[openocd.git] / src / jtag / jlink.c

/***************************************************************************
 *   Copyright (C) 2007 by Juergen Stuber <juergen@jstuber.net>            *
 *   based on Dominic Rath's and Benedikt Sauter's usbprog.c               *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "replacements.h"

#include "jtag.h"

#include <usb.h>
#include <string.h>

#include "log.h"

/* enable this to debug communication
 */
#if 0
#define _DEBUG_USB_COMMS_
#endif

#ifdef _DEBUG_JTAG_IO_
#define DEBUG_JTAG_IO(expr ...) LOG_DEBUG(expr)
#else
#define DEBUG_JTAG_IO(expr ...)
#endif

#define VID 0x1366
#define PID 0x0101

#define JLINK_WRITE_ENDPOINT    0x02
#define JLINK_READ_ENDPOINT             0x81

#define JLINK_USB_TIMEOUT               100

#define JLINK_IN_BUFFER_SIZE    2064
#define JLINK_OUT_BUFFER_SIZE   2064

/* Global USB buffers */
static u8 usb_in_buffer[JLINK_IN_BUFFER_SIZE];
static u8 usb_out_buffer[JLINK_OUT_BUFFER_SIZE];

/* Constants for JLink command */

/* The JLINK_TAP_SEQUENCE_COMMAND is obsolete *
/* and we should use EMU_CMD_HW_JTAG instead */
#define JLINK_TAP_SEQUENCE_COMMAND              0xcd

#define EMU_CMD_VERSION     0x01
#define EMU_CMD_SET_SPEED   0x05
#define EMU_CMD_GET_STATE   0x07
#define EMU_CMD_HW_JTAG     0xcf
#define EMU_CMD_HW_RESET0   0xdc
#define EMU_CMD_HW_RESET1   0xdd
#define EMU_CMD_HW_TRST0    0xde
#define EMU_CMD_HW_TRST1    0xdf

/* max speed 12MHz v5.0 jlink */
#define JLINK_MAX_SPEED 12000

/* External interface functions */
int jlink_execute_queue(void);
int jlink_speed(int speed);
int jlink_khz(int khz, int *jtag_speed);
int jlink_register_commands(struct command_context_s *cmd_ctx);
int jlink_init(void);
int jlink_quit(void);

/* CLI command handler functions */
int jlink_handle_jlink_info_command(struct command_context_s *cmd_ctx, char *cmd, char **args, int argc);

/* Queue command functions */
void jlink_end_state(enum tap_state state);
void jlink_state_move(void);
void jlink_path_move(int num_states, enum tap_state *path);
void jlink_runtest(int num_cycles);
void jlink_scan(int ir_scan, enum scan_type type, u8 *buffer, int scan_size, scan_command_t *command);
void jlink_reset(int trst, int srst);
void jlink_simple_command(u8 command);
int jlink_get_status(void);

/* J-Link tap buffer functions */
void jlink_tap_init();
int jlink_tap_execute();
void jlink_tap_ensure_space(int scans, int bits);
void jlink_tap_append_step(int tms, int tdi);
void jlink_tap_append_scan(int length, u8 *buffer, scan_command_t *command);

/* Jlink lowlevel functions */
typedef struct jlink_jtag
{
        struct usb_dev_handle* usb_handle;
} jlink_jtag_t;

jlink_jtag_t *jlink_usb_open(void);
void jlink_usb_close(jlink_jtag_t *jlink_jtag);
int jlink_usb_message(jlink_jtag_t *jlink_jtag, int out_length, int in_length);
int jlink_usb_write(jlink_jtag_t *jlink_jtag, int out_length);
int jlink_usb_read(jlink_jtag_t *jlink_jtag);

#ifdef _DEBUG_USB_COMMS_
void jlink_debug_buffer(u8 *buffer, int length);
#endif

jlink_jtag_t* jlink_jtag_handle;

/***************************************************************************/
/* External interface implementation */

jtag_interface_t jlink_interface =
{
        .name = "jlink",
        .execute_queue = jlink_execute_queue,
        .speed = jlink_speed,
        .khz = jlink_khz,
        .register_commands = jlink_register_commands,
        .init = jlink_init,
        .quit = jlink_quit
};

int jlink_execute_queue(void)
{
        jtag_command_t *cmd = jtag_command_queue;
        int scan_size;
        enum scan_type type;
        u8 *buffer;
        
        while (cmd != NULL)
        {
                switch (cmd->type)
                {
                        case JTAG_END_STATE:
                                DEBUG_JTAG_IO("end_state: %i", cmd->cmd.end_state->end_state);
                        
