7 frames)
const NROWS: usize = compute_rows(ROWS); // Number of rows per scan
const FRAME_COUNT: usize = compute_frame_count(BITS); // Number of frames for BCM

let mut framebuffer = DmaFrameBuffer::<ROWS, COLS, NROWS, BITS, FRAME_COUNT>::new();
// No need to call format() - framebuffer is ready to use!

Memory placement (⚠️ large buffer)

This framebuffer is a large inline array: one 16-bit word per pixel clock per frame, for (2^BITS)-1 frames. For a 64×64 panel at 3-bit depth that is already tens of kilobytes, and it grows exponentially with BITS. Never bind it to a task-local let — that places the whole buffer on the task stack and overflows it.

The framebuffer is mutable, so give it a 'static home that hands out &'static mut without unsafe — static mut is not an option. Use static_cell::StaticCell. See the crate-level Memory placement section for a worked example.

pub const fn bcm_chunk_count() -> usize

👎Deprecated since 0.11.0:

use BCM_SEQUENCE instead

Returns the number of BCM chunks in this framebuffer (always 1 for single-plane framebuffers — the entire buffer is one contiguous chunk).

pub const fn bcm_chunk_bytes() -> usize

👎Deprecated since 0.11.0:

use BCM_SEQUENCE instead

Returns the byte size of one BCM chunk (for single-plane framebuffers this equals the total DMA buffer size including the tail word, since BCM weighting is baked in).

pub const fn format(&mut self)

Perform full formatting of the framebuffer with timing and control signals.

This sets up all the timing and control signals needed for proper HUB75 operation. This is automatically called by new(), so you typically don’t need to call this unless you want to completely reinitialize the framebuffer.

Example

use hub75_framebuffer::{Color,plain::DmaFrameBuffer,compute_rows,compute_frame_count};

const ROWS: usize = 32;
const COLS: usize = 64;
const BITS: u8 = 3; // Color depth (8 brightness levels, 7 frames)
const NROWS: usize = compute_rows(ROWS); // Number of rows per scan
const FRAME_COUNT: usize = compute_frame_count(BITS); // Number of frames for BCM

let mut framebuffer = DmaFrameBuffer::<ROWS, COLS, NROWS, BITS, FRAME_COUNT>::new();
framebuffer.format(); // Reinitialize if needed

pub fn erase(&mut self)

Fast erase operation that clears all pixel data while preserving timing signals.

This is much faster than format() when you just want to clear the display since it preserves all the timing and control signals that are already set up. Use this for clearing between frames or when you want to start drawing fresh content.

Example

use hub75_framebuffer::{Color,plain::DmaFrameBuffer,compute_rows,compute_frame_count};

const ROWS: usize = 32;
const COLS: usize = 64;
const BITS: u8 = 3; // Color depth (8 brightness levels, 7 frames)
const NROWS: usize = compute_rows(ROWS); // Number of rows per scan
const FRAME_COUNT: usize = compute_frame_count(BITS); // Number of frames for BCM

let mut framebuffer = DmaFrameBuffer::<ROWS, COLS, NROWS, BITS, FRAME_COUNT>::new();
framebuffer.erase();

pub fn set_pixel(&mut self, p: Point, color: Color)

Set a pixel in the framebuffer.

Example

use hub75_framebuffer::{Color,plain::DmaFrameBuffer,compute_rows,compute_frame_count};
use embedded_graphics::prelude::*;

const ROWS: usize = 32;
const COLS: usize = 64;
const BITS: u8 = 3; // Color depth (8 brightness levels, 7 frames)
const NROWS: usize = compute_rows(ROWS); // Number of rows per scan
const FRAME_COUNT: usize = compute_frame_count(BITS); // Number of frames for BCM

let mut framebuffer = DmaFrameBuffer::<ROWS, COLS, NROWS, BITS, FRAME_COUNT>::new();
framebuffer.set_pixel(Point::new(10, 10), Color::RED);

Trait Implementations

impl<const ROWS: usize, const COLS: usize, const NROWS: usize, const BITS: u8, const FRAME_COUNT: usize> Clone for DmaFrameBuffer<ROWS, COLS, NROWS, BITS, FRAME_COUNT>

