File: ula200.c

package info (click to toggle)
lcdproc 0.5.9-3
  • links: PTS, VCS
  • area: main
  • in suites: bullseye, buster, sid
  • size: 5,064 kB
  • sloc: ansic: 59,645; sh: 1,740; perl: 681; makefile: 417
file content (933 lines) | stat: -rw-r--r-- 20,941 bytes parent folder | download
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
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
/** \file server/drivers/ula200.c
 * LCDd \c ula200 driver for the ULA-200 from ELV (http://www.elv.de).
 */

/*-
 * Copyright (C) 2006 Bernhard Walle <bernhard.walle@gmx.de>
 *
 * 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
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301
 */

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

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>

#include <ftdi.h>

#include "lcd.h"
#include "ula200.h"
#include "shared/report.h"
#include "hd44780-charmap.h"
#include "adv_bignum.h"


/* Vars for the server core */
MODULE_EXPORT char *api_version = API_VERSION;
MODULE_EXPORT int stay_in_foreground = 0;
MODULE_EXPORT int supports_multiple = 1;
MODULE_EXPORT char *symbol_prefix = "ula200_";


/* -------------------------- constants ---------------------------------- */
#define DISPLAY_VENDOR_ID    0x0403
#define DISPLAY_PRODUCT_ID   0xf06d

#define CH_STX  0x02
#define CH_ETX  0x03
#define CH_ENQ  0x05
#define CH_ACK  0x06
#define CH_NAK  0x15
#define CH_DC2  0x12
#define CH_DC3  0x13

#define MAX_KEY_MAP 6
static char *default_key_map[MAX_KEY_MAP] = {"Up", "Down", "Left", "Right", "Enter", "Escape"};

#define CELLWIDTH  5
#define CELLHEIGHT 8

/* repeat conts for responses */
#define MAX_REPEATS 20

/* commands for senddata */
#define RS_DATA     0x00
#define RS_INSTR    0x01
#define SETCHAR     0x40

/* boolean data type */
#ifndef bool
# define bool short
# define true 1
# define false 0
#endif

/* ----------- Key ring implementation from CFontz633io ------------------ */

/* KeyRing management */
#define KEYRINGSIZE	16

typedef struct ula200_keyring {
	unsigned char contents[KEYRINGSIZE];
	int head;
	int tail;
} KeyRing;

/*
 * KeyRing handling functions. This separates the producer from the consumer.
 * It is just a small fifo of unsigned char.
 */

/** initialize/empty key ring by resetting its read & write pointers */
void
EmptyKeyRing(KeyRing *kr)
{
	kr->head = kr->tail = 0;
}


/** add byte to key ring; return success (byte added) / failure (key ring is full) */
int
AddKeyToKeyRing(KeyRing *kr, unsigned char key)
{
	if (((kr->head + 1) % KEYRINGSIZE) != (kr->tail % KEYRINGSIZE)) {

		kr->contents[kr->head % KEYRINGSIZE] = key;
		kr->head = (kr->head + 1) % KEYRINGSIZE;
		return 1;
	}

	/* KeyRing overflow: do not accept extra key */
	return 0;
}


/** get byte from key ring (or '\\0' if key ring is empty) */
unsigned char
GetKeyFromKeyRing(KeyRing *kr)
{
	unsigned char retval = '\0';

	kr->tail %= KEYRINGSIZE;

	if ((kr->head % KEYRINGSIZE) != kr->tail) {
		retval = kr->contents[kr->tail];
		kr->tail = (kr->tail + 1) % KEYRINGSIZE;
	}

	return retval;
}


/* ---------------------- ULA-200 specific functions --------------------- */

/** private data for the \c ula200 driver */
typedef struct ula200_private_data {
	struct ftdi_context ftdic;	/**< handle for the USB FTDI library */
	int width;			/**< display width in characters */
	int height;			/**< display height in characters */
	unsigned char *framebuf;	/**< framebuffer LCDd writes to */
	unsigned char *lcd_contents;	/**< content of screen for incr. upd. */
	unsigned char all_dirty;	/**< first time => all is dirty */
	int backlight;			/**< backlight: -1=unset, 0=off, 1=on */
	KeyRing keyring;		/**< input key ring */
	char *key_map[MAX_KEY_MAP];	/**< mapping of input keys */
} PrivateData;


