X-Git-Url: https://review.openocd.org/gitweb?p=openocd.git;a=blobdiff_plain;f=src%2Fjtag%2Fpresto.c;h=b4ba3f44aa4e251af640dc341b14fa75e1a69162;hp=95c59303b0d68fa936a1857a07f66369c0659408;hb=98723c4ecdbe06f90c66f3abec27b792c3b38e34;hpb=20e4e77cdf366dedac21ff5670c54291feadfc05

diff --git a/src/jtag/presto.c b/src/jtag/presto.c
index 95c59303b0..b4ba3f44aa 100644
--- a/src/jtag/presto.c
+++ b/src/jtag/presto.c
@@ -23,55 +23,49 @@
 
 #if IS_CYGWIN == 1
 #include "windows.h"
-#undef ERROR
 #endif
 
-#include "replacements.h"
-
-/* project specific includes */
-#include "log.h"
-#include "types.h"
-#include "jtag.h"
-#include "configuration.h"
+#include "interface.h"
 #include "time_support.h"
 #include "bitq.h"
 
-/* system includes */
-#include <string.h>
-#include <stdlib.h>
-#include <unistd.h>
-
-#include <sys/time.h>
-#include <time.h>
-
-#include "ftd2xx.h"
 
+/* PRESTO access library includes */
+#if BUILD_PRESTO_FTD2XX == 1
+#include <ftd2xx.h>
+#elif BUILD_PRESTO_LIBFTDI == 1
+#include <ftdi.h>
+#else
+#error "BUG: either FTD2XX and LIBFTDI has to be used"
+#endif
 
-int presto_jtag_speed(int speed);
-int presto_jtag_register_commands(struct command_context_s *cmd_ctx);
-int presto_jtag_init(void);
-int presto_jtag_quit(void);
+static int presto_jtag_speed(int speed);
+static int presto_jtag_khz(int khz, int *jtag_speed);
+static int presto_jtag_speed_div(int speed, int *khz);
+static int presto_jtag_register_commands(struct command_context *cmd_ctx);
+static int presto_jtag_init(void);
+static int presto_jtag_quit(void);
 
-jtag_interface_t presto_interface =
+struct jtag_interface presto_interface =
 {
 	.name = "presto",
 	.execute_queue = bitq_execute_queue,
-	.support_pathmove = 1,
 	.speed = presto_jtag_speed,
+	.khz = presto_jtag_khz,
+	.speed_div = presto_jtag_speed_div,
 	.register_commands = presto_jtag_register_commands,
 	.init = presto_jtag_init,
 	.quit = presto_jtag_quit,
 };
 
+static int presto_bitq_out(int tms, int tdi, int tdo_req);
+static int presto_bitq_flush(void);
+static int presto_bitq_sleep(unsigned long us);
+static int presto_bitq_reset(int trst, int srst);
+static int presto_bitq_in_rdy(void);
+static int presto_bitq_in(void);
 
-int presto_bitq_out(int tms, int tdi, int tdo_req);
-int presto_bitq_flush(void);
-int presto_bitq_sleep(unsigned long us);
-int presto_bitq_reset(int rst, int en);
-int presto_bitq_in_rdy(void);
-int presto_bitq_in(void);
-
-bitq_interface_t presto_bitq =
+static struct bitq_interface presto_bitq =
 {
 	.out = presto_bitq_out,
 	.flush = presto_bitq_flush,
@@ -81,33 +75,32 @@ bitq_interface_t presto_bitq =
 	.in = presto_bitq_in,
 };
 
-
 /* -------------------------------------------------------------------------- */
 
-
 #define FT_DEVICE_NAME_LEN 64
 #define FT_DEVICE_SERNUM_LEN 64
 
 #define PRESTO_VID_PID 0x0403f1a0
-
-#define PRST_OK 0
-#define PRST_ERR 1
-#define PRST_TIMEOUT 2
+#define PRESTO_VID (0x0403)
+#define PRESTO_PID (0xf1a0)
 
 #define BUFFER_SIZE (64*62)
 
-
-typedef struct presto_s
-{
+struct presto {
+#if BUILD_PRESTO_FTD2XX == 1
 	FT_HANDLE handle;
 	FT_STATUS status;
-	
+#elif BUILD_PRESTO_LIBFTDI == 1
+	struct ftdi_context ftdic;
+	int retval;
+#endif
+
 	char serial[FT_DEVICE_SERNUM_LEN];
 
-	BYTE buff_out[BUFFER_SIZE];
+	uint8_t buff_out[BUFFER_SIZE];
 	int buff_out_pos;
 
-	BYTE buff_in[BUFFER_SIZE];
+	uint8_t buff_in[BUFFER_SIZE];
 	int buff_in_exp; /* expected in buffer length */
 	int buff_in_len; /* length of data received */
 	int buff_in_pos;
@@ -117,382 +110,699 @@ typedef struct presto_s
 
 	int jtag_tms; /* last tms state */
 	int jtag_tck; /* last tck state */
+	int jtag_rst; /* last trst state */
 
 	int jtag_tdi_data;
 	int jtag_tdi_count;
 
