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//! Sharp display driver
//!
//! This is an early attempt at a "frame buffer" style display driver. It provides a
//! [emb_display service][kernel::services::emb_display] server, and uses the
//! d1-core specific [SpiSender] service as an SPI "backend" for rendering.
//!
//! This implementation is sort of a work in progress, it isn't really a *great*
//! long-term solution, but rather "okay for now".
//!
//! A framebuffer of pixels is allocated for the entire display on registration.
//! This could be, for example, 400x240 pixels.
//!
//! The driver will then allow for a certain number of "sub frames" to be requested.
//!
//! These sub frames could be for the entire display (400x240), or a portion of it,
//! for example 200x120 pixels.
//!
//! Clients of the driver can draw into the sub-frames that they receive, then send
//! them back to be rendered into the total frame. Any data in the client's sub-frame
//! will replace the current contents of the whole frame buffer.
//!
//! ## Wire format
//!
//! Reference: <https://www.sharpsde.com/fileadmin/products/Displays/2016_SDE_App_Note_for_Memory_LCD_programming_V1.3.pdf>
use core::{convert::identity, time::Duration};
use embedded_graphics::{pixelcolor::Gray8, prelude::*, primitives::Rectangle};
use kernel::{
maitake::sync::{Mutex, WaitQueue},
mnemos_alloc::containers::{Arc, FixedVec},
registry::{self, listener},
services::emb_display::{
DisplayMetadata, EmbDisplayService, FrameChunk, FrameError, FrameKind, MonoChunk, Request,
Response,
},
Kernel,
};
use crate::drivers::spim::{SpiSender, SpiSenderClient};
const WIDTH: usize = 400;
const HEIGHT: usize = 240;
// Every pixel is one bit
const WIDTH_BYTES: usize = WIDTH / 8;
// Foreach LINE (240x) - 52 bytes total:
// * 1 byte for line number
// * (400bits / 8 = 50bytes) of data (one bit per pixel)
// * 1 "dummy" byte
const LINE_COMMAND_BYTES: usize = 1;
const LINE_DUMMY_BYTES: usize = 1;
const LINE_DATA_BYTES: usize = WIDTH_BYTES;
const LINE_BYTES: usize = LINE_COMMAND_BYTES + LINE_DATA_BYTES + LINE_DUMMY_BYTES;
// Every FRAME gets a 1 byte command, all of the lines, and one extra dummy byte
const FRAME_COMMAND_BYTES: usize = 1;
const FRAME_DUMMY_BYTES: usize = 1;
const FRAME_DATA_BYTES: usize = HEIGHT * LINE_BYTES;
const FRAME_BYTES: usize = FRAME_COMMAND_BYTES + FRAME_DATA_BYTES + FRAME_DUMMY_BYTES;
mod commands {
pub const TOGGLE_VCOM: u8 = 0b0000_0000;
pub const WRITE_LINE: u8 = 0b0000_0001;
pub const VCOM_MASK: u8 = 0b0000_0010;
}
/// Implements the [`EmbDisplayService`] service interface
pub struct SharpDisplay;
#[derive(Debug)]
pub enum RegistrationError {
/// Failed to register a display: either the kernel reported that there is
/// already an existing EmbDisplay, or the registry is full.
Registration(registry::RegistrationError),
/// No SPI sender service exists.
NoSpiSender(registry::ConnectError<SpiSender>),
}
impl SharpDisplay {
pub const WIDTH: usize = WIDTH;
pub const HEIGHT: usize = HEIGHT;
const CAPACITY: usize = 2;
/// Register the driver instance
///
/// Registration will also start the simulated display, meaning that the display
/// window will appear.
#[tracing::instrument(
name = "SharpDisplay::register",
level = tracing::Level::INFO,
skip(kernel),
err(Debug),
)]
pub async fn register(kernel: &'static Kernel) -> Result<(), RegistrationError> {
tracing::info!(
width = WIDTH,
height = HEIGHT,
queue_capacity = Self::CAPACITY,
"Starting SharpDisplay driver",
);
// acquire a SPI client first, so that we don't register the display
// service unless we can get a SPI client.
let spim = SpiSenderClient::from_registry(kernel)
.await
.map_err(RegistrationError::NoSpiSender)?;
// bind a listener
let cmd = kernel
.registry()
.bind_konly(Self::CAPACITY)
.await
.map_err(RegistrationError::Registration)?
