Merge pull request #1699 from mvniekerk/main

RP2040: PIO UART example

1 files changed, 413 insertions, 0 deletions

diff --git a/examples/rp/src/bin/pio_uart.rs b/examples/rp/src/bin/pio_uart.rs
new file mode 100644
index 000000000..ca1c7f394
--- /dev/null
+++ b/examples/rp/src/bin/pio_uart.rs
@@ -0,0 +1,413 @@
+//! This example shows how to use the PIO module in the RP2040 chip to implement a duplex UART.
+//! The PIO module is a very powerful peripheral that can be used to implement many different
+//! protocols. It is a very flexible state machine that can be programmed to do almost anything.
+//!
+//! This example opens up a USB device that implements a CDC ACM serial port. It then uses the
+//! PIO module to implement a UART that is connected to the USB serial port. This allows you to
+//! communicate with a device connected to the RP2040 over USB serial.
+
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+#![feature(async_fn_in_trait)]
+
+use defmt::{info, panic, trace};
+use embassy_executor::Spawner;
+use embassy_futures::join::{join, join3};
+use embassy_rp::bind_interrupts;
+use embassy_rp::peripherals::{PIO0, USB};
+use embassy_rp::pio::InterruptHandler as PioInterruptHandler;
+use embassy_rp::usb::{Driver, Instance, InterruptHandler};
+use embassy_sync::blocking_mutex::raw::NoopRawMutex;
+use embassy_sync::pipe::Pipe;
+use embassy_usb::class::cdc_acm::{CdcAcmClass, Receiver, Sender, State};
+use embassy_usb::driver::EndpointError;
+use embassy_usb::{Builder, Config};
+use embedded_io::asynch::{Read, Write};
+use {defmt_rtt as _, panic_probe as _};
+
+use crate::uart::PioUart;
+use crate::uart_rx::PioUartRx;
+use crate::uart_tx::PioUartTx;
+
+bind_interrupts!(struct Irqs {
+    USBCTRL_IRQ => InterruptHandler<USB>;
+    PIO0_IRQ_0 => PioInterruptHandler<PIO0>;
+});
+
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    info!("Hello there!");
+
+    let p = embassy_rp::init(Default::default());
+
+    // Create the driver, from the HAL.
+    let driver = Driver::new(p.USB, Irqs);
+
+    // Create embassy-usb Config
+    let mut config = Config::new(0xc0de, 0xcafe);
+    config.manufacturer = Some("Embassy");
+    config.product = Some("PIO UART example");
+    config.serial_number = Some("12345678");
+    config.max_power = 100;
+    config.max_packet_size_0 = 64;
+
+    // Required for windows compatibility.
+    // https://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.9.1/kconfig/CONFIG_CDC_ACM_IAD.html#help
+    config.device_class = 0xEF;
+    config.device_sub_class = 0x02;
+    config.device_protocol = 0x01;
+    config.composite_with_iads = true;
+
+    // Create embassy-usb DeviceBuilder using the driver and config.
+    // It needs some buffers for building the descriptors.
+    let mut device_descriptor = [0; 256];
+    let mut config_descriptor = [0; 256];
+    let mut bos_descriptor = [0; 256];
+    let mut control_buf = [0; 64];
+
+    let mut state = State::new();
+
+    let mut builder = Builder::new(
+        driver,
+        config,
+        &mut device_descriptor,
+        &mut config_descriptor,
+        &mut bos_descriptor,
+        &mut control_buf,
+    );
+
+    // Create classes on the builder.
+    let class = CdcAcmClass::new(&mut builder, &mut state, 64);
+
+    // Build the builder.
+    let mut usb = builder.build();
+
+    // Run the USB device.