-} presto_t;
+	int jtag_speed;
+};
 
-presto_t presto_state;
-presto_t *presto=&presto_state;
+static struct presto presto_state;
+static struct presto *presto = &presto_state;
 
-BYTE presto_init_seq[] =
+static uint8_t presto_init_seq[] =
 {
-	0x80,	0xA0,	0xA8,	0xB0,	0xC0,	0xE0
+	0x80, 0xA0, 0xA8, 0xB0, 0xC0, 0xE0
 };
 
+static int presto_write(uint8_t *buf, uint32_t size)
+{
+#if BUILD_PRESTO_FTD2XX == 1
+	DWORD ftbytes;
+	if ((presto->status = FT_Write(presto->handle, buf, size, &ftbytes)) != FT_OK)
+	{
+		LOG_ERROR("FT_Write returned: %lu", presto->status);
+		return ERROR_JTAG_DEVICE_ERROR;
+	}
+
+#elif BUILD_PRESTO_LIBFTDI == 1
+	uint32_t ftbytes;
+	if ((presto->retval = ftdi_write_data(&presto->ftdic, buf, size)) < 0)
+	{
+		LOG_ERROR("ftdi_write_data: %s", ftdi_get_error_string(&presto->ftdic));
+		return ERROR_JTAG_DEVICE_ERROR;
+	}
+	ftbytes = presto->retval;
+#endif
+
+	if (ftbytes != size)
+	{
+		LOG_ERROR("couldn't write the requested number of bytes to PRESTO (%u < %u)",
+			  (unsigned)ftbytes, (unsigned)size);
+		return ERROR_JTAG_DEVICE_ERROR;
+	}
+
+	return ERROR_OK;
+}
 
-int presto_open(char *req_serial)
+static int presto_read(uint8_t* buf, uint32_t size)
 {
-	int i;
+#if BUILD_PRESTO_FTD2XX == 1
+	DWORD ftbytes;
+	if ((presto->status = FT_Read(presto->handle, buf, size, &ftbytes)) != FT_OK)
+	{
+		LOG_ERROR("FT_Read returned: %lu", presto->status);
+		return ERROR_JTAG_DEVICE_ERROR;
+	}
+
+#elif BUILD_PRESTO_LIBFTDI == 1
+	uint32_t ftbytes = 0;
+
+	struct timeval timeout, now;
+	gettimeofday(&timeout, NULL);
+	timeval_add_time(&timeout, 1, 0); /* one second timeout */
+
+	while (ftbytes < size)
+	{
+		if ((presto->retval = ftdi_read_data(&presto->ftdic, buf + ftbytes, size - ftbytes)) < 0)
+		{
+			LOG_ERROR("ftdi_read_data: %s", ftdi_get_error_string(&presto->ftdic));
+			return ERROR_JTAG_DEVICE_ERROR;
+		}
+		ftbytes += presto->retval;
+
+		gettimeofday(&now, NULL);
+		if ((now.tv_sec > timeout.tv_sec) || ((now.tv_sec == timeout.tv_sec) && (now.tv_usec > timeout.tv_usec)))
+			break;
+	}
+#endif
+
+	if (ftbytes != size)
+	{
+		/* this is just a warning, there might have been timeout when detecting PRESTO, which is not fatal */
+		LOG_WARNING("couldn't read the requested number of bytes from PRESTO (%u < %u)",
+			    (unsigned)ftbytes, (unsigned)size);
+		return ERROR_JTAG_DEVICE_ERROR;
+	}
+
+	return ERROR_OK;
+}
+
+#if BUILD_PRESTO_FTD2XX == 1
+static int presto_open_ftd2xx(char *req_serial)
+{
+	uint32_t i;
 	DWORD numdevs;
 	DWORD vidpid;
 	char devname[FT_DEVICE_NAME_LEN];
 	FT_DEVICE device;
 
 	BYTE presto_data;
-	unsigned long ftbytes;
+	DWORD ftbytes;
 
 	presto->handle = (FT_HANDLE)INVALID_HANDLE_VALUE;
 
-	presto->buff_out_pos=0;
-	presto->buff_in_pos=0;
-	presto->buff_in_len=0;
-	presto->buff_in_exp=0;
-
-	presto->total_out=0;
-	presto->total_in=0;
+#if IS_WIN32 == 0
+	/* Add non-standard Vid/Pid to the linux driver */
+	if ((presto->status = FT_SetVIDPID(PRESTO_VID, PRESTO_PID)) != FT_OK)
+	{
+		LOG_ERROR("couldn't add PRESTO VID/PID");
+		exit(-1);
+	}
+#endif
 
-	presto->jtag_tms=0;
-	presto->jtag_tck=0;
-	presto->jtag_tdi_data=0;
-	presto->jtag_tdi_count=0;
+	if ((presto->status = FT_ListDevices(&numdevs, NULL, FT_LIST_NUMBER_ONLY)) != FT_OK)
+	{
+		LOG_ERROR("FT_ListDevices failed: %i", (int)presto->status);
+		return ERROR_JTAG_DEVICE_ERROR;
+	}
 
