1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
|
//! LPUART Ring Buffer DMA example for MCXA276.
//!
//! This example demonstrates using the high-level `LpuartRxDma::setup_ring_buffer()`
//! API for continuous circular DMA reception from a UART peripheral.
//!
//! # Features demonstrated:
//! - `LpuartRxDma::setup_ring_buffer()` for continuous peripheral-to-memory DMA
//! - `RingBuffer` for async reading of received data
//! - Handling of potential overrun conditions
//! - Half-transfer and complete-transfer interrupts for timely wakeups
//!
//! # How it works:
//! 1. Create an `LpuartRxDma` driver with a DMA channel
//! 2. Call `setup_ring_buffer()` which handles all low-level DMA configuration
//! 3. Application asynchronously reads data as it arrives via `ring_buf.read()`
//! 4. Both half-transfer and complete-transfer interrupts wake the reader
#![no_std]
#![no_main]
use embassy_executor::Spawner;
use embassy_mcxa::clocks::config::Div8;
use embassy_mcxa::lpuart::{Config, LpuartDma, LpuartTxDma};
use static_cell::ConstStaticCell;
use {defmt_rtt as _, embassy_mcxa as hal, panic_probe as _};
// Ring buffer for RX - power of 2 is ideal for modulo efficiency
static RX_RING_BUFFER: ConstStaticCell<[u8; 64]> = ConstStaticCell::new([0; 64]);
/// Helper to write a byte as hex to UART
fn write_hex<T: embassy_mcxa::lpuart::Instance, C: embassy_mcxa::dma::Channel>(
tx: &mut LpuartTxDma<'_, T, C>,
byte: u8,
) {
const HEX: &[u8; 16] = b"0123456789ABCDEF";
let buf = [HEX[(byte >> 4) as usize], HEX[(byte & 0x0F) as usize]];
tx.blocking_write(&buf).ok();
}
#[embassy_executor::main]
async fn main(_spawner: Spawner) {
// Small delay to allow probe-rs to attach after reset
for _ in 0..100_000 {
cortex_m::asm::nop();
}
let mut cfg = hal::config::Config::default();
cfg.clock_cfg.sirc.fro_12m_enabled = true;
cfg.clock_cfg.sirc.fro_lf_div = Some(Div8::no_div());
let p = hal::init(cfg);
defmt::info!("LPUART Ring Buffer DMA example starting...");
// Create UART configuration
let config = Config {
baudrate_bps: 115_200,
..Default::default()
};
// Create LPUART with DMA support for both TX and RX, then split
// This is the proper Embassy pattern - create once, split into TX and RX
let lpuart = LpuartDma::new(p.LPUART2, p.P2_2, p.P2_3, p.DMA_CH1, p.DMA_CH0, config).unwrap();
let (mut tx, rx) = lpuart.split();
tx.blocking_write(b"LPUART Ring Buffer DMA Example\r\n").unwrap();
tx.blocking_write(b"==============================\r\n\r\n").unwrap();
tx.blocking_write(b"Setting up circular DMA for UART RX...\r\n")
.unwrap();
let buf = RX_RING_BUFFER.take();
// Set up the ring buffer with circular DMA
let mut ring_buf = rx.into_ring_dma_rx(buf);
tx.blocking_write(b"Ring buffer ready! Type characters to see them echoed.\r\n")
.unwrap();
tx.blocking_write(b"The DMA continuously receives in the background.\r\n\r\n")
.unwrap();
// Main loop: read from ring buffer and echo back
let mut read_buf = [0u8; 16];
let mut total_received: usize = 0;
loop {
// Async read - waits until data is available
match ring_buf.read(&mut read_buf).await {
Ok(n) if n > 0 => {
total_received += n;
// Echo back what we received
tx.blocking_write(b"RX[").unwrap();
for (i, &byte) in read_buf.iter().enumerate().take(n) {
write_hex(&mut tx, byte);
if i < n - 1 {
tx.blocking_write(b" ").unwrap();
}
}
tx.blocking_write(b"]: ").unwrap();
tx.blocking_write(&read_buf[..n]).unwrap();
tx.blocking_write(b"\r\n").unwrap();
defmt::info!("Received {} bytes, total: {}", n, total_received);
}
Ok(_) => {
// No data, shouldn't happen with async read
}
Err(_) => {
// Overrun detected
tx.blocking_write(b"ERROR: Ring buffer overrun!\r\n").unwrap();
defmt::error!("Ring buffer overrun!");
ring_buf.clear();
}
}
}
}
|