+    let usb_fut = usb.run();
+
+    // PIO UART setup
+    let uart = PioUart::new(9600, p.PIO0, p.PIN_4, p.PIN_5);
+    let (mut uart_tx, mut uart_rx) = uart.split();
+
+    // Pipe setup
+    let usb_pipe: Pipe<NoopRawMutex, 20> = Pipe::new();
+    let mut usb_pipe_writer = usb_pipe.writer();
+    let mut usb_pipe_reader = usb_pipe.reader();
+
+    let uart_pipe: Pipe<NoopRawMutex, 20> = Pipe::new();
+    let mut uart_pipe_writer = uart_pipe.writer();
+    let mut uart_pipe_reader = uart_pipe.reader();
+
+    let (mut usb_tx, mut usb_rx) = class.split();
+
+    // Read + write from USB
+    let usb_future = async {
+        loop {
+            info!("Wait for USB connection");
+            usb_rx.wait_connection().await;
+            info!("Connected");
+            let _ = join(
+                usb_read(&mut usb_rx, &mut uart_pipe_writer),
+                usb_write(&mut usb_tx, &mut usb_pipe_reader),
+            )
+            .await;
+            info!("Disconnected");
+        }
+    };
+
+    // Read + write from UART
+    let uart_future = join(
+        uart_read(&mut uart_rx, &mut usb_pipe_writer),
+        uart_write(&mut uart_tx, &mut uart_pipe_reader),
+    );
+
+    // Run everything concurrently.
+    // If we had made everything `'static` above instead, we could do this using separate tasks instead.
+    join3(usb_fut, usb_future, uart_future).await;
+}
+
+struct Disconnected {}
+
+impl From<EndpointError> for Disconnected {
+    fn from(val: EndpointError) -> Self {
+        match val {
+            EndpointError::BufferOverflow => panic!("Buffer overflow"),
+            EndpointError::Disabled => Disconnected {},
+        }
+    }
+}
+
+/// Read from the USB and write it to the UART TX pipe
+async fn usb_read<'d, T: Instance + 'd>(
+    usb_rx: &mut Receiver<'d, Driver<'d, T>>,
+    uart_pipe_writer: &mut embassy_sync::pipe::Writer<'_, NoopRawMutex, 20>,
+) -> Result<(), Disconnected> {
+    let mut buf = [0; 64];
+    loop {
+        let n = usb_rx.read_packet(&mut buf).await?;
+        let data = &buf[..n];
+        trace!("USB IN: {:x}", data);
+        uart_pipe_writer.write(data).await;
+    }
+}
+
+/// Read from the USB TX pipe and write it to the USB
+async fn usb_write<'d, T: Instance + 'd>(
+    usb_tx: &mut Sender<'d, Driver<'d, T>>,
+    usb_pipe_reader: &mut embassy_sync::pipe::Reader<'_, NoopRawMutex, 20>,
+) -> Result<(), Disconnected> {
+    let mut buf = [0; 64];
+    loop {
+        let n = usb_pipe_reader.read(&mut buf).await;
+        let data = &buf[..n];
+        trace!("USB OUT: {:x}", data);
+        usb_tx.write_packet(&data).await?;
+    }
+}
+
+/// Read from the UART and write it to the USB TX pipe
+async fn uart_read(
+    uart_rx: &mut PioUartRx<'_>,
+    usb_pipe_writer: &mut embassy_sync::pipe::Writer<'_, NoopRawMutex, 20>,
+) -> ! {
+    let mut buf = [0; 64];
+    loop {
+        let n = uart_rx.read(&mut buf).await.expect("UART read error");
+        if n == 0 {
+            continue;
+        }
+        let data = &buf[..n];
+        trace!("UART IN: {:x}", buf);
+        usb_pipe_writer.write(data).await;
+    }
+}
+
+/// Read from the UART TX pipe and write it to the UART
+async fn uart_write(
+    uart_tx: &mut PioUartTx<'_>,
+    uart_pipe_reader: &mut embassy_sync::pipe::Reader<'_, NoopRawMutex, 20>,
+) -> ! {
+    let mut buf = [0; 64];
+    loop {
+        let n = uart_pipe_reader.read(&mut buf).await;
+        let data = &buf[..n];
+        trace!("UART OUT: {:x}", data);
+        let _ = uart_tx.write(&data).await;
+    }
+}
+
+mod uart {
+    use embassy_rp::peripherals::PIO0;
+    use embassy_rp::pio::{Pio, PioPin};
+    use embassy_rp::Peripheral;
+
+    use crate::uart_rx::PioUartRx;
+    use crate::uart_tx::PioUartTx;
+    use crate::Irqs;
+
+    pub struct PioUart<'a> {
+        tx: PioUartTx<'a>,
+        rx: PioUartRx<'a>,
+    }
+
+    impl<'a> PioUart<'a> {
+        pub fn new(
+            baud: u64,
+            pio: impl Peripheral<P = PIO0> + 'a,
+            tx_pin: impl PioPin,
+            rx_pin: impl PioPin,
+        ) -> PioUart<'a> {
+            let Pio {
+                mut common, sm0, sm1, ..