                                if (cmd->cmd.end_state->end_state != -1)
                                {
                                        jlink_end_state(cmd->cmd.end_state->end_state);
                                }
                                break;
        
                        case JTAG_RUNTEST:
                                DEBUG_JTAG_IO( "runtest %i cycles, end in %i", cmd->cmd.runtest->num_cycles, \
                                        cmd->cmd.runtest->end_state);
                                
                                if (cmd->cmd.runtest->end_state != -1)
                                {
                                        jlink_end_state(cmd->cmd.runtest->end_state);
                                }
                                jlink_runtest(cmd->cmd.runtest->num_cycles);
                                break;
        
                        case JTAG_STATEMOVE:
                                DEBUG_JTAG_IO("statemove end in %i",
                                cmd->cmd.statemove->end_state);
                        
                                if (cmd->cmd.statemove->end_state != -1)
                                {
                                        jlink_end_state(cmd->cmd.statemove->end_state);
                                }
                                jlink_state_move();
                                break;
        
                        case JTAG_PATHMOVE:
                            DEBUG_JTAG_IO("pathmove: %i states, end in %i",
                                cmd->cmd.pathmove->num_states,
                                cmd->cmd.pathmove->path[cmd->cmd.pathmove->num_states - 1]);
                        
                                jlink_path_move(cmd->cmd.pathmove->num_states, cmd->cmd.pathmove->path);
                                break;
        
                        case JTAG_SCAN:
                                DEBUG_JTAG_IO("scan end in %i", cmd->cmd.scan->end_state);
                        
                                if (cmd->cmd.scan->end_state != -1)
                                {
                                    jlink_end_state(cmd->cmd.scan->end_state);
                                }
                        
                                scan_size = jtag_build_buffer(cmd->cmd.scan, &buffer);
                                DEBUG_JTAG_IO("scan input, length = %d", scan_size);
                                
#ifdef _DEBUG_USB_COMMS_
                                jlink_debug_buffer(buffer, (scan_size + 7) / 8);
#endif
                                type = jtag_scan_type(cmd->cmd.scan);
                                jlink_scan(cmd->cmd.scan->ir_scan, type, buffer, scan_size, cmd->cmd.scan);
                                break;
        
                        case JTAG_RESET:
                                DEBUG_JTAG_IO("reset trst: %i srst %i",
                                cmd->cmd.reset->trst,
                                cmd->cmd.reset->srst);
                        
                                jlink_tap_execute();
                        
                                if (cmd->cmd.reset->trst == 1)
                                {
                                        cur_state = TAP_TLR;
                                }
                                jlink_reset(cmd->cmd.reset->trst, cmd->cmd.reset->srst);
                                break;
        
                        case JTAG_SLEEP:
                                DEBUG_JTAG_IO("sleep %i", cmd->cmd.sleep->us);
                                jlink_tap_execute();
                                jtag_sleep(cmd->cmd.sleep->us);
                                break;
        
                default:
                        LOG_ERROR("BUG: unknown JTAG command type encountered");
                        exit(-1);
                }
                cmd = cmd->next;
        }
        jlink_tap_execute();
        
        return ERROR_OK;
}

/* Sets speed in kHz. */
int jlink_speed(int speed)
{
        int result;
        
//      if ((speed == -1) || ((1 <= speed) && (speed <= JLINK_MAX_SPEED)))
        if (speed <= JLINK_MAX_SPEED)
        {
                /* check for RTCK setting */
                if (speed == 0)
                        speed = -1;
                
                usb_out_buffer[0] = EMU_CMD_SET_SPEED;
                usb_out_buffer[1] = (speed >> 0) & 0xff;
                usb_out_buffer[2] = (speed >> 8) & 0xff;
                
                result = jlink_usb_write(jlink_jtag_handle, 3);
                
