USB device stack, with KL25Z fixes for USB 3.0 hosts and sleep/resume interrupt handling

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Fork of USBDevice by mbed official

This is an overhauled version of the standard mbed USB device-side driver library, with bug fixes for KL25Z devices. It greatly improves reliability and stability of USB on the KL25Z, especially with devices using multiple endpoints concurrently.

I've had some nagging problems with the base mbed implementation for a long time, manifesting as occasional random disconnects that required rebooting the device. Recently (late 2015), I started implementing a USB device on the KL25Z that used multiple endpoints, and suddenly the nagging, occasional problems turned into frequent and predictable crashes. This forced me to delve into the USB stack and figure out what was really going on. Happily, the frequent crashes made it possible to track down and fix the problems. This new version is working very reliably in my testing - the random disconnects seem completely eradicated, even under very stressful conditions for the device.

Summary

  • Overall stability improvements
  • USB 3.0 host support
  • Stalled endpoint fixes
  • Sleep/resume notifications
  • Smaller memory footprint
  • General code cleanup

Update - 2/15/2016

My recent fixes introduced a new problem that made the initial connection fail most of the time on certain hosts. It's not clear if the common thread was a particular type of motherboard or USB chip set, or a specific version of Windows, or what, but several people ran into it. We tracked the problem down to the "stall" fixes in the earlier updates, which we now know weren't quite the right fixes after all. The latest update (2/15/2016) fixes this. It has new and improved "unstall" handling that so far works well with diverse hosts.

Race conditions and overall stability

The base mbed KL25Z implementation has a lot of problems with "race conditions" - timing problems that can happen when hardware interrupts occur at inopportune moments. The library shares a bunch of static variable data between interrupt handler context and regular application context. This isn't automatically a bad thing, but it does require careful coordination to make sure that the interrupt handler doesn't corrupt data that the other code was in the middle of updating when an interrupt occurs. The base mbed code, though, doesn't do any of the necessary coordination. This makes it kind of amazing that the base code worked at all for anyone, but I guess the interrupt rate is low enough in most applications that the glitch rate was below anyone's threshold to seriously investigate.

This overhaul adds the necessary coordination for the interrupt handlers to protect against these data corruptions. I think it's very solid now, and hopefully entirely free of the numerous race conditions in the old code. It's always hard to be certain that you've fixed every possible bug like this because they strike (effectively) at random, but I'm pretty confident: my test application was reliably able to trigger glitches in the base code in a matter of minutes, but the same application (with the overhauled library) now runs for days on end without dropping the connection.

Stalled endpoint fixes

USB has a standard way of handling communications errors called a "stall", which basically puts the connection into an error mode to let both sides know that they need to reset their internal states and sync up again. The original mbed version of the USB device library doesn't seem to have the necessary code to recover from this condition properly. The KL25Z hardware does some of the work, but it also seems to require the software to take some steps to "un-stall" the connection. (I keep saying "seems to" because the hardware reference material is very sketchy about all of this. Most of what I've figured out is from observing the device in action with a Windows host.) This new version adds code to do the necessary re-syncing and get the connection going again, automatically, and transparently to the user.

USB 3.0 Hosts

The original mbed code sometimes didn't work when connecting to hosts with USB 3.0 ports. This didn't affect every host, but it affected many of them. The common element seemed to be the Intel Haswell chip set on the host, but there may be other chip sets affected as well. In any case, the problem affected many PCs from the Windows 7 and 8 generation, as well as many Macs. It was possible to work around the problem by avoiding USB 3.0 ports - you could use a USB 2 port on the host, or plug a USB 2 hub between the host and device. But I wanted to just fix the problem and eliminate the need for such workarounds. This modified version of the library has such a fix, which so far has worked for everyone who's tried.

