Varman
Joined: 16 Jun 2024
Posts: 2
|
| Re: SSD1306 driver for use with less RAM |
 Posted: Sun Jun 16, 2024 3:08 pm |
 |
|
| Ttelmah wrote: | Updated October 2018. An optional alternative way of running for PCD chips.
Updated Nov2017 - I've changed the font and bar graph output to be 0-100
Second amendment Dec 2017 Now supports a new #define to operate the SH1106 display as well. Also slightly more efficient
This is an example of a slightly 'different' SSD1306/SH1106 driver, for people working with restricted RAM.
The problem is that these chips do not allow a read, when in serial mode.
Now if (for instance), you set a pixel, on a 'clear' screen, then this is
not a problem. However if you then go to set a second pixel, you need to test
if any other pixel in the same byte is already set. So you need to 'know'
what is on the screen. The solution with the standard driver, is to have a
RAM buffer carrying a 'copy' of the screen, and then you can test the byte
in this, and if another pixel is set, send the whole byte with both pixels
to the display. However if you are trying to drive the screen on a chip
with very limited RAM, you don't have the space for such a buffer....
This driver allows some operations on the display, using varying amounts of
RAM.
It is in two parts. The first is a 'text' driver for the screen, which
uses a 6*8 font which is designed to be clear even at the small sizes on
the 0.96" displays. It gives you 21*8 text on the screen, with the ability
to also use the font 'double size' to give 10*4 text. It includes
thirteen extra characters in the font, which allow a 'bar graph' to be drawn
using 9 characters, and giving 0-100 (actually 101). for a empty bar to a
full bar. Again the double size mode can be used, to give a bar nearly the
width of the screen.
Key thing 'for' these screens, is they work in a wide range of light
conditions and at low temperatures where LCD's give problems - and they
are cheap!...
The driver is for I2C mode.
Look at the comments in the driver and example, to see how it works:
ssd1306.h
| Code: |
/*
Now the big limitation.....
In serial modes (SPI/I2C), this chip provides no ability to read back it's RAM.
So we have a problem. If we want to write a line across the screen, and leave
another line that is already there 'undestroyed' where they cross, how can we
'know' the other line is there?. Basically the host chip needs to have a copy
of the display memory so it can hold a copy of any graphics and know what is
going on. Problem is that this is just not possible, on a PIC with limited RAM.
So this driver works by overwriting for all text writes....
But see further down for the 'exception' to this.
*/
//It is most efficiently used by preparing the whole line of text first
//and then sending this - it then uses a 'burst' transmission, to give very
//fast updates. It does offer a 'putc' though, but this is slower.
//It does not properly handle wrapping at the end of the line.
//The putc function adds support for \n, \r, and \f.
//Functions:
// OLED_CLS(); //clears the screen
// OLED_gotoxy(x, y); //goto column/row 0-20 for the column
// //0-7 for the row
// OLED_text(*text, number);
// //This sends 'number' bytes from the array
// //pointed to by 'text', to the display
// OLED_putc(c); //sends 'c' to the display. Beware though
// //if you go beyond the end of the line
// //- you'll get partial characters....
// OLED_textbar(width); //Displays a bargraph. With width=50
// //you get a 50:50 display of bar/void.
//Two global variables affect how things are displayed.
// size=NORMAL;
// size=LARGE; //switches between showing 21*8 & 10*4
// size=DOUBLE_HEIGHT //Gives 21*4 - great for the bargraph
// set=TRUE; //default. Pixels are 'set' when written, so
// //turn on.
// set=FALSE; //all write functions now invert.
//The CLS will now set the screen white. Text characters print in black
//Then the second part of the driver is a 'window' driver. With this you can
//define a small graphic 'window', and draw things into this. This can then be
//rapidly copied to the display. So you could (for instance), plot a tiny graph,
//end then draw this on the display.
//The window must be a multiple of 8 pixels high, and can only be placed
//at a 'text' location, so you can't put it (say) 12 pixels down the screen,
//but only 8, 16, 24 etc..
//The size of the window determines how much RAM is used. So a 64*16 window
//uses 128 bytes of RAM (64*16/8).
//Neat thing is though, that you can draw an image on the window, put this on
//the screen, and then draw a second image, and put this somewhere else,
//without using any more memory. At the moment, I have only implemented two
//functions to draw to this window.
//If you don't want the graphic ability, if you #define TEXT_ONLY, then only
//the text mode driver will be loaded.
//With the graphic driver being used, the following extra functions are
//available:
// clear_window(); //clears all pixels 'black' (if set==TRUE), or white.
// set_pixel(x, y); //sets a pixel at x,y in the window.
// //x=0 to WINDOW_WIDTH-1 (left to right)
// //y=0 to WINDOW_HEIGHT-1 (top to bottom)
// line(x1, y1, x2, y2); //draws a line from x1,y1 to x2, y2
// rect(x1, y1, x2, y2); //draws a rectangle
// circle(x, y, radius, fill); //draws a circle
// //This draws a circle of radius 'radius' centred at x,y. If 'fill' is
// //true this is filled....