-	if (FT_ListDevices(&numdevs, NULL, FT_LIST_NUMBER_ONLY)!=FT_OK) return PRST_ERR;
-	for (i=0; i<numdevs; i++)
+	LOG_DEBUG("FTDI devices available: %lu", numdevs);
+	for (i = 0; i < numdevs; i++)
 	{
-		if (FT_Open(i, &(presto->handle))!=FT_OK) continue;
-		if (FT_GetDeviceInfo(presto->handle,&device,&vidpid,presto->serial,devname,NULL)==FT_OK)
+		if ((presto->status = FT_Open(i, &(presto->handle))) != FT_OK)
 		{
-			if (vidpid==PRESTO_VID_PID && (req_serial==NULL || !strcmp(presto->serial,req_serial)))
+			/* this is not fatal, the device may be legitimately open by other process, hence debug message only */
+			LOG_DEBUG("FT_Open failed: %i", (int)presto->status);
+			continue;
+		}
+		LOG_DEBUG("FTDI device %i open", (int)i);
+
+		if ((presto->status = FT_GetDeviceInfo(presto->handle, &device, &vidpid,
+				presto->serial, devname, NULL)) == FT_OK)
+		{
+			if (vidpid == PRESTO_VID_PID
+					&& (req_serial == NULL || !strcmp(presto->serial, req_serial)))
 				break;
 		}
+		else
+			LOG_DEBUG("FT_GetDeviceInfo failed: %lu", presto->status);
+
+		LOG_DEBUG("FTDI device %i does not match, closing", (int)i);
 		FT_Close(presto->handle);
 		presto->handle = (FT_HANDLE)INVALID_HANDLE_VALUE;
 	}
 
-	if (presto->handle == (FT_HANDLE)INVALID_HANDLE_VALUE) return PRST_ERR;
+	if (presto->handle == (FT_HANDLE)INVALID_HANDLE_VALUE)
+		return ERROR_JTAG_DEVICE_ERROR; /* presto not open, return */
+
+	if ((presto->status = FT_SetLatencyTimer(presto->handle, 1)) != FT_OK)
+		return ERROR_JTAG_DEVICE_ERROR;
 
-	if ((presto->status=FT_SetLatencyTimer(presto->handle,1))!=FT_OK) return PRST_ERR;
-	if ((presto->status=FT_SetTimeouts(presto->handle,100,0))!=FT_OK) return PRST_ERR;
-	if ((presto->status=FT_Purge(presto->handle, FT_PURGE_TX|FT_PURGE_RX))!=FT_OK) return PRST_ERR;
 
-	presto_data=0xD0;
-	if ((presto->status=FT_Write(presto->handle,&presto_data,1,&ftbytes))!=FT_OK) return PRST_ERR;
-	if ((presto->status=FT_Read(presto->handle,&presto_data,1,&ftbytes))!=FT_OK) return PRST_ERR;
+	if ((presto->status = FT_SetTimeouts(presto->handle, 100, 0)) != FT_OK)
+		return ERROR_JTAG_DEVICE_ERROR;
 
-	if (ftbytes!=1)
+	if ((presto->status = FT_Purge(presto->handle, FT_PURGE_TX | FT_PURGE_RX)) != FT_OK)
+		return ERROR_JTAG_DEVICE_ERROR;
+
+	presto_data = 0xD0;
+	if ((presto->status = FT_Write(presto->handle, &presto_data, 1, &ftbytes)) != FT_OK)
+		return ERROR_JTAG_DEVICE_ERROR;
+
+	/* delay between first write/read turnaround (after purge?) necessary under Linux for unknown reason,
+	   probably a bug in library threading */
+	usleep(100000);
+	if ((presto->status = FT_Read(presto->handle, &presto_data, 1, &ftbytes)) != FT_OK)
+		return ERROR_JTAG_DEVICE_ERROR;
+
+	if (ftbytes != 1)
 	{
-		if ((presto->status=FT_SetBitMode(presto->handle,0x80,1))!=FT_OK) return PRST_ERR;
-		if ((presto->status=FT_Purge(presto->handle, FT_PURGE_TX|FT_PURGE_RX))!=FT_OK) return PRST_ERR ;
-		if ((presto->status=FT_SetBaudRate(presto->handle,9600))!=FT_OK) return PRST_ERR;
+		LOG_DEBUG("PRESTO reset");
 
-		presto_data=0;
-		for (i=0; i<4*62; i++)
-			if ((presto->status=FT_Write(presto->handle,&presto_data,1,&ftbytes))!=FT_OK) return PRST_ERR;
+		if ((presto->status = FT_Purge(presto->handle, FT_PURGE_TX | FT_PURGE_RX)) != FT_OK)
+			return ERROR_JTAG_DEVICE_ERROR;
+		if ((presto->status = FT_SetBitMode(presto->handle, 0x80, 1)) != FT_OK)
+			return ERROR_JTAG_DEVICE_ERROR;
+		if ((presto->status = FT_SetBaudRate(presto->handle, 9600)) != FT_OK)
+			return ERROR_JTAG_DEVICE_ERROR;
+
+		presto_data = 0;
+		for (i = 0; i < 4 * 62; i++)
+			if ((presto->status = FT_Write(presto->handle, &presto_data, 1, &ftbytes)) != FT_OK)
+				return ERROR_JTAG_DEVICE_ERROR;
 
 		usleep(100000);
 