Sleep/resume notifications

This modified version also contains an innocuous change to the KL25Z USB HAL code to handle sleep and resume interrupts with calls to suspendStateChanged(). The original KL25Z code omitted these calls (and in fact didn't even enable the interrupts), but I think this was an unintentional oversight - the notifier function is part of the generic API, and other supported boards all implement it. I use this feature in my own application so that I can distinguish sleep mode from actual disconnects and handle the two conditions correctly.

Smaller memory footprint

The base mbed version of the code allocates twice as much memory for USB buffers as it really needed to. It looks like the original developers intended to implement the KL25Z USB hardware's built-in double-buffering mechanism, but they ultimately abandoned that effort. But they left in the double memory allocation. This version removes that and allocates only what's actually needed. The USB buffers aren't that big (128 bytes per endpoint), so this doesn't save a ton of memory, but even a little memory is pretty precious on this machine given that it only has 16K.

(I did look into adding the double-buffering support that the original developers abandoned, but after some experimentation I decided they were right to skip it. It just doesn't seem to mesh well with the design of the rest of the mbed USB code. I think it would take a major rewrite to make it work, and it doesn't seem worth the effort given that most applications don't need it - it would only benefit applications that are moving so much data through USB that they're pushing the limits of the CPU. And even for those, I think it would be a lot simpler to build a purely software-based buffer rotation mechanism.)

General code cleanup

The KL25Z HAL code in this version has greatly expanded commentary and a lot of general cleanup. Some of the hardware constants were given the wrong symbolic names (e.g., EVEN and ODD were reversed), and many were just missing (written as hard-coded numbers without explanation). I fixed the misnomers and added symbolic names for formerly anonymous numbers. Hopefully the next person who has to overhaul this code will at least have an easier time understanding what I thought I was doing!

USBDevice/USBHAL_KL25Z.cpp

Committer:
mjr
Date:
2015-12-25
Revision:
35:53e1a208f582
Parent:
34:884405d998bb
Child:
36:20bb47609697

File content as of revision 35:53e1a208f582:

/* Copyright (c) 2010-2011 mbed.org, MIT License
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of this software
* and associated documentation files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all copies or
* substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
* BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/

#if defined(TARGET_KL25Z) | defined(TARGET_KL46Z) | defined(TARGET_K20D5M) | defined(TARGET_K64F)

#include "USBHAL.h"

USBHAL * USBHAL::instance;

// Perform an operation atomically, by disabling interrupts.  This must be
// used for any test-and-write operations in non-IRQ code, including increment, 
// decrement, bit set, and bit clear, on variables that are also written 
// within the IRQ handler.  (Operations *within* the IRQ handler don't require 
// this, because regular code can't interrupt an interrupt handler.)  This
// applies in particular to 'epComplete' and 'Data1' updates, which are both
// bit vectors that are written with bitwise test-and-set operations in
// regular code and IRQ code.
#define atomic(_stm_) \
    do { \
        NVIC_DisableIRQ(USB0_IRQn); \
        _stm_; \
        NVIC_EnableIRQ(USB0_IRQn); \
    } while (0)
    
    
// endpoint completion flags
static volatile int epComplete = 0;

// clear a completion flag - must be atomic, as the IRQ also manipulates these bits
#define clear_completion(endpoint) atomic(epComplete &= ~EP(endpoint))
    

// Convert physical endpoint number to register bit
#define EP(endpoint) (1<<(endpoint))

// Convert physical to logical
#define PHY_TO_LOG(endpoint)    ((endpoint)>>1)

// Get endpoint direction
#define IN_EP(endpoint)     ((endpoint) & 1U ? true : false)
#define OUT_EP(endpoint)    ((endpoint) & 1U ? false : true)

#define BD_OWN_MASK        (1<<7)
#define BD_DATA01_MASK     (1<<6)
#define BD_KEEP_MASK       (1<<5)
#define BD_NINC_MASK       (1<<4)
#define BD_DTS_MASK        (1<<3)
#define BD_STALL_MASK      (1<<2)