/**
 * Reads a character from USB.
 * \param p  Pointer to drivers private data
 * \return  Character read from USB.
 */
static inline int
ula200_ftdi_usb_read(PrivateData *p)
{
	unsigned char buffer[1];
	int err;

	while ((err = ftdi_read_data(&p->ftdic, buffer, 1)) == 0);

	if (err < 0) {
		return -1;
	}
	else {
		return buffer[0];
	}
}


/**
 * Reads the response.
 *
 * \return true   if ACK was responded
 * \return false  if NAK was responded
 */
static bool
ula200_ftdi_read_response(Driver *drvthis)
{
	PrivateData *p = (PrivateData *) drvthis->private_data;
	bool result = false;
	bool answer_read = false;
	int ret;
	int ch;

	while (!answer_read) {
		/* wait until STX */
		while (((ret = ula200_ftdi_usb_read(p)) != CH_STX) && (ret > 0));
		if (ret < 0) {
			return false;
		}

		/* read next char */
		ch = ula200_ftdi_usb_read(p);

		switch (ch) {
		    case 't':
			ch = ula200_ftdi_usb_read(p);
			AddKeyToKeyRing(&p->keyring, (unsigned char)(ch - 0x40));
			break;

		    case CH_ACK:
			answer_read = true;
			result = true;
			break;

		    case CH_NAK:
			answer_read = true;
			break;

		    default:
			answer_read = true;
			report(RPT_INFO, "%s: read invalid answer (0x%02X)", drvthis->name, ch);
		}

		/* wait until ETX */
		while (((ret = ula200_ftdi_usb_read(p)) != CH_ETX) && (ret > 0));
		if (ret < 0) {
			return false;
		}
	}

	return result;
}

/**
 * Write a command to the display. Adds the STX and ETX header/trailer.
 *
 * \param drvthis  Pointer to driver structure
 * \param data     the data bytes
 * \param length   the number of bytes in @p data which are valid
 * \param escape   if the data should be escaped (see the User's Guide of the
 *                 ULA-200)
 * \return  0 on success, negative value on error
 */
static int
ula200_ftdi_write_command(Driver *drvthis, unsigned char *data, int length, bool escape)
{
	PrivateData *p = (PrivateData *) drvthis->private_data;
	int i, err;
	int repeat_count = 0;
	int pos = 0;
	unsigned char buffer[1024];

	if (length > 512) {
		return -EINVAL;
	}

	/* fill the array */
	buffer[pos++] = CH_STX;
	for (i = 0; i < length; i++) {
		if (escape) {
			if (data[i] == CH_STX) {
				buffer[pos++] = CH_ENQ;
				buffer[pos++] = CH_DC2;
			}
			else if (data[i] == CH_ETX) {
				buffer[pos++] = CH_ENQ;
				buffer[pos++] = CH_DC3;
			}
			else if (data[i] == CH_ENQ) {
				buffer[pos++] = CH_ENQ;
				buffer[pos++] = CH_NAK;
			}
			else {
				buffer[pos++] = data[i];
			}
		}
		else {
			buffer[pos++] = data[i];
		}
	}
	buffer[pos++] = CH_ETX;

	do {
		/* bytes */
		err = ftdi_write_data(&p->ftdic, buffer, pos);
		if (err < 0) {
			report(RPT_WARNING, "%s: ftdi_write_data failed", drvthis->name);
			return -1;
		}
	}
	while (!ula200_ftdi_read_response(drvthis)&&(repeat_count++ < MAX_REPEATS));

	return 0;
}

/**
 * Clear the display using display command.
 * \return  Error code from ula200_ftdi_write_command.
 */
static int
ula200_ftdi_clear(Driver *drvthis)
{
	unsigned char command[1];
	int err;

	command[0] = 'l';
	err = ula200_ftdi_write_command(drvthis, command, 1, true);
	if (err < 0) {
		report(RPT_WARNING, "%s: ula200_ftdi_clear: "
		       "ula200_ftdi_write_command failed", drvthis->name);
	}

	return err;
}


/**
 * Set the position.
 */
static int
ula200_ftdi_position(Driver *drvthis, int x, int y)
{
	PrivateData *p = (PrivateData *) drvthis->private_data;
	unsigned char command[5];
	int err;

