Add error handling

dht20/dht20.go

@@ -5,11 +5,16 @@
 package dht20
 
 import (
+	"errors"
 	"time"
 
 	"tinygo.org/x/drivers"
 )
 
+var (
+	errUpdateCalledTooSoon = errors.New("Update() called within 80ms is invalid")
+)
+
 // Device wraps an I2C connection to a DHT20 device.
 type Device struct {
 	bus            drivers.I2C
@@ -63,9 +68,14 @@ func (d *Device) initRegisters() {
 }
 
 // Update reads data from the sensor and updates the temperature and humidity values.
+// Note that the values obtained by this function are from the previous call to Update.
+// If you want to use the most recent values, shorten the interval at which Update is called.
 func (d *Device) Update(which drivers.Measurement) error {
 	// Check if 80ms have passed since the last access
-	if d.prevAccessTime.Add(80 * time.Millisecond).Before(time.Now()) {
+	if time.Since(d.prevAccessTime) < 80*time.Millisecond {
+		return errUpdateCalledTooSoon
+	}
+
 	// Check the status word Bit[7]
 	d.data[0] = 0x71
 	d.bus.Tx(d.Address, d.data[:1], d.data[:1])
@@ -88,7 +98,6 @@ func (d *Device) Update(which drivers.Measurement) error {
 		// Update the previous access time to the current time
 		d.prevAccessTime = time.Now()
 	}
-	}
 	return nil
 }