WIP

2025-07-21 23:12:16 -06:00
parent 2d31e62d82
commit beae5b2fd9
8 changed files with 526 additions and 60 deletions
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -12,6 +12,18 @@ dependencies = [
 "regex",
 ]

+[[package]]
+name = "ahash"
+version = "0.8.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5a15f179cd60c4584b8a8c596927aadc462e27f2ca70c04e0071964a73ba7a75"
+dependencies = [
+ "cfg-if",
+ "once_cell",
+ "version_check",
+ "zerocopy",
+]
+
 [[package]]
 name = "aho-corasick"
 version = "1.1.3"
@@ -126,6 +138,12 @@ version = "0.13.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "46afbd2983a5d5a7bd740ccb198caf5b82f45c40c09c0eed36052d91cb92e719"

+[[package]]
+name = "bitfield"
+version = "0.14.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2d7e60934ceec538daadb9d8432424ed043a904d8e0243f3c6446bce549a46ac"
+
 [[package]]
 name = "bitflags"
 version = "1.3.2"
@@ -215,7 +233,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8ec610d8f49840a5b376c69663b6369e71f4b34484b9b2eb29fb918d92516cb9"
 dependencies = [
 "bare-metal",
- "bitfield",
+ "bitfield 0.13.2",
 "embedded-hal 0.2.7",
 "volatile-register",
 ]
@@ -686,6 +704,21 @@ dependencies = [
 "heapless",
 ]

+[[package]]
+name = "embassy-usb"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6e651b9b7b47b514e6e6d1940a6e2e300891a2c33641917130643602a0cb6386"
+dependencies = [
+ "embassy-futures",
+ "embassy-net-driver-channel",
+ "embassy-sync 0.6.2",
+ "embassy-usb-driver",
+ "heapless",
+ "ssmarshal",
+ "usbd-hid",
+]
+
 [[package]]
 name = "embassy-usb-driver"
 version = "0.1.1"
@@ -822,6 +855,12 @@ dependencies = [
 "log",
 ]

+[[package]]
+name = "encode_unicode"
+version = "0.3.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a357d28ed41a50f9c765dbfe56cbc04a64e53e5fc58ba79fbc34c10ef3df831f"
+
 [[package]]
 name = "equivalent"
 version = "1.0.2"
@@ -996,6 +1035,15 @@ dependencies = [
 "byteorder",
 ]

+[[package]]
+name = "hashbrown"
+version = "0.13.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "43a3c133739dddd0d2990f9a4bdf8eb4b21ef50e4851ca85ab661199821d510e"
+dependencies = [
+ "ahash",
+]
+
 [[package]]
 name = "hashbrown"
 version = "0.15.4"
@@ -1031,7 +1079,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "fe4cd85333e22411419a0bcae1297d25e58c9443848b11dc6a86fefe8c78a661"
 dependencies = [
 "equivalent",
- "hashbrown",
+ "hashbrown 0.15.4",
 ]

 [[package]]
@@ -1370,12 +1418,14 @@ dependencies = [
 "embassy-rp 0.4.0",
 "embassy-sync 0.7.0",
 "embassy-time",
+ "embassy-usb",
 "embedded-graphics",
 "embedded-hal 0.2.7",
 "embedded-hal-async",
 "embedded-hal-bus",
 "embedded-sdmmc",
 "heapless",
+ "num_enum 0.7.4",
 "panic-probe",
 "portable-atomic",
 "spin",
@@ -1710,6 +1760,26 @@ version = "0.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "388a1df253eca08550bef6c72392cfe7c30914bf41df5269b68cbd6ff8f570a3"

+[[package]]
+name = "serde"
+version = "1.0.219"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5f0e2c6ed6606019b4e29e69dbaba95b11854410e5347d525002456dbbb786b6"
+dependencies = [
+ "serde_derive",
+]
+
+[[package]]
+name = "serde_derive"
+version = "1.0.219"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5b0276cf7f2c73365f7157c8123c21cd9a50fbbd844757af28ca1f5925fc2a00"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.104",
+]
+
 [[package]]
 name = "sha2-const-stable"
 version = "0.1.0"
@@ -1765,6 +1835,16 @@ dependencies = [
 "lock_api",
 ]

