path: root/wirish/usb_serial.cpp

/******************************************************************************
 * The MIT License
 *
 * Copyright (c) 2010 Perry Hung.
 *
 * 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.
 *****************************************************************************/

/**
 * @brief USB virtual serial terminal
 */

#include <wirish/usb_serial.h>

#include <string.h>
#include <stdint.h>

#include <libmaple/nvic.h>
#include <libmaple/usb_cdcacm.h>
#include <libmaple/usb.h>

#include <wirish/wirish.h>

/*
 * Hooks used for bootloader reset signalling
 */

#if BOARD_HAVE_SERIALUSB
static void rxHook(unsigned, void*);
static void ifaceSetupHook(unsigned, void*);
#endif

/*
 * USBSerial interface
 */

#define USB_TIMEOUT 50

USBSerial::USBSerial(void) {
#if !BOARD_HAVE_SERIALUSB
    ASSERT(0);
#endif
}

void USBSerial::begin(void) {
#if BOARD_HAVE_SERIALUSB
    usb_cdcacm_enable(BOARD_USB_DISC_DEV, BOARD_USB_DISC_BIT);
    usb_cdcacm_set_hooks(USB_CDCACM_HOOK_RX, rxHook);
    usb_cdcacm_set_hooks(USB_CDCACM_HOOK_IFACE_SETUP, ifaceSetupHook);
#endif
}

void USBSerial::end(void) {
#if BOARD_HAVE_SERIALUSB
    usb_cdcacm_disable(BOARD_USB_DISC_DEV, BOARD_USB_DISC_BIT);
    usb_cdcacm_remove_hooks(USB_CDCACM_HOOK_RX | USB_CDCACM_HOOK_IFACE_SETUP);
#endif
}

void USBSerial::write(uint8 ch) {
    this->write(&ch, 1);
}

void USBSerial::write(const char *str) {
    this->write(str, strlen(str));
}

void USBSerial::write(const void *buf, uint32 len) {
    if (!this->isConnected() || !buf) {
        return;
    }

    uint32 txed = 0;
    uint32 old_txed = 0;
    uint32 start = millis();

    while (txed < len && (millis() - start < USB_TIMEOUT)) {
        txed += usb_cdcacm_tx((const uint8*)buf + txed, len - txed);
        if (old_txed != txed) {
            start = millis();
        }
        old_txed = txed;
    }
}

uint32 USBSerial::available(void) {
    return usb_cdcacm_data_available();
}

uint32 USBSerial::read(void *buf, uint32 len) {
    if (!buf) {
        return 0;
    }

    uint32 rxed = 0;
    while (rxed < len) {
        rxed += usb_cdcacm_rx((uint8*)buf + rxed, len - rxed);
    }

    return rxed;
}

/* Blocks forever until 1 byte is received */
uint8 USBSerial::read(void) {
    uint8 b;
    this->read(&b, 1);
    return b;
}

uint8 USBSerial::pending(void) {
    return usb_cdcacm_get_pending();
}

uint8 USBSerial::isConnected(void) {
    return usb_is_connected(USBLIB) && usb_is_configured(USBLIB);
}

uint8 USBSerial::getDTR(void) {
    return usb_cdcacm_get_dtr();
}

uint8 USBSerial::getRTS(void) {
    return usb_cdcacm_get_rts();
}

#if BOARD_HAVE_SERIALUSB
USBSerial SerialUSB;
#endif

/*
 * Bootloader hook implementations
 */

#if BOARD_HAVE_SERIALUSB

enum reset_state_t {
    DTR_UNSET,
    DTR_HIGH,
    DTR_NEGEDGE,
    DTR_LOW
};

static reset_state_t reset_state = DTR_UNSET;

static void ifaceSetupHook(unsigned hook, void *requestvp) {
    uint8 request = *(uint8*)requestvp;

    // Ignore requests we're not interested in.
    if (request != USB_CDCACM_SET_CONTROL_LINE_STATE) {
        return;
    }

    // We need to see a negative edge on DTR before we start looking
    // for the in-band magic reset byte sequence.
    uint8 dtr = usb_cdcacm_get_dtr();
    switch (reset_state) {
    case DTR_UNSET:
        reset_state = dtr ? DTR_HIGH : DTR_LOW;
        break;
    case DTR_HIGH:
        reset_state = dtr ? DTR_HIGH : DTR_NEGEDGE;
        break;
    case DTR_NEGEDGE:
        reset_state = dtr ? DTR_HIGH : DTR_LOW;
        break;
    case DTR_LOW:
        reset_state = dtr ? DTR_HIGH : DTR_LOW;
        break;
    }
}

#define RESET_DELAY 100000
static void wait_reset(void) {
  delay_us(RESET_DELAY);
  nvic_sys_reset();
}

#define STACK_TOP 0x20000800
#define EXC_RETURN 0xFFFFFFF9
#define DEFAULT_CPSR 0x61000000
static void rxHook(unsigned hook, void *ignored) {
    /* FIXME this is mad buggy; we need a new reset sequence. E.g. NAK
     * after each RX means you can't reset if any bytes are waiting. */
    if (reset_state == DTR_NEGEDGE) {
        reset_state = DTR_LOW;

        if (usb_cdcacm_data_available() >= 4) {
            // The magic reset sequence is "1EAF".
            static const uint8 magic[4] = {'1', 'E', 'A', 'F'};
            uint8 chkBuf[4];

            // Peek at the waiting bytes, looking for reset sequence,
            // bailing on mismatch.
            usb_cdcacm_peek(chkBuf, 4);
            for (unsigned i = 0; i < sizeof(magic); i++) {
                if (chkBuf[i] != magic[i]) {
                    return;
                }
            }

            // Got the magic sequence -> reset, presumably into the bootloader.
            // Return address is wait_reset, but we must set the thumb bit.
            uintptr_t target = (uintptr_t)wait_reset | 0x1;
            asm volatile("mov r0, %[stack_top]      \n\t" // Reset stack
                         "mov sp, r0                \n\t"
                         "mov r0, #1                \n\t"
                         "mov r1, %[target_addr]    \n\t"
                         "mov r2, %[cpsr]           \n\t"
                         "push {r2}                 \n\t" // Fake xPSR
                         "push {r1}                 \n\t" // PC target addr
                         "push {r0}                 \n\t" // Fake LR
                         "push {r0}                 \n\t" // Fake R12
                         "push {r0}                 \n\t" // Fake R3
                         "push {r0}                 \n\t" // Fake R2
                         "push {r0}                 \n\t" // Fake R1
                         "push {r0}                 \n\t" // Fake R0
                         "mov lr, %[exc_return]     \n\t"
                         "bx lr"
                         :
                         : [stack_top] "r" (STACK_TOP),
                           [target_addr] "r" (target),
                           [exc_return] "r" (EXC_RETURN),
                           [cpsr] "r" (DEFAULT_CPSR)
                         : "r0", "r1", "r2");
            /* Can't happen. */
            ASSERT_FAULT(0);
        }
    }
}

#endif  // BOARD_HAVE_SERIALUSB