#define TX    1
#define RX    0
#define ODD   0
#define EVEN  1
// this macro waits a physical endpoint number
#define EP_BDT_IDX(ep, dir, odd) (((ep * 4) + (2 * dir) + (1 *  odd)))

#define SETUP_TOKEN    0x0D
#define IN_TOKEN       0x09
#define OUT_TOKEN      0x01
#define TOK_PID(idx)   ((bdt[idx].info >> 2) & 0x0F)

// for each endpt: 8 bytes
typedef struct BDT {
    uint8_t   info;       // BD[0:7]
    uint8_t   dummy;      // RSVD: BD[8:15]
    uint16_t  byte_count; // BD[16:32]
    uint32_t  address;    // Addr
} BDT;


// there are:
//    * 16 bidirectionnal endpt -> 32 physical endpt
//    * as there are ODD and EVEN buffer -> 32*2 bdt
__attribute__((__aligned__(512))) BDT bdt[NUMBER_OF_PHYSICAL_ENDPOINTS * 2];
uint8_t * endpoint_buffer[NUMBER_OF_PHYSICAL_ENDPOINTS];

static uint8_t set_addr = 0;
static uint8_t addr = 0;


// DATA0/DATA1 setting for next packet on each endpoint
static uint32_t Data1  = 0x55555555;

// set DATA0/DATA1 status on an endpoint (must be atomic as the IRQ handler
// manpulates this variable)
#define set_DATA0(endpoint) atomic(Data1 &= ~EP(endpoint))
#define set_DATA1(endpoint) atomic(Data1 |= EP(endpoint))
#define toggle_DATA01(endpoint) atomic(Data1 ^= EP(endpoint))

static uint32_t frameNumber() {
    return((USB0->FRMNUML | (USB0->FRMNUMH << 8)) & 0x07FF);
}

uint32_t USBHAL::endpointReadcore(uint8_t endpoint, uint8_t *buffer) {
    return 0;
}

USBHAL::USBHAL(void) {
    // Disable IRQ
    NVIC_DisableIRQ(USB0_IRQn);

#if defined(TARGET_K64F)
    MPU->CESR=0;
#endif
    // fill in callback array
    epCallback[0] = &USBHAL::EP1_OUT_callback;
    epCallback[1] = &USBHAL::EP1_IN_callback;
    epCallback[2] = &USBHAL::EP2_OUT_callback;
    epCallback[3] = &USBHAL::EP2_IN_callback;
    epCallback[4] = &USBHAL::EP3_OUT_callback;
    epCallback[5] = &USBHAL::EP3_IN_callback;
    epCallback[6] = &USBHAL::EP4_OUT_callback;
    epCallback[7] = &USBHAL::EP4_IN_callback;
    epCallback[8] = &USBHAL::EP5_OUT_callback;
    epCallback[9] = &USBHAL::EP5_IN_callback;
    epCallback[10] = &USBHAL::EP6_OUT_callback;
    epCallback[11] = &USBHAL::EP6_IN_callback;
    epCallback[12] = &USBHAL::EP7_OUT_callback;
    epCallback[13] = &USBHAL::EP7_IN_callback;
    epCallback[14] = &USBHAL::EP8_OUT_callback;
    epCallback[15] = &USBHAL::EP8_IN_callback;
    epCallback[16] = &USBHAL::EP9_OUT_callback;
    epCallback[17] = &USBHAL::EP9_IN_callback;
    epCallback[18] = &USBHAL::EP10_OUT_callback;
    epCallback[19] = &USBHAL::EP10_IN_callback;
    epCallback[20] = &USBHAL::EP11_OUT_callback;
    epCallback[21] = &USBHAL::EP11_IN_callback;
    epCallback[22] = &USBHAL::EP12_OUT_callback;
    epCallback[23] = &USBHAL::EP12_IN_callback;
    epCallback[24] = &USBHAL::EP13_OUT_callback;
    epCallback[25] = &USBHAL::EP13_IN_callback;
    epCallback[26] = &USBHAL::EP14_OUT_callback;
    epCallback[27] = &USBHAL::EP14_IN_callback;
    epCallback[28] = &USBHAL::EP15_OUT_callback;
    epCallback[29] = &USBHAL::EP15_IN_callback;