                if (result == 3)
                {
                        return ERROR_OK;
                }
                else
                {
                        LOG_ERROR("J-Link setting speed failed (%d)", result);
                        return ERROR_JTAG_DEVICE_ERROR;
                }
        }
        else
        {
                LOG_INFO("Requested speed %dkHz exceeds maximum of %dkHz, ignored", speed, JLINK_MAX_SPEED);
        }
        
        return ERROR_OK;
}

int jlink_khz(int khz, int *jtag_speed)
{
        *jtag_speed = khz;
        
        return ERROR_OK;
}

int jlink_register_commands(struct command_context_s *cmd_ctx)
{
        register_command(cmd_ctx, NULL, "jlink_info", jlink_handle_jlink_info_command, COMMAND_EXEC,
                "query jlink info");
        return ERROR_OK;
}

int jlink_init(void)
{
        int result;
  int len;
  int check_cnt;  
        
        jlink_jtag_handle = jlink_usb_open();
        
        if (jlink_jtag_handle == 0)
        {
                LOG_ERROR("Can't find USB JTAG Interface! Please check connection and permissions.");
                return ERROR_JTAG_INIT_FAILED;
        }
                
  check_cnt = 0;
  while (check_cnt < 3)
  {    
          /* query hardware version */
          jlink_simple_command(EMU_CMD_VERSION);
          result = jlink_usb_read(jlink_jtag_handle);
  
          if (result == 2)
          {
      /* Get length */
                  len = buf_get_u32(usb_in_buffer, 0, 16);
      
      /* Get version */
                  result = jlink_usb_read(jlink_jtag_handle);
                
                  if(result == len)
                  {
                          usb_in_buffer[result] = 0;
                          LOG_INFO(usb_in_buffer);
      
                  /* attempt to get status */
                  jlink_get_status();
        
        break;
                  }
    }    
    
    check_cnt++;
  }    
  
  if (check_cnt == 3)
  {
          LOG_INFO("J-Link initial read failed, don't worry");
  }
        
        LOG_INFO("J-Link JTAG Interface ready");
        
        jlink_reset(0, 0);
        jlink_tap_init();
                
        return ERROR_OK;
}

int jlink_quit(void)
{
        jlink_usb_close(jlink_jtag_handle);
        return ERROR_OK;
}

/***************************************************************************/
/* Queue command implementations */

void jlink_end_state(enum tap_state state)
{
        if (tap_move_map[state] != -1)
        {
                end_state = state;
        }
        else
        {
                LOG_ERROR("BUG: %i is not a valid end state", state);
                exit(-1);
        }
}

/* Goes to the end state. */
void jlink_state_move(void)
{
        int i;
        int tms = 0;
        u8 tms_scan = TAP_MOVE(cur_state, end_state);
        
        for (i = 0; i < 7; i++)
        {
                tms = (tms_scan >> i) & 1;
                jlink_tap_append_step(tms, 0);
        }
        
        cur_state = end_state;
}

void jlink_path_move(int num_states, enum tap_state *path)
{
        int i;
        
        for (i = 0; i < num_states; i++)
        {
                if (path[i] == tap_transitions[cur_state].low)
                {
                        jlink_tap_append_step(0, 0);
                }
                else if (path[i] == tap_transitions[cur_state].high)
                {
                        jlink_tap_append_step(1, 0);
                }
                else
                {
                        LOG_ERROR("BUG: %s -> %s isn't a valid TAP transition", tap_state_strings[cur_state], tap_state_strings[path[i]]);
                        exit(-1);
                }
                
                cur_state = path[i];
        }
        
        end_state = cur_state;
}

void jlink_runtest(int num_cycles)
{
        int i;
        
        enum tap_state saved_end_state = end_state;
        
        /* only do a state_move when we're not already in RTI */
        if (cur_state != TAP_RTI)
        {
                jlink_end_state(TAP_RTI);
                jlink_state_move();
        }
        
        /* execute num_cycles */
        for (i = 0; i < num_cycles; i++)
        {
                jlink_tap_append_step(0, 0);
        }
        
        /* finish in end_state */
        jlink_end_state(saved_end_state);
        if (cur_state != end_state)
        {
                jlink_state_move();
        }
}

void jlink_scan(int ir_scan, enum scan_type type, u8 *buffer, int scan_size, scan_command_t *command)
{
        enum tap_state saved_end_state;
        
        jlink_tap_ensure_space(1, scan_size + 8);
        
        saved_end_state = end_state;
        