//
// draw_window(x, int8 y); //This draws the window onto the screen at
// //x=0 to 128, y=0 to 7.
//What you do is simply draw the shape you want into the window, and then
//this can be drawn onto the screen.
//I have not included font drawing, since this takes a lot more space....
//'set' again controls whether a pen, or eraser is used. So (for example), if you
//wanted a 'thick' circle, you could either draw several using the pen,
//without 'fill' enabled, or could draw one with fill, then change set to
//false, and draw a smaller one, to give a thick ring.
#define COMMAND_ONLY 0b00000000 //next byte is a command only
#define DATA_ONLY 0b01000000 //next byte is data
//directly from the data sheet - commands - not all used
#define S_EXTERNALVCC 0x1
#define S_SWITCHCAPVCC 0x2
#define S_SETLOWCOLUMN 0x00
#define S_SETHIGHCOLUMN 0x10
#define S_MEMORYMODE 0x20
#define S_COLUMNADDR 0x21
#define S_PAGEADDR 0x22
#define S_SETSTARTLINE 0x40
#define S_ROWADDRESS 0xB0
#define S_SETCONTRAST 0x81
#define S_CHARGEPUMP 0x8D
#define S_SEGREMAP 0xA0
#define S_DISPLAYALLON_RESUME 0xA4
#define S_DISPLAYALLON 0xA5
#define S_NORMALDISPLAY 0xA6
#define S_INVERTDISPLAY 0xA7
#define S_SETMULTIPLEX 0xA8
#define S_DISPLAYOFF 0xAE
#define S_DISPLAYON 0xAF
#define S_COMSCANINC 0xC0
#define S_COMSCANDEC 0xC8
#define S_SETDISPLAYOFFSET 0xD3
#define S_SETCOMPINS 0xDA
#define S_SETVCOMDETECT 0xDB
#define S_SETDISPLAYCLOCKDIV 0xD5
#define S_SETPRECHARGE 0xD9
#define DIV_RATIO 0x80 //recommended ratio
#define MULTIPLEX 0x3F //and multiplex
#define INT_VCC 0x14
//Font 6*8 - slightly clearer than most fonts this size.
ROM BYTE font[] =
{
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // Code for char
0x00, 0x00, 0xBE, 0x00, 0x00, 0x00, // Code for char !
0x00, 0x00, 0x03, 0x00, 0x03, 0x00, // Code for char "
0x50, 0xF8, 0x50, 0xF8, 0x50, 0x00, // Code for char #
0x48, 0x54, 0xFE, 0x54, 0x24, 0x00, // Code for char $
0x98, 0x58, 0x20, 0xD0, 0xC8, 0x00, // Code for char %
0x60, 0x9C, 0xAA, 0x44, 0x80, 0x00, // Code for char &
0x00, 0x00, 0x00, 0x03, 0x00, 0x00, // Code for char '
0x00, 0x38, 0x44, 0x82, 0x00, 0x00, // Code for char (
0x00, 0x82, 0x44, 0x38, 0x00, 0x00, // Code for char )
0x02, 0x06, 0x03, 0x06, 0x02, 0x00, // Code for char *
0x10, 0x10, 0x7C, 0x10, 0x10, 0x00, // Code for char +
0xA0, 0x60, 0x00, 0x00, 0x00, 0x00, // Code for char ,
0x10, 0x10, 0x10, 0x10, 0x10, 0x00, // Code for char -
0xC0, 0xC0, 0x00, 0x00, 0x00, 0x00, // Code for char .
0x80, 0x40, 0x20, 0x10, 0x08, 0x00, // Code for char /
0x7C, 0xA2, 0x92, 0x8A, 0x7C, 0x00, // Code for char 0
0x00, 0x84, 0xFE, 0x80, 0x00, 0x00, // Code for char 1
0xC4, 0xA2, 0x92, 0x92, 0x8C, 0x00, // Code for char 2
0x44, 0x82, 0x92, 0x92, 0x6C, 0x00, // Code for char 3
0x18, 0x14, 0x12, 0xFE, 0x10, 0x00, // Code for char 4
0x9E, 0x92, 0x92, 0x92, 0x62, 0x00, // Code for char 5
0x7C, 0x92, 0x92, 0x92, 0x64, 0x00, // Code for char 6
0x06, 0x02, 0xE2, 0x12, 0x0E, 0x00, // Code for char 7
0x6C, 0x92, 0x92, 0x92, 0x6C, 0x00, // Code for char 8
0x4C, 0x92, 0x92, 0x92, 0x7C, 0x00, // Code for char 9
0xCC, 0xCC, 0x00, 0x00, 0x00, 0x00, // Code for char :
0xAC, 0x6C, 0x00, 0x00, 0x00, 0x00, // Code for char ;
0x00, 0x10, 0x28, 0x44, 0x82, 0x00, // Code for char <
0x48, 0x48, 0x48, 0x48, 0x48, 0x00, // Code for char =
0x00, 0x82, 0x44, 0x28, 0x10, 0x00, // Code for char >
0x04, 0x02, 0xB2, 0x12, 0x0C, 0x00, // Code for char ?