.into_request_stream(Self::CAPACITY)
.await;
let linebuf = FixedVec::new(FRAME_BYTES).await;
let ctxt = Arc::new(Mutex::new(Context {
sdisp: FullFrame::new(),
vcom: false,
}))
.await;
let commander = CommanderTask {
cmd,
ctxt: ctxt.clone(),
height: HEIGHT as u32,
width: WIDTH as u32,
};
let vcom = VCom {
kernel,
ctxt: ctxt.clone(),
};
let draw = Draw {
kernel,
buf: linebuf,
spim,
ctxt,
};
kernel.spawn(commander.cmd_run()).await;
kernel.spawn(vcom.vcom_run()).await;
kernel.spawn(draw.draw_run()).await;
Ok(())
}
}
/// One entire frame, stored one bit per pixel
struct FullFrame {
frame: [[u8; WIDTH_BYTES]; HEIGHT],
/// One bool per vertical line to track if there have beem changes.
/// We can draw line-at-a-time with the sharp display, so we can avoid
/// sending lines that haven't changed, as the display is persistent.
dirty_lines: [bool; HEIGHT],
}
impl FullFrame {
pub fn new() -> Self {
Self {
frame: [[0u8; WIDTH_BYTES]; HEIGHT],
dirty_lines: [true; HEIGHT],
}
}
}
impl FullFrame {
#[inline]
fn set_px(&mut self, x: usize, y: usize, color: Gray8) {
if x >= WIDTH || y > HEIGHT {
return;
}
// mark the line as dirty so it will be sent on the next
// update of the display
self.dirty_lines[y] = true;
let byte_x = x / 8;
let bit_x = x % 8;
if color.luma() > 128 {
self.frame[y][byte_x] |= 1 << (bit_x as u8);
} else {
self.frame[y][byte_x] &= !(1 << (bit_x as u8))
}
}
}
impl Dimensions for FullFrame {
fn bounding_box(&self) -> embedded_graphics::primitives::Rectangle {
Rectangle::new(
Point { x: 0, y: 0 },
Size {
width: WIDTH as u32,
height: HEIGHT as u32,
},
)
}
}
//////////////////////////////////////////////////////////////////////////////
// Helper tasks
//
// Friends to help us make things happen
//////////////////////////////////////////////////////////////////////////////
/// VCom - Once a second, update the vcom flag which is sent in every message.
///
/// TODO(AJM): The Beepberry uses a GPIO to toggle this rather than a bit in the
/// SPI messages. This struct should be expanded to toggle the EXT pin at this
/// rate instead, possibly as an optional field.
struct VCom {
kernel: &'static Kernel,
ctxt: Arc<Mutex<Context>>,
}
impl VCom {
#[tracing::instrument(skip(self))]
pub async fn vcom_run(self) {
loop {
self.kernel.sleep(Duration::from_secs(1)).await;
let mut c = self.ctxt.lock().await;
c.vcom = !c.vcom;
tracing::debug!(vcom = c.vcom, "Toggling vcom");
}
}
}
/// Drawing task
///
/// This task draws whenever there are pending (or "dirty") changes to the frame
/// buffer, or at a base rate of 2Hz.
struct Draw {
kernel: &'static Kernel,
buf: FixedVec<u8>,
spim: SpiSenderClient,
ctxt: Arc<Mutex<Context>>,
}
impl Draw {
#[tracing::instrument(skip(self))]
async fn draw_run(mut self) {
loop {
let mut c = self.ctxt.lock().await;
self.buf.clear();
let mut drawn = 0;
// Are there ANY dirty lines?