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<const ROWS: usize, const COLS: usize, const NROWS: usize, const BITS: u8, const FRAME_COUNT: usize> Copy for DmaFrameBuffer<ROWS, COLS, NROWS, BITS, FRAME_COUNT>

impl<const ROWS: usize, const COLS: usize, const NROWS: usize, const BITS: u8, const FRAME_COUNT: usize> Debug for DmaFrameBuffer<ROWS, COLS, NROWS, BITS, FRAME_COUNT>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<const ROWS: usize, const COLS: usize, const NROWS: usize, const BITS: u8, const FRAME_COUNT: usize> Default for DmaFrameBuffer<ROWS, COLS, NROWS, BITS, FRAME_COUNT>

fn default() -> Self

Returns the “default value” for a type.

impl<const ROWS: usize, const COLS: usize, const NROWS: usize, const BITS: u8, const FRAME_COUNT: usize> DrawTarget for DmaFrameBuffer<ROWS, COLS, NROWS, BITS, FRAME_COUNT>

type Color = Rgb888

The pixel color type the targetted display supports.

type Error = !

Error type to return when a drawing operation fails.

fn draw_iter<I>(&mut self, pixels: I) -> Result<(), Self::Error>

where I: IntoIterator<Item = Pixel<Self::Color>>,

Draw individual pixels to the display without a defined order.

fn fill_contiguous<I>( &mut self, area: &Rectangle, colors: I, ) -> Result<(), Self::Error>

where I: IntoIterator<Item = Self::Color>,

Fill a given area with an iterator providing a contiguous stream of pixel colors.

fn fill_solid( &mut self, area: &Rectangle, color: Self::Color, ) -> Result<(), Self::Error>

Fill a given area with a solid color.

fn clear(&mut self, color: Self::Color) -> Result<(), Self::Error>

Fill the entire display with a solid color.

impl<const ROWS: usize, const COLS: usize, const NROWS: usize, const BITS: u8, const FRAME_COUNT: usize> FrameBuffer for DmaFrameBuffer<ROWS, COLS, NROWS, BITS, FRAME_COUNT>

const BCM_SEQUENCE: [BcmLenReps; 10]

Static (len, reps) of the segments in one sequence, in scan order.

const BCM_SEQUENCE_LEN: usize = 1

Number of BCM segments in one sequence, i.e. the number of meaningful entries in BCM_SEQUENCE.

const BCM_SEQUENCE_COUNT: usize = 1

Number of times the sequence repeats in one complete panel refresh: NROWS for row-major framebuffers (one sequence per row), 1 for frame-major and threshold framebuffers (the sequence covers the whole frame).

type Word = u16

The DMA word type used by this framebuffer (u8 for latched, u16 for direct-drive). Driver implementations can use this to enforce that pin configurations match the framebuffer at compile time.

fn bcm_segment_ptr(&self, index: usize) -> *const u8

Returns the byte pointer for the index-th BCM segment.

const BCM_SEGMENT_COUNT: usize = _

Total number of BCM segments streamed for one complete panel refresh (all rows, all planes).

const BCM_SEGMENTS_PER_GROUP: usize = 1

Number of consecutive segments that a driver may chain into a single DMA transfer. Must divide BCM_SEQUENCE_LEN: groups never straddle a sequence boundary.

fn bcm_segment_count(&self) -> usize

Total number of BCM segments streamed for one complete panel refresh.

fn bcm_segment(&self, index: usize) -> BcmSegment

Returns the index-th BCM segment.

fn bcm_segments_per_group(&self) -> usize

Number of consecutive segments that form one transfer group.

impl<const ROWS: usize, const COLS: usize, const NROWS: usize, const BITS: u8, const FRAME_COUNT: usize> FrameBufferOperations for DmaFrameBuffer<ROWS, COLS, NROWS, BITS, FRAME_COUNT>

fn erase(&mut self)

Erase pixel colors while preserving control bits. This is much faster than format() and is the typical way to clear the display.

fn set_pixel(&mut self, p: Point, color: Color)

Set a pixel in the framebuffer.

impl<const ROWS: usize, const COLS: usize, const NROWS: usize, const BITS: u8, const FRAME_COUNT: usize> MutableFrameBuffer for DmaFrameBuffer<ROWS, COLS, NROWS, BITS, FRAME_COUNT>

impl<const ROWS: usize, const COLS: usize, const NROWS: usize, const BITS: u8, const FRAME_COUNT: usize> OriginDimensions for DmaFrameBuffer<ROWS, COLS, NROWS, BITS, FRAME_COUNT>

fn size(&self) -> Size

Returns the size of the bounding box.

impl<const ROWS: usize, const COLS: usize, const NROWS: usize, const BITS: u8, const FRAME_COUNT: usize> OriginDimensions for &mut DmaFrameBuffer<ROWS, COLS, NROWS, BITS, FRAME_COUNT>

fn size(&self) -> Size

Returns the size of the bounding box.