0x7C, 0x82, 0xBA, 0xAA, 0xBC, 0x00, // Code for char @
0xF8, 0x14, 0x12, 0x14, 0xF8, 0x00, // Code for char A
0xFE, 0x92, 0x92, 0x92, 0x6C, 0x00, // Code for char B
0x7C, 0x82, 0x82, 0x82, 0x44, 0x00, // Code for char C
0xFE, 0x82, 0x82, 0x44, 0x38, 0x00, // Code for char D
0xFE, 0x92, 0x92, 0x82, 0x82, 0x00, // Code for char E
0xFE, 0x12, 0x12, 0x02, 0x02, 0x00, // Code for char F
0x7C, 0x82, 0x92, 0x92, 0xF4, 0x00, // Code for char G
0xFE, 0x10, 0x10, 0x10, 0xFE, 0x00, // Code for char H
0x00, 0x82, 0xFE, 0x82, 0x00, 0x00, // Code for char I
0x60, 0x80, 0x80, 0x80, 0x7E, 0x00, // Code for char J
0xFE, 0x10, 0x18, 0x24, 0xC2, 0x00, // Code for char K
0xFE, 0x80, 0x80, 0x80, 0x80, 0x00, // Code for char L
0xFE, 0x04, 0x38, 0x04, 0xFE, 0x00, // Code for char M
0xFE, 0x04, 0x08, 0x10, 0xFE, 0x00, // Code for char N
0x7C, 0x82, 0x82, 0x82, 0x7C, 0x00, // Code for char O
0xFE, 0x12, 0x12, 0x12, 0x0C, 0x00, // Code for char P
0x7C, 0x82, 0xA2, 0xC2, 0xFC, 0x00, // Code for char Q
0xFE, 0x12, 0x12, 0x12, 0xEC, 0x00, // Code for char R
0x4C, 0x92, 0x92, 0x92, 0x64, 0x00, // Code for char S
0x02, 0x02, 0xFE, 0x02, 0x02, 0x00, // Code for char T
0x7E, 0x80, 0x80, 0x80, 0x7E, 0x00, // Code for char U
0x3E, 0x40, 0x80, 0x40, 0x3E, 0x00, // Code for char V
0xFE, 0x80, 0x70, 0x80, 0xFE, 0x00, // Code for char W
0xC6, 0x28, 0x10, 0x28, 0xC6, 0x00, // Code for char X
0x06, 0x08, 0xF0, 0x08, 0x06, 0x00, // Code for char Y
0xC2, 0xA2, 0x92, 0x8A, 0x86, 0x00, // Code for char Z
0x00, 0xFE, 0x82, 0x82, 0x00, 0x00, // Code for char [
0x08, 0x10, 0x20, 0x40, 0x80, 0x00, // Code for char BackSlash
0x00, 0x82, 0x82, 0xFE, 0x00, 0x00, // Code for char ]
0x00, 0x08, 0x04, 0x02, 0x04, 0x08, // Code for char ^
0x80, 0x80, 0x80, 0x80, 0x80, 0x00, // Code for char _
0x00, 0x00, 0x02, 0x04, 0x00, 0x00, // Code for char `
0x40, 0xA8, 0xA8, 0xA8, 0xF0, 0x00, // Code for char a
0xFE, 0x88, 0x88, 0x88, 0x70, 0x00, // Code for char b
0x70, 0x88, 0x88, 0x88, 0x10, 0x00, // Code for char c
0x70, 0x88, 0x88, 0x88, 0xFE, 0x00, // Code for char d
0x70, 0xA8, 0xA8, 0xA8, 0x30, 0x00, // Code for char e
0x10, 0xFC, 0x12, 0x12, 0x04, 0x00, // Code for char f
0x90, 0xA8, 0xA8, 0xA8, 0x70, 0x00, // Code for char g
0xFE, 0x10, 0x10, 0x10, 0xE0, 0x00, // Code for char h
0x00, 0x90, 0xF4, 0x80, 0x00, 0x00, // Code for char i
0x40, 0x80, 0x80, 0x90, 0x74, 0x00, // Code for char j
0xFE, 0x20, 0x50, 0x88, 0x00, 0x00, // Code for char k
0x7E, 0x80, 0x80, 0x00, 0x00, 0x00, // Code for char l
0xF8, 0x08, 0x70, 0x08, 0xF0, 0x00, // Code for char m
0xF8, 0x08, 0x08, 0x08, 0xF0, 0x00, // Code for char n
0x70, 0x88, 0x88, 0x88, 0x70, 0x00, // Code for char o
0xF8, 0x28, 0x28, 0x28, 0x10, 0x00, // Code for char p
0x10, 0x28, 0x28, 0xF8, 0x80, 0x00, // Code for char q
0xF8, 0x08, 0x08, 0x08, 0x10, 0x00, // Code for char r
0x90, 0xA8, 0xA8, 0xA8, 0x48, 0x00, // Code for char s
0x08, 0x08, 0xFE, 0x88, 0x88, 0x00, // Code for char t
0x78, 0x80, 0x80, 0x80, 0xF8, 0x00, // Code for char u
0x38, 0x40, 0x80, 0x40, 0x38, 0x00, // Code for char v
0xF8, 0x80, 0x70, 0x80, 0xF8, 0x00, // Code for char w
0x88, 0x50, 0x20, 0x50, 0x88, 0x00, // Code for char x
0x18, 0xA0, 0xA0, 0xA0, 0x78, 0x00, // Code for char y
0x88, 0xC8, 0xA8, 0x98, 0x88, 0x00, // Code for char z
