ssd1306: avoid unnecessary heap allocations (#767)

* ssd1306: avoid unnecessary heap allocations

* ssd1306: extract i2c and spi bus implementations

* ssd1306: refactor tests -- show fps and heap usage

* ssd1306: bring back the lost exported methods

* Adjust examples

* Fix smoketests for ssd1306

examples/ssd1306/i2c_128x32/main.go

@@ -1,51 +0,0 @@
-package main
-
-import (
-	"machine"
-
-	"image/color"
-	"time"
-
-	"tinygo.org/x/drivers/ssd1306"
-)
-
-func main() {
-	machine.I2C0.Configure(machine.I2CConfig{
-		Frequency: machine.TWI_FREQ_400KHZ,
-	})
-
-	display := ssd1306.NewI2C(machine.I2C0)
-	display.Configure(ssd1306.Config{
-		Address: ssd1306.Address_128_32,
-		Width:   128,
-		Height:  32,
-	})
-
-	display.ClearDisplay()
-
-	x := int16(0)
-	y := int16(0)
-	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 == 127 {
-			deltaX = -deltaX
-		}
-
-		if y == 0 || y == 31 {
-			deltaY = -deltaY
-		}
-		time.Sleep(1 * time.Millisecond)
-	}
-}

examples/ssd1306/i2c_128x64/main.go

@@ -1,60 +0,0 @@
-// This example shows how to use 128x64 display over I2C
-// Tested on Seeeduino XIAO Expansion Board https://wiki.seeedstudio.com/Seeeduino-XIAO-Expansion-Board/
-//
-// According to manual, I2C address of the display is 0x78, but that's 8-bit address.
-// TinyGo operates on 7-bit addresses and respective 7-bit address would be 0x3C, which we use below.
-//
-// To learn more about different types of I2C addresses, please see following page
-// https://www.totalphase.com/support/articles/200349176-7-bit-8-bit-and-10-bit-I2C-Slave-Addressing
-
-package main
-
-import (
-	"machine"
-
-	"image/color"
-	"time"
-
-	"tinygo.org/x/drivers/ssd1306"
-)
-
-func main() {
-	machine.I2C0.Configure(machine.I2CConfig{
-		Frequency: machine.TWI_FREQ_400KHZ,
-	})
-
-	display := ssd1306.NewI2C(machine.I2C0)
-	display.Configure(ssd1306.Config{
-		Address: 0x3C,
-		Width:   128,
-		Height:  64,
-	})
-
-	display.ClearDisplay()
-
-	x := int16(0)
-	y := int16(0)
-	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 == 127 {
-			deltaX = -deltaX
-		}
-
-		if y == 0 || y == 63 {
-			deltaY = -deltaY
-		}
-		time.Sleep(1 * time.Millisecond)
-	}
-}

examples/ssd1306/main.go

@@ -0,0 +1,59 @@
+package main
+
+// This example shows how to use SSD1306 OLED display driver over I2C and SPI.
+//
+// Check the `newSSD1306Display()` functions for I2C and SPI initializations.
+
+import (
+	"runtime"
+
+	"image/color"
+	"time"
+)
+
+func main() {
+
+	display := newSSD1306Display()
+	display.ClearDisplay()
+
+	w, h := display.Size()
+	x := int16(0)
+	y := int16(0)
+	deltaX := int16(1)
+	deltaY := int16(1)
+
+	traceTime := time.Now().UnixMilli() + 1000
+	frames := 0
+	ms := runtime.MemStats{}
+
+	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 == w-1 {
+			deltaX = -deltaX
+		}
+
+		if y == 0 || y == h-1 {
+			deltaY = -deltaY
+		}
+
+		frames++
+		now := time.Now().UnixMilli()
+		if now >= traceTime {
+			runtime.ReadMemStats(&ms)
+			println("TS", now, "| FPS", frames, "| HeapInuse", ms.HeapInuse)
+			traceTime = now + 1000
+			frames = 0
+		}
+	}
+
+}

