aboutsummaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorherp <herp@3ae390bd-cb1e-0410-b409-cd5a39f66f1f>2000-05-03 09:37:32 +0000
committerherp <herp@3ae390bd-cb1e-0410-b409-cd5a39f66f1f>2000-05-03 09:37:32 +0000
commit1df2f43206a2cb86e2792d8315b5e14f269ed83f (patch)
treeb62a26f48017e053965e916e1a245164b4b135ab
parent6373b1b0c309ef99f98295cfc70b5411c96afce2 (diff)
downloadlcd4linux-1df2f43206a2cb86e2792d8315b5e14f269ed83f.tar.gz
[lcd4linux @ 2000-05-03 09:37:32 by herp]
git-svn-id: https://ssl.bulix.org/svn/lcd4linux/trunk@55 3ae390bd-cb1e-0410-b409-cd5a39f66f1f
Diffstat (limited to '')
-rw-r--r--Crystalfontz.c545
-rw-r--r--Crystalfontz.h69
-rw-r--r--README.Crystalfontz44
3 files changed, 658 insertions, 0 deletions
diff --git a/Crystalfontz.c b/Crystalfontz.c
new file mode 100644
index 0000000..377382b
--- /dev/null
+++ b/Crystalfontz.c
@@ -0,0 +1,545 @@
+/*
+ * driver for display modules from Crystalfontz
+ *
+ * Copyright 2000 by Herbert Rosmanith (herp@wildsau.idv.uni-linz.ac.at)
+ *
+ * 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, 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., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <termios.h>
+#include <unistd.h>
+#include <signal.h>
+#include <fcntl.h>
+
+#include "cfg.h"
+#include "lock.h"
+#include "display.h"
+#include "Crystalfontz.h"
+
+#define XRES 6
+#define YRES 8
+#define BARS ( BAR_L | BAR_R )
+
+static LCD Lcd;
+static char *Port=NULL;
+static speed_t Speed;
+static int Device=-1;
+
+static char *Txtbuf,*BackupTxtbuf; /* text (+backup) buffer */
+static char *Barbuf,*BackupBarbuf; /* bar (+backup) buffer */
+static char *CustCharMap;
+static int tdim,bdim; /* text/bar dimension */
+static char isTxtDirty;
+static char *isBarDirty;
+static char isAnyBarDirty;
+
+static void cryfonquit() {
+
+ close(Device);
+ unlock_port(Port);
+ exit(0);
+}
+
+static int cryfonopen() {
+int fd;
+pid_t pid;
+struct termios portset;
+
+ if ((pid=lock_port(Port))!=0) {
+ if (pid==-1) fprintf(stderr,"Crystalfontz: port %s could not be locked\n",Port);
+ else fprintf(stderr,"Crystalfontz: port %s is locked by process %d\n",Port,pid);
+ return -1;
+ }
+ fd=open(Port,O_RDWR|O_NOCTTY|O_NDELAY);
+ if (fd==-1) {
+ fprintf(stderr,"Crystalfontz: open(%s) failed: %s\n",
+ Port,strerror(errno));
+ return -1;
+ }
+ if (tcgetattr(fd,&portset)==-1) {
+ fprintf(stderr,"Crystalfontz: tcgetattr(%s) failed: %s\n",
+ Port,strerror(errno));
+ return -1;
+ }
+ cfmakeraw(&portset);
+ cfsetospeed(&portset,Speed);
+ if (tcsetattr(fd, TCSANOW, &portset)==-1) {
+ fprintf(stderr,"Crystalfontz: tcsetattr(%s) failed: %s\n",
+ Port,strerror(errno));
+ return -1;
+ }
+ return fd;
+}
+
+static int cryfoninit(LCD *Self) {
+char *port;
+char *speed;
+char *backlight;
