Direct to the panel

Talking to the ST7735 without the framebuffer: chip select, commands, address windows, DMA fills and raw blits. More...

Functions
void	gfx_select (void)
	Asserts the panel's chip select.
void	gfx_deselect (void)
	Waits for the last byte to leave SPI1, then releases the panel's chip select.
void	gfx_setWindow (uint8_t x, uint8_t y, uint8_t w, uint8_t h)
	Sets the panel's address window and starts a memory write (CASET, RASET, RAMWR).
void	gfx_cmd (uint8_t c)
	Sends one command byte (D/C low), then sets D/C back to data.
void	gfx_data8 (uint8_t d)
	Sends one data byte (D/C high).
void	gfx_writeColorLut (void)
	Programs the ST7735 RGBSET (2Dh) colour-depth conversion LUT for the current mode.
void	gfx_setWriteColorLut (bool on)
	Chooses whether entering 12 bpp writes the colour LUT (gfx_writeColorLut()).
void	gfx_directFillRect (uint8_t x, uint8_t y, uint8_t w, uint8_t h, uint16_t rgb565)
	Fills a rectangle of the panel with one colour by DMA, bypassing the framebuffer.
void	gfx_directBlit (const void *data, uint32_t bytes, bool halfword)
	Sends a caller-owned buffer, already in panel format, by DMA and waits for it.
void	gfx_blockingWrite (const uint8_t *data, uint32_t bytes)
	Sends bytes one at a time in a polled loop, for baseline comparisons.

Detailed Description

Talking to the ST7735 without the framebuffer: chip select, commands, address windows, DMA fills and raw blits.

These write to the panel at once, so call them only when no flush is in flight (after gfx_wait()); the SD card shares the bus too. Raw pixel data must already be in the panel's current format.

gfx_wait();
gfx_select();
gfx_setWindow(0, 0, 32, 32);
gfx_directBlit(pixels565, 32 * 32 * 2, true);
gfx_deselect();

Function Documentation

gfx_select()

void gfx_select

(

void

)

Asserts the panel's chip select.

Assert once, stream a whole frame, deassert - that is the entire performance thesis of this driver in two functions. The panel latches nothing while CS is high.

gfx_deselect()

void gfx_deselect

(

void

)

Waits for the last byte to leave SPI1, then releases the panel's chip select.

gfx_setWindow()

void gfx_setWindow	(	uint8_t	x,
		uint8_t	y,
		uint8_t	w,
		uint8_t	h
	)

Sets the panel's address window and starts a memory write (CASET, RASET, RAMWR).

Pixel data sent after it fills the window left to right, top to bottom. The panel offsets (gfx_setPanelOffsets()) are added; nothing is clipped. Needs gfx_select() first.

Parameters

x	Left edge, in screen pixels.
y	Top edge, in screen pixels.
w	Width in pixels, 1 or more.
h	Height in pixels, 1 or more.

gfx_cmd()

void gfx_cmd

(

uint8_t

c

)

Sends one command byte (D/C low), then sets D/C back to data.

Parameters

c	ST7735 command.

gfx_data8()

void gfx_data8

(

uint8_t

d

)

Sends one data byte (D/C high).

Parameters

d

The byte.

gfx_writeColorLut()

void gfx_writeColorLut

(

void

)

Programs the ST7735 RGBSET (2Dh) colour-depth conversion LUT for the current mode.

Done automatically for 12 bpp because the datasheet says the table powers up "Random"; call gfx_setWriteColorLut(false) before gfx_setColorMode() if you would rather trust the factory contents.

gfx_setWriteColorLut()

void gfx_setWriteColorLut

(

bool

on

)

Chooses whether entering 12 bpp writes the colour LUT (gfx_writeColorLut()).

Parameters

on	true (the default) to write it, false to trust the panel's factory contents.

gfx_directFillRect()

void gfx_directFillRect	(	uint8_t	x,
		uint8_t	y,
		uint8_t	w,
		uint8_t	h,
		uint16_t	rgb565
	)

Fills a rectangle of the panel with one colour by DMA, bypassing the framebuffer.

DMA with memory-increment DISABLED: the DMA engine re-reads one halfword N times. Zero RAM, zero CPU, full wire speed. Waits for any flush in flight; handles chip select itself; not clipped.

Parameters

x	Left edge, in screen pixels.
y	Top edge, in screen pixels.
w	Width in pixels.
h	Height in pixels.
rgb565	The colour, in RGB565.

Warning

16 bpp only - a 12 bpp solid colour has a 3-byte repeat that does not fit in a single halfword.

gfx_directBlit()

void gfx_directBlit	(	const void *	data,
		uint32_t	bytes,
		bool	halfword
	)

Sends a caller-owned buffer, already in panel format, by DMA and waits for it.

Needs gfx_select() and gfx_setWindow() first.

Parameters

data	The pixel data.
bytes	Its length in bytes (even when halfword).
halfword	true to send 16-bit SPI frames (RGB565 as uint16_t, 16 bpp), false for bytes (12 and 18 bpp).

gfx_blockingWrite()

void gfx_blockingWrite	(	const uint8_t *	data,
		uint32_t	bytes
	)

Sends bytes one at a time in a polled loop, for baseline comparisons.

Parameters

data	The bytes.
bytes	How many.