	if (y >= 2) {
		y -= 2;
		x += p->width;
	}

	command[0] = 'p';
	command[1] = x;
	command[2] = y;
	err = ula200_ftdi_write_command(drvthis, command, 3, true);
	if (err < 0) {
		report(RPT_WARNING, "%s: ula200_ftdi_position(%d,%d): "
		       "ula200_ftdi_write_command failed",
		       drvthis->name, x, y);
	}

	return err;
}


/**
 * Send raw data.
 *
 * \param drvthis  Pointer to driver
 * \param flags    Flag indicating byte is command or data
 * \param ch       Data byte to send
 * \return  Error code from ula200_ftdi_write_command.
 */
static int
ula200_ftdi_rawdata(Driver *drvthis, unsigned char flags, unsigned char ch)
{
	unsigned char command[3];
	int err;

	command[0] = 'R';
	command[1] = flags == (RS_DATA) ? '2' : '0';
	command[2] = ch;
	err = ula200_ftdi_write_command(drvthis, command, 3, false);
	if (err < 0) {
		report(RPT_ERR, "%s: ftdi_write_command() failed", drvthis->name);
	}

	return err;
}


/**
 * Writes a string to the display.
 *
 * \param drvthis  Pointer to driver
 * \param string   Pointer to string
 * \param len      Length of the string
 * \return  -EINVAL  If the string is to long (max 80 characters)
 * \return  err      Error code from ula200_ftdi_write_command
 */
static int
ula200_ftdi_string(Driver *drvthis, const unsigned char *string, int len)
{
	unsigned char buffer[128];
	int err;
	int i;

	if (len > 80) {
		return -EINVAL;
	}

	buffer[0] = 's';
	buffer[1] = len;
	for (i = 0; i < len; i++) {
		buffer[i + 2] = HD44780_charmap[(unsigned char)string[i]];
	}

	err = ula200_ftdi_write_command(drvthis, buffer, len + 2, true);
	if (err < 0) {
		report(RPT_WARNING, "%s: ula200_ftdi_string: "
		       "ula200_ftdi_write_command() failed", drvthis->name);
	}

	return err;
}


/**
 * Enables the raw register access mode.
 * \param drvthis  Pointer to driver
 * \return  Error code from ula200_ftdi_write_command.
 */
static int
ula200_ftdi_enable_raw_mode(Driver *drvthis)
{
	unsigned char command[3];

	report(RPT_DEBUG, "%s: enable raw mode", drvthis->name);

	command[0] = 'R';
	command[1] = 'E';
	command[2] = '1';
	return ula200_ftdi_write_command(drvthis, command, 3, false);
}

/**
 * Loads custom characters in the display.
 */
static int
ula200_load_custom_chars(Driver *drvthis)
{
	int i, row;
	int err = 0;
	unsigned char mask = (1 << CELLWIDTH) - 1;
	char custom_chars[8][CELLHEIGHT] = {
		{
			b__XXXXX,
			b__XXXXX,
			b__XXXXX,
			b__XXXXX,
			b__XXXXX,
			b__XXXXX,
			b__XXXXX,
			b__XXXXX
		},
		{
			b__XXXXX,
			b__X_X_X,
			b_______,
			b_______,
			b_______,
			b__X___X,
			b__XX_XX,
			b__XXXXX
		},
		{
			b__XXXXX,
			b__X_X_X,
			b___X_X_,
			b___XXX_,
			b___XXX_,
			b__X_X_X,
			b__XX_XX,
			b__XXXXX
		},
		{
			b____X__,
			b___XXX_,
			b__X_X_X,
			b____X__,
			b____X__,
			b____X__,
			b____X__,
			b_______
		},
		{
			b____X__,
			b____X__,
			b____X__,
			b____X__,
			b__X_X_X,
			b___XXX_,
			b____X__,
			b_______
		},
		{
			b_______,
			b_______,
			b__XXXXX,
			b__X___X,
			b__X___X,
			b__X___X,
			b__XXXXX,
			b_______
		},
		{
			b____X__,
			b____X__,
			b__XXX_X,
			b__X_XX_,
			b__X_X_X,
			b__X___X,
			b__XXXXX,
			b_______
		},
		{
			b_______,
			b_______,
			b__XXXXX,
			b__X_X_X,
			b__XX_XX,
			b__X_X_X,
			b__XXXXX,
			b_______
		}
	};

	for (i = 0; i < 8 && err == 0; i++) {
		/* Tell the HD44780 we will redefine char number i */
		ula200_ftdi_rawdata(drvthis, RS_INSTR, SETCHAR | i * 8);
		if (err < 0) {
			report(RPT_WARNING, "%s: ula200_ftdi_rawdata failed", drvthis->name);
			break;
		}