+char *contrast;
+char cmd_backlight[2]={ CRYFON_BACKLIGHT_CTRL, };
+char cmd_contrast[2]={ CRYFON_CONTRAST_CTRL, };
+
+ Lcd=*Self;
+
+ if (Port) {
+ free(Port);
+ Port=NULL;
+ }
+
+ if ((port=cfg_get("Port"))==NULL || *port=='\0') {
+ fprintf(stderr,"CrystalFontz: no 'Port' entry in %s\n",
+ cfg_file());
+ return -1;
+ }
+ if (port[0]=='/') Port=strdup(port);
+ else {
+ Port=(char *)malloc(5/*/dev/ */+strlen(port)+1);
+ sprintf(Port,"/dev/%s",port);
+ }
+
+ speed=cfg_get("Speed")?:"9600";
+ switch(atoi(speed)) {
+ case 1200:
+ Speed=B1200;
+ break;
+ case 2400:
+ Speed=B2400;
+ break;
+ case 9600:
+ Speed=B9600;
+ break;
+ case 19200:
+ Speed=B19200;
+ break;
+ default:
+ fprintf(stderr,"CrystalFontz: unsupported speed '%s' in '%s'\n",
+ speed,cfg_file());
+ return -1;
+ }
+
+ if ((Device=cryfonopen())==-1)
+ return -1;
+
+ tdim=Lcd.rows*Lcd.cols;
+ bdim=Lcd.rows*Lcd.cols*2;
+
+ Txtbuf=(char *)malloc(tdim);
+ if (Txtbuf==NULL) {
+ fprintf(stderr,"CrystalFontz: out of memory\n");
+ return -1;
+ }
+ CustCharMap=(char *)malloc(tdim);
+ if (CustCharMap==NULL) {
+ fprintf(stderr,"CrystalFontz: out of memory\n");
+ return -1;
+ }
+ BackupTxtbuf=(char *)malloc(tdim);
+ if (BackupTxtbuf==NULL) {
+ fprintf(stderr,"CrystalFontz: out of memory\n");
+ return -1;
+ }
+ Barbuf=(char *)malloc(bdim);
+ if (Barbuf==NULL) {
+ fprintf(stderr,"CrystalFontz: out of memory\n");
+ return -1;
+ }
+ BackupBarbuf=(char *)malloc(bdim);
+ if (BackupBarbuf==NULL) {
+ fprintf(stderr,"CrystalFontz: out of memory\n");
+ return -1;
+ }
+ isBarDirty=(char *)malloc(Lcd.rows);
+ if (isBarDirty==NULL) {
+ fprintf(stderr,"CrystalFontz: out of memory\n");
+ return -1;
+ }
+ memset(Txtbuf,' ',tdim);
+ memset(CustCharMap,-1,tdim);
+ memset(BackupTxtbuf,255,tdim);
+ memset(Barbuf,0,bdim);
+ memset(BackupBarbuf,0,bdim);
+ memset(isBarDirty,0,Lcd.rows);
+ isAnyBarDirty=0;
+ isTxtDirty=0;
+
+ signal(SIGINT,cryfonquit);
+ signal(SIGQUIT,cryfonquit);
+ signal(SIGTERM,cryfonquit);
+
+ usleep(350000);
+ write(Device, CRYFON_HIDE_CURSOR CRYFON_SCROLL_OFF CRYFON_WRAP_OFF,3);
+ backlight=cfg_get("Backlight")?:NULL;
+ if (backlight) {
+ cmd_backlight[1]=atoi(backlight);
+ write(Device,cmd_backlight,4);
+ }
+
+ contrast=cfg_get("Contrast")?:NULL;
+ if (contrast) {
+ cmd_contrast[1]=atoi(contrast);
+ write(Device,cmd_contrast,2);
+ }
+
+ return 0;
+}
+
+static int cryfonclear() {
+ memset(Txtbuf,' ',tdim);
+ memset(Barbuf,0,bdim);
+ return 0;
+}
+
+static int cryfonput(int row,int col,char *text) {
+int pos;
+
+ pos=row*Lcd.cols+col;
+ memcpy(Txtbuf+pos,text,strlen(text));
+ isTxtDirty|=memcmp(Txtbuf+pos,BackupTxtbuf+pos,strlen(text));
+ return 0;
+}
+
+static unsigned char p1[] = { 0x3f,0x1f,0x0f,0x07,0x03,0x01,0x00 };
+static unsigned char p2[] = { 0x00,0x20,0x30,0x38,0x3c,0x3e,0x3f };
