From c636252335d06d27eff6d84bd066aca14a8e5731 Mon Sep 17 00:00:00 2001
From: Gabriel Dobato <dobatog@gmail.com>
Date: Mon, 13 May 2024 23:22:10 +0200
Subject: [PATCH] Remove ref to static mut

---
 examples/usb_echo.rs | 36 ++++++++++++++++++++++--------------
 1 file changed, 22 insertions(+), 14 deletions(-)

diff --git a/examples/usb_echo.rs b/examples/usb_echo.rs
index f7ed433..b109ee9 100644
--- a/examples/usb_echo.rs
+++ b/examples/usb_echo.rs
@@ -6,6 +6,8 @@
 #![no_std]
 #![no_main]
 
+use core::mem::MaybeUninit;
+
 use cortex_m::singleton;
 use portenta_h7::{
     board::{self, Board, UsbBus, USB},
@@ -17,15 +19,15 @@ use rtic_monotonics::systick::*;
 use usb_device::prelude::*;
 use usbd_serial::CdcAcmClass;
 
-const USB_BUS_BUFFER_SIZE: usize = 1024;
-static mut USB_BUS_BUFFER: [u32; USB_BUS_BUFFER_SIZE] = [0u32; USB_BUS_BUFFER_SIZE];
-const USB_HS_MAX_PACKET_SIZE: usize = 512;
-static mut USB_APP_BUFFER: [u8; USB_HS_MAX_PACKET_SIZE] = [0u8; USB_HS_MAX_PACKET_SIZE];
+const USB_HS_MAX_PACKET_SIZE: usize = 64;
 
 #[app(device = portenta_h7::hal::pac, peripherals = false)]
 mod app {
     use super::*;
 
+    const USB_BUS_BUFFER_SIZE: usize = 1024;
+    static mut USB_BUS_BUFFER: MaybeUninit<[u32; USB_BUS_BUFFER_SIZE]> = MaybeUninit::uninit();
+
     #[shared]
     struct Shared {}
 
@@ -41,6 +43,16 @@ mod app {
         log_init!();
 
         let systick_mono_token = rtic_monotonics::create_systick_token!();
+
+        // Init usb buffer
+        unsafe {
+            let usb_buffer: &mut [MaybeUninit<u32>; USB_BUS_BUFFER_SIZE] =
+                &mut *(core::ptr::addr_of_mut!(USB_BUS_BUFFER) as *mut _);
+            for element in usb_buffer.iter_mut() {
+                element.as_mut_ptr().write(0);
+            }
+        }
+
         Systick::start(
             cx.core.SYST,
             board::CORE_FREQUENCY.raw(),
@@ -50,12 +62,7 @@ mod app {
         // Get board resources
         let Board { led_blue, usb, .. } = Board::take();
 
-        // Init USB stack
-        let usb_bus = singleton!(
-            : usb_device::class_prelude::UsbBusAllocator<UsbBus<USB>> =
-                UsbBus::new(usb, unsafe { &mut USB_BUS_BUFFER })
-        )
-        .unwrap();
+        let usb_bus = singleton!(:usb_device::class_prelude::UsbBusAllocator<UsbBus<USB>> = UsbBus::new(usb, unsafe {USB_BUS_BUFFER.assume_init_mut()})).unwrap();
 
         let usb_serial_port = usbd_serial::CdcAcmClass::new(usb_bus, USB_HS_MAX_PACKET_SIZE as u16);
         let usb_dev = UsbDeviceBuilder::new(usb_bus, UsbVidPid(0x1234, 0xABCD))
@@ -87,18 +94,19 @@ mod app {
         // Trigger internal state machine. It should be called either from ISR on USB event,
         // or every 10 ms from normal execution context
         if usb_dev.poll(&mut [usb_serial_port]) {
+            let mut app_buff = [0u8; USB_HS_MAX_PACKET_SIZE];
+
             // Read from reception fifo
-            match usb_serial_port.read_packet(unsafe { &mut USB_APP_BUFFER[..] }) {
+            match usb_serial_port.read_packet(&mut app_buff) {
                 Ok(cnt) if cnt > 0 => {
                     #[cfg(debug_assertions)]
                     log!(
                         "Received {} bytes: {}",
                         cnt,
-                        core::str::from_utf8(unsafe { &USB_APP_BUFFER[..cnt] })
-                            .unwrap_or("not valid")
+                        core::str::from_utf8(&app_buff[..cnt]).unwrap_or("not valid")
                     );
                     // Send back received data
-                    match usb_serial_port.write_packet(unsafe { &USB_APP_BUFFER[..cnt] }) {
+                    match usb_serial_port.write_packet(&app_buff[..cnt]) {
                         Ok(_) => (),
                         Err(err) => {
                             log!("Error in transmission: {:?}", err)