add example usage

internal/regmap/regmap_test.go

@@ -0,0 +1,34 @@
+package regmap
+
+import (
+	"fmt"
+
+	"tinygo.org/x/drivers"
+)
+
+func ExampleDevice8Txer() {
+	// Initialization.
+	var dtx Device8Txer
+	dtx.SetTxBuffers(make([]byte, 256), make([]byte, 256))
+
+	// Usage.
+	const (
+		defaultAddr = 65
+		REG_WRITE   = 0x1f
+		IOCTL_CALL  = 0xc0
+	)
+	tx, err := dtx.Tx(REG_WRITE)
+	if err != nil {
+		panic(err)
+	}
+	err = tx.AddWriteData(IOCTL_CALL, 0x80, 0x80)
+	if err != nil {
+		panic(err)
+	}
+	var bus drivers.I2C
+	readData, err := tx.DoTxI2C(bus, defaultAddr, 20)
+	if err != nil {
+		panic(err)
+	}
+	fmt.Println(readData)
+}