+[[package]]
+name = "ssmarshal"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f3e6ad23b128192ed337dfa4f1b8099ced0c2bf30d61e551b65fda5916dbb850"
+dependencies = [
+ "encode_unicode",
+ "serde",
+]
+
 [[package]]
 name = "st7365p-lcd"
 version = "0.11.0"
@@ -1983,6 +2063,53 @@ version = "0.2.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ebc1c04c71510c7f702b52b7c350734c9ff1295c464a03335b00bb84fc54f853"

+[[package]]
+name = "usb-device"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "98816b1accafbb09085168b90f27e93d790b4bfa19d883466b5e53315b5f06a6"
+dependencies = [
+ "heapless",
+ "portable-atomic",
+]
+
+[[package]]
+name = "usbd-hid"
+version = "0.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e6f291ab53d428685cc780f08a2eb9d5d6ff58622db2b36e239a4f715f1e184c"
+dependencies = [
+ "serde",
+ "ssmarshal",
+ "usb-device",
+ "usbd-hid-macros",
+]
+
+[[package]]
+name = "usbd-hid-descriptors"
+version = "0.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0eee54712c5d778d2fb2da43b1ce5a7b5060886ef7b09891baeb4bf36910a3ed"
+dependencies = [
+ "bitfield 0.14.0",
+]
+
+[[package]]
+name = "usbd-hid-macros"
+version = "0.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bb573c76e7884035ac5e1ab4a81234c187a82b6100140af0ab45757650ccda38"
+dependencies = [
+ "byteorder",
+ "hashbrown 0.13.2",
+ "log",
+ "proc-macro2",
+ "quote",
+ "serde",
+ "syn 1.0.109",
+ "usbd-hid-descriptors",
+]
+
 [[package]]
 name = "uuid"
 version = "1.17.0"
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -45,8 +45,9 @@ embassy-rp = { version = "0.4.0", features = [
 ] }
 embassy-futures = "0.1.1"
 embassy-time = "0.4.0"
-embassy-embedded-hal = "0.3.0"
-embassy-sync = { version = "0.7" }
+embassy-embedded-hal = "0.3.1"
+embassy-sync = "0.7"
+embassy-usb = "0.4.0"
 trouble-host = { version = "0.1", features = [
  "derive",
  "scan",
@@ -78,3 +79,4 @@ bitflags = "2.9.1"
 talc = "4.4.3"
 spin = "0.10.0"
 heapless = "0.8.0"
+num_enum = { version = "0.7.4", default-features = false }
--- a/src/display.rs
+++ b/src/display.rs
@@ -21,8 +21,6 @@ use embedded_hal_bus::spi::ExclusiveDevice;
 use portable_atomic::AtomicBool;
 use st7365p_lcd::{FrameBuffer, ST7365P};

-use crate::LAST_TEXT_RECT;
-
 const SCREEN_WIDTH: usize = 320;
 const SCREEN_HEIGHT: usize = 320;

@@ -58,24 +56,7 @@ pub async fn display_handler(
    loop {
        DISPLAY_SIGNAL.wait().await;

-        let text_string = crate::STRING.lock().await.clone();
-
-        let text = Text::with_alignment(
-            &text_string,
-            Point::new(160, 160),
-            MonoTextStyle::new(&FONT_10X20, Rgb565::RED),
-            Alignment::Center,
-        );
-
-        {
-            let rect = LAST_TEXT_RECT.lock().await;
-            if let Some(rect) = *rect.borrow() {
-                framebuffer.fill_solid(&rect, Rgb565::BLACK).unwrap();
-            }
-            *rect.borrow_mut() = Some(text.bounding_box());
-        }
-
-        text.draw(&mut framebuffer).unwrap();
+        // text.draw(&mut framebuffer).unwrap();

        let start = Instant::now();
        framebuffer
--- a/src/main.rs
+++ b/src/main.rs
@@ -6,6 +6,8 @@
 use crate::{
    display::DISPLAY_SIGNAL,
    peripherals::keyboard::{KeyCode, KeyState, read_keyboard_fifo},
+    storage::SdCard,
+    usb::usb_handler,
 };

