From 0cc461488899f71b5d98faf10cfac040a3c30416 Mon Sep 17 00:00:00 2001
From: 9names <60134748+9names@users.noreply.github.com>
Date: Thu, 9 Sep 2021 23:03:12 +1000
Subject: [PATCH] Add interrupt-driven USB example

---
 .../examples/pico_usb_serial_interrupt.rs     | 178 ++++++++++++++++++
 1 file changed, 178 insertions(+)
 create mode 100644 boards/pico/examples/pico_usb_serial_interrupt.rs

diff --git a/boards/pico/examples/pico_usb_serial_interrupt.rs b/boards/pico/examples/pico_usb_serial_interrupt.rs
new file mode 100644
index 0000000..e43d708
--- /dev/null
+++ b/boards/pico/examples/pico_usb_serial_interrupt.rs
@@ -0,0 +1,178 @@
+//! Creates a USB Serial device on a Pico board, with the USB driver running in the USB interrupt
+//!
+//! This will create a USB Serial device echoing anything it receives converting to caps the ASCII
+//! alphabetical caracters.
+#![no_std]
+#![no_main]
+
+use crate::pac::interrupt;
+use cortex_m_rt::entry;
+use panic_halt as _;
+use pico::{
+    hal::{
+        self,
+        clocks::{init_clocks_and_plls, Clock},
+        pac,
+        sio::Sio,
+        usb::UsbBus,
+        watchdog::Watchdog,
+    },
+    XOSC_CRYSTAL_FREQ,
+};
+use usb_device::{class_prelude::*, prelude::*};
+use usbd_serial::SerialPort;
+
+#[link_section = ".boot2"]
+#[used]
+pub static BOOT2: [u8; 256] = rp2040_boot2::BOOT_LOADER;
+
+// Static data so that it can be accessed in both main and interrupt context
+static mut USB_DEVICE: Option<UsbDevice<UsbBus>> = None;
+static mut USB_BUS: Option<UsbBusAllocator<UsbBus>> = None;
+static mut USB_SERIAL: Option<SerialPort<UsbBus>> = None;
+static mut SAID_HELLO: bool = false;
+
+// Blinky-related imports, not needed for USB
+use embedded_hal::digital::v2::OutputPin;
+use embedded_time::rate::*;
+use pico::Pins;
+
+#[entry]
+fn main() -> ! {
+    let mut pac = pac::Peripherals::take().unwrap();
+    let mut watchdog = Watchdog::new(pac.WATCHDOG);
+
+    let clocks = init_clocks_and_plls(
+        XOSC_CRYSTAL_FREQ,
+        pac.XOSC,
+        pac.CLOCKS,
+        pac.PLL_SYS,
+        pac.PLL_USB,
+        &mut pac.RESETS,
+        &mut watchdog,
+    )
+    .ok()
+    .unwrap();
+
+    let usb_bus = UsbBusAllocator::new(UsbBus::new(
+        pac.USBCTRL_REGS,
+        pac.USBCTRL_DPRAM,
+        clocks.usb_clock,
+        true,
+        &mut pac.RESETS,
+    ));
+    unsafe {
+        USB_BUS = Some(usb_bus);
+    }
+
+    let serial = SerialPort::new(unsafe { USB_BUS.as_ref().unwrap() });
+    unsafe {
+        USB_SERIAL = Some(serial);
+    }
+
+    let usb_dev = UsbDeviceBuilder::new(
+        unsafe { USB_BUS.as_ref().unwrap() },
+        UsbVidPid(0x16c0, 0x27dd),
+    )
+    .manufacturer("Fake company")
+    .product("Serial port")
+    .serial_number("TEST")
+    .max_packet_size_0(64)
+    .device_class(2) // from: https://www.usb.org/defined-class-codes
+    .build();
+    unsafe {
+        USB_DEVICE = Some(usb_dev);
+    }
+
+    // The USB driver doesn't enable key interrupts yet, so manually do that here
+    unsafe {
+        let p = pac::Peripherals::steal();
+        // Enable interrupts for when a buffer is done, when the bus is reset,
+        // and when a setup packet is received
+        p.USBCTRL_REGS.inte.modify(|_, w| {
+            w.buff_status()
+                .set_bit()
+                .bus_reset()
+                .set_bit()
+                .setup_req()
+                .set_bit()
+        });
+    }
+    // Enable the USB interrupt
+    unsafe {
+        pac::NVIC::unmask(hal::pac::Interrupt::USBCTRL_IRQ);
+    };
+
+    // No more USB code after this point in main!
+    // We can do anything we want in here since USB is handled
+    // in the interrupt - let's blink an LED.
+    let core = pac::CorePeripherals::take().unwrap();
+    let mut delay = cortex_m::delay::Delay::new(core.SYST, clocks.system_clock.freq().integer());
+
+    let sio = Sio::new(pac.SIO);
+    let pins = Pins::new(
+        pac.IO_BANK0,
+        pac.PADS_BANK0,
+        sio.gpio_bank0,
+        &mut pac.RESETS,
+    );
+    let mut led_pin = pins.led.into_push_pull_output();
+    loop {
+        led_pin.set_high().unwrap();
+        delay.delay_ms(500);
+        led_pin.set_low().unwrap();
+        delay.delay_ms(500);
+    }
+}
+
+#[allow(non_snake_case)]
+#[interrupt]
+unsafe fn USBCTRL_IRQ() {
+    let mut buf = [0u8; 64];
+    let usb_dev = USB_DEVICE.as_mut().unwrap();
+    let serial = USB_SERIAL.as_mut().unwrap();
+
+    if !SAID_HELLO {
+        SAID_HELLO = true;
+        let _ = serial.write(b"HelloWorld!\r\n");
+    }
+
+    if usb_dev.poll(&mut [serial]) {
+        let _ = serial.read(&mut buf).map(|count| {
+            if count == 0 {
+                return;
+            }
+
+            // Echo back in upper case
+            buf.iter_mut().take(count).for_each(|c| {
+                if let 0x61..=0x7a = *c {
+                    *c &= !0x20;
+                }
+            });
+
+            let mut wr_ptr = &buf[..count];
+            while !wr_ptr.is_empty() {
+                let _ = serial.write(wr_ptr).map(|len| {
+                    wr_ptr = &wr_ptr[len..];
+                });
+            }
+        });
+    }
+
+    // Clear pending interrupt flags here.
+    // We could also move some of our code into these states to handle events
+    let p = pac::Peripherals::steal();
+    let status = &p.USBCTRL_REGS.sie_status;
+    if status.read().ack_rec().bit_is_set() {
+        status.modify(|_r, w| w.ack_rec().set_bit());
+    }
+    if status.read().setup_rec().bit_is_set() {
+        status.modify(|_r, w| w.setup_rec().set_bit());
+    }
+    if status.read().trans_complete().bit_is_set() {
+        status.modify(|_r, w| w.trans_complete().set_bit());
+    }
+    if status.read().bus_reset().bit_is_set() {
+        status.modify(|_r, w| w.bus_reset().set_bit());
+    }
+}