-		if ((presto->status=FT_SetBitMode(presto->handle,0x00,0))!=FT_OK) return PRST_ERR;
-		if ((presto->status=FT_Purge(presto->handle, FT_PURGE_TX|FT_PURGE_RX))!=FT_OK) return PRST_ERR;
+		if ((presto->status = FT_SetBitMode(presto->handle, 0x00, 0)) != FT_OK)
+			return ERROR_JTAG_DEVICE_ERROR;
+
+		if ((presto->status = FT_Purge(presto->handle, FT_PURGE_TX | FT_PURGE_RX)) != FT_OK)
+			return ERROR_JTAG_DEVICE_ERROR;
+
+		presto_data = 0xD0;
+		if ((presto->status = FT_Write(presto->handle, &presto_data, 1, &ftbytes)) != FT_OK)
+			return ERROR_JTAG_DEVICE_ERROR;
 
-		presto_data=0xD0;
-		if ((presto->status=FT_Write(presto->handle,&presto_data,1,&ftbytes))!=FT_OK) return PRST_ERR;
-		if ((presto->status=FT_Read(presto->handle,&presto_data,1,&ftbytes))!=FT_OK) return PRST_ERR;
-		if (ftbytes!=1) return PRST_ERR;
+		/* delay between first write/read turnaround (after purge?) necessary under Linux for unknown reason,
+		   probably a bug in library threading */
+		usleep(100000);
+		if ((presto->status = FT_Read(presto->handle, &presto_data, 1, &ftbytes)) != FT_OK)
+			return ERROR_JTAG_DEVICE_ERROR;
+
+		if (ftbytes != 1)
+		{
+			LOG_DEBUG("PRESTO not responding");
+			return ERROR_JTAG_DEVICE_ERROR;
+		}
 	}
 
-	if ((presto->status=FT_SetTimeouts(presto->handle,0,0))!=FT_OK) return PRST_ERR;
+	if ((presto->status = FT_SetTimeouts(presto->handle, 0, 0)) != FT_OK)
+		return ERROR_JTAG_DEVICE_ERROR;
 
-	presto->status=FT_Write(presto->handle,&presto_init_seq,sizeof(presto_init_seq),&ftbytes);
-	if (presto->status!=FT_OK) return PRST_ERR;
-	if (ftbytes!=sizeof(presto_init_seq)) return PRST_TIMEOUT;
 
-	return PRST_OK;
-}
+	presto->status = FT_Write(presto->handle, &presto_init_seq, sizeof(presto_init_seq), &ftbytes);
+	if (presto->status != FT_OK || ftbytes != sizeof(presto_init_seq))
+		return ERROR_JTAG_DEVICE_ERROR;
 
+	return ERROR_OK;
+}
 
-int presto_close(void)
+#elif BUILD_PRESTO_LIBFTDI == 1
+static int presto_open_libftdi(char *req_serial)
 {
-	unsigned long ftbytes;
+	uint8_t presto_data;
 
-	int result=PRST_OK;
+	LOG_DEBUG("searching for PRESTO using libftdi");
 
-	if (presto->handle == (FT_HANDLE)INVALID_HANDLE_VALUE) return result;
+	/* initialize FTDI context structure */
+	if (ftdi_init(&presto->ftdic) < 0)
+	{
+		LOG_ERROR("unable to init libftdi: %s", presto->ftdic.error_str);
+		return ERROR_JTAG_DEVICE_ERROR;
+	}
 
-	presto->status=FT_Write(presto->handle,&presto_init_seq,sizeof(presto_init_seq),&ftbytes);
-	if (presto->status!=FT_OK) result=PRST_ERR;
-	if (ftbytes!=sizeof(presto_init_seq)) result=PRST_TIMEOUT;
+	/* context, vendor id, product id */
+	if (ftdi_usb_open_desc(&presto->ftdic, PRESTO_VID, PRESTO_PID, NULL, req_serial) < 0)
+	{
+		LOG_ERROR("unable to open PRESTO: %s", presto->ftdic.error_str);
+		return ERROR_JTAG_DEVICE_ERROR;
+	}
 
-	if ((presto->status=FT_SetLatencyTimer(presto->handle,16))!=FT_OK) result=PRST_ERR;
+	if (ftdi_usb_reset(&presto->ftdic) < 0)
+	{
+		LOG_ERROR("unable to reset PRESTO device");
+		return ERROR_JTAG_DEVICE_ERROR;
+	}
 
