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lcd/st7789: fix incorrect buffer count for 3 wire RAM write

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If st7789_wrram is called with count = 1, then the entire buffer should
be sent. However, in 3 wire mode, the driver has to send the buffer
row by row because of additional data flag. The number of rows (count)
can't be ST7789_YRES in this case, but only the number of rows in
the buffer (this is write size / row size , where row size is
ST7789_XRES * ST7789_BYTESPP). This also applies only if we want to
write size larger than row size, because st7789_putrun allows to
write just a part of a row.

This fixes the incorrect behavior of the display in 3 wire mode if
the display is split into more buffer writes (as in LCD driver for
example, FB driver did not face this issue).

Signed-off-by: Michal Lenc <michallenc@seznam.cz>
Co-authored-by: Martin Krasula <krasula@atlas.cz>
This commit is contained in:
Michal Lenc
2025-02-17 15:03:27 +01:00
committed by Mateusz Szafoni
parent 54954e55b5
commit 425ddc7f72
1 changed files with 7 additions and 4 deletions
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drivers/lcd/st7789.c
+7 -4
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@@ -584,19 +584,22 @@ static void st7789_wrram(FAR struct st7789_dev_s *dev,
size_t i;
#ifdef CONFIG_LCD_ST7789_3WIRE
size_t j;
size_t rowsiz;
#endif
st7789_sendcmd(dev, ST7789_RAMWR);
#ifdef CONFIG_LCD_ST7789_3WIRE
if (count == 1)
rowsiz = ST7789_XRES * ST7789_BYTESPP;
if (count == 1 && size > rowsiz)
{
/* We cannot send the entire buffer at once, split it to
* separate rows.
*/
count = ST7789_YRES;
size = ST7789_XRES * ST7789_BYTESPP;
count = size / rowsiz;
size = rowsiz;
}
st7789_select(dev->spi, LCD_ST7789_SPI_BITS);
@@ -607,7 +610,7 @@ static void st7789_wrram(FAR struct st7789_dev_s *dev,
{
/* Copy data to rowbuff and add 9th bit */
for (j = 0; j < ST7789_XRES * ST7789_BYTESPP; j += 2)
for (j = 0; j < size; j += 2)
{
/* Take care of correct byte order. */