summaryrefslogtreecommitdiffstats
path: root/drivers/usb/serial/ftdi_sio.h
blob: a79a1325b4d9614861d936caf769e38cb96a7b79 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Driver definitions for the FTDI USB Single Port Serial Converter -
 * known as FTDI_SIO (Serial Input/Output application of the chipset)
 *
 * For USB vendor/product IDs (VID/PID), please see ftdi_sio_ids.h
 *
 *
 * The example I have is known as the USC-1000 which is available from
 * http://www.dse.co.nz - cat no XH4214 It looks similar to this:
 * http://www.dansdata.com/usbser.htm but I can't be sure There are other
 * USC-1000s which don't look like my device though so beware!
 *
 * The device is based on the FTDI FT8U100AX chip. It has a DB25 on one side,
 * USB on the other.
 *
 * Thanx to FTDI (http://www.ftdichip.com) for so kindly providing details
 * of the protocol required to talk to the device and ongoing assistence
 * during development.
 *
 * Bill Ryder - bryder@sgi.com formerly of Silicon Graphics, Inc.- wrote the
 * FTDI_SIO implementation.
 *
 */

/* Commands */
#define FTDI_SIO_RESET			0 /* Reset the port */
#define FTDI_SIO_MODEM_CTRL		1 /* Set the modem control register */
#define FTDI_SIO_SET_FLOW_CTRL		2 /* Set flow control register */
#define FTDI_SIO_SET_BAUD_RATE		3 /* Set baud rate */
#define FTDI_SIO_SET_DATA		4 /* Set the data characteristics of
					     the port */
#define FTDI_SIO_GET_MODEM_STATUS	5 /* Retrieve current value of modem
					     status register */
#define FTDI_SIO_SET_EVENT_CHAR		6 /* Set the event character */
#define FTDI_SIO_SET_ERROR_CHAR		7 /* Set the error character */
#define FTDI_SIO_SET_LATENCY_TIMER	9 /* Set the latency timer */
#define FTDI_SIO_GET_LATENCY_TIMER	0x0a /* Get the latency timer */
#define FTDI_SIO_SET_BITMODE		0x0b /* Set bitbang mode */
#define FTDI_SIO_READ_PINS		0x0c /* Read immediate value of pins */
#define FTDI_SIO_READ_EEPROM		0x90 /* Read EEPROM */

/* Interface indices for FT2232, FT2232H and FT4232H devices */
#define INTERFACE_A		1
#define INTERFACE_B		2
#define INTERFACE_C		3
#define INTERFACE_D		4


/*
 *   BmRequestType:  1100 0000b
 *   bRequest:       FTDI_E2_READ
 *   wValue:         0
 *   wIndex:         Address of word to read
 *   wLength:        2
 *   Data:           Will return a word of data from E2Address
 *
 */

/* Port Identifier Table */
#define PIT_DEFAULT		0 /* SIOA */
#define PIT_SIOA		1 /* SIOA */
/* The device this driver is tested with one has only one port */
#define PIT_SIOB		2 /* SIOB */
#define PIT_PARALLEL		3 /* Parallel */

/* FTDI_SIO_RESET */
#define FTDI_SIO_RESET_REQUEST FTDI_SIO_RESET
#define FTDI_SIO_RESET_REQUEST_TYPE 0x40
#define FTDI_SIO_RESET_SIO 0
#define FTDI_SIO_RESET_PURGE_RX 1
#define FTDI_SIO_RESET_PURGE_TX 2

/*
 * BmRequestType:  0100 0000B
 * bRequest:       FTDI_SIO_RESET
 * wValue:         Control Value
 *                   0 = Reset SIO
 *                   1 = Purge RX buffer
 *                   2 = Purge TX buffer
 * wIndex:         Port
 * wLength:        0
 * Data:           None
 *
 * The Reset SIO command has this effect:
 *
 *    Sets flow control set to 'none'
 *    Event char = $0D
 *    Event trigger = disabled
 *    Purge RX buffer
 *    Purge TX buffer
 *    Clear DTR
 *    Clear RTS
 *    baud and data format not reset
 *
 * The Purge RX and TX buffer commands affect nothing except the buffers
 *
   */