		/* Send the subsequent rows */
		for (row = 0; row < CELLHEIGHT; row++) {
			int value = custom_chars[i][row] & mask;
			err = ula200_ftdi_rawdata(drvthis, RS_DATA, value);
			if (err < 0) {
				report(RPT_WARNING, "%s: ula200_ftdi_rawdata failed", drvthis->name);
				break;
			}
		}
	}

	return err;
}

/* --------------------------- API functions ----------------------------- */

/**
 * Initialize the driver.
 * \param drvthis  Pointer to driver structure.
 * \retval 0       Success.
 * \retval <0      Error.
 */
MODULE_EXPORT int
ula200_init(Driver *drvthis)
{
	PrivateData *p;
	int err, i;
	const char *s;

	/* Allocate and store private data */
	p = (PrivateData *) malloc(sizeof(PrivateData));
	if (p == NULL) {
		return -1;
	}
	if (drvthis->store_private_ptr(drvthis, p)){
		return -1;
	}

	p->backlight = -1;
	p->all_dirty = 1;
	EmptyKeyRing(&p->keyring);

	/* Get and parse size */
	s = drvthis->config_get_string(drvthis->name, "size", 0, "20x4");
	if ((sscanf(s, "%dx%d", &(p->width), &(p->height)) != 2)
	    || (p->width <= 0) || (p->width > LCD_MAX_WIDTH)
	    || (p->height <= 0) || (p->height > LCD_MAX_HEIGHT)) {
		report(RPT_ERR, "%s: cannot read Size %s", drvthis->name, s);
		return -1;
	}

	/* read the keymap */
	for (i = 0; i < MAX_KEY_MAP; i++) {
		char buf[40];

		/* First fill with default value */
		p->key_map[i] = default_key_map[i];

		/* Read config value */
		sprintf(buf, "KeyMap_%c", i + 'A');
		s = drvthis->config_get_string(drvthis->name, buf, 0, NULL);

		/* Was a key specified in the config file ? */
		if (s != NULL) {
			p->key_map[i] = strdup(s);
			report(RPT_INFO, "%s: Key '%c' mapped to \"%s\"",
			       drvthis->name, i + 'A', s);
		}
	}

	/* End of config file parsing */


	/* Allocate framebuffer */
	p->framebuf = (unsigned char *) malloc(p->width * p->height);
	if (p->framebuf == NULL) {
		report(RPT_ERR, "%s: unable to allocate framebuffer", drvthis->name);
		goto err_begin;
	}

	/* Allocate and clear the buffer for incremental updates */
	p->lcd_contents = (unsigned char *) malloc(p->width * p->height);
	if (p->lcd_contents == NULL) {
		report(RPT_ERR, "%s: unable to allocate framebuffer backing store", drvthis->name);
		goto err_framebuf;
	}
	memset(p->lcd_contents, 0, p->width * p->height);

	/* open the FTDI library */
	ftdi_init(&p->ftdic);
	(&p->ftdic)->usb_write_timeout = 20;
	(&p->ftdic)->usb_read_timeout = 20;

	/* open the device */
	err = ftdi_usb_open(&p->ftdic, DISPLAY_VENDOR_ID, DISPLAY_PRODUCT_ID);
	if (err < 0) {
		report(RPT_ERR, "%s: cannot open USB device", drvthis->name);
		goto err_lcd;
	}

	/* set the baudrate */
	err = ftdi_set_baudrate(&p->ftdic, 19200);
	if (err < 0) {
		report(RPT_ERR, "%s: cannot set baudrate", drvthis->name);
		goto err_ftdi;
	}

	/* set communication parameters */
	err = ftdi_set_line_property(&p->ftdic, BITS_8, STOP_BIT_1, EVEN);
	if (err < 0) {
		report(RPT_ERR, "%s: cannot set line properties", drvthis->name);
		goto err_ftdi;
	}

