Merge #934

934: (embassy-rp): Add Buffered UART implementation r=MathiasKoch a=MathiasKoch

### Questions & concerns: 
- ~~Would it make sense to add `RxBufferedUart` and `TxBufferedUart`, for cases where you would want to only buffer one way?~~
- ~~Do I need to be monitoring more interrupt flags than `Receive` & `Receive timeout`?~~

This PR adds working `BufferedUart` implementation, along with `RxBufferedUart` and `TxBufferedUart`. The implementation leaves room for improvement with respect to performance, as it still does not utilize DMA nor the internal UART buffers.

Co-authored-by: Mathias <[email protected]>
Co-authored-by: Dario Nieuwenhuis <[email protected]>

3 files changed, 46 insertions, 1 deletions

diff --git a/tests/rp/.cargo/config.toml b/tests/rp/.cargo/config.toml
index 0330025e4..9611db3a0 100644
--- a/tests/rp/.cargo/config.toml
+++ b/tests/rp/.cargo/config.toml
@@ -3,7 +3,7 @@ build-std = ["core"]
 build-std-features = ["panic_immediate_abort"]
 
 [target.'cfg(all(target_arch = "arm", target_os = "none"))']
-#runner = "teleprobe client run --target bluepill-stm32f103c8 --elf"
+#runner = "teleprobe client run --target rpi-pico --elf"
 runner = "teleprobe local run --chip RP2040 --elf"
 
 rustflags = [
diff --git a/tests/rp/Cargo.toml b/tests/rp/Cargo.toml
index 7e2717ddf..503373759 100644
--- a/tests/rp/Cargo.toml
+++ b/tests/rp/Cargo.toml
@@ -20,6 +20,7 @@ embedded-hal-1 = { package = "embedded-hal", version = "1.0.0-alpha.8" }
 embedded-hal-async = { version = "0.1.0-alpha.1" }
 panic-probe = { version = "0.3.0", features = ["print-defmt"] }
 futures = { version = "0.3.17", default-features = false, features = ["async-await"] }
+embedded-io = { version = "0.3.0", features = ["async"] }
 
 [profile.dev]
 debug = 2
diff --git a/tests/rp/src/bin/uart_buffered.rs b/tests/rp/src/bin/uart_buffered.rs
new file mode 100644
index 000000000..9cc20bb98
--- /dev/null
+++ b/tests/rp/src/bin/uart_buffered.rs
@@ -0,0 +1,44 @@
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+use defmt::{assert_eq, *};
+use embassy_executor::Spawner;
+use embassy_rp::interrupt;
+use embassy_rp::uart::{BufferedUart, Config, State, Uart};
+use embedded_io::asynch::{Read, Write};
+use {defmt_rtt as _, panic_probe as _};
+
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    let p = embassy_rp::init(Default::default());
+    info!("Hello World!");
+
+    let (tx, rx, uart) = (p.PIN_0, p.PIN_1, p.UART0);
+
+    let config = Config::default();
+    let uart = Uart::new_blocking(uart, tx, rx, config);
+
+    let irq = interrupt::take!(UART0_IRQ);
+    let tx_buf = &mut [0u8; 16];
+    let rx_buf = &mut [0u8; 16];
+    let mut state = State::new();
+    let mut uart = BufferedUart::new(&mut state, uart, irq, tx_buf, rx_buf);
+
+    // Make sure we send more bytes than fits in the FIFO, to test the actual
+    // bufferedUart.
+
+    let data = [
+        1_u8, 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,
+    ];
+    uart.write_all(&data).await.unwrap();
+    info!("Done writing");
+
+    let mut buf = [0; 32];
+    uart.read_exact(&mut buf).await.unwrap();
+    assert_eq!(buf, data);
+
+    info!("Test OK");
+    cortex_m::asm::bkpt();
+}