-	if ((presto->status=FT_Close(presto->handle))!=FT_OK) result=PRST_ERR;
-	else presto->handle = (FT_HANDLE)INVALID_HANDLE_VALUE;
+	if (ftdi_set_latency_timer(&presto->ftdic, 1) < 0)
+	{
+		LOG_ERROR("unable to set latency timer");
+		return ERROR_JTAG_DEVICE_ERROR;
+	}
 
-	return result;
+	if (ftdi_usb_purge_buffers(&presto->ftdic) < 0)
+	{
+		LOG_ERROR("unable to purge PRESTO buffers");
+		return ERROR_JTAG_DEVICE_ERROR;
+	}
+
+	presto_data = 0xD0;
+	if (presto_write(&presto_data, 1) != ERROR_OK)
+	{
+		LOG_ERROR("error writing to PRESTO");
+		return ERROR_JTAG_DEVICE_ERROR;
+	}
+
+	if (presto_read(&presto_data, 1) != ERROR_OK)
+	{
+		LOG_DEBUG("no response from PRESTO, retrying");
+
+		if (ftdi_usb_purge_buffers(&presto->ftdic) < 0)
+			return ERROR_JTAG_DEVICE_ERROR;
+
+		presto_data = 0xD0;
+		if (presto_write(&presto_data, 1) != ERROR_OK)
+			return ERROR_JTAG_DEVICE_ERROR;
+
+		if (presto_read(&presto_data, 1) != ERROR_OK)
+		{
+			LOG_ERROR("no response from PRESTO, giving up");
+			return ERROR_JTAG_DEVICE_ERROR;
+		}
+	}
+
+	if (presto_write(presto_init_seq, sizeof(presto_init_seq)) != ERROR_OK)
+	{
+		LOG_ERROR("error writing PRESTO init sequence");
+		return ERROR_JTAG_DEVICE_ERROR;
+	}
+
+	return ERROR_OK;
 }
+#endif /* BUILD_PRESTO_LIBFTDI == 1 */
 
+static int presto_open(char *req_serial)
+{
+	presto->buff_out_pos = 0;
+	presto->buff_in_pos = 0;
+	presto->buff_in_len = 0;
+	presto->buff_in_exp = 0;
+
+	presto->total_out = 0;
+	presto->total_in = 0;
+
+	presto->jtag_tms = 0;
+	presto->jtag_tck = 0;
+	presto->jtag_rst = 0;
+	presto->jtag_tdi_data = 0;
+	presto->jtag_tdi_count = 0;
+
+	presto->jtag_speed = 0;
+
+#if BUILD_PRESTO_FTD2XX == 1
+	return presto_open_ftd2xx(req_serial);
+#elif BUILD_PRESTO_LIBFTDI == 1
+	return presto_open_libftdi(req_serial);
+#endif
+}
 
-int presto_flush(void)
+static int presto_close(void)
 {
+
+	int result = ERROR_OK;
+
+#if BUILD_PRESTO_FTD2XX == 1
 	unsigned long ftbytes;
 
-	if (presto->buff_out_pos==0) return PRST_OK;
-	if (presto->status!=FT_OK) return PRST_ERR;
+	if (presto->handle == (FT_HANDLE)INVALID_HANDLE_VALUE)
+		return result;
 
-	if ((presto->status=FT_Write(presto->handle, presto->buff_out, presto->buff_out_pos, &ftbytes))!=FT_OK)
-	{
-		presto->buff_out_pos=0;
-		return PRST_ERR;
-	}
+	presto->status = FT_Purge(presto->handle, FT_PURGE_TX | FT_PURGE_RX);
+	if (presto->status != FT_OK)
+		result = ERROR_JTAG_DEVICE_ERROR;
 
-	presto->total_out+=ftbytes;
+	presto->status = FT_Write(presto->handle, &presto_init_seq, sizeof(presto_init_seq), &ftbytes);
+	if (presto->status != FT_OK || ftbytes != sizeof(presto_init_seq))
+		result = ERROR_JTAG_DEVICE_ERROR;
 
-	if (presto->buff_out_pos!=ftbytes)
-	{
-		presto->buff_out_pos=0;
-		return PRST_TIMEOUT;
-	}
+	if ((presto->status = FT_SetLatencyTimer(presto->handle, 16)) != FT_OK)
+		result = ERROR_JTAG_DEVICE_ERROR;
+
+	if ((presto->status = FT_Close(presto->handle)) != FT_OK)
+		result = ERROR_JTAG_DEVICE_ERROR;
+	else
+		presto->handle = (FT_HANDLE)INVALID_HANDLE_VALUE;
+
+#elif BUILD_PRESTO_LIBFTDI == 1
+
+	if ((presto->retval = ftdi_write_data(&presto->ftdic, presto_init_seq, sizeof(presto_init_seq))) != sizeof(presto_init_seq))
+		result = ERROR_JTAG_DEVICE_ERROR;
+
+	if ((presto->retval = ftdi_set_latency_timer(&presto->ftdic, 16)) < 0)
+		result = ERROR_JTAG_DEVICE_ERROR;
+
+	if ((presto->retval = ftdi_usb_close(&presto->ftdic)) < 0)
+		result = ERROR_JTAG_DEVICE_ERROR;
+	else
+		ftdi_deinit(&presto->ftdic);
+#endif
 