 use {defmt_rtt as _, panic_probe as _};
@@ -13,70 +15,74 @@ use {defmt_rtt as _, panic_probe as _};
 use core::cell::RefCell;
 use embassy_executor::Spawner;
 use embassy_futures::join::join;
-use embassy_rp::peripherals::I2C1;
+use embassy_rp::{
+    gpio::{Input, Level, Output, Pull},
+    peripherals::{I2C1, USB},
+    spi::Spi,
+    usb as embassy_rp_usb,
+};
 use embassy_rp::{i2c, i2c::I2c, spi};
 use embassy_sync::blocking_mutex::raw::ThreadModeRawMutex;
 use embassy_sync::mutex::Mutex;
-use embassy_time::Timer;
+use embassy_time::{Delay, Timer};
 use embedded_graphics::primitives::Rectangle;
+use embedded_hal_bus::spi::ExclusiveDevice;
+use embedded_sdmmc::asynchronous::SdCard as SdmmcSdCard;
 use heapless::String;

 mod peripherals;
 use peripherals::conf_peripherals;
 mod display;
 use display::display_handler;
+mod scsi;
+mod storage;
+mod usb;

 embassy_rp::bind_interrupts!(struct Irqs {
    I2C1_IRQ => i2c::InterruptHandler<I2C1>;
+    USBCTRL_IRQ => embassy_rp_usb::InterruptHandler<USB>;
 });

-static STRING: Mutex<ThreadModeRawMutex, String<25>> = Mutex::new(String::new());
-static LAST_TEXT_RECT: Mutex<ThreadModeRawMutex, RefCell<Option<Rectangle>>> =
-    Mutex::new(RefCell::new(None));
-
 #[embassy_executor::main]
 async fn main(_spawner: Spawner) {
    let p = embassy_rp::init(Default::default());

-    STRING.lock().await.push_str("Press Del").unwrap();
-
-    // configure keyboard event handler
+    // MCU i2c bus for peripherals
    let mut config = i2c::Config::default();
    config.frequency = 400_000;
    let i2c1 = I2c::new_async(p.I2C1, p.PIN_7, p.PIN_6, Irqs, config);
    conf_peripherals(i2c1).await;

+    // SPI1 bus display
    let mut config = spi::Config::default();
    config.frequency = 16_000_000;
    let spi1 = spi::Spi::new(
        p.SPI1, p.PIN_10, p.PIN_11, p.PIN_12, p.DMA_CH0, p.DMA_CH1, config,
    );