        /* Move to appropriate scan state */
        jlink_end_state(ir_scan ? TAP_SI : TAP_SD);
        
        jlink_state_move();
        jlink_end_state(saved_end_state);
        
        /* Scan */
        jlink_tap_append_scan(scan_size, buffer, command);
        
        /* We are in Exit1, go to Pause */
        jlink_tap_append_step(0, 0);
        
        cur_state = ir_scan ? TAP_PI : TAP_PD;
        
        if (cur_state != end_state)
        {
                jlink_state_move();
        }
}

void jlink_reset(int trst, int srst)
{
        LOG_DEBUG("trst: %i, srst: %i", trst, srst);
        
        /* Signals are active low */
        if (trst == 0)
        {
                jlink_simple_command(EMU_CMD_HW_TRST1);
        }
        else if (trst == 1)
        {
                jlink_simple_command(EMU_CMD_HW_TRST0);
        }
        
        if (srst == 0)
        {
                jlink_simple_command(EMU_CMD_HW_RESET1);
        }
        else if (srst == 1)
        {
                jlink_simple_command(EMU_CMD_HW_RESET0);
        }
}

void jlink_simple_command(u8 command)
{
        int result;
        
        DEBUG_JTAG_IO("0x%02x", command);
        
        usb_out_buffer[0] = command;
        result = jlink_usb_write(jlink_jtag_handle, 1);
        
        if (result != 1)
        {
                LOG_ERROR("J-Link command 0x%02x failed (%d)", command, result);
        }
}

int jlink_get_status(void)
{
        int result;
        
        jlink_simple_command(EMU_CMD_GET_STATE);
        result = jlink_usb_read(jlink_jtag_handle);
        
        if(result == 8)
        {
                int vref = usb_in_buffer[0] + (usb_in_buffer[1] << 8);
                LOG_INFO("Vref = %d.%d TCK=%d TDI=%d TDO=%d TMS=%d SRST=%d TRST=%d\n", \
                        vref / 1000, vref % 1000, \
                        usb_in_buffer[2], usb_in_buffer[3], usb_in_buffer[4], \
                        usb_in_buffer[5], usb_in_buffer[6], usb_in_buffer[7]);
                
                if(vref < 1500)
                {
                        LOG_ERROR("Vref too low. Eventually the target isn't powered or disconnected?\n");
                }
        }
        else
        {
                LOG_ERROR("J-Link command EMU_CMD_GET_STATE failed (%d)\n", result);
        }
        
        return ERROR_OK;
}

int jlink_handle_jlink_info_command(struct command_context_s *cmd_ctx, char *cmd, char **args, int argc)
{
        int result;
        int len = 0;
        
        /* query hardware version */
        jlink_simple_command(EMU_CMD_VERSION);
        result = jlink_usb_read(jlink_jtag_handle);
        
        if (result == 2)
        {
                len = buf_get_u32(usb_in_buffer, 0, 16);
                result = jlink_usb_read(jlink_jtag_handle);
                
                if(result == len)
                {
                        usb_in_buffer[result] = 0;
                        LOG_INFO(usb_in_buffer);
                }
                
                /* attempt to get status */
                jlink_get_status();
        }
        else
        {
                LOG_ERROR("J-Link command EMU_CMD_VERSION failed (%d)\n", result);
        }
        
        return ERROR_OK;
}

/***************************************************************************/
/* J-Link tap functions */

/* We use the maximal value observed */
#define JLINK_TAP_BUFFER_SIZE 390

static int tap_length;
static u8 tms_buffer[JLINK_TAP_BUFFER_SIZE];
static u8 tdi_buffer[JLINK_TAP_BUFFER_SIZE];
static u8 tdo_buffer[JLINK_TAP_BUFFER_SIZE];

typedef struct
{
        int first;      /* First bit position in tdo_buffer to read */
        int length; /* Number of bits to read */
        scan_command_t *command; /* Corresponding scan command */
        u8 *buffer;
} pending_scan_result_t;

