diff --git a/vallox.go b/vallox.go
index aac1e0f..451deea 100644
--- a/vallox.go
+++ b/vallox.go
@@ -220,6 +220,10 @@ func valueToSpeed(value byte) int8 {
 	return -1
 }
 
+func speedToValue(speed int8) byte {
+	return fanSpeedConversion[speed-1]
+}
+
 func valueToTemp(value byte) int8 {
 	return tempConversion[value]
 }
diff --git a/vallox_test.go b/vallox_test.go
new file mode 100644
index 0000000..423f3f5
--- /dev/null
+++ b/vallox_test.go
@@ -0,0 +1,39 @@
+package valloxrs485
+
+import (
+	"testing"
+)
+
+func TestValueToTemp(t *testing.T) {
+	assertTemp(0, -74, t)
+	assertTemp(255, 100, t)
+	assertTemp(246, 97, t)
+	assertTemp(247, 100, t)
+}
+
+func TestValueToSpeed(t *testing.T) {
+	assertSpeed(1, 1, t)
+	assertSpeed(3, 2, t)
+	assertSpeed(7, 3, t)
+	assertSpeed(15, 4, t)
+	assertSpeed(31, 5, t)
+	assertSpeed(63, 6, t)
+	assertSpeed(127, 7, t)
+	assertSpeed(255, 8, t)
+}
+
+func assertTemp(raw byte, value int8, t *testing.T) {
+	if c := valueToTemp(raw); c != value {
+		t.Errorf("temp %d was not converted to %d but to %d", raw, value, c)
+	}
+}
+
+func assertSpeed(raw byte, value int8, t *testing.T) {
+	if c := valueToSpeed(raw); c != value {
+		t.Errorf("raw %d to speed was not converted to %d but to %d", raw, value, c)
+	}
+
+	if c := speedToValue(value); c != raw {
+		t.Errorf("speed %d to raw was not converted to %d but to %d", value, raw, c)
+	}
+}