    // choose usb src as PLL
    SIM->SOPT2 |= (SIM_SOPT2_USBSRC_MASK | SIM_SOPT2_PLLFLLSEL_MASK);

    // enable OTG clock
    SIM->SCGC4 |= SIM_SCGC4_USBOTG_MASK;

    // Attach IRQ
    instance = this;
    NVIC_SetVector(USB0_IRQn, (uint32_t)&_usbisr);
    NVIC_EnableIRQ(USB0_IRQn);

    // USB Module Configuration
    // Reset USB Module
    USB0->USBTRC0 |= USB_USBTRC0_USBRESET_MASK;
    while(USB0->USBTRC0 & USB_USBTRC0_USBRESET_MASK);

    // Set BDT Base Register
    USB0->BDTPAGE1 = (uint8_t)((uint32_t)bdt>>8);
    USB0->BDTPAGE2 = (uint8_t)((uint32_t)bdt>>16);
    USB0->BDTPAGE3 = (uint8_t)((uint32_t)bdt>>24);

    // Clear interrupt flag
    USB0->ISTAT = 0xff;

    // USB Interrupt Enablers
    USB0->INTEN |= USB_INTEN_TOKDNEEN_MASK |
                   USB_INTEN_SOFTOKEN_MASK |
                   USB_INTEN_ERROREN_MASK  |
                   USB_INTEN_SLEEPEN_MASK |
                   USB_INTEN_RESUMEEN_MASK |
                   USB_INTEN_USBRSTEN_MASK;

    // Disable weak pull downs
    USB0->USBCTRL &= ~(USB_USBCTRL_PDE_MASK | USB_USBCTRL_SUSP_MASK);

    USB0->USBTRC0 |= 0x40;
}

USBHAL::~USBHAL(void) { }

void USBHAL::connect(void) {
    // enable USB
    USB0->CTL |= USB_CTL_USBENSOFEN_MASK;
    // Pull up enable
    USB0->CONTROL |= USB_CONTROL_DPPULLUPNONOTG_MASK;
}

void USBHAL::disconnect(void) 
{
    // disable USB
    USB0->CTL &= ~USB_CTL_USBENSOFEN_MASK;

    // Pull up disable
    USB0->CONTROL &= ~USB_CONTROL_DPPULLUPNONOTG_MASK;

    //Free buffers if required:
    for (int i = 0 ; i < NUMBER_OF_PHYSICAL_ENDPOINTS ; i++) {
        free(endpoint_buffer[i]);
        endpoint_buffer[i] = NULL;
    }
}

void USBHAL::configureDevice(void) {
    // not needed
}

void USBHAL::unconfigureDevice(void) {
    // not needed
}

void USBHAL::setAddress(uint8_t address) {
    // we don't set the address now otherwise the usb controller does not ack
    // we set a flag instead
    // see usbisr when an IN token is received
    set_addr = 1;
    addr = address;
 }

bool USBHAL::realiseEndpoint(uint8_t endpoint, uint32_t maxPacket, uint32_t flags) 
{
    uint32_t handshake_flag;
    uint32_t alo_size;

    if (endpoint >= NUMBER_OF_PHYSICAL_ENDPOINTS)
        return false;

    uint32_t log_endpoint = PHY_TO_LOG(endpoint);
    
    if (flags & ISOCHRONOUS) {
        handshake_flag = 0;
        alo_size = 1023;
    }
    else {
        handshake_flag = USB_ENDPT_EPHSHK_MASK;
        alo_size = 64;
    }
    
    if (endpoint_buffer[endpoint] == 0)
        endpoint_buffer[endpoint] = (uint8_t *)malloc(alo_size);