-	presto->buff_out_pos=0;
+	return result;
+}
 
-	if (presto->buff_in_exp==0) return PRST_OK;
+static int presto_flush(void)
+{
+	if (presto->buff_out_pos == 0)
+		return ERROR_OK;
 
-	presto->buff_in_pos=0;
-	presto->buff_in_len=0;
+#if BUILD_PRESTO_FTD2XX == 1
+	if (presto->status != FT_OK)
+#elif BUILD_PRESTO_LIBFTDI == 1
+	if (presto->retval < 0)
+#endif
+	{
+		LOG_DEBUG("error in previous communication, canceling I/O operation");
+		return ERROR_JTAG_DEVICE_ERROR;
+	}
 
-	if ((presto->status=FT_Read(presto->handle, presto->buff_in, presto->buff_in_exp, &ftbytes))!=FT_OK)
+	if (presto_write(presto->buff_out, presto->buff_out_pos) != ERROR_OK)
 	{
-		presto->buff_in_exp=0;
-		return PRST_ERR;
+		presto->buff_out_pos = 0;
+		return ERROR_JTAG_DEVICE_ERROR;
 	}
 
-	presto->total_in+=ftbytes;
+	presto->total_out += presto->buff_out_pos;
+	presto->buff_out_pos = 0;
+
+	if (presto->buff_in_exp == 0)
+		return ERROR_OK;
+
+	presto->buff_in_pos = 0;
+	presto->buff_in_len = 0;
 
-	if (ftbytes!=presto->buff_in_exp)
+	if (presto_read(presto->buff_in, presto->buff_in_exp) != ERROR_OK)
 	{
-		presto->buff_in_exp=0;
-		return PRST_TIMEOUT;
+		presto->buff_in_exp = 0;
+		return ERROR_JTAG_DEVICE_ERROR;
 	}
 
-	presto->buff_in_len=presto->buff_in_exp;
-	presto->buff_in_exp=0;
+	presto->total_in += presto->buff_in_exp;
+	presto->buff_in_len = presto->buff_in_exp;
+	presto->buff_in_exp = 0;
 
-	return PRST_OK;
+	return ERROR_OK;
 }
 
-
-int presto_sendbyte(int data)
+static int presto_sendbyte(int data)
 {
-	if (data==EOF) return presto_flush();
+	if (data == EOF) return presto_flush();
 
 	if (presto->buff_out_pos < BUFFER_SIZE)
 	{
-		presto->buff_out[presto->buff_out_pos++]=(BYTE)data;
-		if (((data&0xC0)==0x40) || ((data&0xD0)==0xD0))
+		presto->buff_out[presto->buff_out_pos++] = (uint8_t)data;
+		if (((data & 0xC0) == 0x40) || ((data & 0xD0)== 0xD0))
 			presto->buff_in_exp++;
 	}
-	else return PRST_ERR;
+	else
+		return ERROR_JTAG_DEVICE_ERROR;
 
-	if (presto->buff_out_pos >= BUFFER_SIZE) return presto_flush();
-	return PRST_OK;
-}
+#if BUILD_PRESTO_FTD2XX == 1
+	if (presto->buff_out_pos >= BUFFER_SIZE)
+#elif BUILD_PRESTO_LIBFTDI == 1
+	/* libftdi does not do background read, be sure that USB IN buffer does not overflow (128 bytes only!) */
+	if (presto->buff_out_pos >= BUFFER_SIZE || presto->buff_in_exp == 128)
+#endif
+		return presto_flush();
 
+	return ERROR_OK;
+}
 
-int presto_getbyte(void)
+#if 0
+static int presto_getbyte(void)
 {
-	if (presto->buff_in_pos<presto->buff_in_len)
+	if (presto->buff_in_pos < presto->buff_in_len)
 		return presto->buff_in[presto->buff_in_pos++];
 
-	if (presto->buff_in_exp==0) return -1;
-	if (presto_flush()!=PRST_OK) return -1;
+	if (presto->buff_in_exp == 0)
+		return -1;
 
-	if (presto->buff_in_pos<presto->buff_in_len)
+	if (presto_flush() != ERROR_OK)
+		return -1;
+
+	if (presto->buff_in_pos < presto->buff_in_len)
 		return presto->buff_in[presto->buff_in_pos++];
 
 	return -1;
 }
-
+#endif
 
 /* -------------------------------------------------------------------------- */
 
-
-int presto_bitq_out(int tms, int tdi, int tdo_req)
+static int presto_tdi_flush(void)
 {
-	unsigned char cmdparam;
+	if (presto->jtag_tdi_count == 0)
+		return 0;
 
-	if (presto->jtag_tck==0)
+	if (presto->jtag_tck == 0)
 	{
-		presto_sendbyte(0xA4);
-		presto->jtag_tck=1;
+		LOG_ERROR("BUG: unexpected TAP condition, TCK low");
+		return -1;
 	}
 
