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//! This example shows powerful PIO module in the RP2040 chip to communicate with a HD44780 display.
//! See (https://www.sparkfun.com/datasheets/LCD/HD44780.pdf)
#![no_std]
#![no_main]
#![feature(type_alias_impl_trait)]
use core::fmt::Write;
use embassy_executor::Spawner;
use embassy_rp::dma::{AnyChannel, Channel};
use embassy_rp::peripherals::PIO0;
use embassy_rp::pio::{
Config, Direction, FifoJoin, InterruptHandler, Pio, PioPin, ShiftConfig, ShiftDirection, StateMachine,
};
use embassy_rp::pwm::{self, Pwm};
use embassy_rp::{bind_interrupts, into_ref, Peripheral, PeripheralRef};
use embassy_time::{Duration, Instant, Timer};
use {defmt_rtt as _, panic_probe as _};
bind_interrupts!(pub struct Irqs {
PIO0_IRQ_0 => InterruptHandler<PIO0>;
});
#[embassy_executor::main]
async fn main(_spawner: Spawner) {
// this test assumes a 2x16 HD44780 display attached as follow:
// rs = PIN0
// rw = PIN1
// e = PIN2
// db4 = PIN3
// db5 = PIN4
// db6 = PIN5
// db7 = PIN6
// additionally a pwm signal for a bias voltage charge pump is provided on pin 15,
// allowing direct connection of the display to the RP2040 without level shifters.
let p = embassy_rp::init(Default::default());
let _pwm = Pwm::new_output_b(p.PWM_CH7, p.PIN_15, {
let mut c = pwm::Config::default();
c.divider = 125.into();
c.top = 100;
c.compare_b = 50;
c
});
let mut hd = HD44780::new(
p.PIO0, Irqs, p.DMA_CH3, p.PIN_0, p.PIN_1, p.PIN_2, p.PIN_3, p.PIN_4, p.PIN_5, p.PIN_6,
)
.await;
loop {
struct Buf<const N: usize>([u8; N], usize);
impl<const N: usize> Write for Buf<N> {
fn write_str(&mut self, s: &str) -> Result<(), core::fmt::Error> {
for b in s.as_bytes() {
if self.1 >= N {
return Err(core::fmt::Error);
}
self.0[self.1] = *b;
self.1 += 1;
}
Ok(())
}
}
let mut buf = Buf([0; 16], 0);
write!(buf, "up {}s", Instant::now().as_micros() as f32 / 1e6).unwrap();
hd.add_line(&buf.0[0..buf.1]).await;
Timer::after(Duration::from_secs(1)).await;
}
}
pub struct HD44780<'l> {
dma: PeripheralRef<'l, AnyChannel>,
sm: StateMachine<'l, PIO0, 0>,
buf: [u8; 40],
}
impl<'l> HD44780<'l> {
pub async fn new(
pio: impl Peripheral<P = PIO0> + 'l,
irq: Irqs,
dma: impl Peripheral<P = impl Channel> + 'l,
rs: impl PioPin,
rw: impl PioPin,
e: impl PioPin,
db4: impl PioPin,
db5: impl PioPin,
db6: impl PioPin,
db7: impl PioPin,
) -> HD44780<'l> {
into_ref!(dma);
let Pio {
mut common,
mut irq0,
mut sm0,
..
} = Pio::new(pio, irq);
// takes command words (<wait:24> <command:4> <0:4>)
let prg = pio_proc::pio_asm!(
r#"
.side_set 1 opt
.origin 20
loop:
out x, 24
delay:
jmp x--, delay
out pins, 4 side 1
out null, 4 side 0
jmp !osre, loop
irq 0
"#,
);
let rs = common.make_pio_pin(rs);
let rw = common.make_pio_pin(rw);
let e = common.make_pio_pin(e);
let db4 = common.make_pio_pin(db4);
let db5 = common.make_pio_pin(db5);
let db6 = common.make_pio_pin(db6);
let db7 = common.make_pio_pin(db7);
sm0.set_pin_dirs(Direction::Out, &[&rs, &rw, &e, &db4, &db5, &db6, &db7]);
let mut cfg = Config::default();
cfg.use_program(&common.load_program(&prg.program), &[&e]);
cfg.clock_divider = 125u8.into();
cfg.set_out_pins(&[&db4, &db5, &db6, &db7]);
cfg.shift_out = ShiftConfig {
auto_fill: true,
direction: ShiftDirection::Left,
threshold: 32,
};
cfg.fifo_join = FifoJoin::TxOnly;
sm0.set_config(&cfg);
sm0.set_enable(true);
// init to 8 bit thrice
sm0.tx().push((50000 << 8) | 0x30);
sm0.tx().push((5000 << 8) | 0x30);
sm0.tx().push((200 << 8) | 0x30);
// init 4 bit
sm0.tx().push((200 << 8) | 0x20);
// set font and lines
sm0.tx().push((50 << 8) | 0x20);
sm0.tx().push(0b1100_0000);
irq0.wait().await;
sm0.set_enable(false);
// takes command sequences (<rs:1> <count:7>, data...)
// many side sets are only there to free up a delay bit!
let prg = pio_proc::pio_asm!(
r#"
.origin 27
.side_set 1
.wrap_target
pull side 0
out x 1 side 0 ; !rs
out y 7 side 0 ; #data - 1
; rs/rw to e: >= 60ns
; e high time: >= 500ns
; e low time: >= 500ns
; read data valid after e falling: ~5ns
; write data hold after e falling: ~10ns
loop:
pull side 0
jmp !x data side 0
command:
set pins 0b00 side 0
jmp shift side 0
data:
set pins 0b01 side 0
shift:
out pins 4 side 1 [9]
nop side 0 [9]
out pins 4 side 1 [9]
mov osr null side 0 [7]
out pindirs 4 side 0
set pins 0b10 side 0
busy:
nop side 1 [9]
jmp pin more side 0 [9]
mov osr ~osr side 1 [9]
nop side 0 [4]
out pindirs 4 side 0
jmp y-- loop side 0
.wrap
more:
nop side 1 [9]
jmp busy side 0 [9]
"#
);
let mut cfg = Config::default();
cfg.use_program(&common.load_program(&prg.program), &[&e]);
cfg.clock_divider = 8u8.into(); // ~64ns/insn
cfg.set_jmp_pin(&db7);
cfg.set_set_pins(&[&rs, &rw]);
cfg.set_out_pins(&[&db4, &db5, &db6, &db7]);
cfg.shift_out.direction = ShiftDirection::Left;
cfg.fifo_join = FifoJoin::TxOnly;
sm0.set_config(&cfg);
sm0.set_enable(true);
// display on and cursor on and blinking, reset display
sm0.tx().dma_push(dma.reborrow(), &[0x81u8, 0x0f, 1]).await;
Self {
dma: dma.map_into(),
sm: sm0,
buf: [0x20; 40],
}
}
pub async fn add_line(&mut self, s: &[u8]) {
// move cursor to 0:0, prepare 16 characters
self.buf[..3].copy_from_slice(&[0x80, 0x80, 15]);
// move line 2 up
self.buf.copy_within(22..38, 3);
// move cursor to 1:0, prepare 16 characters
self.buf[19..22].copy_from_slice(&[0x80, 0xc0, 15]);
// file line 2 with spaces
self.buf[22..38].fill(0x20);
// copy input line
let len = s.len().min(16);
self.buf[22..22 + len].copy_from_slice(&s[0..len]);
// set cursor to 1:15
self.buf[38..].copy_from_slice(&[0x80, 0xcf]);
self.sm.tx().dma_push(self.dma.reborrow(), &self.buf).await;
}
}
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