Rework fast blinking after reset

It doesn't work with windows. It seems that the USB device goes into low
power state and then the serial number string descriptor cannot be read.

src/main.rs

@@ -16,6 +16,7 @@ use usbd_storage::subclass::Command;
 use usbd_storage::transport::bbb::{BulkOnly, BulkOnlyError};
 use usbd_storage::transport::TransportError;
 
+
 #[link_section = ".start_block"]
 #[used]
 pub static IMAGE_DEF: hal::block::ImageDef = hal::block::ImageDef::secure_exe();
@@ -95,20 +96,7 @@ fn main() -> ! {
         &mut pac.RESETS,
     );
 
-    let mut led_pin = pins.gpio25.into_push_pull_output();
-
-    let mut start_time: u64 = 0;
-    let mut count: u64 = 0;
-    loop {
-        if timer.get_counter().ticks() - start_time > 25_000 {
-            count += 1;
-            let _ = led_pin.toggle();
-            start_time = timer.get_counter().ticks();
-            if count == 125 {
-                break;
-            }
-        }
-    }
+    let mut led_pin = pins.gpio12.into_push_pull_output();
 
     let usb_bus = UsbBusAllocator::new(hal::usb::UsbBus::new(
         pac.USB,
@@ -130,8 +118,6 @@ fn main() -> ! {
         .self_powered(false)
         .build();
 
-    let mut start_time: u64 = 0;
-
     let mut storage: [u8; (DISK_BLOCK_SIZE * DISK_BLOCK_NUM) as usize] = [0u8; (DISK_BLOCK_SIZE * DISK_BLOCK_NUM) as usize];
 
     const LBA: u32 = DISK_BLOCK_NUM - 1;
@@ -147,8 +133,7 @@ fn main() -> ! {
 
     const OEM: [u8; 8] = *b"mkfs.fat";
     const FILESYSTEM_ID: [u8; 4] = [0xDE, 0xAD, 0xBE, 0xEF];
-    const FILESYSTEM_NAME: [u8; 11] = *b"RAM_USB\0\0\0\0";
-    const MEDIA_SECTORS: u32 = DISK_BLOCK_NUM - 256;
+    const FILESYSTEM_LABEL: [u8; 11] = *b"RAM_USB    ";
 
     storage[0x1B9] = 0x10;
     storage[0x1BE..0x1C3].copy_from_slice(&[0x00, 0x00, 0x02, 0x00, 0x0c]);
@@ -165,26 +150,23 @@ fn main() -> ! {
     // FAT12 Partition
     storage[0x200..0x203].copy_from_slice(&[0xEB, 0x3C, 0x90]);
     storage[0x203..0x20B].copy_from_slice(&OEM);
-    storage[0x20B..0x227].copy_from_slice(&[0x00, 0x02, 0x04, 0x01, 0x00,
-        0x02, 0x00, 0x02, (MEDIA_SECTORS & 0xff) as u8,
-                                (MEDIA_SECTORS >> 8) as u8,
-                                      0xF8, 0x01, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00,
-        0x00, 0x00, 0x00, 0x00, 0x80, 0x00, 0x29]);
+    storage[0x20B..0x21d].copy_from_slice(&[0x00, 0x02, 0x04, 0x01, 0x00,
+        0x02, 0x00, 0x02, (LBA & 0xff) as u8,
+                                (LBA >> 8) as u8,
+                                      0xF8, 0x01, 0x00, 0x01, 0x00, 0x01, 0x00, 0x01]);
+    storage[0x224..0x227].copy_from_slice(&[0x80, 0x00, 0x29]);
     storage[0x227..0x22B].copy_from_slice(&FILESYSTEM_ID);
-    storage[0x22B..0x236].copy_from_slice(&FILESYSTEM_NAME);
+    storage[0x22B..0x236].copy_from_slice(&FILESYSTEM_LABEL);
     storage[0x236..0x23E].copy_from_slice(b"FAT12   ");
     storage[0x3FE..0x400].copy_from_slice(&[0x55, 0xAA]);
 
     storage[0x400..0x403].copy_from_slice(&[0xF8, 0xFF, 0xFF]);
     storage[0x600..0x603].copy_from_slice(&[0xF8, 0xFF, 0xFF]);
-    storage[0x800..0x80B].copy_from_slice(&FILESYSTEM_NAME);
-    storage[0x80B..0x81A].copy_from_slice(&[0x08, 0x00, 0x00, 0x00, 0x00,
-        0x21, 0x00, 0x21, 0x00, 0x00, 0x00, 0xFA, 0x01, 0x83, 0x5A
-    ]);
-    storage[0x5000..0x5010].copy_from_slice(&[
-        0x2E, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
-        0x20, 0x20, 0x20, 0x10, 0x00, 0x00, 0xA5, 0xBD
-    ]);
+    storage[0x800..0x80B].copy_from_slice(&FILESYSTEM_LABEL);
+    storage[0x80B] = 0x08; // file attribute 0x08 = volume label
+
+    // https://de.wikipedia.org/wiki/File_Allocation_Table
+    // Remove bootloader code: dd if=/dev/zero conv=notrunc of=foo bs=1 count=420 seek=602
 
     let mut state: State = State {
         storage_offset: 0,
@@ -195,20 +177,26 @@ fn main() -> ! {
 
     defmt::info!("entering main loop");
 
+    let mut start_time: u64 = 0;
     loop {
-        let interval = match (usb_device.state(), led_pin.is_set_high().unwrap_or_else(|_| false)) {
-            // The USB device has just been created or reset.
-            (UsbDeviceState::Default, true) => 100_000,
-            (UsbDeviceState::Default, false) => 100_000,
-            // The USB device has received an address from the host.
-            (UsbDeviceState::Addressed, true) => 250_000,
-            (UsbDeviceState::Addressed, false) => 250_000,
-            // The USB device has been configured and is fully functional.
-            (UsbDeviceState::Configured, true) => 1_000_000,
-            (UsbDeviceState::Configured, false) => 0,
-            // The USB device has been suspended by the host or it has been unplugged from the USB bus.
-            (UsbDeviceState::Suspend, true) => 25_000,
-            (UsbDeviceState::Suspend, false) => 2_000_000,
+        let interval = if timer.get_counter().ticks() < 2_000_000 {
+            25_000
+        }
+        else {
+            match (usb_device.state(), led_pin.is_set_high().unwrap_or_else(|_| false)) {
+                // The USB device has just been created or reset.
+                (UsbDeviceState::Default, true) => 100_000,
+                (UsbDeviceState::Default, false) => 100_000,
+                // The USB device has received an address from the host.
+                (UsbDeviceState::Addressed, true) => 250_000,
+                (UsbDeviceState::Addressed, false) => 250_000,
+                // The USB device has been configured and is fully functional.
+                (UsbDeviceState::Configured, true) => 8,
+                (UsbDeviceState::Configured, false) => 16,
+                // The USB device has been suspended by the host or it has been unplugged from the USB bus.
+                (UsbDeviceState::Suspend, true) => 10_000,
+                (UsbDeviceState::Suspend, false) => 2_000_000,
+            }
         };
         if timer.get_counter().ticks() - start_time > interval {
             let _ = led_pin.toggle();