-	else if (!tdo_req && tms==presto->jtag_tms)
+	presto->jtag_tdi_data |= (presto->jtag_tdi_count - 1) << 4;
+	presto_sendbyte(presto->jtag_tdi_data);
+	presto->jtag_tdi_count = 0;
+	presto->jtag_tdi_data = 0;
+
+	return 0;
+}
+
+static int presto_tck_idle(void)
+{
+	if (presto->jtag_tck == 1)
 	{
-		if (presto->jtag_tdi_count==0) presto->jtag_tdi_data=(tdi!=0);
-		else presto->jtag_tdi_data|=(tdi!=0)<<presto->jtag_tdi_count;
-		if (++presto->jtag_tdi_count==4)
-		{
-			presto->jtag_tdi_data|=(presto->jtag_tdi_count-1)<<4;
-			presto_sendbyte(presto->jtag_tdi_data);
-			presto->jtag_tdi_count=0;
-		}
-		return 0;
+		presto_sendbyte(0xCA);
+		presto->jtag_tck = 0;
 	}
 
-	if (presto->jtag_tdi_count)
+	return 0;
+}
+
+/* -------------------------------------------------------------------------- */
+
+static int presto_bitq_out(int tms, int tdi, int tdo_req)
+{
+	int i;
+	unsigned char cmd;
+
+	if (presto->jtag_tck == 0)
 	{
-		presto->jtag_tdi_data|=(presto->jtag_tdi_count-1)<<4;
-		presto_sendbyte(presto->jtag_tdi_data);
-		presto->jtag_tdi_count=0;
+		presto_sendbyte(0xA4); /* LED idicator - JTAG active */
 	}
+	else if (presto->jtag_speed == 0 && !tdo_req && tms == presto->jtag_tms)
+	{
+		presto->jtag_tdi_data |= (tdi != 0) << presto->jtag_tdi_count;
 
-	if (tdi) cmdparam=0x0B;
-	else cmdparam=0x0A;
+		if (++presto->jtag_tdi_count == 4)
+			presto_tdi_flush();
 
-	presto_sendbyte(0xC0|cmdparam);
+		return 0;
+	}
+
+	presto_tdi_flush();
+
+	cmd = tdi ? 0xCB : 0xCA;
+	presto_sendbyte(cmd);
 
-	if (tms!=presto->jtag_tms)
+	if (tms != presto->jtag_tms)
 	{
-		if (tms) presto_sendbyte(0xEC);
-		else presto_sendbyte(0xE8);
-		presto->jtag_tms=tms;
+		presto_sendbyte((tms ? 0xEC : 0xE8) | (presto->jtag_rst ? 0x02 : 0));
+		presto->jtag_tms = tms;
 	}
 
-	if (tdo_req) presto_sendbyte(0xD4|cmdparam);
-	else presto_sendbyte(0xC4|cmdparam);
+	/* delay with TCK low */
+	for (i = presto->jtag_speed; i > 1; i--)
+		presto_sendbyte(cmd);
+
+	cmd |= 0x04;
+	presto_sendbyte(cmd | (tdo_req ? 0x10 : 0));
+
+	/* delay with TCK high */
+	for (i = presto->jtag_speed; i > 1; i--)
+		presto_sendbyte(cmd);
+
+	presto->jtag_tck = 1;
 
 	return 0;
 }
 
-
-int presto_bitq_flush(void)
+static int presto_bitq_flush(void)
 {
-	if (presto->jtag_tdi_count)
-	{
-		presto->jtag_tdi_data|=(presto->jtag_tdi_count-1)<<4;
-		presto_sendbyte(presto->jtag_tdi_data);
-		presto->jtag_tdi_count=0;
-	}
+	presto_tdi_flush();
+	presto_tck_idle();
 
-	presto_sendbyte(0xCA);
-	presto->jtag_tck=0;
-
-	presto_sendbyte(0xA0);
+	presto_sendbyte(0xA0); /* LED idicator - JTAG idle */
 
 	return presto_flush();
 }
 
-
-int presto_bitq_in_rdy(void)
+static int presto_bitq_in_rdy(void)
 {
-	if (presto->buff_in_pos>=presto->buff_in_len) return 0;
+	if (presto->buff_in_pos >= presto->buff_in_len)
+		return 0;
 	return presto->buff_in_len-presto->buff_in_pos;
 }
 
-
-int presto_bitq_in(void)
+static int presto_bitq_in(void)
 {
-	if (presto->buff_in_pos>=presto->buff_in_len) return -1;
+	if (presto->buff_in_pos >= presto->buff_in_len)
+		return -1;
 	if (presto->buff_in[presto->buff_in_pos++]&0x08) return 1;
 	return 0;
 }
 
-
-int presto_bitq_sleep(unsigned long us)
+static int presto_bitq_sleep(unsigned long us)
 {
 	long waits;
 