+            } = Pio::new(pio, Irqs);
+
+            let (tx, origin) = PioUartTx::new(&mut common, sm0, tx_pin, baud, None);
+            let (rx, _) = PioUartRx::new(&mut common, sm1, rx_pin, baud, Some(origin));
+
+            PioUart { tx, rx }
+        }
+
+        pub fn split(self) -> (PioUartTx<'a>, PioUartRx<'a>) {
+            (self.tx, self.rx)
+        }
+    }
+}
+
+mod uart_tx {
+    use core::convert::Infallible;
+
+    use embassy_rp::gpio::Level;
+    use embassy_rp::peripherals::PIO0;
+    use embassy_rp::pio::{Common, Config, Direction, FifoJoin, PioPin, ShiftDirection, StateMachine};
+    use embassy_rp::relocate::RelocatedProgram;
+    use embedded_io::asynch::Write;
+    use embedded_io::Io;
+    use fixed::traits::ToFixed;
+    use fixed_macro::types::U56F8;
+
+    pub struct PioUartTx<'a> {
+        sm_tx: StateMachine<'a, PIO0, 0>,
+    }
+
+    impl<'a> PioUartTx<'a> {
+        pub fn new(
+            common: &mut Common<'a, PIO0>,
+            mut sm_tx: StateMachine<'a, PIO0, 0>,
+            tx_pin: impl PioPin,
+            baud: u64,
+            origin: Option<u8>,
+        ) -> (Self, u8) {
+            let mut prg = pio_proc::pio_asm!(
+                r#"
+                .side_set 1 opt
+
+                ; An 8n1 UART transmit program.
+                ; OUT pin 0 and side-set pin 0 are both mapped to UART TX pin.
+
+                    pull       side 1 [7]  ; Assert stop bit, or stall with line in idle state
+                    set x, 7   side 0 [7]  ; Preload bit counter, assert start bit for 8 clocks
+                bitloop:                   ; This loop will run 8 times (8n1 UART)
+                    out pins, 1            ; Shift 1 bit from OSR to the first OUT pin
+                    jmp x-- bitloop   [6]  ; Each loop iteration is 8 cycles.
+            "#
+            );
+            prg.program.origin = origin;
+            let tx_pin = common.make_pio_pin(tx_pin);
+            sm_tx.set_pins(Level::High, &[&tx_pin]);
+            sm_tx.set_pin_dirs(Direction::Out, &[&tx_pin]);
+
+            let relocated = RelocatedProgram::new(&prg.program);
+
+            let mut cfg = Config::default();
+
+            cfg.set_out_pins(&[&tx_pin]);
+            cfg.use_program(&common.load_program(&relocated), &[&tx_pin]);
+            cfg.shift_out.auto_fill = false;
+            cfg.shift_out.direction = ShiftDirection::Right;
+            cfg.fifo_join = FifoJoin::TxOnly;
+            cfg.clock_divider = (U56F8!(125_000_000) / (8 * baud)).to_fixed();
+            sm_tx.set_config(&cfg);
+            sm_tx.set_enable(true);
+
+            // The 4 state machines of the PIO each have their own program counter that starts taking
+            // instructions at an offset (origin) of the 32 instruction "space" the PIO device has.
+            // It is up to the programmer to sort out where to place these instructions.
+            // From the pio_asm! macro you get a ProgramWithDefines which has a field .program.origin
+            // which takes an Option<u8>.
+            //
+            // When you load more than one RelocatedProgram into the PIO,
+            // you load your first program at origin = 0.
+            // The RelocatedProgram has .code().count() which returns a usize,
+            // for which you can then use as your next program's origin.
