Added basic test for CHIP PWM functions

Signed-off-by: Erik Agsjö <erik.agsjo@gmail.com>

platforms/chip/chip_adaptor_test.go

@@ -15,6 +15,7 @@ import (
 var _ gobot.Adaptor = (*Adaptor)(nil)
 var _ gpio.DigitalReader = (*Adaptor)(nil)
 var _ gpio.DigitalWriter = (*Adaptor)(nil)
+var _ gpio.ServoWriter = (*Adaptor)(nil)
 var _ i2c.Connector = (*Adaptor)(nil)
 
 type NullReadWriteCloser struct {
@@ -90,3 +91,13 @@ func TestChipAdaptorI2c(t *testing.T) {
 
 	gobottest.Assert(t, a.Finalize(), nil)
 }
+
+func TestChipAdaptorInvalidPWMPin(t *testing.T) {
+	a := initTestChipAdaptor()
+
+	err := a.PwmWrite("LCD-D2", 42)
+	gobottest.Refute(t, err, nil)
+
+	err = a.ServoWrite("LCD-D2", 120)
+	gobottest.Refute(t, err, nil)
+}

platforms/chip/chip_pwm.go

@@ -37,8 +37,6 @@ func unexportPWM() (err error) {
 	return err
 }
 
-//	return fmt.Errorf("PWM is not available, check device tree setup")
-
 func (c *Adaptor) initPWM(pwmFrequency float64) (err error) {
 	const basePath = pwmSysfsPath + "/pwm0"