/* FTDI_SIO_SET_BAUDRATE */
#define FTDI_SIO_SET_BAUDRATE_REQUEST_TYPE 0x40
#define FTDI_SIO_SET_BAUDRATE_REQUEST 3

/*
 * BmRequestType:  0100 0000B
 * bRequest:       FTDI_SIO_SET_BAUDRATE
 * wValue:         BaudDivisor value - see below
 * wIndex:         Port
 * wLength:        0
 * Data:           None
 * The BaudDivisor values are calculated as follows:
 * - BaseClock is either 12000000 or 48000000 depending on the device.
 *   FIXME: I wish I knew how to detect old chips to select proper base clock!
 * - BaudDivisor is a fixed point number encoded in a funny way.
 *   (--WRONG WAY OF THINKING--)
 *   BaudDivisor is a fixed point number encoded with following bit weighs:
 *   (-2)(-1)(13..0). It is a radical with a denominator of 4, so values
 *   end with 0.0 (00...), 0.25 (10...), 0.5 (01...), and 0.75 (11...).
 *   (--THE REALITY--)
 *   The both-bits-set has quite different meaning from 0.75 - the chip
 *   designers have decided it to mean 0.125 instead of 0.75.
 *   This info looked up in FTDI application note "FT8U232 DEVICES \ Data Rates
 *   and Flow Control Consideration for USB to RS232".
 * - BaudDivisor = (BaseClock / 16) / BaudRate, where the (=) operation should
 *   automagically re-encode the resulting value to take fractions into
 *   consideration.
 * As all values are integers, some bit twiddling is in order:
 *   BaudDivisor = (BaseClock / 16 / BaudRate) |
 *   (((BaseClock / 2 / BaudRate) & 4) ? 0x4000    // 0.5
 *    : ((BaseClock / 2 / BaudRate) & 2) ? 0x8000  // 0.25
 *    : ((BaseClock / 2 / BaudRate) & 1) ? 0xc000  // 0.125
 *    : 0)
 *
 * For the FT232BM, a 17th divisor bit was introduced to encode the multiples
 * of 0.125 missing from the FT8U232AM.  Bits 16 to 14 are coded as follows
 * (the first four codes are the same as for the FT8U232AM, where bit 16 is
 * always 0):
 *   000 - add .000 to divisor
 *   001 - add .500 to divisor
 *   010 - add .250 to divisor
 *   011 - add .125 to divisor
 *   100 - add .375 to divisor
 *   101 - add .625 to divisor
 *   110 - add .750 to divisor
 *   111 - add .875 to divisor
 * Bits 15 to 0 of the 17-bit divisor are placed in the urb value.  Bit 16 is
 * placed in bit 0 of the urb index.
 *
 * Note that there are a couple of special cases to support the highest baud
 * rates.  If the calculated divisor value is 1, this needs to be replaced with
 * 0.  Additionally for the FT232BM, if the calculated divisor value is 0x4001
 * (1.5), this needs to be replaced with 0x0001 (1) (but this divisor value is
 * not supported by the FT8U232AM).
 */

enum ftdi_chip_type {
	SIO = 1,
	FT8U232AM = 2,
	FT232BM = 3,
	FT2232C = 4,
	FT232RL = 5,
	FT2232H = 6,
	FT4232H = 7,
	FT232H  = 8,
	FTX     = 9,
};

enum ftdi_sio_baudrate {
	ftdi_sio_b300 = 0,
	ftdi_sio_b600 = 1,
	ftdi_sio_b1200 = 2,
	ftdi_sio_b2400 = 3,
	ftdi_sio_b4800 = 4,
	ftdi_sio_b9600 = 5,
	ftdi_sio_b19200 = 6,
	ftdi_sio_b38400 = 7,
	ftdi_sio_b57600 = 8,
	ftdi_sio_b115200 = 9
};