+
+static void blacken(int bitfrom,int len,int pos,int startbyte,int endbyte) {
+
+ if (startbyte==endbyte)
+ Barbuf[pos] |=
+ (p1[bitfrom%XRES] & p2[1+((bitfrom+len-1)%XRES)]);
+ else {
+ int n;
+ Barbuf[pos] |= p1[bitfrom%XRES];
+ n=endbyte-startbyte-1;
+ if (n>0) memset(Barbuf+pos+1,0x3f,n);
+ Barbuf[pos+n+1] |= p2[1+((bitfrom+len-1)%XRES)];
+
+ }
+}
+
+static void whiten(int bitfrom,int len,int pos,int startbyte,int endbyte) {
+
+ if (startbyte==endbyte)
+ Barbuf[pos] &=
+ (p2[bitfrom%XRES] | p1[1+((bitfrom+len-1)%XRES)]);
+ else {
+ int n;
+ Barbuf[pos] &= p2[bitfrom%XRES];
+ n=endbyte-startbyte-1;
+ if (n>0) memset(Barbuf+pos+1,0x00,n);
+ Barbuf[pos+n+1] &= p1[1+((bitfrom+len-1)%XRES)];
+ }
+}
+
+static int cryfonbar(int type,int row,int col,int max,int len1,int len2) {
+int endb,maxb;
+int bitfrom;
+int pos;
+
+ if (len1<1) len1=1;
+ else if (len1>max) len1=max;
+
+ if (len2<1) len2=1;
+ else if (len2>max) len2=max;
+
+ bitfrom=col*XRES;
+ endb=(bitfrom+len1-1)/XRES;
+ pos=row*Lcd.cols*2;
+
+ switch(type) {
+ case BAR_L:
+ blacken(bitfrom,len1,pos+col,col,endb);
+ endb=(bitfrom+len1)/XRES;
+ maxb=(bitfrom+max-1)/XRES;
+ whiten(bitfrom+len1,max-len1,pos+endb,endb,maxb);
+ if (len1==len2)
+ memcpy(Barbuf+pos+col+Lcd.cols,
+ Barbuf+pos+col,
+ maxb-col+1);
+ else {
+ pos+=Lcd.cols;
+ endb=(bitfrom+len2-1)/XRES;
+ blacken(bitfrom,len2,pos+col,col,endb);
+ endb=(bitfrom+len2)/XRES;
+ whiten(bitfrom+len2,max-len2,pos+endb,endb,maxb);
+ }
+ break;
+ case BAR_R:
+ blacken(bitfrom,len1,pos+col,col,endb);
+ endb=(bitfrom+len1)/XRES;
+ maxb=(bitfrom+max-1)/XRES;
+ whiten(bitfrom+len1,max-len1,pos+endb,endb,maxb);
+ if (len1==len2)
+ memcpy(Barbuf+pos+col+Lcd.cols,
+ Barbuf+pos+col,
+ maxb-col+1);
+ else {
+ pos+=Lcd.cols;
+ endb=(bitfrom+len2-1)/XRES;
+ blacken(bitfrom,len2,pos+col,col,endb);
+ endb=(bitfrom+len2)/XRES;
+ whiten(bitfrom+len2,max-len2,pos+endb,endb,maxb);
+ }
+ break;
+ }
+ isBarDirty[row]=1;
+ isAnyBarDirty=1; /* dont know exactly, check anyway */
+ return 0;
+}
+
+static int txt_lc=-1,txt_lr=-1;
+
+static void writeTxt(char r,char c,int itxt,int len) {
+static char cmd_goto[3]=CRYFON_GOTO;
+
+ if (txt_lr!=r || txt_lc!=c) {
+ if (r==0 && c==0) write(Device,CRYFON_HOME,1);
+ else {
+ cmd_goto[1]=(unsigned char)c;
+ cmd_goto[2]=(unsigned char)r;
+ write(Device,(char *)&cmd_goto,3);
+ }
+ }
+ txt_lr=r;
+ txt_lc=c+len;
+ write(Device,Txtbuf+itxt,len);
+}
+
+static void writeTxtDiff() {
+int spos,scol;
+int i,j,k;
+
+ k=0;
+ txt_lr=txt_lc=-1;
+ for (i=0;i<Lcd.rows;i++) {
+ spos=-1;
+ scol=0; /* make gcc happy */
+ for (j=0;j<Lcd.cols;j++) {
+ if (Txtbuf[k]^BackupTxtbuf[k]) {
+ if (spos==-1) {
+ spos=k;
+ scol=j;
+ }
+ } else if (spos>-1) {
+ writeTxt((char)i,(char)scol,spos,k-spos);