-	if (us>100000)
+	presto_tdi_flush();
+	presto_tck_idle();
+
+	if (us > 100000)
 	{
 		presto_bitq_flush();
 		jtag_sleep(us);
 		return 0;
 	}
 
-	waits=us/170+2;
-	while (waits--) presto_sendbyte(0x80);
+	waits = us / 170 + 2;
+	while (waits--)
+		presto_sendbyte(0x80);
 
 	return 0;
 }
 
-
-int presto_bitq_reset(int trst, int srst)
+static int presto_bitq_reset(int trst, int srst)
 {
-	unsigned char cmd;
+	presto_tdi_flush();
+	presto_tck_idle();
 
-	cmd=0xE8;
-	if (presto->jtag_tms) cmd|=0x04;
+	/* add a delay after possible TCK transition */
+	presto_sendbyte(0x80);
+	presto_sendbyte(0x80);
 
-	if (trst || srst) cmd|=0x02;
+	presto->jtag_rst = trst || srst;
+	presto_sendbyte((presto->jtag_rst ? 0xEA : 0xE8) | (presto->jtag_tms ? 0x04 : 0));
 
-	presto_sendbyte(cmd);
 	return 0;
 }
 
-
 /* -------------------------------------------------------------------------- */
 
+static int presto_jtag_khz(int khz, int *jtag_speed)
+{
+	if (khz < 0)
+	{
+		*jtag_speed = 0;
+		return ERROR_INVALID_ARGUMENTS;
+	}
 
-int presto_jtag_speed(int speed)
+	if (khz >= 3000) *jtag_speed = 0;
+	else *jtag_speed = (1000 + khz-1)/khz;
+
+	return 0;
+}
+
+static int presto_jtag_speed_div(int speed, int *khz)
 {
-	jtag_speed=speed;
-	return ERROR_OK;
+	if ((speed < 0) || (speed > 1000))
+	{
+		*khz = 0;
+		return ERROR_INVALID_ARGUMENTS;
+	}
+
+	if (speed == 0) *khz = 3000;
+	else *khz = 1000/speed;
+
+	return 0;
 }
 
+static int presto_jtag_speed(int speed)
+{
+	int khz;
 
-char *presto_serial;
+	if (presto_jtag_speed_div(speed, &khz))
+	{
+		return ERROR_INVALID_ARGUMENTS;
+	}
 
-int presto_handle_serial_command(struct command_context_s *cmd_ctx, char *cmd, char **args, int argc)
+	presto->jtag_speed = speed;
+
+	if (khz%1000 == 0)
+		LOG_INFO("setting speed to %d, max. TCK freq. is %d MHz", speed, khz/1000);
+	else
+		LOG_INFO("setting speed to %d, max. TCK freq. is %d kHz", speed, khz);
+
+	return 0;
+}
+
+static char *presto_serial;
+
+COMMAND_HANDLER(presto_handle_serial_command)
 {
 	if (argc == 1)
 	{
-		if (presto_serial) free(presto_serial);
+		if (presto_serial)
+			free(presto_serial);
 		presto_serial = strdup(args[0]);
 	}
 	else
 	{
-		ERROR("expected exactly one argument to presto_serial <serial-number>");
+		LOG_ERROR("expected exactly one argument to presto_serial <serial-number>");
 	}
 
 	return ERROR_OK;
 }
 
-
-int presto_jtag_register_commands(struct command_context_s *cmd_ctx)
+static int presto_jtag_register_commands(struct command_context *cmd_ctx)
 {
 	register_command(cmd_ctx, NULL, "presto_serial", presto_handle_serial_command,
 		COMMAND_CONFIG, NULL);
 	return ERROR_OK;
 }
 
-
-int presto_jtag_init(void)
+static int presto_jtag_init(void)
 {
-	if (presto_open(presto_serial)!=0)
+	if (presto_open(presto_serial) != ERROR_OK)
 	{
 		presto_close();
-		if (presto_serial!=NULL) ERROR("Cannot open PRESTO, serial number %s", presto_serial);
-		else ERROR("Cannot open PRESTO");
+		if (presto_serial != NULL)
+			LOG_ERROR("Cannot open PRESTO, serial number '%s'", presto_serial);
+		else
+			LOG_ERROR("Cannot open PRESTO");
 		return ERROR_JTAG_INIT_FAILED;
 	}
-	INFO("PRESTO open, serial number %s", presto->serial);
-	
-	bitq_interface=&presto_bitq;
+	LOG_INFO("PRESTO open, serial number '%s'", presto->serial);
+
+	/* use JTAG speed setting from configuration file */
+	presto_jtag_speed(jtag_get_speed());
+
+	bitq_interface = &presto_bitq;
 	return ERROR_OK;
 }
 
-
-int presto_jtag_quit(void)
+static int presto_jtag_quit(void)
 {
 	bitq_cleanup();
 	presto_close();
-	INFO("PRESTO closed");
+	LOG_INFO("PRESTO closed");
 
 	if (presto_serial)
 	{
 		free(presto_serial);
-		presto_serial=NULL;
+		presto_serial = NULL;
 	}
 
 	return ERROR_OK;