0x00, 0x10, 0x6C, 0x82, 0x00, 0x00, // Code for char {
0x00, 0x00, 0xFE, 0x00, 0x00, 0x00, // Code for char |
0x00, 0x82, 0x6C, 0x10, 0x00, 0x00, // Code for char }
0x00, 0x08, 0x04, 0x08, 0x10, 0x08, // Code for char ~
0x7C, 0x7C, 0x00, 0x00, 0x00, 0x00, // Code for char
//Characters 32 to 127
//The next eleven characters are above 127, and give the shapes used for
//the bar graph capability - remove if not needed
0x82, 0x82, 0x82, 0x82, 0x82, 0x82, //top and bottom bars only 128
0xFE, 0x82, 0x82, 0x82, 0x82, 0x82, //Open for bar 129
0xFE, 0xFE, 0x82, 0x82, 0x82, 0x82, //second bar
0xFE, 0xFE, 0xFE, 0x82, 0x82, 0x82,
0xFE, 0xFE, 0xFE, 0xFE, 0x82, 0x82,
0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0x82,
0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
//Full block for bar 134
0x82, 0x82, 0x82, 0x82, 0xFE, 0xFE, //final one cloing shape 135
0xFE, 0x82, 0x82, 0x82, 0xFE, 0xFE, //single left and double right
0xFE, 0xFE, 0x82, 0x82, 0xFE, 0xFE,
0xFE, 0xFE, 0xFE, 0x82, 0xFE, 0xFE,
0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE,
0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE //New closing point for 0..100
//final one closing shape 140
};
//Character 140
ROM BYTE init_sequence[] = S_DISPLAYOFF,
S_SETDISPLAYCLOCKDIV,
DIV_RATIO,
S_SETMULTIPLEX,
MULTIPLEX,
S_SETDISPLAYOFFSET,
0, // no offset
S_SETSTARTLINE,
S_CHARGEPUMP,
INT_VCC, // using internal VCC
S_MEMORYMODE, //Since byte is vertical writing column by column
0, // default horizontal addressing
(S_SEGREMAP | 0x1), // rotate screen 180
S_COMSCANDEC,
S_SETCOMPINS,
0x12,
S_SETCONTRAST,
0xEF, //experiment.... 0xCf for 1306
S_SETPRECHARGE,
0xF1,
S_SETVCOMDETECT,
0x40,
S_DISPLAYALLON_RESUME,
S_NORMALDISPLAY,
S_DISPLAYON; //switch on OLED
//Initilalisation sequence
#define NORMAL 0
#define DOUBLE_HEIGHT 1
#define DOUBLE_WIDTH 2
#define LARGE DOUBLE_HEIGHT+DOUBLE_WIDTH
unsigned int8 O_current_col,O_current_row; //where text is currently 'working'
int8 size=NORMAL;
//Global flag for drawing mode
int1 set=TRUE; //allow funstions to set or reset - inverts drawing functions
#ifndef TEXT_ONLY
unsigned int8 window_buffer[WINDOW_WIDTH*WINDOW_HEIGHT/8];
//so with the example given, 128 bytes of RAM - much more practical on small chips!...
//This is the 'graphic window' buffer, so not needed for text only
#endif
#ifdef PSV
void OLED_commands(byte * commands, unsigned int8 number)
#else
void OLED_commands(rom byte* commands, unsigned int8 number)
#endif
//send a multiple command, or commands to the display - number says how many
//from a ROM buffer
{
int8 ctr; //counter for the transmission
i2c_start ();
i2c_write (SSDADDR); //select the display
i2c_write (COMMAND_ONLY); //we are sending a command
for (ctr=0;ctr<number;ctr++)
{
I2c_write(commands[ctr]);
}
i2c_stop();
}
void OLED_data(unsigned int8 * data, unsigned int8 number)
//send 'number' bytes of data to display - from RAM
{
unsigned int8 ctr; //updated to allow 128bytes on PIC24/30 etc..
i2c_start ();
i2c_write (SSDADDR); //select the display
i2c_write (DATA_ONLY); //we are sending data(s)
for (ctr=0;ctr<number;ctr++)
i2c_write(data[ctr]); //send the byte(s)
i2c_stop ();
}
void OLED_address(unsigned int8 x, unsigned int8 y)
{
//routine to move the memory pointers to x,y.