+ memcpy(BackupTxtbuf+spos,Txtbuf+spos,k-spos);
+ spos=-1;
+ }
+ k++;
+ }
+ if (spos>-1) {
+ writeTxt((char)i,(char)scol,spos,k-spos);
+ memcpy(BackupTxtbuf+spos,Txtbuf+spos,k-spos);
+ }
+ }
+}
+
+/* private bar flushing routines */
+
+static char BarCharBuf[256];
+static int bi=0;
+
+static void flushBarCharBuf() {
+ if (bi) {
+ write(Device,BarCharBuf,bi); /* flush buffer */
+ tcdrain(Device);
+ bi=0;
+ }
+}
+
+static void writeBarCharBuf(char *s,int len) {
+ if (bi+len>=sizeof(BarCharBuf)) {
+ flushBarCharBuf();
+ }
+ memcpy(BarCharBuf+bi,s,len);
+ bi+=len;
+}
+
+static struct {
+ char use_count; /* 0 - unused */
+ char data[8];
+} cust_chars[8] = {
+ { 0, }, { 0, }, { 0, }, { 0, }, { 0, }, { 0, }, { 0, }, { 0, }
+};
+
+static int search_cust_char(char c1,char c2) {
+int i;
+ for (i=0;i<8;i++) {
+ if (cust_chars[i].data[0]==c1
+ && cust_chars[i].data[4]==c2) {
+ return i;
+ }
+ }
+ return -1; /* not found */
+}
+
+static void set_cust_char(int ci,char c1,char c2) {
+static char cmd_cust[10] = CRYFON_SET_CUSTOM_CHAR_BITMAP;
+
+ memset(cust_chars[ci].data,c1,4);
+ memset(cust_chars[ci].data+4,c2,4);
+ cmd_cust[1]=ci;
+ memset(cmd_cust+2,c1,4);
+ memset(cmd_cust+6,c2,4);
+ writeBarCharBuf(cmd_cust,10);
+}
+
+static int alloc_cust_char(char c1,char c2) {
+static char allzero[8]={0, };
+int i;
+
+ /* first, try to allocate a never used entry */
+
+ for(i=0;i<8;i++)
+ if (memcmp(cust_chars[i].data,allzero,8)==0) {
+ set_cust_char(i,c1,c2);
+ return i;
+ }
+
+ /* if that fails, pick an entry with is not yet in use */
+
+ for(i=0;i<8;i++)
+ if (cust_chars[i].use_count==0) {
+ set_cust_char(i,c1,c2);
+ return i;
+ }
+ return -1; /* no free char */
+}
+
+static void use_cust_char(int i,int j,int ci) {
+int x;
+ x=i*Lcd.cols+j;
+ if (CustCharMap[x]==-1) {
+ cust_chars[ci].use_count++;
+ CustCharMap[x]=ci;
+ }
+ /* else: internal consistency failure */
+ else {
+ printf("Crystalfontz: internal consistency failure 1\n");
+ exit(0);
+ }
+}
+
+static void unuse_cust_char(int i,int j) {
+int ci,x;
+ x=i*Lcd.cols+j;
+ ci=CustCharMap[x];
+ if (ci>-1) {
+ CustCharMap[x]=-1;
+ cust_chars[ci].use_count--;
+ if (cust_chars[i].use_count==-1) {
+ printf("Crystalfontz: internal consistency failure 2\n");
+ exit(0);
+ }
+ }
+}
+
+static int bar_lc=-1,bar_lr=-1;
+
+
+static void writeChar(unsigned char r,unsigned char c,unsigned char ch) {
+static char cmd_goto[3]=CRYFON_GOTO;
+
+ if (bar_lr!=r || bar_lc!=c) {
+ if (r==0 && c==0) writeBarCharBuf(CRYFON_HOME,1);
+ else {
+ cmd_goto[1]=(unsigned char)c;
+ cmd_goto[2]=(unsigned char)r;
+ writeBarCharBuf((char *)&cmd_goto,3);
+ }
+ }
+ bar_lr=r;
+ bar_lc=c++;
+ writeBarCharBuf(&ch,1);
+}
+
+static void writeBarDiff() {
+char c1,c2;
+int i,j,k1,k2,ci;
+
+ for (i=0;i<Lcd.rows;i++) {
