ssd1331: make SPI TX faster

same change as PR #89

ssd1331/ssd1331.go

@@ -34,7 +34,7 @@ type Config struct {
 	Height int16
 }
 
-// New creates a new ST7735 connection. The SPI wire must already be configured.
+// New creates a new SSD1331 connection. The SPI wire must already be configured.
 func New(bus machine.SPI, resetPin, dcPin, csPin machine.Pin) Device {
 	dcPin.Configure(machine.PinConfig{Mode: machine.PinOutput})
 	resetPin.Configure(machine.PinConfig{Mode: machine.PinOutput})
@@ -250,21 +250,8 @@ func (d *Device) Data(data uint8) {
 
 // Tx sends data to the display
 func (d *Device) Tx(data []byte, isCommand bool) {
-	if isCommand {
+	d.dcPin.Set(!isCommand)
-		d.csPin.High()
+	d.bus.Tx(data, nil)
-		d.dcPin.Low()
-		d.csPin.Low()
-
-		d.bus.Tx(data, nil)
-		d.csPin.High()
-	} else {
-		d.csPin.High()
-		d.dcPin.High()
-		d.csPin.Low()
-
-		d.bus.Tx(data, nil)
-		d.csPin.High()
-	}
 }
 
 // Size returns the current size of the display.