#define MAX_PENDING_SCAN_RESULTS 16

static int pending_scan_results_length;
static pending_scan_result_t pending_scan_results_buffer[MAX_PENDING_SCAN_RESULTS];

static int last_tms;

void jlink_tap_init()
{
        tap_length = 0;
        pending_scan_results_length = 0;
}

void jlink_tap_ensure_space(int scans, int bits)
{
        int available_scans = MAX_PENDING_SCAN_RESULTS - pending_scan_results_length;
        int available_bits = JLINK_TAP_BUFFER_SIZE * 8 - tap_length;
        
        if (scans > available_scans || bits > available_bits)
        {
                jlink_tap_execute();
        }
}

void jlink_tap_append_step(int tms, int tdi)
{
        last_tms = tms;
        int index = tap_length / 8;
        
        if (index < JLINK_TAP_BUFFER_SIZE)
        {
                int bit_index = tap_length % 8;
                u8 bit = 1 << bit_index;
                
                if (tms)
                {
                        tms_buffer[index] |= bit;
                }
                else
                {
                        tms_buffer[index] &= ~bit;
                }
                
                if (tdi)
                {
                        tdi_buffer[index] |= bit;
                }
                else
                {
                        tdi_buffer[index] &= ~bit;
                }
                
                tap_length++;
        }
        else
        {
                LOG_ERROR("jlink_tap_append_step, overflow");
        }
}

void jlink_tap_append_scan(int length, u8 *buffer, scan_command_t *command)
{
        pending_scan_result_t *pending_scan_result = &pending_scan_results_buffer[pending_scan_results_length];
        int i;
        
        pending_scan_result->first = tap_length;
        pending_scan_result->length = length;
        pending_scan_result->command = command;
        pending_scan_result->buffer = buffer;
        
        for (i = 0; i < length; i++)
        {
                jlink_tap_append_step((i < length-1 ? 0 : 1), (buffer[i/8] >> (i%8)) & 1);
        }
        pending_scan_results_length++;
}

/* Pad and send a tap sequence to the device, and receive the answer.
 * For the purpose of padding we assume that we are in idle or pause state. */
int jlink_tap_execute()
{
        int byte_length;
        int tms_offset;
        int tdi_offset;
        int i;
        int result;
        
        if (tap_length > 0)
        {
                /* Pad last byte so that tap_length is divisible by 8 */
                while (tap_length % 8 != 0)
                {
                        /* More of the last TMS value keeps us in the same state,
                         * analogous to free-running JTAG interfaces. */
                        jlink_tap_append_step(last_tms, 0);
                }
        
                byte_length = tap_length / 8;
        
                usb_out_buffer[0] = JLINK_TAP_SEQUENCE_COMMAND;
                usb_out_buffer[1] = (tap_length >> 0) & 0xff;
                usb_out_buffer[2] = (tap_length >> 8) & 0xff;
        
                tms_offset = 3;
                for (i = 0; i < byte_length; i++)
                {
                    usb_out_buffer[tms_offset + i] = tms_buffer[i];
                }
                
                tdi_offset = tms_offset + byte_length;
                for (i = 0; i < byte_length; i++)
                {
                    usb_out_buffer[tdi_offset + i] = tdi_buffer[i];
                }
        
                result = jlink_usb_message(jlink_jtag_handle, 3 + 2 * byte_length, byte_length);
        
                if (result == byte_length)
                {
                        for (i = 0; i < byte_length; i++)
                        {
                                tdo_buffer[i] = usb_in_buffer[i];
                        }
                        
                        for (i = 0; i < pending_scan_results_length; i++)
                        {
                                pending_scan_result_t *pending_scan_result = &pending_scan_results_buffer[i];
                                u8 *buffer = pending_scan_result->buffer;
                                int length = pending_scan_result->length;
                                int first = pending_scan_result->first;
                                scan_command_t *command = pending_scan_result->command;
        
                                /* Copy to buffer */
                                buf_set_buf(tdo_buffer, first, buffer, 0, length);
        
                                DEBUG_JTAG_IO("pending scan result, length = %d", length);
                                
#ifdef _DEBUG_USB_COMMS_
                                jlink_debug_buffer(buffer, byte_length);
#endif
        
                        if (jtag_read_buffer(buffer, command) != ERROR_OK)
                        {
                                jlink_tap_init();
                                        return ERROR_JTAG_QUEUE_FAILED;
                        }
                