+ if (isBarDirty[i]) {
+ k1=i*Lcd.cols*2;
+ k2=k1+Lcd.cols;
+ bar_lr=bar_lc=-1;
+ for (j=0;j<Lcd.cols;j++) {
+ c1=Barbuf[k1];
+ c2=Barbuf[k2];
+ if (c1^BackupBarbuf[k1] ||
+ c2^BackupBarbuf[k2]) {
+
+ if (c1==0 && c2==0) { /* blank */
+ unuse_cust_char(i,j);
+ writeChar(i,j,' ');
+ }
+ else if (c1==0x1f && c2==0x1f) { /*boxlike*/
+ unuse_cust_char(i,j);
+ writeChar(i,j,0xff);
+ }
+ else {
+ /* search cust char */
+ ci=search_cust_char(c1,c2);
+ if (ci>-1) { /* found: reuse that char */
+ unuse_cust_char(i,j);
+ writeChar(i,j,128+ci);
+ use_cust_char(i,j,ci);
+ }
+ else { /* not found: get a new one */
+ ci=alloc_cust_char(c1,c2);
+ if (ci>-1) {
+ unuse_cust_char(i,j);
+ writeChar(i,j,128+ci);
+ use_cust_char(i,j,ci);
+ }
+ else printf("failed to alloc a custom char\n");
+ }
+ }
+ BackupBarbuf[k1]=c1;
+ BackupBarbuf[k2]=c2;
+ }
+ k1++;
+ k2++;
+ }
+ }
+ isBarDirty[i]=0;
+ }
+ flushBarCharBuf();
+}
+
+static int cryfonflush() {
+
+ if (isTxtDirty) {
+ writeTxtDiff();
+ isTxtDirty=0;
+ }
+ if (isAnyBarDirty) {
+ writeBarDiff();
+ isAnyBarDirty=0;
+ }
+
+ return 0;
+}
+
+LCD Crystalfontz[] = {
+ { "626", 2, 16, XRES, YRES, BARS, cryfoninit, cryfonclear, cryfonput, cryfonbar, cryfonflush },
+ { "636", 2, 16, XRES, YRES, BARS, cryfoninit, cryfonclear, cryfonput, cryfonbar, cryfonflush },
+ { "632", 2, 16, XRES, YRES, BARS, cryfoninit, cryfonclear, cryfonput, cryfonbar, cryfonflush },
+ { "634", 4, 20, XRES, YRES, BARS, cryfoninit, cryfonclear, cryfonput, cryfonbar, cryfonflush },
+ { NULL }
+};
diff --git a/Crystalfontz.h b/Crystalfontz.h
new file mode 100644
index 0000000..fb77c0d
--- /dev/null
+++ b/Crystalfontz.h
@@ -0,0 +1,69 @@
+/*
+ * driver for display modules from Crystalfontz
+ *
+ * Copyright 2000 by Herbert Rosmanith (herp@wildsau.idv.uni-linz.ac.at)
+ *
+ * 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, 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., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ */
+
+
+/* see: 634full.pdf, avail. from www.crystalfontz.com
+ * values here are octal
+ */
+
+#define CRYFON_NULL "\000"
+#define CRYFON_CURSOR_HOME "\001"
+#define CRYFON_HOME CRYFON_CURSOR_HOME
+#define CRYFON_HIDE_DISPLAY "\002"
+#define CRYFON_RESTORE_DISPLAY "\003"
+#define CRYFON_HIDE_CURSOR "\004"
+#define CRYFON_SHOW_UL_CURSOR "\005"
+#define CRYFON_SHOW_BLK_CURSOR "\006"
+#define CRYFON_SHOW_INV_CURSOR "\007"
+#define CRYFON_BACKSPACE "\010"
+/*not used: 9 (tab), 011 octal */
+#define CRYFON_LF "\012"
+#define CRYFON_DEL_IN_PLACE "\013"
+#define CRYFON_FF "\014"
+#define CRYFON_CR "\015"
+#define CRYFON_BACKLIGHT_CTRL "\016"
+#define CRYFON_CONTRAST_CTRL "\017"
+/*not used: 16, 020 octal */
+#define CRYFON_SET_CURSOR_POS "\021"
+#define CRYFON_GOTO CRYFON_SET_CURSOR_POS