-    join(
-        async {
-            loop {
-                Timer::after_millis(20).await;
-                if let Some(key) = read_keyboard_fifo().await
-                    && key.state == KeyState::Pressed
-                {
-                    let mut string = STRING.lock().await;
-                    match key.key {
-                        KeyCode::Backspace => {
-                            string.pop().unwrap();
-                        }
-                        KeyCode::Del => {
-                            string.clear();
-                        }
-                        KeyCode::Char(c) => {
-                            string.push(c).unwrap();
-                        }
-                        _ => (),
-                    }
-                    DISPLAY_SIGNAL.signal(());
-                }
-            }
-        },
-        display_handler(spi1, p.PIN_13, p.PIN_14, p.PIN_15),
-    )
-    .await;
+    let usb = embassy_rp_usb::Driver::new(p.USB, Irqs);
+
+    let sdcard = {
+        let mut config = spi::Config::default();
+        config.frequency = 400_000;
+        let spi = Spi::new(
+            p.SPI0,
+            p.PIN_18,
+            p.PIN_19,
+            p.PIN_16,
+            p.DMA_CH2,
+            p.DMA_CH3,
+            config.clone(),
+        );
+        let cs = Output::new(p.PIN_5, Level::High);
+
+        let device = ExclusiveDevice::new(spi, cs, Delay).unwrap();
+        let sdcard = SdmmcSdCard::new(device, Delay);
+
+        config.frequency = 32_000_000;
+        sdcard.spi(|dev| dev.bus_mut().set_config(&config));
+        SdCard::new(sdcard, Input::new(p.PIN_22, Pull::None))
+    };
+
+    usb_handler(usb, sdcard).await;
 }
--- a/src/scsi/mod.rs
+++ b/src/scsi/mod.rs
@@ -0,0 +1,107 @@
+use embassy_usb::driver::{Driver, EndpointIn, EndpointOut};
+use embassy_usb::types::StringIndex;
+use embassy_usb::{Builder, Config};
+
+mod scsi_types;
+use scsi_types::*;
+
+use crate::storage::SdCard;
+
+pub struct MassStorageClass<'d, 'c, D: Driver<'d>> {
+    sdcard: SdCard<'c>,
+    bulk_out: D::EndpointOut,
+    bulk_in: D::EndpointIn,
+}
+
+impl<'d, 'c, D: Driver<'d>> MassStorageClass<'d, 'c, D> {
+    pub fn new(builder: &mut Builder<'d, D>, sdcard: SdCard<'c>) -> Self {
+        let mut function = builder.function(0x08, 0x06, 0x50); // Mass Storage class
+        let mut interface = function.interface();
+        let mut alt = interface.alt_setting(0x08, 0x06, 0x50, None);
+
+        let bulk_out = alt.endpoint_bulk_out(64);
+        let bulk_in = alt.endpoint_bulk_in(64);
+
+        Self {
+            bulk_out,
+            bulk_in,
+            sdcard,
+        }
+    }
+
+    pub async fn poll(&mut self) {
+        let mut cbw_buf = [0u8; 31];
+        if let Ok(n) = self.bulk_out.read(&mut cbw_buf).await {
+            if let Some(cbw) = CommandBlockWrapper::parse(&cbw_buf[..n]) {
+                self.handle_command(&cbw.CBWCB).await;
+            }
+        }
+    }
+
+    async fn handle_command(&self, cbw: &[u8]) {
+        match parse_cb(cbw) {
+            ScsiCommand::Unknown => {
+                #[cfg(feature = "defmt")]
+                defmt::info!("Got unexpected scsi command: {}", cbw);
+            }
+            ScsiCommand::Inquiry {
+                evpd,
+                page_code,
+                alloc_len,
+            } => todo!(),
+            ScsiCommand::TestUnitReady => todo!(),
+            ScsiCommand::RequestSense { desc, alloc_len } => todo!(),
+            ScsiCommand::ModeSense6 {
+                dbd,
+                page_control,
+                page_code,
+                subpage_code,
+                alloc_len,
+            } => todo!(),
+            ScsiCommand::ModeSense10 {
+                dbd,
+                page_control,
+                page_code,
+                subpage_code,
+                alloc_len,
+            } => todo!(),
+            ScsiCommand::ReadCapacity10 => todo!(),
+            ScsiCommand::ReadCapacity16 { alloc_len } => todo!(),
+            ScsiCommand::Read { lba, len } => todo!(),
+            ScsiCommand::Write { lba, len } => todo!(),
+            ScsiCommand::ReadFormatCapacities { alloc_len } => todo!(),