	/* user is able to write commands */
	err = ula200_ftdi_enable_raw_mode(drvthis);
	if (err < 0) {
		report(RPT_ERR, "%s: unable to enable the raw mode", drvthis->name);
		goto err_ftdi;
	}

	/* load the chars */
	err = ula200_load_custom_chars(drvthis);
	if (err < 0) {
		report(RPT_ERR, "%s: unable to write the custom characters", drvthis->name);
		goto err_ftdi;
	}

	report(RPT_DEBUG, "%s: init() done", drvthis->name);

	return 0;

err_ftdi:
	ftdi_usb_close(&p->ftdic);
	ftdi_deinit(&p->ftdic);
err_lcd:
	free(p->lcd_contents);
err_framebuf:
	free(p->framebuf);
err_begin:
	return -1;
}


/**
 * Close the driver (do necessary clean-up).
 * \param drvthis  Pointer to driver structure.
 */
MODULE_EXPORT void
ula200_close(Driver *drvthis)
{
	PrivateData *p = (PrivateData *) drvthis->private_data;

	if (p != NULL) {
		ftdi_usb_purge_buffers(&p->ftdic);
		ftdi_usb_close(&p->ftdic);
		ftdi_deinit(&p->ftdic);

		if (p->framebuf != NULL)
			free(p->framebuf);

		if (p->lcd_contents != NULL)
			free(p->lcd_contents);

		free(p);
	}
	drvthis->store_private_ptr(drvthis, NULL);
}


/**
 * Return the display width in characters.
 * \param drvthis  Pointer to driver structure.
 * \return         Number of characters the display is wide.
 */
MODULE_EXPORT int
ula200_width(Driver *drvthis)
{
	PrivateData *p = (PrivateData *) drvthis->private_data;
	return p->width;
}


/**
 * Return the display height in characters.
 * \param drvthis  Pointer to driver structure.
 * \return         Number of characters the display is high.
 */
MODULE_EXPORT int
ula200_height(Driver *drvthis)
{
	PrivateData *p = (PrivateData *) drvthis->private_data;
	return p->height;
}


/**
 * Clear the screen.
 * \param drvthis  Pointer to driver structure.
 */
MODULE_EXPORT void
ula200_clear(Driver *drvthis)
{
	PrivateData *p = (PrivateData *) drvthis->private_data;
	memset(p->framebuf, ' ', p->width * p->height);
}


/**
 * Print a character on the screen at position (x,y).
 * The upper-left corner is (1,1), the lower-right corner is (p->width, p->height).
 * \param drvthis  Pointer to driver structure.
 * \param x        Horizontal character position (column).
 * \param y        Vertical character position (row).
 * \param c        Character that gets written.
 */
MODULE_EXPORT void
ula200_chr(Driver *drvthis, int x, int y, char c)
{
	PrivateData *p = (PrivateData *) drvthis->private_data;
	y--;
	x--;

	if ((x >= 0) && (y >= 0) && (x < p->width) && (y < p->height))
		p->framebuf[(y * p->width) + x] = c;
}


/**
 * Print a string on the screen at position (x,y).
 * The upper-left corner is (1,1), the lower-right corner is (p->width, p->height).
 * \param drvthis  Pointer to driver structure.
 * \param x        Horizontal character position (column).
 * \param y        Vertical character position (row).
 * \param string   String that gets written.
 */
MODULE_EXPORT void
ula200_string(Driver *drvthis, int x, int y, const char string[])
{
	PrivateData *p = (PrivateData *) drvthis->private_data;
	int i;

	x--;			/* Convert 1-based coords to 0-based */
	y--;

	for (i = 0; string[i] != '\0'; i++) {
		/* Check for buffer overflows... */
		if ((y * p->width) + x + i > (p->width * p->height))
			break;
		p->framebuf[(y * p->width) + x + i] = string[i];
	}
}


/**
 * Turn the LCD backlight on or off.
 * \param drvthis  Pointer to driver structure.
 * \param on       New backlight status.
 */
MODULE_EXPORT void
ula200_backlight(Driver *drvthis, int on)
{
	PrivateData *p = (PrivateData *) drvthis->private_data;
	unsigned char command[2];
	int err;

	if (p->backlight != on) {
		p->backlight = on;

		command[0] = 'h';
		command[1] = (on) ? '1' : '0';
		err = ula200_ftdi_write_command(drvthis, command, 2, false);
		if (err < 0)
			report(RPT_WARNING, "%s: error in ula200_ftdi_write_command",
			       drvthis->name);
		else
			report(RPT_INFO, "%s: turn backlight %s",
			       drvthis->name, (on) ? "on" : "off");
	}
}


