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georpo
Joined: 18 Nov 2008
Posts: 281
Location: Athens, Greece.
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| LCD12864 |
 Posted: Wed May 02, 2018 2:27 am |
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Hello,
I am making my custom library to set/clear pixel on a 128*64 LCD with ST7920.
I got it working but I have this in my code:
| Code: |
if (px==0 || px==8 || px==16 || px==24 || px==32 || px==40 || px==48 || px==56 || px==64 || px==72 || px==80 || px==88 || px==96 || px==104 || px==112 || px==120) Pix=128;
else if (px==1 || px==9 || px==17 || px==25 || px==33 || px==41 || px==49 || px==57 || px==65 || px==73 || px==81 || px==89 || px==97 || px==105 || px==113 || px==121) Pix=64;
else if (px==2 || px==10 || px==18 || px==26 || px==34 || px==42 || px==50 || px==58 || px==66 || px==74 || px==82 || px==90 || px==98 || px==106 || px==114 || px==122) Pix=32;
else if (px==3 || px==11 || px==19 || px==27 || px==35 || px==43 || px==51 || px==59 || px==67 || px==75 || px==73 || px==91 || px==99 || px==107 || px==115 || px==123) Pix=16;
else if (px==4 || px==12 || px==20 || px==28 || px==36 || px==44 || px==52 || px==60 || px==68 || px==76 || px==84 || px==92 || px==100 || px==108 || px==116 || px==124) Pix=8;
else if (px==5 || px==13 || px==21 || px==29 || px==37 || px==45 || px==53 || px==61 || px==69 || px==77 || px==85 || px==93 || px==101 || px==109 || px==117 || px==125) Pix=4;
else if (px==6 || px==14 || px==22 || px==30 || px==38 || px==46 || px==54 || px==62 || px==70 || px==78 || px==86 || px==94 || px==102 || px==110 || px==118 || px==126) Pix=2;
else if (px==7 || px==15 || px==23 || px==31 || px==39 || px==47 || px==55 || px==63 || px==71 || px==79 || px==87 || px==95 || px==103 || px==111 || px==119 || px==127) Pix=1;
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Is there a better/more efficient way to do this?
Thanks!
_________________
George. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19520
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| Posted: Wed May 02, 2018 2:42 am |
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| Code: |
int8 temp;
const pxval[]={128,64,32,16,8,4,2,1};
temp=px%8;
Pix=pxval[temp];
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I think that should give the right values. |
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georpo
Joined: 18 Nov 2008
Posts: 281
Location: Athens, Greece.
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| Posted: Wed May 02, 2018 3:18 am |
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It works 
I have no idea how but it works!
thanks a lot Ttelmah!
Just noticed that your trick saved me 14% of ROM 
_________________
George.
Last edited by georpo on Wed May 02, 2018 3:31 am; edited 1 time in total |
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georpo
Joined: 18 Nov 2008
Posts: 281
Location: Athens, Greece.
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| Posted: Wed May 02, 2018 3:25 am |
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BTW, in some other part of my "setpixel" code:
| Code: |
if(px<8) X=0; //0-7
else if((px>7) && (px<16)) X=1; //8-15
else if((px>15) && (px<24)) X=2; //16-23
else if((px>23) && (px<32)) X=3; //24-31
else if((px>31) && (px<40)) X=4; //32-39
else if((px>39) && (px<48)) X=5; //40-47
else if((px>47) && (px<56)) X=6; //48-55
else if((px>55) && (px<64)) X=7; //56-63
else if((px>63) && (px<72)) X=8; //64-71
else if((px>71) && (px<80)) X=9; //72-79
else if((px>79) && (px<88)) X=10; //80-87
else if((px>87) && (px<96)) X=11; //88-95
else if((px>95) && (px<104)) X=12; //96-103
else if((px>103) && (px<112)) X=13; //104-111
else if((px>111) && (px<120)) X=14; //112-119
else if((px>119) && (px<128)) X=15; //120-127
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The above decides in which X offset the pixel belongs to.
Is there any magic here? 
_________________
George. |
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temtronic
Joined: 01 Jul 2010
Posts: 9229
Location: Greensville,Ontario
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| Posted: Wed May 02, 2018 4:55 am |
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It's early for me but
this...
else if((px>7) && (px<16)) X=1; //8-15
could be simplified to
else if(px<16)) X=1; //8-15
providing the IFs are in the correct order
something like this...
if(px<8) X=0; //0-7
else if(px<16)) X=1; //8-15
else if(px<24)) X=2; //16-23
else if(px<32)) X=3; //24-31
...
should work fine
when I look at it is says
if px<8 x becomes 0 and leave else then if px<16 x become 2.....
The other option would be to use the 'SWITCH...' statement. Actually you should code both and see what compiles,dump the listing(programname.lst file) to see It may be the SWITCH method produces smaller,faster code which means less ROM space and faster execution. |
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georpo
Joined: 18 Nov 2008
Posts: 281
Location: Athens, Greece.
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| Posted: Wed May 02, 2018 5:15 am |
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I get the point.
Thanks a million!
_________________
George. |
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temtronic
Joined: 01 Jul 2010
Posts: 9229
Location: Greensville,Ontario
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| Posted: Wed May 02, 2018 5:37 am |
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great cause I'm still sleepy over here in canada......
always amazes me the WORLDWIDE appeal of PICs !
ohpa |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19520
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| Posted: Wed May 02, 2018 7:03 am |
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| georpo wrote: | It works
I have no idea how but it works!
thanks a lot Ttelmah!
Just noticed that your trick saved me 14% of ROM |
OK lets go through it....
| Code: |
int8 temp;
const pxval[]={128,64,32,16,8,4,2,1};
temp=px%8;
//Now this gives the remainder from dividing by 8. so just 1 to 7
//'1' for the first line of your tests, '2' for the next, etc. etc..
Pix=pxval[temp];
//This gives '128' for '1', '64' for '2' etc..
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