//x is 0 to 127 (column), y (row) is 0 to 7 (page only)
#ifdef SH1106
x+=2;
#endif
i2c_start();
i2c_write (SSDADDR); //select the display
i2c_write(COMMAND_ONLY); //we are sending command(s)
i2c_write(S_ROWADDRESS | y); //select the display row
i2c_write(S_SETLOWCOLUMN | (x & 0x0F)); //low col address
i2c_write(S_SETHIGHCOLUMN | ((x>>4) & 0x0F)); //high col address
i2c_stop();
} //also made more efficient
void OLED_gotoxy(unsigned int8 x, unsigned int8 y)
{
//text x,y position bases on 8 lines/character and 6 columsn
//0 to 20 columns, 0 to 7 rows
if (x>(S_LCDWIDTH/6)-1) return;
if (y>(S_LCDHEIGHT/8)-1) return;
O_current_col=x; //efficient *6
O_current_row=y;
OLED_address((unsigned int16)x*4+(unsigned int16)x*2,y); //position display
}
void OLED_CLS(void)
{
unsigned int8 row, col;
//Just fill the memory with zeros
for (row=0;row<S_LCDHEIGHT/8;row++)
{
OLED_address(0,row); //take the addresses back to 0,0 0,1 etc..
i2c_start();
i2c_write(SSDADDR); //select the display
i2c_write(DATA_ONLY); //we are sending data(s)
for (col=0;col<S_LCDWIDTH;col++)
{
if (set)
i2c_write (0); //send 1024 zeros
else
i2c_write(255); //or the inverse
}
i2c_stop ();
}
OLED_gotoxy(0,0); //and text back to the top corner
}
//Macros to efficiently double bits from a nibble
#define DOUBLE_BIT(N, S, D) if (bit_test(S,N)) { bit_set(D,(N*2)); bit_set(D,(N*2)+1); }
#define DOUBLE_B_HIGH(N, S, D) if (bit_test(S,N+4)) { bit_set(D,(N*2)); bit_set(D,(N*2)+1); }
void invert(unsigned int8 * buffer, unsigned int8 number) //routine to invert
{//data when'set==FALSE'
do
{
*buffer^=0xFF;
buffer++;
} while(--number); //invert all the bits in the buffer
}
//Change here to allow multiple fonts
//This routine can be used by multiple output routines
#ifdef PSV
void FONT_line(byte * font_data, unsigned int8 count)
#else
void FONT_line(ROM byte * font_data, unsigned int8 count)
#endif
{
//new function to transfer a line of data from the font table.
//designed to optimise the handling of double size fonts
//Sends one line of 'count' characters from the font to the display,
//with doubling of width if necessary. Maximum 12 chars.
unsigned int8 cols[24], ctr=0, width, inc_col, tchr, temp=0;
if (size & DOUBLE_WIDTH)
{
width=count*2;
inc_col=2;
}
else
{
width=count;
inc_col=1;
}
for (ctr=0;ctr<width;ctr+=inc_col) //for columns
{
cols[ctr]=0;
tchr=font_data[temp++]; //one byte of character from the font
if (size & DOUBLE_HEIGHT)
{
DOUBLE_BIT(0,tchr,cols[ctr])
DOUBLE_BIT(1,tchr,cols[ctr])
DOUBLE_BIT(2,tchr,cols[ctr])
DOUBLE_BIT(3,tchr,cols[ctr])
} //efficently double the bits from the low nibble
else
cols[ctr]=tchr;
if (size & DOUBLE_WIDTH)
cols[ctr+1]=cols[ctr]; //duplicate the byte
}
if (set==FALSE)
invert(cols,width);
OLED_data(cols,width);
//Now if doubling in height repeat usiong the other nibble
if (size & DOUBLE_HEIGHT)
{
temp=0; //back to the start of the font character
OLED_address((unsigned int16)O_current_col*4+O_current_col*2,O_current_row+1); //next row
for (ctr=0;ctr<width;ctr+=inc_col) //through the columns again
{
cols[ctr]=0;
tchr=font_data[temp++]; //one byte of character from the font
DOUBLE_B_HIGH(0,tchr,cols[ctr])
DOUBLE_B_HIGH(1,tchr,cols[ctr])
DOUBLE_B_HIGH(2,tchr,cols[ctr])
DOUBLE_B_HIGH(3,tchr,cols[ctr])
//efficently double the bits from the high nibble
if (size & DOUBLE_WIDTH)
cols[ctr+1]=cols[ctr]; //duplicate the byte if double_width
}
if (set==FALSE)
invert(cols,width);
//Now send the bytes for the second row
OLED_data(cols,width);
}
}
//Fastest text mode. No support for any control. Standard font only.