examples/ssd1306/main_i2c_xiao-ble.go

@@ -0,0 +1,38 @@
+//go:build xiao_ble
+
+// This initializes SSD1306 OLED display driver over I2C.
+//
+// Seeed XIAO BLE board + SSD1306 128x32 I2C OLED display.
+//
+// Wiring:
+// - XIAO GND      -> OLED GND
+// - XIAO 3v3      -> OLED VCC
+// - XIAO D4 (SDA) -> OLED SDA
+// - XIAO D5 (SCL) -> OLED SCK
+//
+// For your case:
+// - Connect the display to I2C pins on your board.
+// - Adjust I2C address and display size as needed.
+
+package main
+
+import (
+	"machine"
+
+	"tinygo.org/x/drivers/ssd1306"
+)
+
+func newSSD1306Display() *ssd1306.Device {
+	machine.I2C0.Configure(machine.I2CConfig{
+		Frequency: 400 * machine.KHz,
+		SDA:       machine.SDA0_PIN,
+		SCL:       machine.SCL0_PIN,
+	})
+	display := ssd1306.NewI2C(machine.I2C0)
+	display.Configure(ssd1306.Config{
+		Address: ssd1306.Address_128_32, // or ssd1306.Address
+		Width:   128,
+		Height:  32, // or 64
+	})
+	return display
+}

examples/ssd1306/main_spi_thumby.go

@@ -0,0 +1,27 @@
+//go:build thumby
+
+// This initializes SSD1306 OLED display driver over SPI.
+//
+// Thumby board has a tiny built-in 72x40 display.
+//
+// As the display is built-in, no wiring is needed.
+
+package main
+
+import (
+	"machine"
+
+	"tinygo.org/x/drivers/ssd1306"
+)
+
+func newSSD1306Display() *ssd1306.Device {
+	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},
+	})
+	return display
+}

examples/ssd1306/main_spi_xiao-rp2040.go

@@ -0,0 +1,40 @@
+//go:build xiao_rp2040
+
+// This initializes SSD1306 OLED display driver over SPI.
+//
+// Seeed XIAO RP2040 board + SSD1306 128x64 SPI OLED display.
+//
+// Wiring:
+// - XIAO GND       -> OLED GND
+// - XIAO 3v3       -> OLED VCC
+// - XIAO D8 (SCK)  -> OLED D0
+// - XIAO D10 (SDO) -> OLED D1
+// - XIAO D4        -> OLED RES
+// - XIAO D5        -> OLED DC
+// - XIAO D6        -> OLED CS
+//
+// For your case:
+// - Connect the display to SPI pins on your board.
+// - Adjust RES, DC and CS pins as needed.
+// - Adjust SPI frequency as needed.
+// - Adjust display size as needed.
+
+package main
+
+import (
+	"machine"
+
+	"tinygo.org/x/drivers/ssd1306"
+)
+
+func newSSD1306Display() *ssd1306.Device {
+	machine.SPI0.Configure(machine.SPIConfig{
+		Frequency: 50 * machine.MHz,
+	})
+	display := ssd1306.NewSPI(machine.SPI0, machine.D5, machine.D4, machine.D6)
+	display.Configure(ssd1306.Config{
+		Width:  128,
+		Height: 64,
+	})
+	return display
+}

examples/ssd1306/spi_128x64/main.go

@@ -1,48 +0,0 @@
-package main
-
-import (
-	"image/color"
-	"machine"
-	"time"
-
-	"tinygo.org/x/drivers/ssd1306"
-)
-
-func main() {
-	machine.SPI0.Configure(machine.SPIConfig{
-		Frequency: 8000000,
-	})
-	display := ssd1306.NewSPI(machine.SPI0, machine.P8, machine.P7, machine.P9)
-	display.Configure(ssd1306.Config{
-		Width:  128,
-		Height: 64,
-	})
-
-	display.ClearDisplay()
-
-	x := int16(64)
-	y := int16(32)
-	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 == 127 {
-			deltaX = -deltaX
-		}
-
-		if y == 0 || y == 63 {
-			deltaY = -deltaY
-		}
-		time.Sleep(1 * time.Millisecond)
-	}
-}

examples/ssd1306/spi_thumby/main.go

@@ -1,50 +0,0 @@
-// 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)
-	}
-}

