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ssd1306: avoid unnecessary heap allocations #767

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ssd1306: avoid unnecessary heap allocations #767

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28 changes: 10 additions & 18 deletions ssd1306/ssd1306.go
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Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,6 @@ import (
"time"

"tinygo.org/x/drivers"
"tinygo.org/x/drivers/internal/legacy"
"tinygo.org/x/drivers/pixel"
)

Expand Down Expand Up @@ -128,7 +127,7 @@ func (d *Device) Configure(cfg Config) {
d.resetPage = ResetValue{0, uint8(d.height/8) - 1}
}
d.bufferSize = d.width * d.height / 8
d.buffer = make([]byte, d.bufferSize)
d.buffer = make([]byte, d.bufferSize+1) // +1 for the I2C command byte
d.canReset = cfg.Address != 0 || d.width != 128 || d.height != 64 // I2C or not 128x64

d.bus.configure()
Expand Down Expand Up @@ -268,7 +267,8 @@ func (d *Device) GetBuffer() []byte {

// Command sends a command to the display
func (d *Device) Command(command uint8) {
d.bus.tx([]byte{command}, true)
d.buffer[1] = command // The second byte is the actual command
d.bus.tx(d.buffer[0:2], true)
}

// setAddress sets the address to the I2C bus
Expand Down Expand Up @@ -310,32 +310,24 @@ func (d *Device) Tx(data []byte, isCommand bool) error {
// 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)
data[0] = 0x00 // Command mode
} else {
return legacy.WriteRegister(b.wire, uint8(b.Address), 0x40, data)
data[0] = 0x40 // Data mode
}
return b.wire.Tx(uint16(b.Address), data, nil)
}

// tx sends data to the display (SPIBus implementation)
func (b *SPIBus) tx(data []byte, isCommand bool) error {
var err error

b.csPin.High()
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()
}

b.csPin.Low()
err := b.wire.Tx(data[1:], nil) // The first byte is reserved for I2C communcation, strip it
b.csPin.High()
return err
}

Expand Down