+#define CRYFON_HORIZONTAL_BAR "\022"
+#define CRYFON_SCROLL_ON "\023"
+#define CRYFON_SCROLL_OFF "\024"
+#define CRYFON_SET_SCROLL_MARQU "\025"
+#define CRYFON_ENABLE_SCROLL_MARQU "\026"
+#define CRYFON_WRAP_ON "\027"
+#define CRYFON_WRAP_OFF "\030"
+#define CRYFON_SET_CUSTOM_CHAR_BITMAP "\031"
+#define CRYFON_REBOOT "\032"
+#define CRYFON_ESC "\033"
+#define CRYFON_LARGE_BLK_NUM "\034"
+/*not used: 29, 035 octal*/
+#define CRYFON_SEND_DATA_DIRECT "\036"
+#define CRYFON_SHOW_INFO "\037"
+#define CRYFON_CUST_CHAR0 "\200"
+#define CRYFON_CUST_CHAR1 "\201"
+#define CRYFON_CUST_CHAR2 "\202"
+#define CRYFON_CUST_CHAR3 "\203"
+#define CRYFON_CUST_CHAR4 "\204"
+#define CRYFON_CUST_CHAR5 "\205"
+#define CRYFON_CUST_CHAR6 "\206"
+#define CRYFON_CUST_CHAR7 "\207"
+
diff --git a/README.Crystalfontz b/README.Crystalfontz
new file mode 100644
index 0000000..4c76b45
--- /dev/null
+++ b/README.Crystalfontz
@@ -0,0 +1,44 @@
+
+This is the README file for the Crystalfontz display driver for lcd4linux
+
+This driver supports the 632/634 LCD-Modules from Crystalfontz, but should
+work for the 626 and 636 modules too. The 634 is a 20x4 character display,
+while the others only display 16x2. I've written the driver using a
+634 module.
+
+The driver understands the following configuration parameters:
+
+Display: any of 626, 632, 634 and 636.
+
+Port: serial device (i.e. ttyS0) the LCD module is connnected
+ to.
+
+Speed: any of 1200, 2400, 9600 and 19200. By default, the driver
+ uses 9600 which is the speed the LCD modules are hardwired
+ at. If your module works at a different speed than 9600,
+ use this parameter. Otherwise omit it (i.e. omit it when
+ you have a 634).
+
+Backlight: controls the backlight brightness. Quote from 634.pdf from
+ the Crystalfonts-Webserver[1]: "0=OFF 100=ON. Intermediate
+ values vary the brightness. There are a total of 25 possible
+ brightness levels."
+
+Contrast: controls the contrast settings. Quote[1]: "0=very light,
+ 100 = very dark. 50 is typical. There are a total of 25
+ possible contrast levels."
+
+
+Known bugs:
+When you draw a bar over a previously drawn textfield, the white portion
+the bar will not erase the text. Only when the black portion of the bar
+has reached the full bar length, the text will be erased. I did not bother
+to implement that, since in lcd4linux, the whole display-screen is erased
+prior to switching to a different 'screen'. Implementing this feature would
+just add to program-overhead. Yes, you guessed it: I did not use the "bar"-
+command that comes with the LCD-module, but wrote my own instead.
+lcd4linux also supports "split-" or "dual-bars" (two bars in one segment),
+which are not available on the Crystalfontz firmware.
+
+ [1] http://www.crystalfontz.com
+