ssd1306: improvements needed for Thumby SPI display

Signed-off-by: deadprogram <ron@hybridgroup.com>

examples/ssd1306/spi_thumby/main.go

@@ -0,0 +1,50 @@
+// This example using the SSD1306 OLED display over SPI on the Thumby board
+// A very tiny 72x40 display.
+package main
+
+import (
+	"image/color"
+	"machine"
+	"time"
+
+	"tinygo.org/x/drivers/ssd1306"
+)
+
+func main() {
+	machine.SPI0.Configure(machine.SPIConfig{})
+	display := ssd1306.NewSPI(machine.SPI0, machine.THUMBY_DC_PIN, machine.THUMBY_RESET_PIN, machine.THUMBY_CS_PIN)
+	display.Configure(ssd1306.Config{
+		Width:     72,
+		Height:    40,
+		ResetCol:  ssd1306.ResetValue{28, 99},
+		ResetPage: ssd1306.ResetValue{0, 5},
+	})
+
+	display.ClearDisplay()
+
+	x := int16(36)
+	y := int16(20)
+	deltaX := int16(1)
+	deltaY := int16(1)
+	for {
+		pixel := display.GetPixel(x, y)
+		c := color.RGBA{255, 255, 255, 255}
+		if pixel {
+			c = color.RGBA{0, 0, 0, 255}
+		}
+		display.SetPixel(x, y, c)
+		display.Display()
+
+		x += deltaX
+		y += deltaY
+
+		if x == 0 || x == 71 {
+			deltaX = -deltaX
+		}
+
+		if y == 0 || y == 39 {
+			deltaY = -deltaY
+		}
+		time.Sleep(1 * time.Millisecond)
+	}
+}

ssd1306/ssd1306.go

@@ -13,6 +13,8 @@ import (
 	"tinygo.org/x/drivers/internal/legacy"
 )
 
+type ResetValue [2]byte
+
 // Device wraps I2C or SPI connection.
 type Device struct {
 	bus        Buser
@@ -22,6 +24,8 @@ type Device struct {
 	bufferSize int16
 	vccState   VccMode
 	canReset   bool
+	resetCol   ResetValue
+	resetPage  ResetValue
 }
 
 // Config is the configuration for the display
@@ -30,6 +34,13 @@ type Config struct {
 	Height   int16
 	VccState VccMode
 	Address  uint16
+	// ResetCol and ResetPage are used to reset the screen to 0x0
+	// This is useful for some screens that have a different size than 128x64
+	// For example, the Thumby's screen is 72x40
+	// The default values are normally set automatically based on the size.
+	// If you're using a different size, you might need to set these values manually.
+	ResetCol  ResetValue
+	ResetPage ResetValue
 }
 
 type I2CBus struct {
@@ -79,6 +90,7 @@ func NewSPI(bus drivers.SPI, dcPin, resetPin, csPin machine.Pin) Device {
 
 // Configure initializes the display with default configuration
 func (d *Device) Configure(cfg Config) {
+	var zeroReset ResetValue
 	if cfg.Width != 0 {
 		d.width = cfg.Width
 	} else {
@@ -97,6 +109,16 @@ func (d *Device) Configure(cfg Config) {
 	} else {
 		d.vccState = SWITCHCAPVCC
 	}
+	if cfg.ResetCol != zeroReset {
+		d.resetCol = cfg.ResetCol
+	} else {
+		d.resetCol = ResetValue{0, uint8(d.width - 1)}
+	}
+	if cfg.ResetPage != zeroReset {
+		d.resetPage = cfg.ResetPage
+	} else {
+		d.resetPage = ResetValue{0, uint8(d.height/8) - 1}
+	}
 	d.bufferSize = d.width * d.height / 8
 	d.buffer = make([]byte, d.bufferSize)
 	d.canReset = cfg.Address != 0 || d.width != 128 || d.height != 64 // I2C or not 128x64
@@ -186,11 +208,11 @@ func (d *Device) Display() error {
 	// Since we're printing the whole buffer, avoid resetting it in this case
 	if d.canReset {
 		d.Command(COLUMNADDR)
-		d.Command(0)
-		d.Command(uint8(d.width - 1))
+		d.Command(d.resetCol[0])
+		d.Command(d.resetCol[1])
 		d.Command(PAGEADDR)
-		d.Command(0)
-		d.Command(uint8(d.height/8) - 1)
+		d.Command(d.resetPage[0])
+		d.Command(d.resetPage[1])
 	}
 
 	return d.Tx(d.buffer, false)