+        }
+    }
+}
+
+#[repr(C, packed)]
+struct CommandBlockWrapper {
+    dCBWSignature: u32,
+    dCBWTag: u32,
+    dCBWDataTransferLength: u32,
+    bmCBWFlags: u8,
+    bCBWLUN: u8,
+    bCBWCBLength: u8,
+    CBWCB: [u8; 16],
+}
+
+impl CommandBlockWrapper {
+    fn parse(buf: &[u8]) -> Option<Self> {
+        if buf.len() < 31 {
+            return None;
+        }
+        let dCBWSignature = u32::from_le_bytes(buf[0..4].try_into().unwrap());
+        if dCBWSignature != 0x43425355 {
+            return None; // invalid signature
+        }
+        Some(Self {
+            dCBWSignature,
+            dCBWTag: u32::from_le_bytes(buf[4..8].try_into().unwrap()),
+            dCBWDataTransferLength: u32::from_le_bytes(buf[8..12].try_into().unwrap()),
+            bmCBWFlags: buf[12],
+            bCBWLUN: buf[13],
+            bCBWCBLength: buf[14],
+            CBWCB: buf[15..31].try_into().unwrap(),
+        })
+    }
+}
--- a/src/scsi/scsi_types.rs
+++ b/src/scsi/scsi_types.rs
@@ -0,0 +1,140 @@
+use num_enum::TryFromPrimitive;
+
+/// THE CODE BELOW ORIGINATES FROM: https://github.com/apohrebniak/usbd-storage/blob/master/usbd-storage/src/subclass/scsi.rs
+
+/// SCSI device subclass code
+pub const SUBCLASS_SCSI: u8 = 0x06; // SCSI Transparent command set
+
+/* SCSI codes */
+
+/* SPC */
+const TEST_UNIT_READY: u8 = 0x00;
+const REQUEST_SENSE: u8 = 0x03;
+const INQUIRY: u8 = 0x12;
+const MODE_SENSE_6: u8 = 0x1A;
+const MODE_SENSE_10: u8 = 0x5A;
+
+/* SBC */
+const READ_10: u8 = 0x28;
+const READ_16: u8 = 0x88;
+const READ_CAPACITY_10: u8 = 0x25;
+const READ_CAPACITY_16: u8 = 0x9E;
+const WRITE_10: u8 = 0x2A;
+
+/* MMC */
+const READ_FORMAT_CAPACITIES: u8 = 0x23;
+
+/// SCSI command
+///
+/// Refer to specifications (SPC,SAM,SBC,MMC,etc.)
+#[derive(Copy, Clone, Debug)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[non_exhaustive]
+pub enum ScsiCommand {
+    Unknown,
+
+    /* SPC */
+    Inquiry {
+        evpd: bool,
+        page_code: u8,
+        alloc_len: u16,
+    },
+    TestUnitReady,
+    RequestSense {
+        desc: bool,
+        alloc_len: u8,
+    },
+    ModeSense6 {
+        dbd: bool,
+        page_control: PageControl,
+        page_code: u8,
+        subpage_code: u8,
+        alloc_len: u8,
+    },
+    ModeSense10 {
+        dbd: bool,
+        page_control: PageControl,
+        page_code: u8,
+        subpage_code: u8,
+        alloc_len: u16,
+    },
+
+    /* SBC */
+    ReadCapacity10,
+    ReadCapacity16 {
+        alloc_len: u32,
+    },
+    Read {
+        lba: u64,
+        len: u64,
+    },
+    Write {
+        lba: u64,
+        len: u64,
+    },
+
+    /* MMC */
+    ReadFormatCapacities {
+        alloc_len: u16,
+    },
+}
+
+#[repr(u8)]
+#[derive(Copy, Clone, Debug, TryFromPrimitive)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub enum PageControl {
+    CurrentValues = 0b00,
+    ChangeableValues = 0b01,
+    DefaultValues = 0b10,
+    SavedValues = 0b11,
+}
+
+#[allow(dead_code)]
+pub fn parse_cb(cb: &[u8]) -> ScsiCommand {
+    match cb[0] {
+        TEST_UNIT_READY => ScsiCommand::TestUnitReady,
+        INQUIRY => ScsiCommand::Inquiry {
+            evpd: (cb[1] & 0b00000001) != 0,
+            page_code: cb[2],
+            alloc_len: u16::from_be_bytes([cb[3], cb[4]]),
+        },
+        REQUEST_SENSE => ScsiCommand::RequestSense {
+            desc: (cb[1] & 0b00000001) != 0,
+            alloc_len: cb[4],
+        },
+        READ_CAPACITY_10 => ScsiCommand::ReadCapacity10,
+        READ_CAPACITY_16 => ScsiCommand::ReadCapacity16 {
+            alloc_len: u32::from_be_bytes([cb[10], cb[11], cb[12], cb[13]]),
+        },
+        READ_10 => ScsiCommand::Read {
+            lba: u32::from_be_bytes([cb[2], cb[3], cb[4], cb[5]]) as u64,
+            len: u16::from_be_bytes([cb[7], cb[8]]) as u64,
+        },
+        READ_16 => ScsiCommand::Read {
+            lba: u64::from_be_bytes((&cb[2..10]).try_into().unwrap()),
+            len: u32::from_be_bytes((&cb[10..14]).try_into().unwrap()) as u64,
+        },
+        WRITE_10 => ScsiCommand::Write {
+            lba: u32::from_be_bytes([cb[2], cb[3], cb[4], cb[5]]) as u64,