/*
 * The ftdi_8U232AM_xxMHz_byyy constants have been removed. The encoded divisor
 * values are calculated internally.
 */
#define FTDI_SIO_SET_DATA_REQUEST	FTDI_SIO_SET_DATA
#define FTDI_SIO_SET_DATA_REQUEST_TYPE	0x40
#define FTDI_SIO_SET_DATA_PARITY_NONE	(0x0 << 8)
#define FTDI_SIO_SET_DATA_PARITY_ODD	(0x1 << 8)
#define FTDI_SIO_SET_DATA_PARITY_EVEN	(0x2 << 8)
#define FTDI_SIO_SET_DATA_PARITY_MARK	(0x3 << 8)
#define FTDI_SIO_SET_DATA_PARITY_SPACE	(0x4 << 8)
#define FTDI_SIO_SET_DATA_STOP_BITS_1	(0x0 << 11)
#define FTDI_SIO_SET_DATA_STOP_BITS_15	(0x1 << 11)
#define FTDI_SIO_SET_DATA_STOP_BITS_2	(0x2 << 11)
#define FTDI_SIO_SET_BREAK		(0x1 << 14)
/* FTDI_SIO_SET_DATA */

/*
 * BmRequestType:  0100 0000B
 * bRequest:       FTDI_SIO_SET_DATA
 * wValue:         Data characteristics (see below)
 * wIndex:         Port
 * wLength:        0
 * Data:           No
 *
 * Data characteristics
 *
 *   B0..7   Number of data bits
 *   B8..10  Parity
 *           0 = None
 *           1 = Odd
 *           2 = Even
 *           3 = Mark
 *           4 = Space
 *   B11..13 Stop Bits
 *           0 = 1
 *           1 = 1.5
 *           2 = 2
 *   B14
 *           1 = TX ON (break)
 *           0 = TX OFF (normal state)
 *   B15 Reserved
 *
 */



/* FTDI_SIO_MODEM_CTRL */
#define FTDI_SIO_SET_MODEM_CTRL_REQUEST_TYPE 0x40
#define FTDI_SIO_SET_MODEM_CTRL_REQUEST FTDI_SIO_MODEM_CTRL

/*
 * BmRequestType:   0100 0000B
 * bRequest:        FTDI_SIO_MODEM_CTRL
 * wValue:          ControlValue (see below)
 * wIndex:          Port
 * wLength:         0
 * Data:            None
 *
 * NOTE: If the device is in RTS/CTS flow control, the RTS set by this
 * command will be IGNORED without an error being returned
 * Also - you can not set DTR and RTS with one control message
 */

#define FTDI_SIO_SET_DTR_MASK 0x1
#define FTDI_SIO_SET_DTR_HIGH ((FTDI_SIO_SET_DTR_MASK  << 8) | 1)
#define FTDI_SIO_SET_DTR_LOW  ((FTDI_SIO_SET_DTR_MASK  << 8) | 0)
#define FTDI_SIO_SET_RTS_MASK 0x2
#define FTDI_SIO_SET_RTS_HIGH ((FTDI_SIO_SET_RTS_MASK << 8) | 2)
#define FTDI_SIO_SET_RTS_LOW  ((FTDI_SIO_SET_RTS_MASK << 8) | 0)

/*
 * ControlValue
 * B0    DTR state
 *          0 = reset
 *          1 = set
 * B1    RTS state
 *          0 = reset
 *          1 = set
 * B2..7 Reserved
 * B8    DTR state enable
 *          0 = ignore
 *          1 = use DTR state
 * B9    RTS state enable
 *          0 = ignore
 *          1 = use RTS state
 * B10..15 Reserved
 */

/* FTDI_SIO_SET_FLOW_CTRL */
#define FTDI_SIO_SET_FLOW_CTRL_REQUEST_TYPE 0x40
#define FTDI_SIO_SET_FLOW_CTRL_REQUEST FTDI_SIO_SET_FLOW_CTRL
#define FTDI_SIO_DISABLE_FLOW_CTRL 0x0
#define FTDI_SIO_RTS_CTS_HS (0x1 << 8)
#define FTDI_SIO_DTR_DSR_HS (0x2 << 8)
#define FTDI_SIO_XON_XOFF_HS (0x4 << 8)
/*
 *   BmRequestType:  0100 0000b
 *   bRequest:       FTDI_SIO_SET_FLOW_CTRL
 *   wValue:         Xoff/Xon
 *   wIndex:         Protocol/Port - hIndex is protocol / lIndex is port
 *   wLength:        0
 *   Data:           None
 *
 * hIndex protocol is:
 *   B0 Output handshaking using RTS/CTS
 *       0 = disabled
 *       1 = enabled
 *   B1 Output handshaking using DTR/DSR
 *       0 = disabled
 *       1 = enabled
 *   B2 Xon/Xoff handshaking
 *       0 = disabled
 *       1 = enabled
 *
 * A value of zero in the hIndex field disables handshaking
 *
 * If Xon/Xoff handshaking is specified, the hValue field should contain the
 * XOFF character and the lValue field contains the XON character.
 */