smoketest.sh

@@ -65,8 +65,9 @@ tinygo build -size short -o ./build/test.hex -target=pybadge ./examples/shifter/
 tinygo build -size short -o ./build/test.hex -target=microbit ./examples/sht3x/main.go
 tinygo build -size short -o ./build/test.hex -target=microbit ./examples/sht4x/main.go
 tinygo build -size short -o ./build/test.hex -target=microbit ./examples/shtc3/main.go
-tinygo build -size short -o ./build/test.hex -target=microbit ./examples/ssd1306/i2c_128x32/main.go
+tinygo build -size short -o ./build/test.hex -target=xiao-ble ./examples/ssd1306/
-tinygo build -size short -o ./build/test.hex -target=microbit ./examples/ssd1306/spi_128x64/main.go
+tinygo build -size short -o ./build/test.hex -target=xiao-rp2040 ./examples/ssd1306/
+tinygo build -size short -o ./build/test.hex -target=thumby ./examples/ssd1306/
 tinygo build -size short -o ./build/test.hex -target=microbit ./examples/ssd1331/main.go
 tinygo build -size short -o ./build/test.hex -target=microbit ./examples/st7735/main.go
 tinygo build -size short -o ./build/test.hex -target=microbit ./examples/st7789/main.go

ssd1306/ssd1306.go

@@ -6,11 +6,9 @@ package ssd1306 // import "tinygo.org/x/drivers/ssd1306"
 import (
 	"errors"
 	"image/color"
-	"machine"
 	"time"
 
 	"tinygo.org/x/drivers"
-	"tinygo.org/x/drivers/internal/legacy"
 	"tinygo.org/x/drivers/pixel"
 )
 
@@ -23,16 +21,15 @@ type ResetValue [2]byte
 
 // Device wraps I2C or SPI connection.
 type Device struct {
-	bus        Buser
+	bus       Buser
-	buffer     []byte
+	buffer    []byte
-	width      int16
+	width     int16
-	height     int16
+	height    int16
-	bufferSize int16
+	vccState  VccMode
-	vccState   VccMode
+	canReset  bool
-	canReset   bool
+	resetCol  ResetValue
-	resetCol   ResetValue
+	resetPage ResetValue
-	resetPage  ResetValue
+	rotation  drivers.Rotation
-	rotation   drivers.Rotation
 }
 
 // Config is the configuration for the display
@@ -51,51 +48,15 @@ type Config struct {
 	Rotation  drivers.Rotation
 }
 
-type I2CBus struct {
-	wire    drivers.I2C
-	Address uint16
-}
-
-type SPIBus struct {
-	wire     drivers.SPI
-	dcPin    machine.Pin
-	resetPin machine.Pin
-	csPin    machine.Pin
-}
-
 type Buser interface {
-	configure() error
+	configure(address uint16, size int16) []byte // configure the bus and return the image buffer to use
-	tx(data []byte, isCommand bool) error
+	command(cmd uint8) error                     // send a command to the display
-	setAddress(address uint16) error
+	flush() error                                // send the image to the display, faster than "tx()" in i2c case since avoids slice copy
+	tx(data []byte, isCommand bool) error        // generic transmit function
 }
 
 type VccMode uint8
 
-// NewI2C creates a new SSD1306 connection. The I2C wire must already be configured.
-func NewI2C(bus drivers.I2C) Device {
-	return Device{
-		bus: &I2CBus{
-			wire:    bus,
-			Address: Address,
-		},
-	}
-}
-
-// NewSPI creates a new SSD1306 connection. The SPI wire must already be configured.
-func NewSPI(bus drivers.SPI, dcPin, resetPin, csPin machine.Pin) Device {
-	dcPin.Configure(machine.PinConfig{Mode: machine.PinOutput})
-	resetPin.Configure(machine.PinConfig{Mode: machine.PinOutput})
-	csPin.Configure(machine.PinConfig{Mode: machine.PinOutput})
-	return Device{
-		bus: &SPIBus{
-			wire:     bus,
-			dcPin:    dcPin,
-			resetPin: resetPin,
-			csPin:    csPin,
-		},
-	}
-}
-
 // Configure initializes the display with default configuration
 func (d *Device) Configure(cfg Config) {
 	var zeroReset ResetValue
@@ -109,9 +70,6 @@ func (d *Device) Configure(cfg Config) {
 	} else {
 		d.height = 64
 	}
-	if cfg.Address != 0 {
-		d.bus.setAddress(cfg.Address)
-	}
 	if cfg.VccState != 0 {
 		d.vccState = cfg.VccState
 	} else {
@@ -127,11 +85,9 @@ func (d *Device) Configure(cfg Config) {
 	} 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
 