    // IN endpt -> device to host (TX)
    if (IN_EP(endpoint)) {
        USB0->ENDPOINT[log_endpoint].ENDPT |= handshake_flag |        // ep handshaking (not if iso endpoint)
                                              USB_ENDPT_EPTXEN_MASK;  // en TX (IN) tran
        bdt[EP_BDT_IDX(log_endpoint, TX, ODD )].address = (uint32_t) endpoint_buffer[endpoint];
        bdt[EP_BDT_IDX(log_endpoint, TX, EVEN)].address = 0;
    }
    // OUT endpt -> host to device (RX)
    else {
        USB0->ENDPOINT[log_endpoint].ENDPT |= handshake_flag |        // ep handshaking (not if iso endpoint)
                                              USB_ENDPT_EPRXEN_MASK;  // en RX (OUT) tran.
        bdt[EP_BDT_IDX(log_endpoint, RX, ODD )].byte_count = maxPacket;
        bdt[EP_BDT_IDX(log_endpoint, RX, ODD )].address    = (uint32_t) endpoint_buffer[endpoint];
        bdt[EP_BDT_IDX(log_endpoint, RX, EVEN)].address    = 0;
        bdt[EP_BDT_IDX(log_endpoint, RX, ODD )].info       = BD_OWN_MASK | BD_DTS_MASK;
        bdt[EP_BDT_IDX(log_endpoint, RX, EVEN)].info       = 0;
    }

    set_DATA1(endpoint);
    clear_completion(endpoint);

    return true;
}

// read setup packet
void USBHAL::EP0setup(uint8_t *buffer) {
    uint32_t sz;
    endpointReadResult(EP0OUT, buffer, &sz);
}

void USBHAL::EP0readStage(void) {
    set_DATA0(EP0OUT);                              // set DATA0 for the next packet
    bdt[0].info = (BD_DTS_MASK | BD_OWN_MASK);      // start the read
}

void USBHAL::EP0read(void) {
    uint32_t idx = EP_BDT_IDX(PHY_TO_LOG(EP0OUT), RX, 0);
    bdt[idx].byte_count = MAX_PACKET_SIZE_EP0;
}

uint32_t USBHAL::EP0getReadResult(uint8_t *buffer) {
    uint32_t sz;
    endpointReadResult(EP0OUT, buffer, &sz);
    return sz;
}

void USBHAL::EP0write(uint8_t *buffer, uint32_t size) {
    endpointWrite(EP0IN, buffer, size);
}

void USBHAL::EP0getWriteResult(void) {
}

void USBHAL::EP0stall(void) {
    stallEndpoint(EP0OUT);
}

EP_STATUS USBHAL::endpointRead(uint8_t endpoint, uint32_t maximumSize) 
{
    return EP_PENDING;
}

EP_STATUS USBHAL::endpointReadResult(uint8_t endpoint, uint8_t * buffer, uint32_t *bytesRead) 
{
    // validate the endpoint number
    if (endpoint >= NUMBER_OF_PHYSICAL_ENDPOINTS)
        return EP_INVALID;

    // we can only read an OUT endpoint
    if (IN_EP(endpoint))
        return EP_INVALID;

    // get the logical endpoint number
    uint32_t log_endpoint = PHY_TO_LOG(endpoint);

    // get the BDT index
    int idx = EP_BDT_IDX(log_endpoint, RX, 0);

    // make sure we're marked as complete (except for isochronous endpoints)
    bool iso = !(USB0->ENDPOINT[log_endpoint].ENDPT & USB_ENDPT_EPHSHK_MASK);
    if ((log_endpoint != 0) && !iso && !(epComplete & EP(endpoint)))
        return EP_PENDING;

    // this consumes the read status - clear the completion flag to prepare for the next read
    clear_completion(endpoint);

    // copy the data from the hardware buffer to the caller's buffer
    uint8_t *ep_buf = (uint8_t *)bdt[idx].address;
    uint32_t sz = *bytesRead = bdt[idx].byte_count;
    for (uint32_t n = 0; n < sz; n++)
        buffer[n] = ep_buf[n];
    
