diff --git a/ep0099/doc.go b/ep0099/doc.go
index 1af7270..7455bdd 100644
--- a/ep0099/doc.go
+++ b/ep0099/doc.go
@@ -1,12 +1,9 @@
-// Copyright 2018 The Periph Authors. All rights reserved.
+// Copyright 2021 The Periph Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that caan be found in the LICENSE file.
 
-// Package ep0099
+// Package ep0099 controls a EP-0099 Raspberry Pi HAT with 4 relays via I2C.
 //
 // Datasheet
 // https://wiki.52pi.com/index.php/DockerPi_4_Channel_Relay_SKU:_EP-0099
-//
-// Examples
-// https://github.com/geeekpi/dockerpi
 package ep0099
diff --git a/ep0099/ep0099.go b/ep0099/ep0099.go
index df267a9..a58fb15 100644
--- a/ep0099/ep0099.go
+++ b/ep0099/ep0099.go
@@ -1,4 +1,4 @@
-// Copyright 2018 The Periph Authors. All rights reserved.
+// Copyright 2021 The Periph Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
@@ -10,14 +10,14 @@ import (
 	"periph.io/x/conn/v3/i2c"
 )
 
-var InvalidAddressError = errors.New("Invalid EP-0099 address")
-var InvalidChannelError = errors.New("Invalid EP-0099 channel")
+var errInvalidAddress = errors.New("Invalid EP-0099 address")
+var errInvalidChannel = errors.New("Invalid EP-0099 channel")
 
 type State byte
 
 const (
 	StateOff State = 0x00
-	StateOn  State = 0x01
+	StateOn  State = 0xFF
 )
 
 type Dev struct {
@@ -107,12 +107,12 @@ func isValidAddress(address uint16) error {
 		}
 	}
 
-	return InvalidAddressError
+	return errInvalidAddress
 }
 
 func (d *Dev) isValidChannel(channel uint8) error {
 	if _, exists := d.state[channel]; !exists {
-		return InvalidChannelError
+		return errInvalidChannel
 	}
 	return nil
 }
diff --git a/ep0099/ep0099_test.go b/ep0099/ep0099_test.go
index f5324bf..d9a999d 100644
--- a/ep0099/ep0099_test.go
+++ b/ep0099/ep0099_test.go
@@ -1,4 +1,4 @@
-// Copyright 2018 The Periph Authors. All rights reserved.
+// Copyright 2021 The Periph Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
@@ -36,7 +36,7 @@ func TestNewReturnsInvalidAddress(t *testing.T) {
 	bus := initTestBus()
 
 	_, err := New(bus, 0x00)
-	if !errors.Is(err, InvalidAddressError) {
+	if !errors.Is(err, errInvalidAddress) {
 		t.Fatal("New should return address validation error, got: ", err)
 	}
 }
@@ -81,7 +81,7 @@ func TestOn(t *testing.T) {
 		t.Fatal("Should not return error, got ", err)
 	}
 
-	checkBusWrites(t, bus, 0, []byte{3, byte(StateOn)})
+	checkBusHasWrite(t, bus, []byte{3, byte(StateOn)})
 	checkChannelState(t, dev, 3, StateOn)
 }
 
@@ -97,7 +97,7 @@ func TestOff(t *testing.T) {
 		t.Fatal("Should not return error, got ", err)
 	}
 
-	checkBusWrites(t, bus, 0, []byte{4, byte(StateOff)})
+	checkBusHasWrite(t, bus, []byte{4, byte(StateOff)})
 	checkChannelState(t, dev, 4, StateOff)
 }
 
@@ -105,11 +105,11 @@ func TestReturnErrorForInvalidChannel(t *testing.T) {
 	bus := initTestBus()
 	dev, _ := New(bus, testDefaultValidAddress)
 
-	if err := dev.On(98); err != InvalidChannelError {
+	if err := dev.On(98); err != errInvalidChannel {
 		t.Fatal("On should return invalid channel error, got ", err)
 	}
 
-	if err := dev.Off(98); err != InvalidChannelError {
+	if err := dev.Off(98); err != errInvalidChannel {
 		t.Fatal("Off should return invalid channel error, got ", err)
 	}
 }
@@ -132,22 +132,25 @@ func checkChannelState(t *testing.T, dev *Dev, channel uint8, state State) {
 	}
 }
 
-func checkBusWrites(t *testing.T, bus *i2ctest.Record, index int, data []byte) {
-	if !bytes.Equal(bus.Ops[index].W, data) {
-		t.Fatal("Expected data ", data, " to be written, got ", bus.Ops[index].W)
+func checkBusHasWrite(t *testing.T, bus *i2ctest.Record, data []byte) {
+	for _, op := range bus.Ops {
+		if bytes.Equal(op.W, data) {
+			return
+		}
 	}
+	t.Fatal("Expected data ", data, " to be written but it never did")
 }
 
 func checkDevReset(t *testing.T, dev *Dev, bus *i2ctest.Record) {
-	checkBusWrites(t, bus, 0, []byte{1, byte(StateOff)})
+	checkBusHasWrite(t, bus, []byte{1, byte(StateOff)})
 	checkChannelState(t, dev, 1, StateOff)
 
-	checkBusWrites(t, bus, 1, []byte{2, byte(StateOff)})
+	checkBusHasWrite(t, bus, []byte{2, byte(StateOff)})
 	checkChannelState(t, dev, 2, StateOff)
 
-	checkBusWrites(t, bus, 2, []byte{3, byte(StateOff)})
+	checkBusHasWrite(t, bus, []byte{3, byte(StateOff)})
 	checkChannelState(t, dev, 3, StateOff)
 
-	checkBusWrites(t, bus, 3, []byte{4, byte(StateOff)})
+	checkBusHasWrite(t, bus, []byte{4, byte(StateOff)})
 	checkChannelState(t, dev, 4, StateOff)
 }
diff --git a/ep0099/example_test.go b/ep0099/example_test.go
index 15d2520..b0d5b9d 100644
--- a/ep0099/example_test.go
+++ b/ep0099/example_test.go
@@ -1,4 +1,4 @@
-// Copyright 2018 The Periph Authors. All rights reserved.
+// Copyright 2021 The Periph Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.