+            len: u16::from_be_bytes([cb[7], cb[8]]) as u64,
+        },
+        MODE_SENSE_6 => ScsiCommand::ModeSense6 {
+            dbd: (cb[1] & 0b00001000) != 0,
+            page_control: PageControl::try_from_primitive(cb[2] >> 6).unwrap(),
+            page_code: cb[2] & 0b00111111,
+            subpage_code: cb[3],
+            alloc_len: cb[4],
+        },
+        MODE_SENSE_10 => ScsiCommand::ModeSense10 {
+            dbd: (cb[1] & 0b00001000) != 0,
+            page_control: PageControl::try_from_primitive(cb[2] >> 6).unwrap(),
+            page_code: cb[2] & 0b00111111,
+            subpage_code: cb[3],
+            alloc_len: u16::from_be_bytes([cb[7], cb[8]]),
+        },
+        READ_FORMAT_CAPACITIES => ScsiCommand::ReadFormatCapacities {
+            alloc_len: u16::from_be_bytes([cb[7], cb[8]]),
+        },
+        _ => ScsiCommand::Unknown,
+    }
+}
--- a/src/storage.rs
+++ b/src/storage.rs
@@ -0,0 +1,66 @@
+use embassy_rp::gpio::{Input, Output};
+use embassy_rp::peripherals::SPI0;
+use embassy_rp::spi::{Async, Spi};
+use embedded_hal_bus::spi::ExclusiveDevice;
+use embedded_sdmmc;
+use embedded_sdmmc::asynchronous::{
+    Directory, SdCard as SdmmcSdCard, Volume, VolumeIdx, VolumeManager,
+};
+use embedded_sdmmc::blocking::{TimeSource, Timestamp};
+
+pub const MAX_DIRS: usize = 4;
+pub const MAX_FILES: usize = 5;
+pub const MAX_VOLUMES: usize = 1;
+
+type Device = ExclusiveDevice<Spi<'static, SPI0, Async>, Output<'static>, embassy_time::Delay>;
+type SD = SdmmcSdCard<Device, embassy_time::Delay>;
+type VolMgr = VolumeManager<SD, DummyTimeSource, MAX_DIRS, MAX_FILES, MAX_VOLUMES>;
+type Vol<'a> = Volume<'a, SD, DummyTimeSource, MAX_DIRS, MAX_FILES, MAX_VOLUMES>;
+type Dir<'a> = Directory<'a, SD, DummyTimeSource, MAX_DIRS, MAX_FILES, MAX_VOLUMES>;
+
+pub struct DummyTimeSource {}
+impl TimeSource for DummyTimeSource {
+    fn get_timestamp(&self) -> Timestamp {
+        Timestamp::from_calendar(2022, 1, 1, 0, 0, 0).unwrap()
+    }
+}
+
+pub struct SdCard<'a> {
+    det: Input<'static>,
+    volume_mgr: VolMgr,
+    volume: Option<Vol<'a>>,
+    root: Option<Dir<'a>>,
+}
+
+impl<'a> SdCard<'a> {
+    pub fn new(sdcard: SD, det: Input<'static>) -> Self {
+        let volume_mgr = VolumeManager::<_, _, MAX_DIRS, MAX_FILES, MAX_VOLUMES>::new_with_limits(
+            sdcard,
+            DummyTimeSource {},
+            5000,
+        );
+        Self {
+            det: det,
+            volume_mgr,
+            volume: None,
+            root: None,
+        }
+    }
+
+    /// Returns true if an SD card is inserted.
+    /// The DET pin is active-low via mechanical switch in the socket.
+    fn attached(&self) -> bool {
+        self.det.is_low()
+    }
+
+    async fn get_root(&'a mut self) {
+        let vol = self.volume.as_mut().unwrap();
+        let root = vol.open_root_dir().unwrap();
+        self.root = Some(root);
+    }
+
+    async fn get_volume(&'a mut self) {
+        let vol = self.volume_mgr.open_volume(VolumeIdx(0)).await.unwrap();
+        self.volume = Some(vol);
+    }
+}
--- a/src/usb.rs
+++ b/src/usb.rs
@@ -0,0 +1,37 @@
+use crate::{scsi::MassStorageClass, storage::SdCard};
+use embassy_futures::join::{self, join};
+use embassy_rp::{
+    gpio::Output,
+    peripherals::{SPI0, USB},
+    spi::{Async, Spi},
+    usb::Driver,
+};
+use embassy_time::Delay;
+use embassy_usb::{Builder, Config};
+
+pub async fn usb_handler(driver: Driver<'static, USB>, mut sdcard: SdCard<'_>) {
+    let mut config = Config::new(0xc0de, 0xcafe);
+    config.manufacturer = Some("LegitCamper");
+    config.product = Some("PicoCalc");
+    config.serial_number = Some("01001100");
+    config.max_power = 100;
+    config.max_packet_size_0 = 64;
+
+    let mut config_descriptor = [0; 256];
+    let mut bos_descriptor = [0; 64];
+    let mut control_buf = [0; 64];
+
+    let mut builder = Builder::new(
+        driver,
+        config,
+        &mut config_descriptor,
+        &mut bos_descriptor,
+        &mut [],
+        &mut control_buf,
+    );
+
+    let mut scsi = MassStorageClass::new(&mut builder, sdcard);
+    let mut usb = builder.build();
+
+    join(usb.run(), scsi.poll()).await;
+}