void OLED_text(unsigned int8 * text, unsigned int8 number)
{
unsigned int8 inc_col;
unsigned int16 temp;
//size allows double height & double width
//Here double height/width
//for this I have to do two transfers each of double the amount of data
//and reposition between each
if (size & DOUBLE_WIDTH)
{
inc_col=2;
}
else
{
inc_col=1;
}
do {
temp=(*text)-32;
if (temp>108)
temp=0; //block illegal characters
temp=((unsigned int16)temp*2)+((unsigned int16)temp*4); //efficient *6
FONT_line(&font[temp],6); //six characters from the font
//Now because I'll be in the wrong position (may be one line down)
//have to re-locate
O_current_col+=inc_col;
OLED_address((unsigned int16)O_current_col*4+O_current_col*2,O_current_row); //ready for next character
text++; //and select the next character
} while (--number); //and on to the next character
}
void OLED_putc(unsigned int8 chr)
{
//this is a putc wrapper for the text function - note much slower
//than sending the entire line directly
if (chr=='\f')
{
OLED_CLS(); //handle Clear screen (form feed)
return;
}
if (chr=='\r')
{
OLED_gotoxy(0,O_current_row); //carriage return
return;
}
if (chr=='\n')
{
if (size==NORMAL)
OLED_gotoxy(O_current_col,O_current_row+1);
else
OLED_gotoxy(O_current_col,O_current_row+2);
return;
}
OLED_text(&chr,1);
}
void OLED_textbar(unsigned int8 width)
{
//This draws a bar graph using text characters
int8 ctr;
unsigned int8 bar[9];
//graph is now 0 to 100.
//prints at current text location.
width/=2;
width+=2; //ensure >0 - g1ves 2 to 52
if (width>52)
width=52;
for (ctr=0;ctr<8;ctr++)
{
if (width>=6)
{
bar[ctr]=134; //full bar
width-=6;
}
else
{
bar[ctr]=128+width; //partial bars
width=0;
}
}
//now handle the right hand end of the bar
bar[8]=135+width;
OLED_text(bar,9);
}
//Now comes the 'exception' part to the driver
//Basic line & circle code writing to a small _window_ that can then
//be burst transmitted to the LED. Neat thing is that the same window
//can be used multiple times. So (for instance) you could write text on the
//left of the display, then have a 64*32 window. Draw something into this
//and display it at 64, 0 (text row) on the display, then draw something
//different (using the same window), and put this at 64, 4. The location
//the window is drawn has to be a byte boundary (so 0 to 7, for 0 to 63
//on the display.
//The sequence would be clear_window, line, circle etc.. Then draw_window(x,y)
//If you don't want to use the smace for this, then #define TEXT_ONLY at the start
//of the code
#ifndef TEXT_ONLY
void clear_window(void)
{
memset(window_buffer,(set)?0:255,WINDOW_WIDTH*WINDOW_HEIGHT/8); //clear the buffer
}
//Basic pixel routine
#inline
void set_pixel(unsigned int8 x, unsigned int8 y)
{
unsigned int16 locn; //This can be int8, if buffer is restricted to max 256 bytes
//potentially slightly faster. However 1616 is 'generic'.
if (x>=WINDOW_WIDTH) return;
if (y>=WINDOW_HEIGHT) return; //Limit check - ensures I do not try to write
//outside buffer boundaries
locn=((y/8)*WINDOW_WIDTH)+x; //location in buffer
//handle setting or resetting the pixel according to flag 'set'
if (set)
bit_set(window_buffer[locn],(y & 7)); //set the bit (to 1)
else
bit_clear(window_buffer[locn],(y & 7)); //set the bit (to 0)
}
//efficient line routine
void line(unsigned int8 x1, unsigned int8 y1, unsigned int8 x2, unsigned int8 y2)
{
unsigned int16 i;
int1 _plot;
signed int16 _dx,_dy;
unsigned int16 _ix,_iy,_inc,_plotx,_ploty,_x,_y;
//line from X1,Y1 to X2,Y2
//first the differences between the coordinate pairs
_dx=(signed int16) x2-x1;
_dy=(signed int16) y2-y1;
// ix & iy are the absolute increments required
_ix=(_dx<0)?(-_dx):_dx;
_iy=(_dy<0)?(-_dy):_dy;
// we must step the longest length (x or y)
_inc=(_ix>_iy)?_ix:_iy;
// make dx and dy the step required.