+            let offset = relocated.code().count() as u8 + origin.unwrap_or_default();
+            (Self { sm_tx }, offset)
+        }
+
+        pub async fn write_u8(&mut self, data: u8) {
+            self.sm_tx.tx().wait_push(data as u32).await;
+        }
+    }
+
+    impl Io for PioUartTx<'_> {
+        type Error = Infallible;
+    }
+
+    impl Write for PioUartTx<'_> {
+        async fn write(&mut self, buf: &[u8]) -> Result<usize, Infallible> {
+            for byte in buf {
+                self.write_u8(*byte).await;
+            }
+            Ok(buf.len())
+        }
+    }
+}
+
+mod uart_rx {
+    use core::convert::Infallible;
+
+    use embassy_rp::gpio::Level;
+    use embassy_rp::peripherals::PIO0;
+    use embassy_rp::pio::{Common, Config, Direction, FifoJoin, PioPin, ShiftDirection, StateMachine};
+    use embassy_rp::relocate::RelocatedProgram;
+    use embedded_io::asynch::Read;
+    use embedded_io::Io;
+    use fixed::traits::ToFixed;
+    use fixed_macro::types::U56F8;
+
+    pub struct PioUartRx<'a> {
+        sm_rx: StateMachine<'a, PIO0, 1>,
+    }
+
+    impl<'a> PioUartRx<'a> {
+        pub fn new(
+            common: &mut Common<'a, PIO0>,
+            mut sm_rx: StateMachine<'a, PIO0, 1>,
+            rx_pin: impl PioPin,
+            baud: u64,
+            origin: Option<u8>,
+        ) -> (Self, u8) {
+            let mut prg = pio_proc::pio_asm!(
+                r#"
+                ; Slightly more fleshed-out 8n1 UART receiver which handles framing errors and
+                ; break conditions more gracefully.
+                ; IN pin 0 and JMP pin are both mapped to the GPIO used as UART RX.
+
+                start:
+                    wait 0 pin 0        ; Stall until start bit is asserted
+                    set x, 7    [10]    ; Preload bit counter, then delay until halfway through
+                rx_bitloop:                ; the first data bit (12 cycles incl wait, set).
+                    in pins, 1          ; Shift data bit into ISR
+                    jmp x-- rx_bitloop [6] ; Loop 8 times, each loop iteration is 8 cycles
+                    jmp pin good_rx_stop   ; Check stop bit (should be high)
+
+                    irq 4 rel           ; Either a framing error or a break. Set a sticky flag,
+                    wait 1 pin 0        ; and wait for line to return to idle state.
+                    jmp start           ; Don't push data if we didn't see good framing.
+
+                good_rx_stop:              ; No delay before returning to start; a little slack is
+                    push                ; important in case the TX clock is slightly too fast.
+            "#
+            );
+            prg.program.origin = origin;
+            let relocated = RelocatedProgram::new(&prg.program);
+            let mut cfg = Config::default();
+            cfg.use_program(&common.load_program(&relocated), &[]);
+
+            let rx_pin = common.make_pio_pin(rx_pin);
+            sm_rx.set_pins(Level::High, &[&rx_pin]);
+            cfg.set_in_pins(&[&rx_pin]);
+            cfg.set_jmp_pin(&rx_pin);
+            sm_rx.set_pin_dirs(Direction::In, &[&rx_pin]);
+
+            cfg.clock_divider = (U56F8!(125_000_000) / (8 * baud)).to_fixed();
+            cfg.shift_out.auto_fill = false;
+            cfg.shift_out.direction = ShiftDirection::Right;
+            cfg.fifo_join = FifoJoin::RxOnly;
+            sm_rx.set_config(&cfg);
+            sm_rx.set_enable(true);
+
+            let offset = relocated.code().count() as u8 + origin.unwrap_or_default();
+            (Self { sm_rx }, offset)
+        }
+
+        pub async fn read_u8(&mut self) -> u8 {
+            self.sm_rx.rx().wait_pull().await as u8
+        }
+    }
+
+    impl Io for PioUartRx<'_> {
+        type Error = Infallible;
+    }
+
+    impl Read for PioUartRx<'_> {
+        async fn read(&mut self, buf: &mut [u8]) -> Result<usize, Infallible> {
+            let mut i = 0;
+            while i < buf.len() {
+                buf[i] = self.read_u8().await;
+                i += 1;
+            }
+            Ok(i)
+        }
+    }
+}