refactor(machine): Refactor UART inversion with pin setter helpers.

RP2: Extract setOutOver/setInOver methods on Pin, removing inline
IO control register manipulation from UART configure.

SAM: Switch to SetCTRLA_TXINV/SetCTRLA_RXINV methods, dropping
the unused device/sam import and raw SetBits/ClearBits calls.

Author: Konstantin Sharlaimov

src/machine/machine_rp2_gpio.go

@@ -141,6 +141,16 @@ func (p Pin) setSchmitt(trigger bool) {
 	p.padCtrl().ReplaceBits(boolToBit(trigger)<<rp.PADS_BANK0_GPIO0_SCHMITT_Pos, rp.PADS_BANK0_GPIO0_SCHMITT_Msk, 0)
 }
 
+// setOutOver sets the output override (OUTOVER field) for the pin.
+func (p Pin) setOutOver(over uint32) {
+	p.ioCtrl().ReplaceBits(over<<rp.IO_BANK0_GPIO0_CTRL_OUTOVER_Pos, rp.IO_BANK0_GPIO0_CTRL_OUTOVER_Msk, 0)
+}
+
+// setInOver sets the input override (INOVER field) for the pin.
+func (p Pin) setInOver(over uint32) {
+	p.ioCtrl().ReplaceBits(over<<rp.IO_BANK0_GPIO0_CTRL_INOVER_Pos, rp.IO_BANK0_GPIO0_CTRL_INOVER_Msk, 0)
+}
+
 // setFunc will set pin function to fn.
 func (p Pin) setFunc(fn pinFunc) {
 	// Set input enable, Clear output disable

src/machine/machine_rp2_uart.go

@@ -53,17 +53,17 @@ func (uart *UART) Configure(config UARTConfig) error {
 	if config.TX != NoPin {
 		config.TX.Configure(PinConfig{Mode: PinUART})
 		if config.InvertTX {
-			config.TX.ioCtrl().ReplaceBits(rp.IO_BANK0_GPIO0_CTRL_OUTOVER_INVERT<<rp.IO_BANK0_GPIO0_CTRL_OUTOVER_Pos, rp.IO_BANK0_GPIO0_CTRL_OUTOVER_Msk, 0)
+			config.TX.setOutOver(rp.IO_BANK0_GPIO0_CTRL_OUTOVER_INVERT)
 		} else {
-			config.TX.ioCtrl().ReplaceBits(rp.IO_BANK0_GPIO0_CTRL_OUTOVER_NORMAL<<rp.IO_BANK0_GPIO0_CTRL_OUTOVER_Pos, rp.IO_BANK0_GPIO0_CTRL_OUTOVER_Msk, 0)
+			config.TX.setOutOver(rp.IO_BANK0_GPIO0_CTRL_OUTOVER_NORMAL)
 		}
 	}
 	if config.RX != NoPin {
 		config.RX.Configure(PinConfig{Mode: PinUART})
 		if config.InvertRX {
-			config.RX.ioCtrl().ReplaceBits(rp.IO_BANK0_GPIO0_CTRL_INOVER_INVERT<<rp.IO_BANK0_GPIO0_CTRL_INOVER_Pos, rp.IO_BANK0_GPIO0_CTRL_INOVER_Msk, 0)
+			config.RX.setInOver(rp.IO_BANK0_GPIO0_CTRL_INOVER_INVERT)
 		} else {
-			config.RX.ioCtrl().ReplaceBits(rp.IO_BANK0_GPIO0_CTRL_INOVER_NORMAL<<rp.IO_BANK0_GPIO0_CTRL_INOVER_Pos, rp.IO_BANK0_GPIO0_CTRL_INOVER_Msk, 0)
+			config.RX.setInOver(rp.IO_BANK0_GPIO0_CTRL_INOVER_NORMAL)
 		}
 	}
 	if config.RTS != 0 {

src/machine/machine_sam_uart_invert.go

@@ -2,18 +2,16 @@
 
 package machine
 
-import "device/sam"
-
 // Configure UART TX/RX line inversion using SVD-generated APIs.
 func (uart *UART) setInversion(config UARTConfig) {
 	if config.InvertTX {
-		uart.Bus.CTRLA.SetBits(sam.SERCOM_USART_INT_CTRLA_TXINV)
+		uart.Bus.SetCTRLA_TXINV(1)
 	} else {
-		uart.Bus.CTRLA.ClearBits(sam.SERCOM_USART_INT_CTRLA_TXINV)
+		uart.Bus.SetCTRLA_TXINV(0)
 	}
 	if config.InvertRX {
-		uart.Bus.CTRLA.SetBits(sam.SERCOM_USART_INT_CTRLA_RXINV)
+		uart.Bus.SetCTRLA_RXINV(1)
 	} else {
-		uart.Bus.CTRLA.ClearBits(sam.SERCOM_USART_INT_CTRLA_RXINV)
+		uart.Bus.SetCTRLA_RXINV(0)
 	}
 }