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!

Committer:
samux
Date:
Fri Mar 01 13:10:29 2013 +0000
Revision:
8:335f2506f422
Parent:
6:d0945750af57
Child:
15:849c0c0f2769
add FRDM-KL25Z support

Who changed what in which revision?

UserRevisionLine numberNew contents of line
samux 1:80ab0d068708 1 /* Copyright (c) 2010-2011 mbed.org, MIT License
samux 1:80ab0d068708 2 *
samux 1:80ab0d068708 3 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
samux 1:80ab0d068708 4 * and associated documentation files (the "Software"), to deal in the Software without
samux 1:80ab0d068708 5 * restriction, including without limitation the rights to use, copy, modify, merge, publish,
samux 1:80ab0d068708 6 * distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the
samux 1:80ab0d068708 7 * Software is furnished to do so, subject to the following conditions:
samux 1:80ab0d068708 8 *
samux 1:80ab0d068708 9 * The above copyright notice and this permission notice shall be included in all copies or
samux 1:80ab0d068708 10 * substantial portions of the Software.
samux 1:80ab0d068708 11 *
samux 1:80ab0d068708 12 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
samux 1:80ab0d068708 13 * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
samux 1:80ab0d068708 14 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
samux 1:80ab0d068708 15 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
samux 1:80ab0d068708 16 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
samux 1:80ab0d068708 17 */
samux 1:80ab0d068708 18
samux 1:80ab0d068708 19 #ifndef USBCDC_H
samux 1:80ab0d068708 20 #define USBCDC_H
samux 1:80ab0d068708 21
samux 1:80ab0d068708 22 /* These headers are included for child class. */
samux 1:80ab0d068708 23 #include "USBEndpoints.h"
samux 1:80ab0d068708 24 #include "USBDescriptor.h"
samux 1:80ab0d068708 25 #include "USBDevice_Types.h"
samux 1:80ab0d068708 26
samux 1:80ab0d068708 27 #include "USBDevice.h"
samux 1:80ab0d068708 28
samux 1:80ab0d068708 29 class USBCDC: public USBDevice {
samux 1:80ab0d068708 30 public:
samux 1:80ab0d068708 31
samux 1:80ab0d068708 32 /*
samux 1:80ab0d068708 33 * Constructor
samux 1:80ab0d068708 34 *
samux 1:80ab0d068708 35 * @param vendor_id Your vendor_id
samux 1:80ab0d068708 36 * @param product_id Your product_id
samux 1:80ab0d068708 37 * @param product_release Your preoduct_release
samux 1:80ab0d068708 38 */
samux 1:80ab0d068708 39 USBCDC(uint16_t vendor_id, uint16_t product_id, uint16_t product_release);
samux 1:80ab0d068708 40
samux 1:80ab0d068708 41 protected:
samux 1:80ab0d068708 42
samux 1:80ab0d068708 43 /*
samux 1:80ab0d068708 44 * Get device descriptor. Warning: this method has to store the length of the report descriptor in reportLength.
samux 1:80ab0d068708 45 *
samux 1:80ab0d068708 46 * @returns pointer to the device descriptor
samux 1:80ab0d068708 47 */
samux 1:80ab0d068708 48 virtual uint8_t * deviceDesc();
samux 1:80ab0d068708 49
samux 1:80ab0d068708 50 /*
samux 1:80ab0d068708 51 * Get string product descriptor
samux 1:80ab0d068708 52 *
samux 1:80ab0d068708 53 * @returns pointer to the string product descriptor
samux 1:80ab0d068708 54 */
samux 1:80ab0d068708 55 virtual uint8_t * stringIproductDesc();
samux 1:80ab0d068708 56
samux 1:80ab0d068708 57 /*
samux 1:80ab0d068708 58 * Get string interface descriptor
samux 1:80ab0d068708 59 *
samux 1:80ab0d068708 60 * @returns pointer to the string interface descriptor
samux 1:80ab0d068708 61 */
samux 1:80ab0d068708 62 virtual uint8_t * stringIinterfaceDesc();
samux 1:80ab0d068708 63
samux 1:80ab0d068708 64 /*
samux 1:80ab0d068708 65 * Get configuration descriptor
samux 1:80ab0d068708 66 *
samux 1:80ab0d068708 67 * @returns pointer to the configuration descriptor
samux 1:80ab0d068708 68 */
samux 1:80ab0d068708 69 virtual uint8_t * configurationDesc();
samux 1:80ab0d068708 70
samux 1:80ab0d068708 71 /*
samux 1:80ab0d068708 72 * Send a buffer
samux 1:80ab0d068708 73 *
samux 1:80ab0d068708 74 * @param endpoint endpoint which will be sent the buffer
samux 1:80ab0d068708 75 * @param buffer buffer to be sent
samux 1:80ab0d068708 76 * @param size length of the buffer
samux 1:80ab0d068708 77 * @returns true if successful
samux 1:80ab0d068708 78 */
samux 1:80ab0d068708 79 bool send(uint8_t * buffer, uint32_t size);
samux 1:80ab0d068708 80
samux 1:80ab0d068708 81 /*
samux 1:80ab0d068708 82 * Read a buffer from a certain endpoint. Warning: blocking
samux 1:80ab0d068708 83 *
samux 1:80ab0d068708 84 * @param endpoint endpoint to read
samux 1:80ab0d068708 85 * @param buffer buffer where will be stored bytes
samux 1:80ab0d068708 86 * @param size the number of bytes read will be stored in *size
samux 1:80ab0d068708 87 * @param maxSize the maximum length that can be read
samux 1:80ab0d068708 88 * @returns true if successful
samux 1:80ab0d068708 89 */
samux 1:80ab0d068708 90 bool readEP(uint8_t * buffer, uint32_t * size);
samux 1:80ab0d068708 91
samux 1:80ab0d068708 92 /*
samux 1:80ab0d068708 93 * Read a buffer from a certain endpoint. Warning: non blocking
samux 1:80ab0d068708 94 *
samux 1:80ab0d068708 95 * @param endpoint endpoint to read
samux 1:80ab0d068708 96 * @param buffer buffer where will be stored bytes
samux 1:80ab0d068708 97 * @param size the number of bytes read will be stored in *size
samux 1:80ab0d068708 98 * @param maxSize the maximum length that can be read
samux 1:80ab0d068708 99 * @returns true if successful
samux 1:80ab0d068708 100 */
samux 1:80ab0d068708 101 bool readEP_NB(uint8_t * buffer, uint32_t * size);
samux 6:d0945750af57 102
samux 6:d0945750af57 103 protected:
samux 1:80ab0d068708 104 virtual bool USBCallback_request();
samux 1:80ab0d068708 105 virtual bool USBCallback_setConfiguration(uint8_t configuration);
samux 6:d0945750af57 106 volatile bool terminal_connected;
samux 1:80ab0d068708 107
samux 1:80ab0d068708 108 };
samux 1:80ab0d068708 109
samux 1:80ab0d068708 110 #endif