if c.sdisp.dirty_lines.iter().copied().any(identity) {
// render into the buffer
let mut cmd = commands::WRITE_LINE;
if c.vcom {
cmd |= commands::VCOM_MASK;
}
// Write the command
let _ = self.buf.try_push(cmd);
let FullFrame { frame, dirty_lines } = &mut c.sdisp;
// Filter out to only the dirty lines, clearing the dirty flag
let all_lines = dirty_lines.iter_mut().zip(frame.iter()).enumerate();
let dirty = all_lines.filter_map(|(idx, (dirty, line))| {
if *dirty {
*dirty = false;
Some((idx, line))
} else {
None
}
});
// Now we need to write all the dirty lines, zip together the dest buffer
// with our current frame buffer
let res: Result<(), ()> = dirty.into_iter().try_for_each(|(line, iline)| {
// Lines are 1-indexed on the wire
self.buf.try_push((line as u8) + 1).map_err(drop)?;
// We keep our internal frame buffer in the same format as the wire
self.buf.try_extend_from_slice(iline)?;
// dummy byte
self.buf.try_push(0).map_err(drop)?;
drawn += 1;
Ok(())
});
res.expect("Failed to push data to SPI buffer!");
} else {
// No buffer to write, just toggle vcom
let mut cmd = commands::TOGGLE_VCOM;
if c.vcom {
cmd |= commands::VCOM_MASK;
}
// Write the command
self.buf
.try_push(cmd)
.expect("SPI buffer should be large enough");
}
// Write one final dummy byte
self.buf
.try_push(0)
.expect("SPI buffer should be large enough");
// Drop the mutex once we're done using the framebuffer data
drop(c);
if drawn > 0 {
tracing::debug!(drawn, "Drew all dirty lines");
} else {
tracing::trace!("No dirty lines, didn't draw anything...");
}
self.buf = self.spim.send_wait(self.buf).await.map_err(drop).unwrap();
// Wait a reasonable amount of time to redraw
let _ = self
.kernel
.timeout(Duration::from_millis(500), DIRTY.wait())
.await;
}
}
}
/// This task is spawned by the call to [`SharpDisplay::register`]. It is a single
/// async function that will process requests, and periodically redraw the
/// framebuffer.
struct CommanderTask {
cmd: listener::RequestStream<EmbDisplayService>,
ctxt: Arc<Mutex<Context>>,
width: u32,
height: u32,
}
impl CommanderTask {
/// The entrypoint for the driver execution
#[tracing::instrument(skip(self))]
async fn cmd_run(self) {
// This loop services incoming client requests.
//
// Generally, don't handle errors when replying to clients, this indicates that they
// sent us a message and "hung up" without waiting for a response.
loop {
let (req, env, reply_tx) = self.cmd.next_request().await.split();
match req {
Request::Draw(FrameChunk::Mono(fc)) => {
tracing::debug!("Processing Draw Mono command");
self.draw_mono(&fc, &self.ctxt).await;
DIRTY.wake_all();
let response = env.fill(Ok(Response::DrawComplete(fc.into())));
let _ = reply_tx.reply_konly(response).await;
}
Request::GetMeta => {
let meta = DisplayMetadata {
kind: FrameKind::Mono,
width: self.width,
height: self.height,
};
let response = env.fill(Ok(Response::FrameMeta(meta)));
let _ = reply_tx.reply_konly(response).await;
}
_ => {
let response = env.fill(Err(FrameError::InternalError));
let _ = reply_tx.reply_konly(response).await;
}
}
}
}
/// Draw the given MonoChunk to the persistent framebuffer
async fn draw_mono(&self, fc: &MonoChunk, mutex: &Mutex<Context>) {
let mut guard = mutex.lock().await;
let ctx: &mut Context = &mut guard;
let Context { sdisp, .. } = ctx;
draw_to(sdisp, fc, self.width, self.height);
}
}
//////////////////////////////////////////////////////////////////////////////
// Helper types and methods
//////////////////////////////////////////////////////////////////////////////
/// Shared state between tasks
struct Context {
sdisp: FullFrame,
vcom: bool,
}
/// Waiter for "changes have been made to the working frame buffer"
static DIRTY: WaitQueue = WaitQueue::new();
fn draw_to(dest: &mut FullFrame, src: &MonoChunk, width: u32, height: u32) {
let meta = src.meta();
let data = src.data();
let mask = src.mask();
let start_x = meta.start_x();
let start_y = meta.start_y();
let src_width = meta.width();
if start_y >= height {
return;
}
if start_x >= width {
return;
}
let s = data
.chunks(src_width as usize)
.zip(mask.chunks(src_width as usize));
let before = dest.dirty_lines.iter().filter(|b| **b).count();
for (src_y, (src_data_line, src_mask_line)) in s.enumerate() {
// Any data on this line?
if src_mask_line.iter().all(|b| *b == 0) {
continue;
}
let sl = src_data_line.iter().zip(src_mask_line.iter());
for (src_x, (s_data, s_mask)) in sl.enumerate() {
if *s_mask != 0 {
let val = if *s_data < 128 {
Gray8::BLACK
} else {
Gray8::WHITE
};
dest.set_px(start_x as usize + src_x, start_y as usize + src_y, val);
}
}
}
let after = dest.dirty_lines.iter().filter(|b| **b).count();
tracing::trace!(
made_dirty = (after - before),
"Finished rendering to frame buffer"
);
}