//! # Pico USB Serial Example
//!
//! Creates a USB Serial device on a Pico board, with the USB driver running in
//! the main thread.
//!
//! This will create a USB Serial device echoing anything it receives. Incoming
//! ASCII characters are converted to upercase, so you can tell it is working
//! and not just local-echo!
//!
//! See the `Cargo.toml` file for Copyright and license details.

#![no_std]
#![no_main]

// The macro for our start-up function
use cortex_m_rt::entry;

// Ensure we halt the program on panic (if we don't mention this crate it won't
// be linked)
use panic_halt as _;

// A shorter alias for the Peripheral Access Crate, which provides low-level
// register access
use rp_pico::hal::pac;

// A shorter alias for the Hardware Abstraction Layer, which provides
// higher-level drivers.
use rp_pico::hal;

// USB Device support
use usb_device::{class_prelude::*, prelude::*};

// USB Communications Class Device support
use usbd_serial::SerialPort;

/// Entry point to our bare-metal application.
///
/// The `#[entry]` macro ensures the Cortex-M start-up code calls this function
/// as soon as all global variables are initialised.
///
/// The function configures the RP2040 peripherals, then echoes any characters
/// received over USB Serial.
#[entry]
fn main() -> ! {
    // Grab our singleton objects
    let mut pac = pac::Peripherals::take().unwrap();

    // Set up the watchdog driver - needed by the clock setup code
    let mut watchdog = hal::Watchdog::new(pac.WATCHDOG);

    // Configure the clocks
    //
    // The default is to generate a 125 MHz system clock
    let clocks = hal::clocks::init_clocks_and_plls(
        rp_pico::XOSC_CRYSTAL_FREQ,
        pac.XOSC,
        pac.CLOCKS,
        pac.PLL_SYS,
        pac.PLL_USB,
        &mut pac.RESETS,
        &mut watchdog,
    )
    .ok()
    .unwrap();

    // Set up the USB driver
    let usb_bus = UsbBusAllocator::new(hal::usb::UsbBus::new(
        pac.USBCTRL_REGS,
        pac.USBCTRL_DPRAM,
        clocks.usb_clock,
        true,
        &mut pac.RESETS,
    ));

    // Set up the USB Communications Class Device driver
    let mut serial = SerialPort::new(&usb_bus);

    // Create a USB device with a fake VID and PID
    let mut usb_dev = UsbDeviceBuilder::new(&usb_bus, UsbVidPid(0x16c0, 0x27dd))
        .manufacturer("Fake company")
        .product("Serial port")
        .serial_number("TEST")
        .device_class(2) // from: https://www.usb.org/defined-class-codes
        .build();

    let timer = hal::Timer::new(pac.TIMER, &mut pac.RESETS);
    let mut said_hello = false;
    loop {
        // A welcome message at the beginning
        if !said_hello && timer.get_counter() >= 2_000_000 {
            said_hello = true;
            let _ = serial.write(b"Hello, World!\r\n");
        }

        // Check for new data
        if usb_dev.poll(&mut [&mut serial]) {
            let mut buf = [0u8; 64];
            match serial.read(&mut buf) {
                Err(_e) => {
                    // Do nothing
                }
                Ok(0) => {
                    // Do nothing
                }
                Ok(count) => {
                    // Convert to upper case
                    buf.iter_mut().take(count).for_each(|b| {
                        b.make_ascii_uppercase();
                    });
                    // Send back to the host
                    let mut wr_ptr = &buf[..count];
                    while !wr_ptr.is_empty() {
                        match serial.write(wr_ptr) {
                            Ok(len) => wr_ptr = &wr_ptr[len..],
                            // On error, just drop unwritten data.
                            // One possible error is Err(WouldBlock), meaning the USB
                            // write buffer is full.
                            Err(_) => break,
                        };
                    }
                }
            }
        }
    }
}

// End of file