if (_dx>0) _dx=1; else if (_dx<0) _dx=-1;
if (_dy>0) _dy=1; else if (_dy<0) _dy=-1;
// actual plotting points
_plotx=x1;
_ploty=y1;
// start at 0
_x=0;
_y=0;
// set endpoint
set_pixel(_plotx,_ploty);
/* we implement Bressenhams algorithm for a line using integer steps
and only plotting the point when we get to a new co-ord pair */
for (i=0;i<=_inc;++i)
{
_x += _ix;
_y += _iy;
// do not plot yet
_plot=FALSE;
//if we are at a new pair - set the plot flag and increment
//the phsical plotting point
if (_x > _inc)
{
_plot = TRUE;
_x -= _inc;
_plotx += _dx;
}
if (_y > _inc)
{
_plot = TRUE;
_y -= _inc;
_ploty += _dy;
}
// now plot the point
if (_plot)
{
set_pixel(_plotx,_ploty); //this automatically handles set/reset
}
}
}
void rect(unsigned int8 x1, unsigned int8 y1, unsigned int8 x2, unsigned int8 y2)
{
//outline a rectangle
line(x1, y1, x2, y1); //Just draw four sides
line(x1, y2, x2, y2);
line(x1, y1, x1, y2);
line(x2, y1, x2, y2);
}
void circle(unsigned int8 x, unsigned int8 y, unsigned int8 radius, int1 fill)
{
signed int8 a, b, P;
a = 0;
b = radius;
P = 1 - radius;
do
{
if(fill)
{
line(x-a, y+b, x+a, y+b);
line(x-a, y-b, x+a, y-b);
line(x-b, y+a, x+b, y+a);
line(x-b, y-a, x+b, y-a); //inefficient but easy to code....
}
else
{
set_pixel(a+x, b+y);
set_pixel(b+x, a+y);
set_pixel(x-a, b+y);
set_pixel(x-b, a+y);
set_pixel(b+x, y-a);
set_pixel(a+x, y-b);
set_pixel(x-a, y-b);
set_pixel(x-b, y-a); //othewise draw the octant points
}
if(P < 0)
P += 3 + 2 * a++;
else
P += 5 + 2 * (a++ - b--);
} while(a <= b);
}
void draw_window(unsigned int8 x, unsigned int8 y)
{
unsigned int8 yctr;
unsigned int16 transfer=WINDOW_WIDTH;
//routine to copy the window to the display.
//x is in pixels, y in bytes (0 to 8). Uses burst transmission for each line
if ((x+transfer)>=S_LCDWIDTH)
{
//here the window would go off the edge of the screen...
transfer=(S_LCDWIDTH-1)-x;
}
for (yctr=0;yctr<(WINDOW_HEIGHT/8);yctr++)
{
if (y+yctr>7) return; //off the end of RAM
OLED_address(x,y+yctr); //position to the byte at the start of the line
//transfer the line
OLED_data(window_buffer+((unsigned int16)yctr*WINDOW_WIDTH),transfer);
//again int16 only needed here if buffer>256 bytes
}
}
#endif
|
Now an example program using the driver in 'text mode' only:
mainssdtext.c
| Code: |
#include <18F13K22.h>
#fuses INTRC_IO, PLLEN, NOXINST, NOMCLR, NOLVP, STVREN, PCLKEN, NOFCMEN
#fuses NOIESO, NOPUT, BORV22, NODEBUG, NOPROTECT, NOWDT, WDT512
#fuses HFOFST, NOCPD, NOCPB, NOWRTD, NOWRTC, NOWRTB
#USE DELAY(INTERNAL=32MHz)
#USE I2C(I2C1, MASTER, FAST=400000, FORCE_HW)
//display dimensions - the physical LCD
#define S_LCDWIDTH 128
#define S_LCDHEIGHT 64
//If you want to use the SH1106, add this #define
//#define SH1106
#define TEXT_ONLY //If this is defined, gives a smaller text driver only
#define SSDADDR 0x78 //address for the chip - usually 0x7C or 0x78.
#include <string.h>
#include "ssd1306.h" //The OLED driver
void main()
{
int8 ctr;
char text[9]; //temporary text buffer
delay_ms(250); //OLED takes time to wake
//now try to initialise OLED
OLED_commands(init_sequence,sizeof(init_sequence)); //initialise the OLED
//Now try some text
set=TRUE;
size=NORMAL;
OLED_CLS(); //clear the physical screen
OLED_gotoxy(0,0);
strcpy(text,"Hello");
OLED_text(text,strlen(text)); //This is the fastest way to write text
delay_ms(2000); //pause for two seconds
OLED_gotoxy(0,4);
size=LARGE;
OLED_text(text,strlen(text)); //try some large text
delay_ms(2000);
//Now the printf mode
size=LARGE;
//now testing putc
printf(OLED_putc,"\f12345\n\r67890\n\r");
//Note how the line feed moves down by the large line when in
//large mode
delay_ms(2000);
//Now printf in normal mode to the same screen
size=NORMAL;
printf(OLED_putc,"ABCDEFGHI");
delay_ms(2000); //delay again so you can see what it has done
//Now mixed size with a bar graph
size=LARGE;
printf(OLED_putc,"\fV=");
for (ctr=0;ctr<101;ctr++)
{
size=NORMAL;
OLED_gotoxy(4,1);
printf(OLED_putc,"%3d ",ctr);
OLED_gotoxy(1,3);
size=LARGE;
OLED_textbar(ctr);
delay_ms(250); //So you can see what is displayed!...