/**
 * Flush data on screen to the LCD.
 * \param drvthis  Pointer to driver structure.
 */
MODULE_EXPORT void
ula200_flush(Driver *drvthis)
{
	PrivateData *p = (PrivateData *) drvthis->private_data;
	int x, y;
	int wid = p->width;
	char ch;
	int firstdiff;
	int lastdiff;

	if (p->all_dirty) {
		ula200_ftdi_clear(drvthis);
		p->all_dirty = 0;
	}

	/* Update LCD incrementally by comparing with last contents */
	for (y = 0; y < p->height; y++) {
		firstdiff = -1;
		lastdiff = 0;
		for (x = 0; x < wid; x++) {
			ch = p->framebuf[(y * wid) + x];
			if (ch != p->lcd_contents[(y * wid) + x]) {
				p->lcd_contents[(y * wid) + x] = ch;
				if (firstdiff == -1) {
					firstdiff = x;
				}
				lastdiff = x;
			}
		}

		if (firstdiff >= 0) {
			ula200_ftdi_position(drvthis, firstdiff, y);
			ula200_ftdi_string(drvthis, p->framebuf + (y * wid) + firstdiff,
					   lastdiff - firstdiff + 1);
		}
	}
}


/**
 * Place an icon on the screen.
 * \param drvthis  Pointer to driver structure.
 * \param x        Horizontal character position (column).
 * \param y        Vertical character position (row).
 * \param icon     synbolic value representing the icon.
 * \retval 0       Icon has been successfully defined/written.
 * \retval <0      Server core shall define/write the icon.
 */
MODULE_EXPORT int
ula200_icon(Driver *drvthis, int x, int y, int icon)
{
	switch (icon) {
		case ICON_BLOCK_FILLED:
		ula200_chr(drvthis, x, y, 0xff);
		break;
	    case ICON_HEART_FILLED:
		ula200_chr(drvthis, x, y, 2);
		break;
	    case ICON_HEART_OPEN:
		ula200_chr(drvthis, x, y, 1);
		break;
	    case ICON_ARROW_UP:
		ula200_chr(drvthis, x, y, 3);
		break;
	    case ICON_ARROW_DOWN:
		ula200_chr(drvthis, x, y, 4);
		break;
	    case ICON_ARROW_LEFT:
		ula200_chr(drvthis, x, y, 0x1B);
		break;
	    case ICON_ARROW_RIGHT:
		ula200_chr(drvthis, x, y, 0x1A);
		break;
	    case ICON_CHECKBOX_OFF:
		ula200_chr(drvthis, x, y, 5);
		break;
	    case ICON_CHECKBOX_ON:
		ula200_chr(drvthis, x, y, 6);
		break;
	    case ICON_CHECKBOX_GRAY:
		ula200_chr(drvthis, x, y, 7);
		break;
	    default:
		return -1;	/* Let the core do other icons */
	}
	return 0;
}


/**
 * Get key from the device.
 * \param drvthis  Pointer to driver structure.
 * \return         String representation of the key;
 *                 \c NULL for nothing available / unmapped key.
 */
MODULE_EXPORT const char *
ula200_get_key(Driver *drvthis)
{
	PrivateData *p = drvthis->private_data;
	unsigned char key;
	int i;

	/*
	 * The libftdi has no non-blocking read (`select' system call), so we
	 * force a read that could not block by updating one character on the
	 * display. As long as lcdproc is single-threaded, we can write to
	 * the display because we're not inside a read here.
	 */
	ula200_ftdi_position(drvthis, 0, 0);
	ula200_ftdi_string(drvthis, p->lcd_contents, 1);

	key = GetKeyFromKeyRing(&p->keyring);

	/* search the bit that was set by the hardware */
	for (i = 0; i < MAX_KEY_MAP; i++) {
		if (key & (1 << i))
			return p->key_map[i];
	}

	if (key != '\0') {
		report(RPT_INFO, "%s: Untreated key 0x%02X", drvthis->name, key);
	}
	return NULL;
}