/*
 * FTDI_SIO_GET_LATENCY_TIMER
 *
 * Set the timeout interval. The FTDI collects data from the slave
 * device, transmitting it to the host when either A) 62 bytes are
 * received, or B) the timeout interval has elapsed and the buffer
 * contains at least 1 byte.  Setting this value to a small number
 * can dramatically improve performance for applications which send
 * small packets, since the default value is 16ms.
 */
#define  FTDI_SIO_GET_LATENCY_TIMER_REQUEST FTDI_SIO_GET_LATENCY_TIMER
#define  FTDI_SIO_GET_LATENCY_TIMER_REQUEST_TYPE 0xC0

/*
 *  BmRequestType:   1100 0000b
 *  bRequest:        FTDI_SIO_GET_LATENCY_TIMER
 *  wValue:          0
 *  wIndex:          Port
 *  wLength:         0
 *  Data:            latency (on return)
 */

/*
 * FTDI_SIO_SET_LATENCY_TIMER
 *
 * Set the timeout interval. The FTDI collects data from the slave
 * device, transmitting it to the host when either A) 62 bytes are
 * received, or B) the timeout interval has elapsed and the buffer
 * contains at least 1 byte.  Setting this value to a small number
 * can dramatically improve performance for applications which send
 * small packets, since the default value is 16ms.
 */
#define  FTDI_SIO_SET_LATENCY_TIMER_REQUEST FTDI_SIO_SET_LATENCY_TIMER
#define  FTDI_SIO_SET_LATENCY_TIMER_REQUEST_TYPE 0x40

/*
 *  BmRequestType:   0100 0000b
 *  bRequest:        FTDI_SIO_SET_LATENCY_TIMER
 *  wValue:          Latency (milliseconds)
 *  wIndex:          Port
 *  wLength:         0
 *  Data:            None
 *
 * wValue:
 *   B0..7   Latency timer
 *   B8..15  0
 *
 */

/*
 * FTDI_SIO_SET_EVENT_CHAR
 *
 * Set the special event character for the specified communications port.
 * If the device sees this character it will immediately return the
 * data read so far - rather than wait 40ms or until 62 bytes are read
 * which is what normally happens.
 */


#define  FTDI_SIO_SET_EVENT_CHAR_REQUEST FTDI_SIO_SET_EVENT_CHAR
#define  FTDI_SIO_SET_EVENT_CHAR_REQUEST_TYPE 0x40


/*
 *  BmRequestType:   0100 0000b
 *  bRequest:        FTDI_SIO_SET_EVENT_CHAR
 *  wValue:          EventChar
 *  wIndex:          Port
 *  wLength:         0
 *  Data:            None
 *
 * wValue:
 *   B0..7   Event Character
 *   B8      Event Character Processing
 *             0 = disabled
 *             1 = enabled
 *   B9..15  Reserved
 *
 */

/* FTDI_SIO_SET_ERROR_CHAR */

/*
 * Set the parity error replacement character for the specified communications
 * port
 */

/*
 *  BmRequestType:  0100 0000b
 *  bRequest:       FTDI_SIO_SET_EVENT_CHAR
 *  wValue:         Error Char
 *  wIndex:         Port
 *  wLength:        0
 *  Data:           None
 *
 *Error Char
 *  B0..7  Error Character
 *  B8     Error Character Processing
 *           0 = disabled
 *           1 = enabled
 *  B9..15 Reserved
 *
 */