                        if (pending_scan_result->buffer != NULL)
                        {
                                        free(pending_scan_result->buffer);
                        }
                }
                }
                else
                {
                        LOG_ERROR("jlink_tap_execute, wrong result %d, expected %d", result, byte_length);
                        return ERROR_JTAG_QUEUE_FAILED;
                }
                
                jlink_tap_init();
        }
        
        return ERROR_OK;
}

/*****************************************************************************/
/* JLink USB low-level functions */

jlink_jtag_t* jlink_usb_open()
{
        struct usb_bus *busses;
        struct usb_bus *bus;
        struct usb_device *dev;
        
        jlink_jtag_t *result;
        
        result = (jlink_jtag_t*) malloc(sizeof(jlink_jtag_t));
        
        usb_init();
        usb_find_busses();
        usb_find_devices();
        
        busses = usb_get_busses();
        
        /* find jlink_jtag device in usb bus */
        
        for (bus = busses; bus; bus = bus->next)
        {
                for (dev = bus->devices; dev; dev = dev->next)
                {
                        if ((dev->descriptor.idVendor == VID) && (dev->descriptor.idProduct == PID))
                        {
                                result->usb_handle = usb_open(dev);
                                
                                /* usb_set_configuration required under win32 */
                                usb_set_configuration(result->usb_handle, dev->config[0].bConfigurationValue);
                                usb_claim_interface(result->usb_handle, 0);
                                usb_set_altinterface(result->usb_handle, 0);
                                return result;
                        }
                }
        }
        
        free(result);
        return NULL;
}

void jlink_usb_close(jlink_jtag_t *jlink_jtag)
{
        usb_close(jlink_jtag->usb_handle);
        free(jlink_jtag);
}

/* Send a message and receive the reply. */
int jlink_usb_message(jlink_jtag_t *jlink_jtag, int out_length, int in_length)
{
        int result;
        
        result = jlink_usb_write(jlink_jtag, out_length);
        if (result == out_length)
        {
                result = jlink_usb_read(jlink_jtag);
                if (result == in_length)
                {
                        return result;
                }
            else
            {
                        LOG_ERROR("usb_bulk_read failed (requested=%d, result=%d)", in_length, result);
                        return -1;
            }
        }
        else
        {
                LOG_ERROR("usb_bulk_write failed (requested=%d, result=%d)", out_length, result);
            return -1;
        }
}

/* Write data from out_buffer to USB. */
int jlink_usb_write(jlink_jtag_t *jlink_jtag, int out_length)
{
        int result;
        
        if (out_length > JLINK_OUT_BUFFER_SIZE)
        {
                LOG_ERROR("jlink_jtag_write illegal out_length=%d (max=%d)", out_length, JLINK_OUT_BUFFER_SIZE);
                return -1;
        }
        
        result = usb_bulk_write(jlink_jtag->usb_handle, JLINK_WRITE_ENDPOINT, \
                usb_out_buffer, out_length, JLINK_USB_TIMEOUT);
        
        DEBUG_JTAG_IO("jlink_usb_write, out_length = %d, result = %d", out_length, result);
        
#ifdef _DEBUG_USB_COMMS_
        jlink_debug_buffer(usb_out_buffer, out_length);
#endif
        return result;
}

/* Read data from USB into in_buffer. */
int jlink_usb_read(jlink_jtag_t *jlink_jtag)
{
        int result = usb_bulk_read(jlink_jtag->usb_handle, JLINK_READ_ENDPOINT, \
                usb_in_buffer, JLINK_IN_BUFFER_SIZE, JLINK_USB_TIMEOUT);

        DEBUG_JTAG_IO("jlink_usb_read, result = %d", result);
        
#ifdef _DEBUG_USB_COMMS_
        jlink_debug_buffer(usb_in_buffer, result);
#endif
    return result;
}

#ifdef _DEBUG_USB_COMMS_
#define BYTES_PER_LINE  16

void jlink_debug_buffer(u8 *buffer, int length)
{
        char line[81];
        char s[4];
        int i;
        int j;
        
        for (i = 0; i < length; i += BYTES_PER_LINE)
        {
                snprintf(line, 5, "%04x", i);
                for (j = i; j < i + BYTES_PER_LINE && j < length; j++)
                {
                        snprintf(s, 4, " %02x", buffer[j]);
                        strcat(line, s);
                }
                LOG_DEBUG(line);
        }
}
#endif