    // Figure the DATA0/DATA1 value for the next packet.  If we have a
    // SETUP token with no data stage, it's DATA0.  Otherwise we just
    // flip the last value, assuming the new token matches what we expect.
    bool setup = (log_endpoint == 0 && TOK_PID(idx) == SETUP_TOKEN);
    if (((Data1 >> endpoint) & 1) == ((bdt[idx].info >> 6) & 1)) {
        if (setup && (buffer[6] == 0)) {
            set_DATA0(EP0OUT);          // no setup data stage, so set DATA0
        }
        else {
            toggle_DATA01(endpoint);    // in other cases, toggle the DATA0/DATA1 status on each packet 
        }
    }

    // hand off the BDT to start the next read
    bdt[idx].info = BD_OWN_MASK | BD_DTS_MASK | (((Data1 >> endpoint) & 1) << 6);

    // turn off the "suspend token busy" flag (the hardware sets this for
    // SETUP tokens to let us process tokens sequentially in this special case)
    USB0->CTL &= ~USB_CTL_TXSUSPENDTOKENBUSY_MASK;
    
    // operation completed
    return EP_COMPLETED;
}

EP_STATUS USBHAL::endpointWrite(uint8_t endpoint, uint8_t *data, uint32_t size) 
{
    // validate the endpoint number
    if (endpoint >= NUMBER_OF_PHYSICAL_ENDPOINTS)
        return EP_INVALID;

    // if write on a OUT endpoint -> error
    if (OUT_EP(endpoint))
        return EP_INVALID;

    // get the BDT entry for the endpoint
    int idx = EP_BDT_IDX(PHY_TO_LOG(endpoint), TX, 0);

    // if the buffer is owned by the SIE, there's a previous write that
    // hasn't finished yet - we can't start a new one yet
    if (bdt[idx].info & BD_OWN_MASK)
        return EP_BUSY;

    // copy the bytes to the endpoint hardware buffer
    uint8_t *ep_buf = (uint8_t *)bdt[idx].address;
    bdt[idx].byte_count = size;
    for (uint32_t n = 0 ; n < size ; n++)
        ep_buf[n] = data[n];

    // toggle DATA0/DATA1 on each packet
    toggle_DATA01(endpoint);

    // hand the buffer to the SIE
    bdt[idx].info = BD_OWN_MASK | BD_DTS_MASK | (((Data1 >> endpoint) & 1) << 6);

    // the packet is now pending
    return EP_PENDING;
}

EP_STATUS USBHAL::endpointWriteResult(uint8_t endpoint) 
{
    if (epComplete & EP(endpoint)) {
        clear_completion(endpoint);
        return EP_COMPLETED;
    }

    return EP_PENDING;
}

void USBHAL::stallEndpoint(uint8_t endpoint) {
    USB0->ENDPOINT[PHY_TO_LOG(endpoint)].ENDPT |= USB_ENDPT_EPSTALL_MASK;
}

void USBHAL::unstallEndpoint(uint8_t endpoint) {
    USB0->ENDPOINT[PHY_TO_LOG(endpoint)].ENDPT &= ~USB_ENDPT_EPSTALL_MASK;
}

bool USBHAL::getEndpointStallState(uint8_t endpoint) {
    uint8_t stall = (USB0->ENDPOINT[PHY_TO_LOG(endpoint)].ENDPT & USB_ENDPT_EPSTALL_MASK);
    return (stall) ? true : false;
}

void USBHAL::remoteWakeup(void) {
    // [TODO]
}


void USBHAL::_usbisr(void) {
    instance->usbisr();
}


void USBHAL::usbisr(void) {
    uint8_t i;
    uint8_t istat = USB0->ISTAT;

    // reset interrupt
    if (istat & USB_ISTAT_USBRST_MASK) {
        
        // disable all endpt
        for(i = 0; i < 16; i++) {
            USB0->ENDPOINT[i].ENDPT = 0x00;
        }

