Flip text on ST7565

[Scott216]

I have the ST7565 LCD and I'd like to be able to flip the text so you can read it as if the display was upside down. Is there a function in the library for this?

[adafruit_support_bill]

We don't have a function for that in the ST7565 library. It could probably be done with some modifications to the setPixel function.

[Scott216]

What about creating a second font table where the letters are upside down. I could generate the table with http://microintegrate.com/?/fontgen, but I don't know if there is a way to switch between these two tables.

I'm using the display for a hot tub controller I'm building with an Arduino Mega. If you are in the hot tub, I want to display to be right side up, if you are outside the hot tub I want it upside down.

[adafruit_support_bill]

Two font tables would probably work, although it would consume a lot of memory.

You may also want to look into some of our newer displays that have GFX library support. GFX has direct support for rotating the display:
http://learn.adafruit.com/adafruit-gfx- ... he-display

[Scott216]

Maybe in my next version I'll switch displays. I made a PCB that supports this display. I think I've got plenty of memory in my Mega for another font table. How would I go about switching between the two?

[adafruit_support_bill]

It is only references in one place:

Code: Select all

void ST7565::drawchar(uint8_t x, uint8_t line, char c) {
  for (uint8_t i =0; i<5; i++ ) {
    st7565_buffer[x + (line*128) ] = pgm_read_byte(font+(c*5)+i);
    x++;
  }

  updateBoundingBox(x, line*8, x+5, line*8 + 8);
}

So it should be fairly straightforward to set a "flipped" flag and test for it.

Keep in mind that flipping the font is only half the problem. You will need to write the text right to left & bottom to top too. Might be easier just to hack setPixel.

[Scott216]

What were you thinking in regards to hacking setPixel?

[adafruit_support_bill]

Looks like "my_setpixel" is the one to hack:

Code: Select all

void ST7565::my_setpixel(uint8_t x, uint8_t y, uint8_t color) {
  if ((x >= LCDWIDTH) || (y >= LCDHEIGHT))
    return;

  // x is which column
  if (color)
    st7565_buffer[x+ (y/8)*128] |= _BV(7-(y%8));
  else
    st7565_buffer[x+ (y/8)*128] &= ~_BV(7-(y%8));
}


You could add a test at the beginning:

Code: Select all

  if (flipped)
  {
    x = LCDWIDTH - x;
    y = LCDHEIGHT - y;
  }

[Scott216]

Thanks for the help. I'll try my_setpixel changes and see if it works. That's a much simpler solution then separate font tables and writing backwards.

[Scott216]

Looks like "my_setpixel" is the one to hack:

Code: Select all

void ST7565::my_setpixel(uint8_t x, uint8_t y, uint8_t color) {
  if ((x >= LCDWIDTH) || (y >= LCDHEIGHT))
    return;

  // x is which column
  if (color)
    st7565_buffer[x+ (y/8)*128] |= _BV(7-(y%8));
  else
    st7565_buffer[x+ (y/8)*128] &= ~_BV(7-(y%8));
}


You could add a test at the beginning:

Code: Select all

  if (flipped)
  {
    x = LCDWIDTH - x;
    y = LCDHEIGHT - y;
  }

This worked with glcd.drawbitmap() but not with glcd.drawstring()

[adafruit_support_bill]

It looks like drawChar draws directly to the display buffer without using drawpixel. So you would need to invert the coordinates inside drawChar as well.

[Scott216]

It is only references in one place:

Code: Select all

void ST7565::drawchar(uint8_t x, uint8_t line, char c) {
  for (uint8_t i =0; i<5; i++ ) {
    st7565_buffer[x + (line*128) ] = pgm_read_byte(font+(c*5)+i);
    x++;
  }

  updateBoundingBox(x, line*8, x+5, line*8 + 8);
}

I'm trying to figure out how this is working. So I think the st7565_buffe[] is just a long array where each element corresponds to a pixel. So if st7565_buffe[0] = 1, then the top-left most pixel would be on. If st7565_buffe[128] =1, that's the beginning of the next row of pixels, so the pixel below the top-left would be on.

I assume pgm_read_byte[] is reading one byte from the font table. But this is where I'm staring to have trouble understanding how the bits are going into st7565_buffer[]. It looks to me like the first loop of i the program would put 8 bits into the display, all on the same row. Then the next loop of i would put 8 more bits right below the first row. And so on for 5 rows. But 5 rows is not enough to build a character on the display. Do I have things sideways? Also, since the for loop goes 5 times, then I assume it takes 5 bytes in the font table to display one letter.

[adafruit_support_bill]

The memory layout of the ST7565 is optimized for displaying characters on 8-pixel line boundaries. You are writing 8 pixels at a time vertically with each byte. See the screen layout section of this tutorial:
http://edeca.net/wp/electronics/the-st7 ... ontroller/

[Scott216]

The memory layout of the ST7565 is optimized for displaying characters on 8-pixel line boundaries. You are writing 8 pixels at a time vertically with each byte. See the screen layout section of this tutorial:
http://edeca.net/wp/electronics/the-st7 ... ontroller/

According to the edeca.net article, you can flip the display around by issuing two commands,
Flip horizontally with "ADC Select" command.
Flip vertically with "COM Output Mode Select" command

Any idea how I could send these commands to the display?

[adafruit_support_bill]

That looks like an even easier method.

The command constants are defined in the .h file:

Code: Select all

#define CMD_SET_ADC_NORMAL 0xA0
#define CMD_SET_ADC_REVERSE 0xA1

#define CMD_SET_COM_NORMAL 0xC0
#define CMD_SET_COM_REVERSE 0xC8

You should be able to send them using the st7565_command() function.