}
while(TRUE)
; //and stop
}
|
On the chip used here, this uses 37% ROM (about 3K), and 23% RAM (58 bytes).
Now a larger demo, using the graphics mode
| Code: |
//same processor header
//display dimensions - the physical LCD
#define S_LCDWIDTH 128
#define S_LCDHEIGHT 64
//#define TEXT_ONLY //REM this out
//Size of graphics 'window' see the graphics section for explanation
#define WINDOW_WIDTH 64
#define WINDOW_HEIGHT 16 //sizes of the graphic window in pixels
//height must be a multiple of 8. //these must now be defined
#define SSDADDR 0x78 //address for the chip - usually 0x7C or 0x78.
#include <string.h>
#include "ssd1306.h" //The OLED driver
void main()
{
int8 ctr;
char text[9]; //temporary text buffer
//Remember if you want to use this for longer text, you'll need to
//expand the buffer....
delay_ms(250); //OLED takes time to wake
//now try to initialise OLED
OLED_commands(init_sequence,sizeof(init_sequence)); //initialise the OLED
//First try some text
OLED_CLS(); //clear the physical screen
set=TRUE;
clear_window(); //clear the window buffer
OLED_gotoxy(0,0);
strcpy(text,"Hello");
size=NORMAL;
OLED_text(text,strlen(text));
delay_ms(1000);
//now some graphics
line(0,0,64,16); //draw line in window
line(10,10,61,0);//and a second
//now write the window to the screen
draw_window(64,0); //at 64 pixels across and top of screen
delay_ms(1000);
set=FALSE; //inverted drawing
clear_window(); //clear the window to fully set!
line(0,0,60,15);
line(20,10,40,10);
circle(32,8,8,1); //just touch the edge of the window
draw_window(64,4); //put this window half way down screen
delay_ms(1000);
while (TRUE)
; //and stop
}
|
This is significantly larger (uses 192 bytes of RAM - this is the 128 byte
graphic 'window'), and over 5KB ROM. However still fits merrily in the
small chip. If you don't need things like the circle function, removing
these will reduce the ROM size a little.
Hopefully of use to somebody!... 
As a final comment, somebody posted asking for the minimum code to set a pixel on such a display. The following 'main' does this:
| Code: |
void main()
{
int8 temp=1;
delay_ms(250); //OLED takes time to wake
//now try to initialise OLED
OLED_commands(init_sequence,sizeof(init_sequence)); //initialise the OLED
OLED_CLS(); //clear the physical screen
//Now just write a single byte to the start of the RAM
OLED_data(&temp, 1);
while (TRUE)
;
}
|
Now one final thing. Remember this chip is a 3.3v device. Using 3.3v I2c, you need small pull-ups to run this fast (I used 1.2KR).
You can also use size=DOUBLE_HEIGHT; which is very nice for the bargraph.
But I hear you say, it says it can use 5v Vcc. Yes it can, but the core _chip_ is 3.3v. It has it's own regulator on board for the logic, and the logic can run at 3.3v max. Beware not to overdrive it if running off a 5v device....
Have had it going successfully off a 5v device, by setting this to use SMBUS levels (many PIC's support this), and having the pull-ups to 3.3v. Or if you pull-up to 3.3v, and use _software_ I2C, on a port that supports TTL levels it also works OK.
I've updated this to allow some expansions to the font if required. Have changed the master code involved here, and posted some example expansions below. 5th Jan 2018.
Separate update October 2018.
If using PCD, using ROM *, is quite inefficient because of the maths involved in 3 bytes/word, and then the gap. On some chips this also seems to cause issues.
There is an alternative:
| Code: |
#include <your_processor_file>
#device PSV=16
//Then the rest of your processor setup
#define PSV
//Then include the SSD driver fonts etc.
//Then your code.
|
I've modified the driver, so if it sees 'PSV' defined, it changes the pointers from ROM pointers to normal RAM pointers. The PSV option enables a special mode, where the DsPIC's map 32K or their ROM, into the RAM address space, allowing normal RAM pointers to access this.
Has a slight cost, in that only two bytes get packed per instruction word when this is done. However does bring improvements to overall code efficiency. |
This code is working well for 1.3 inch ( Driver - SSD1306)oled display with pic 16F877a, we need SSD1309 driver code and sample code for 2.4 inch oled display please help us
thank you |
|
FAQ 
Search
Register
Profile 
Log in to check your private messages 
Log in