        // enable control endpoint
        realiseEndpoint(EP0OUT, MAX_PACKET_SIZE_EP0, 0);
        realiseEndpoint(EP0IN, MAX_PACKET_SIZE_EP0, 0);

        Data1 = 0x55555555;
        epComplete = 0;
        USB0->CTL |=  USB_CTL_ODDRST_MASK;

        USB0->ISTAT   =  0xFF;  // clear all interrupt status flags
        USB0->ERRSTAT =  0xFF;  // clear all error flags
        USB0->ERREN   =  0xFF;  // enable error interrupt sources
        USB0->ADDR    =  0x00;  // set default address
        
        // notify upper layers of the bus reset
        busReset();
        
        // we're not suspended
        suspendStateChanged(0);

        return;
    }

    // resume interrupt
    if (istat & USB_ISTAT_RESUME_MASK) {
        USB0->ISTAT = USB_ISTAT_RESUME_MASK;
        suspendStateChanged(0);
    }

    // SOF interrupt
    if (istat & USB_ISTAT_SOFTOK_MASK) {
        USB0->ISTAT = USB_ISTAT_SOFTOK_MASK;
        // SOF event, read frame number
        SOF(frameNumber());
    }

    // stall interrupt
    if (istat & 1<<7) {
        if (USB0->ENDPOINT[0].ENDPT & USB_ENDPT_EPSTALL_MASK)
            USB0->ENDPOINT[0].ENDPT &= ~USB_ENDPT_EPSTALL_MASK;
        USB0->ISTAT |= USB_ISTAT_STALL_MASK;
    }

    // token interrupt
    if (istat & 1<<3) {
        uint32_t num  = (USB0->STAT >> 4) & 0x0F;
        uint32_t dir  = (USB0->STAT >> 3) & 0x01;
        uint32_t ev_odd = (USB0->STAT >> 2) & 0x01;
        int endpoint = (num << 1) | dir;

        // setup packet
        if ((num == 0) && (TOK_PID((EP_BDT_IDX(num, dir, ev_odd))) == SETUP_TOKEN)) {
            Data1 &= ~0x02;
            bdt[EP_BDT_IDX(0, TX, EVEN)].info &= ~BD_OWN_MASK;
            bdt[EP_BDT_IDX(0, TX, ODD)].info  &= ~BD_OWN_MASK;

            // EP0 SETUP event (SETUP data received)
            EP0setupCallback();

        } else {
            // OUT packet
            if (TOK_PID((EP_BDT_IDX(num, dir, ev_odd))) == OUT_TOKEN) {
                if (num == 0)
                    EP0out();
                else {
                    epComplete |= EP(endpoint);
                    if ((instance->*(epCallback[endpoint - 2]))()) {
                        epComplete &= ~EP(endpoint);
                    }
                }
            }

            // IN packet
            if (TOK_PID((EP_BDT_IDX(num, dir, ev_odd))) == IN_TOKEN) {
                if (num == 0) {
                    EP0in();
                    if (set_addr == 1) {
                        USB0->ADDR = addr & 0x7F;
                        set_addr = 0;
                    }
                }
                else {
                    epComplete |= EP(endpoint);
                    if ((instance->*(epCallback[endpoint - 2]))()) {
                        epComplete &= ~EP(endpoint);
                    }
                }
            }
        }

        USB0->ISTAT = USB_ISTAT_TOKDNE_MASK;
    }

    // sleep interrupt
    if (istat & 1<<4) {
        USB0->ISTAT |= USB_ISTAT_SLEEP_MASK;
        suspendStateChanged(1);
    }

    // error interrupt
    if (istat & USB_ISTAT_ERROR_MASK) {
        USB0->ERRSTAT = 0xFF;
        USB0->ISTAT |= USB_ISTAT_ERROR_MASK;
    }
}


#endif