-	d.bus.configure()
+	d.buffer = d.bus.configure(cfg.Address, d.width*d.height/8)
 
 	time.Sleep(100 * time.Nanosecond)
 	d.Command(DISPLAYOFF)
@@ -193,11 +149,22 @@ func (d *Device) Configure(cfg Config) {
 	d.Command(NORMALDISPLAY)
 	d.Command(DEACTIVATE_SCROLL)
 	d.Command(DISPLAYON)
+
+}
+
+// Command sends a command to the display
+func (d *Device) Command(command uint8) {
+	d.bus.command(command)
+}
+
+// Tx sends data to the display; if isCommand is false, this also updates the image buffer.
+func (d *Device) Tx(data []byte, isCommand bool) error {
+	return d.bus.tx(data, isCommand)
 }
 
 // ClearBuffer clears the image buffer
 func (d *Device) ClearBuffer() {
-	for i := int16(0); i < d.bufferSize; i++ {
+	for i := 0; i < len(d.buffer); i++ {
 		d.buffer[i] = 0
 	}
 }
@@ -223,7 +190,7 @@ func (d *Device) Display() error {
 		d.Command(d.resetPage[1])
 	}
 
-	return d.Tx(d.buffer, false)
+	return d.bus.flush()
 }
 
 // SetPixel enables or disables a pixel in the buffer
@@ -252,12 +219,10 @@ func (d *Device) GetPixel(x int16, y int16) bool {
 
 // SetBuffer changes the whole buffer at once
 func (d *Device) SetBuffer(buffer []byte) error {
-	if int16(len(buffer)) != d.bufferSize {
+	if len(buffer) != len(d.buffer) {
 		return errBufferSize
 	}
-	for i := int16(0); i < d.bufferSize; i++ {
+	copy(d.buffer, buffer)
-		d.buffer[i] = buffer[i]
-	}
 	return nil
 }
 
@@ -266,79 +231,6 @@ func (d *Device) GetBuffer() []byte {
 	return d.buffer
 }
 
-// Command sends a command to the display
-func (d *Device) Command(command uint8) {
-	d.bus.tx([]byte{command}, true)
-}
-
-// setAddress sets the address to the I2C bus
-func (b *I2CBus) setAddress(address uint16) error {
-	b.Address = address
-	return nil
-}
-
-// setAddress does nothing, but it's required to avoid reflection
-func (b *SPIBus) setAddress(address uint16) error {
-	// do nothing
-	println("trying to Configure an address on a SPI device")
-	return nil
-}
-
-// configure does nothing, but it's required to avoid reflection
-func (b *I2CBus) configure() error { return nil }
-
-// configure configures some pins with the SPI bus
-func (b *SPIBus) configure() error {
-	b.csPin.Low()
-	b.dcPin.Low()
-	b.resetPin.Low()
-
-	b.resetPin.High()
-	time.Sleep(1 * time.Millisecond)
-	b.resetPin.Low()
-	time.Sleep(10 * time.Millisecond)
-	b.resetPin.High()
-
-	return nil
-}
-
-// Tx sends data to the display
-func (d *Device) Tx(data []byte, isCommand bool) error {
-	return d.bus.tx(data, isCommand)
-}
-
-// tx sends data to the display (I2CBus implementation)
-func (b *I2CBus) tx(data []byte, isCommand bool) error {
-	if isCommand {
-		return legacy.WriteRegister(b.wire, uint8(b.Address), 0x00, data)
-	} else {
-		return legacy.WriteRegister(b.wire, uint8(b.Address), 0x40, data)
-	}
-}
-
-// tx sends data to the display (SPIBus implementation)
-func (b *SPIBus) tx(data []byte, isCommand bool) error {
-	var err error
-
-	if isCommand {
-		b.csPin.High()
-		b.dcPin.Low()
-		b.csPin.Low()
-
-		err = b.wire.Tx(data, nil)
-		b.csPin.High()
-	} else {
-		b.csPin.High()
-		b.dcPin.High()
-		b.csPin.Low()
-
-		err = b.wire.Tx(data, nil)
-		b.csPin.High()
-	}
-
-	return err
-}
-
 // Size returns the current size of the display.
 func (d *Device) Size() (w, h int16) {
 	return d.width, d.height