/* FTDI_SIO_GET_MODEM_STATUS */
/* Retrieve the current value of the modem status register */

#define FTDI_SIO_GET_MODEM_STATUS_REQUEST_TYPE 0xc0
#define FTDI_SIO_GET_MODEM_STATUS_REQUEST FTDI_SIO_GET_MODEM_STATUS
#define FTDI_SIO_CTS_MASK 0x10
#define FTDI_SIO_DSR_MASK 0x20
#define FTDI_SIO_RI_MASK  0x40
#define FTDI_SIO_RLSD_MASK 0x80
/*
 *   BmRequestType:   1100 0000b
 *   bRequest:        FTDI_SIO_GET_MODEM_STATUS
 *   wValue:          zero
 *   wIndex:          Port
 *   wLength:         1
 *   Data:            Status
 *
 * One byte of data is returned
 * B0..3 0
 * B4    CTS
 *         0 = inactive
 *         1 = active
 * B5    DSR
 *         0 = inactive
 *         1 = active
 * B6    Ring Indicator (RI)
 *         0 = inactive
 *         1 = active
 * B7    Receive Line Signal Detect (RLSD)
 *         0 = inactive
 *         1 = active
 */

/* FTDI_SIO_SET_BITMODE */
#define FTDI_SIO_SET_BITMODE_REQUEST_TYPE 0x40
#define FTDI_SIO_SET_BITMODE_REQUEST FTDI_SIO_SET_BITMODE

/* Possible bitmodes for FTDI_SIO_SET_BITMODE_REQUEST */
#define FTDI_SIO_BITMODE_RESET		0x00
#define FTDI_SIO_BITMODE_CBUS		0x20

/* FTDI_SIO_READ_PINS */
#define FTDI_SIO_READ_PINS_REQUEST_TYPE 0xc0
#define FTDI_SIO_READ_PINS_REQUEST FTDI_SIO_READ_PINS

/*
 * FTDI_SIO_READ_EEPROM
 *
 * EEPROM format found in FTDI AN_201, "FT-X MTP memory Configuration",
 * http://www.ftdichip.com/Support/Documents/AppNotes/AN_201_FT-X%20MTP%20Memory%20Configuration.pdf
 */
#define FTDI_SIO_READ_EEPROM_REQUEST_TYPE 0xc0
#define FTDI_SIO_READ_EEPROM_REQUEST FTDI_SIO_READ_EEPROM

