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

Dependents:   frdm_Slider_Keyboard idd_hw2_figlax_PanType idd_hw2_appachu_finger_chording idd_hw3_AngieWangAntonioDeLimaFernandesDanielLim_BladeSymphony ... more

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!

USBAudio/USBAudio.h

Committer:
mjr
Date:
2017-03-17
Revision:
54:2e181d51495a
Parent:
49:03527ce6840e

File content as of revision 54:2e181d51495a:

/* 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.
*/

#ifndef USBAudio_H
#define USBAudio_H

/* These headers are included for child class. */
#include "USBEndpoints.h"
#include "USBDescriptor.h"
#include "USBDevice_Types.h"

#include "USBDevice.h"


/**
* USBAudio example
*
* @code
* #include "mbed.h"
* #include "USBAudio.h"
*
* Serial pc(USBTX, USBRX);
*
* // frequency: 48 kHz
* #define FREQ 48000
*
* // 1 channel: mono
* #define NB_CHA 1
*
* // length of an audio packet: each ms, we receive 48 * 16bits ->48 * 2 bytes. as there is one channel, the length will be 48 * 2 * 1
* #define AUDIO_LENGTH_PACKET 48 * 2 * 1
*
* // USBAudio
* USBAudio audio(FREQ, NB_CHA);
*
* int main() {
*    int16_t buf[AUDIO_LENGTH_PACKET/2];
*
*    while (1) {
*        // read an audio packet
*        audio.read((uint8_t *)buf);
*
*
*        // print packet received
*        pc.printf("recv: ");
*        for(int i = 0; i < AUDIO_LENGTH_PACKET/2; i++) {
*            pc.printf("%d ", buf[i]);
*        }
*        pc.printf("\r\n");
*    }
* }
* @endcode
*/
class USBAudio: public USBDevice {
public:

    /**
    * Constructor
    *
    * @param frequency_in frequency in Hz (default: 48000)
    * @param channel_nb_in channel number (1 or 2) (default: 1)
    * @param frequency_out frequency in Hz (default: 8000)
    * @param channel_nb_out_in channel number (1 or 2) (default: 1)
    * @param vendor_id Your vendor_id
    * @param product_id Your product_id
    * @param product_release Your preoduct_release
    */
    USBAudio(uint32_t frequency_in = 48000, uint8_t channel_nb_in = 1, uint32_t frequency_out = 8000, uint8_t channel_nb_out = 1, uint16_t vendor_id = 0x7bb8, uint16_t product_id = 0x1111, uint16_t product_release = 0x0100);

    /**
    * Get current volume between 0.0 and 1.0
    *
    * @returns volume
    */
    float getVolume();

    /**
    * Read an audio packet. During a frame, only a single reading (you can't write and read an audio packet during the same frame)can be done using this method. Warning: Blocking
    *
    * @param buf pointer on a buffer which will be filled with an audio packet
    *
    * @returns true if successfull
    */
    bool read(uint8_t * buf);

    /**
    * Try to read an audio packet. During a frame, only a single reading (you can't write and read an audio packet during the same frame)can be done using this method. Warning: Non Blocking
    *
    * @param buf pointer on a buffer which will be filled if an audio packet is available
    *
    * @returns true if successfull
    */
    bool readNB(uint8_t * buf);

    /**
    * Write an audio packet. During a frame, only a single writing (you can't write and read an audio packet during the same frame)can be done using this method.
    *
    * @param buf pointer on the audio packet which will be sent
    * @returns true if successful
    */
    bool write(uint8_t * buf);

    /**
    * Write and read an audio packet at the same time (on the same frame)
    *
    * @param buf_read pointer on a buffer which will be filled with an audio packet
    * @param buf_write pointer on the audio packet which will be sent
    * @returns true if successful
    */
    bool readWrite(uint8_t * buf_read, uint8_t * buf_write);


    /** attach a handler to update the volume
     *
     * @param function Function to attach
     *
     */
    void attach(void(*fptr)(void)) {
        updateVol.attach(fptr);
    }

    /** Attach a nonstatic void/void member function to update the volume
     *
     * @param tptr Object pointer
     * @param mptr Member function pointer
     *
     */
    template<typename T>
    void attach(T *tptr, void(T::*mptr)(void)) {
        updateVol.attach(tptr, mptr);
    }


protected:

    /*
    * Called by USBDevice layer. Set configuration of the device.
    * For instance, you can add all endpoints that you need on this function.
    *
    * @param configuration Number of the configuration
    * @returns true if class handles this request
    */
    virtual bool USBCallback_setConfiguration(uint8_t configuration);

    /*
    * Called by USBDevice on Endpoint0 request. Warning: Called in ISR context
    * This is used to handle extensions to standard requests
    * and class specific requests
    *
    * @returns true if class handles this request
    */
    virtual bool USBCallback_request();

    /*
    * Get string product descriptor
    *
    * @returns pointer to the string product descriptor
    */
    virtual const uint8_t *stringIproductDesc();

    /*
    * Get string interface descriptor
    *
    * @returns pointer to the string interface descriptor
    */
    virtual const uint8_t *stringIinterfaceDesc();

    /*
    * Get configuration descriptor
    *
    * @returns pointer to the configuration descriptor
    */
    virtual const uint8_t *configurationDesc();

    /*
     * Called by USBDevice layer. Set interface/alternate of the device.
     *
     * @param interface Number of the interface to be configured
     * @param alternate Number of the alternate to be configured
     * @returns true if class handles this request
     */
    virtual bool USBCallback_setInterface(uint16_t interface, uint8_t alternate);

    /*
    * Called by USBDevice on Endpoint0 request completion
    * if the 'notify' flag has been set to true. Warning: Called in ISR context
    *
    * In this case it is used to indicate that a HID report has
    * been received from the host on endpoint 0
    *
    * @param buf buffer received on endpoint 0
    * @param length length of this buffer
    */
    virtual void USBCallback_requestCompleted(uint8_t * buf, uint32_t length);

    /*
    * Callback called on each Start of Frame event
    */
    virtual void SOF(int frameNumber);

    /*
    * Callback called when a packet is received
    */
    virtual bool EP3_OUT_callback();

    /*
    * Callback called when a packet has been sent
    */
    virtual bool EP3_IN_callback();

private:

    // stream available ?
    volatile bool available;

    // interrupt OUT has been received
    volatile bool interruptOUT;

    // interrupt IN has been received
    volatile bool interruptIN;

    // audio packet has been written
    volatile bool writeIN;

    // FREQ
    uint32_t FREQ_OUT;
    uint32_t FREQ_IN;

    // size of the maximum packet for the isochronous endpoint
    uint32_t PACKET_SIZE_ISO_IN;
    uint32_t PACKET_SIZE_ISO_OUT;

    // mono, stereo,...
    uint8_t channel_nb_in;
    uint8_t channel_nb_out;

    // channel config: master, left, right
    uint8_t channel_config_in;
    uint8_t channel_config_out;

    // mute state
    uint8_t mute;

    // Volume Current Value
    uint16_t volCur;

    // Volume Minimum Value
    uint16_t volMin;

    // Volume Maximum Value
    uint16_t volMax;

    // Volume Resolution
    uint16_t volRes;

    // Buffer containing one audio packet (to be read)
    volatile uint8_t * buf_stream_in;

    // Buffer containing one audio packet (to be written)
    volatile uint8_t * buf_stream_out;

    // callback to update volume
    FunctionPointer updateVol;

    // boolean showing that the SOF handler has been called. Useful for readNB.
    volatile bool SOF_handler;

    volatile float volume;

};

#endif