ssd1306/ssd1306_i2c.go

@@ -0,0 +1,52 @@
+package ssd1306
+
+import (
+	"tinygo.org/x/drivers"
+)
+
+type I2CBus struct {
+	wire    drivers.I2C
+	address uint16
+	buffer  []byte // buffer to avoid heap allocations
+}
+
+// NewI2C creates a new SSD1306 connection. The I2C wire must already be configured.
+func NewI2C(bus drivers.I2C) *Device {
+	return &Device{
+		bus: &I2CBus{
+			wire:    bus,
+			address: Address,
+		},
+	}
+}
+
+// configure address for the I2C bus and allocate the buffer
+func (b *I2CBus) configure(address uint16, size int16) []byte {
+	if address != 0 {
+		b.address = address
+	}
+	b.buffer = make([]byte, size+2) // +1 for the mode and +1 for a command
+	return b.buffer[2:]             // return the image buffer
+}
+
+// command sends a command to the display
+func (b *I2CBus) command(cmd uint8) error {
+	b.buffer[0] = 0x00 // Command mode
+	b.buffer[1] = cmd
+	return b.wire.Tx(b.address, b.buffer[:2], nil)
+}
+
+// flush sends the image to the display
+func (b *I2CBus) flush() error {
+	b.buffer[1] = 0x40 // Data mode
+	return b.wire.Tx(b.address, b.buffer[1:], nil)
+}
+
+// tx sends data to the display
+func (b *I2CBus) tx(data []byte, isCommand bool) error {
+	if isCommand {
+		return b.command(data[0])
+	}
+	copy(b.buffer[2:], data)
+	return b.flush()
+}

ssd1306/ssd1306_spi.go

@@ -0,0 +1,68 @@
+package ssd1306
+
+import (
+	"machine"
+	"time"
+
+	"tinygo.org/x/drivers"
+)
+
+type SPIBus struct {
+	wire     drivers.SPI
+	dcPin    machine.Pin
+	resetPin machine.Pin
+	csPin    machine.Pin
+	buffer   []byte // buffer to avoid heap allocations
+}
+
+// NewSPI creates a new SSD1306 connection. The SPI wire must already be configured.
+func NewSPI(bus drivers.SPI, dcPin, resetPin, csPin machine.Pin) *Device {
+	dcPin.Configure(machine.PinConfig{Mode: machine.PinOutput})
+	resetPin.Configure(machine.PinConfig{Mode: machine.PinOutput})
+	csPin.Configure(machine.PinConfig{Mode: machine.PinOutput})
+	return &Device{
+		bus: &SPIBus{
+			wire:     bus,
+			dcPin:    dcPin,
+			resetPin: resetPin,
+			csPin:    csPin,
+		},
+	}
+}
+
+// configure pins with the SPI bus and allocate the buffer
+func (b *SPIBus) configure(address uint16, size int16) []byte {
+	b.csPin.Low()
+	b.dcPin.Low()
+	b.resetPin.Low()
+
+	b.resetPin.High()
+	time.Sleep(1 * time.Millisecond)
+	b.resetPin.Low()
+	time.Sleep(10 * time.Millisecond)
+	b.resetPin.High()
+
+	b.buffer = make([]byte, size+1) // +1 for a command
+	return b.buffer[1:]             // return the image buffer
+}
+
+// command sends a command to the display
+func (b *SPIBus) command(cmd uint8) error {
+	b.buffer[0] = cmd
+	return b.tx(b.buffer[:1], true)
+}
+
+// flush sends the image to the display
+func (b *SPIBus) flush() error {
+	return b.tx(b.buffer[1:], false)
+}
+
+// tx sends data to the display
+func (b *SPIBus) tx(data []byte, isCommand bool) error {
+	b.csPin.High()
+	b.dcPin.Set(!isCommand)
+	b.csPin.Low()
+	err := b.wire.Tx(data, nil)
+	b.csPin.High()
+	return err
+}