#define FTDI_FTX_CBUS_MUX_GPIO		0x8
#define FTDI_FT232R_CBUS_MUX_GPIO	0xa


/* Descriptors returned by the device
 *
 *  Device Descriptor
 *
 * Offset	Field		Size	Value	Description
 * 0	bLength		1	0x12	Size of descriptor in bytes
 * 1	bDescriptorType	1	0x01	DEVICE Descriptor Type
 * 2	bcdUSB		2	0x0110	USB Spec Release Number
 * 4	bDeviceClass	1	0x00	Class Code
 * 5	bDeviceSubClass	1	0x00	SubClass Code
 * 6	bDeviceProtocol	1	0x00	Protocol Code
 * 7	bMaxPacketSize0 1	0x08	Maximum packet size for endpoint 0
 * 8	idVendor	2	0x0403	Vendor ID
 * 10	idProduct	2	0x8372	Product ID (FTDI_SIO_PID)
 * 12	bcdDevice	2	0x0001	Device release number
 * 14	iManufacturer	1	0x01	Index of man. string desc
 * 15	iProduct	1	0x02	Index of prod string desc
 * 16	iSerialNumber	1	0x02	Index of serial nmr string desc
 * 17	bNumConfigurations 1    0x01	Number of possible configurations
 *
 * Configuration Descriptor
 *
 * Offset	Field			Size	Value
 * 0	bLength			1	0x09	Size of descriptor in bytes
 * 1	bDescriptorType		1	0x02	CONFIGURATION Descriptor Type
 * 2	wTotalLength		2	0x0020	Total length of data
 * 4	bNumInterfaces		1	0x01	Number of interfaces supported
 * 5	bConfigurationValue	1	0x01	Argument for SetCOnfiguration() req
 * 6	iConfiguration		1	0x02	Index of config string descriptor
 * 7	bmAttributes		1	0x20	Config characteristics Remote Wakeup
 * 8	MaxPower		1	0x1E	Max power consumption
 *
 * Interface Descriptor
 *
 * Offset	Field			Size	Value
 * 0	bLength			1	0x09	Size of descriptor in bytes
 * 1	bDescriptorType		1	0x04	INTERFACE Descriptor Type
 * 2	bInterfaceNumber	1	0x00	Number of interface
 * 3	bAlternateSetting	1	0x00	Value used to select alternate
 * 4	bNumEndpoints		1	0x02	Number of endpoints
 * 5	bInterfaceClass		1	0xFF	Class Code
 * 6	bInterfaceSubClass	1	0xFF	Subclass Code
 * 7	bInterfaceProtocol	1	0xFF	Protocol Code
 * 8	iInterface		1	0x02	Index of interface string description
 *
 * IN Endpoint Descriptor
 *
 * Offset	Field			Size	Value
 * 0	bLength			1	0x07	Size of descriptor in bytes
 * 1	bDescriptorType		1	0x05	ENDPOINT descriptor type
 * 2	bEndpointAddress	1	0x82	Address of endpoint
 * 3	bmAttributes		1	0x02	Endpoint attributes - Bulk
 * 4	bNumEndpoints		2	0x0040	maximum packet size
 * 5	bInterval		1	0x00	Interval for polling endpoint
 *
 * OUT Endpoint Descriptor
 *
 * Offset	Field			Size	Value
 * 0	bLength			1	0x07	Size of descriptor in bytes
 * 1	bDescriptorType		1	0x05	ENDPOINT descriptor type
 * 2	bEndpointAddress	1	0x02	Address of endpoint
 * 3	bmAttributes		1	0x02	Endpoint attributes - Bulk
 * 4	bNumEndpoints		2	0x0040	maximum packet size
 * 5	bInterval		1	0x00	Interval for polling endpoint
 *
 * DATA FORMAT
 *
 * IN Endpoint
 *
 * The device reserves the first two bytes of data on this endpoint to contain
 * the current values of the modem and line status registers. In the absence of
 * data, the device generates a message consisting of these two status bytes
 * every 40 ms
 *
 * Byte 0: Modem Status
 *
 * Offset	Description
 * B0	Reserved - must be 1
 * B1	Reserved - must be 0
 * B2	Reserved - must be 0
 * B3	Reserved - must be 0
 * B4	Clear to Send (CTS)
 * B5	Data Set Ready (DSR)
 * B6	Ring Indicator (RI)
 * B7	Receive Line Signal Detect (RLSD)
 *
 * Byte 1: Line Status
 *
 * Offset	Description
 * B0	Data Ready (DR)
 * B1	Overrun Error (OE)
 * B2	Parity Error (PE)
 * B3	Framing Error (FE)
 * B4	Break Interrupt (BI)
 * B5	Transmitter Holding Register (THRE)
 * B6	Transmitter Empty (TEMT)
 * B7	Error in RCVR FIFO
 *
 */
#define FTDI_RS0_CTS	(1 << 4)
#define FTDI_RS0_DSR	(1 << 5)
#define FTDI_RS0_RI	(1 << 6)
#define FTDI_RS0_RLSD	(1 << 7)

#define FTDI_RS_DR	1
#define FTDI_RS_OE	(1<<1)
#define FTDI_RS_PE	(1<<2)
#define FTDI_RS_FE	(1<<3)
#define FTDI_RS_BI	(1<<4)
#define FTDI_RS_THRE	(1<<5)
#define FTDI_RS_TEMT	(1<<6)
#define FTDI_RS_FIFO	(1<<7)

/*
 * OUT Endpoint
 *
 * This device reserves the first bytes of data on this endpoint contain the
 * length and port identifier of the message. For the FTDI USB Serial converter
 * the port identifier is always 1.
 *
 * Byte 0: Line Status
 *
 * Offset	Description
 * B0	Reserved - must be 1
 * B1	Reserved - must be 0
 * B2..7	Length of message - (not including Byte 0)
 *
 */