mirror of
https://github.com/tinygo-org/drivers.git
synced 2026-08-16 12:53:23 +00:00
Ayke van Laethem
5d1b0c39cc
This only implements the 15 bits per pixel mode, not any of the other possible display modes. This matches conventional SPI displays most closely. Future additions might add more display modes. Normally I'd argue interfacing with chip/board specific hardware should be done in the machine package using a generic interface, but the GBA is kind of special and I don't want the machine package to depend on the tinygo.org/x/drivers/pixel package.
86 lines
2.2 KiB
Go
86 lines
2.2 KiB
Go
// Package gbadisplay implements a simple driver for the GameBoy Advance
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// display.
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package gbadisplay
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import (
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"device/gba"
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"errors"
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"image/color"
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"runtime/volatile"
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"unsafe"
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"tinygo.org/x/drivers/pixel"
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)
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// Image buffer type used by the GameBoy Advance.
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type Image = pixel.Image[pixel.RGB555]
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const (
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displayWidth = 240
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displayHeight = 160
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)
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var (
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errOutOfBounds = errors.New("rectangle coordinates outside display area")
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)
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type Device struct{}
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// New returns a new GameBoy Advance display object.
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func New() Device {
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return Device{}
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}
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var displayFrameBuffer = (*[160 * 240]volatile.Register16)(unsafe.Pointer(uintptr(gba.MEM_VRAM)))
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type Config struct {
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// TODO: add more display modes here.
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}
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// Configure the display as a regular 15bpp framebuffer.
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func (d Device) Configure(config Config) {
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// Use video mode 3 (in BG2, a 16bpp bitmap in VRAM) and Enable BG2.
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gba.DISP.DISPCNT.Set(gba.DISPCNT_BGMODE_3<<gba.DISPCNT_BGMODE_Pos |
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gba.DISPCNT_SCREENDISPLAY_BG2_ENABLE<<gba.DISPCNT_SCREENDISPLAY_BG2_Pos)
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}
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// Size returns the fixed size of this display.
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func (d Device) Size() (x, y int16) {
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return displayWidth, displayHeight
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}
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// Display is a no-op: the display framebuffer is modified directly.
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func (d Device) Display() error {
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// Nothing to do here.
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return nil
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}
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// SetPixel changes the pixel at (x, y) to the given color.
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func (d Device) SetPixel(x, y int16, c color.RGBA) {
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if x < 0 || y < 0 || x >= displayWidth || y > displayHeight {
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// Out of bounds, so ignore.
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return
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}
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val := pixel.NewColor[pixel.RGB555](c.R, c.G, c.B)
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displayFrameBuffer[(int(y))*240+int(x)].Set(uint16(val))
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}
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// DrawBitmap updates the rectangle at (x, y) to the image stored in buf.
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func (d Device) DrawBitmap(x, y int16, buf Image) error {
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width, height := buf.Size()
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if x < 0 || y < 0 || int(x)+width > displayWidth || int(y)+height > displayHeight {
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return errOutOfBounds
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}
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// TODO: try to do a 4-byte memcpy if possible. That should significantly
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// speed up the copying of this image.
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for bufY := 0; bufY < int(height); bufY++ {
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for bufX := 0; bufX < int(width); bufX++ {
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val := buf.Get(bufX, bufY)
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displayFrameBuffer[(int(y)+bufY)*240+int(x)+bufX].Set(uint16(val))
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}
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}
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return nil
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}
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