ds3231: basic support for DS3231 RTC device

ds3231/ds3231.go

@@ -0,0 +1,166 @@
+// Package ds3231 provides a driver for the DS3231 RTC
+//
+// Datasheet:
+// https://datasheets.maximintegrated.com/en/ds/DS3231.pdf
+package ds3231
+
+import (
+	"machine"
+	"time"
+)
+
+type Mode uint8
+
+// Device wraps an I2C connection to a DS3231 device.
+type Device struct {
+	bus     machine.I2C
+	Address uint16
+}
+
+// New creates a new DS3231 connection. The I2C bus must already be
+// configured.
+//
+// This function only creates the Device object, it does not touch the device.
+func New(bus machine.I2C) Device {
+	return Device{
+		bus:     bus,
+		Address: Address,
+	}
+}
+
+// Configure sets up the device for communication
+func (d *Device) Configure() bool {
+	return true
+}
+
+// IsTimeValid return true/false is the time in the device is valid
+func (d *Device) IsTimeValid() bool {
+	data := []byte{0}
+	err := d.bus.ReadRegister(uint8(d.Address), REG_STATUS, data)
+	if err != nil {
+		return false
+	}
+	return (data[0] & (1 << OSF)) == 0x00
+}
+
+// IsRunning returns if the oscillator is running
+func (d *Device) IsRunning() bool {
+	data := []uint8{0}
+	err := d.bus.ReadRegister(uint8(d.Address), REG_CONTROL, data)
+	if err != nil {
+		return false
+	}
+	return (data[0] & (1 << EOSC)) == 0x00
+}
+
+// SetRunning starts the internal oscillator
+func (d *Device) SetRunning(isRunning bool) error {
+	data := []uint8{0}
+	err := d.bus.ReadRegister(uint8(d.Address), REG_CONTROL, data)
+	if err != nil {
+		return err
+	}
+	if isRunning {
+		data[0] &^= uint8(1 << EOSC)
+	} else {
+		data[0] |= 1 << EOSC
+	}
+	err = d.bus.WriteRegister(uint8(d.Address), REG_CONTROL, data)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+// SetTime sets the date and time in the DS3231
+func (d *Device) SetTime(dt time.Time) error {
+	data := []byte{0}
+	err := d.bus.ReadRegister(uint8(d.Address), REG_STATUS, data)
+	if err != nil {
+		return err
+	}
+	data[0] &^= 1 << OSF
+	err = d.bus.WriteRegister(uint8(d.Address), REG_STATUS, data)
+	if err != nil {
+		return err
+	}
+
+	data = make([]uint8, 7)
+	data[0] = uint8ToBCD(uint8(dt.Second()))
+	data[1] = uint8ToBCD(uint8(dt.Minute()))
+	data[2] = uint8ToBCD(uint8(dt.Hour()))
+
+	year := uint8(dt.Year() - 2000)
+	centuryFlag := uint8(0)
+	if year >= 100 {
+		year -= 100
+		centuryFlag = 1 << 7
+	}
+
+	data[3] = uint8ToBCD(uint8(dt.Weekday()))
+	data[4] = uint8ToBCD(uint8(dt.Day()))
+	data[5] = uint8ToBCD(uint8(dt.Month()) | centuryFlag)
+	data[6] = uint8ToBCD(year)
+
+	err = d.bus.WriteRegister(uint8(d.Address), REG_TIMEDATE, data)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// ReadTime returns the date and time
+func (d *Device) ReadTime() (dt time.Time, err error) {
+	data := make([]uint8, 7)
+	err = d.bus.ReadRegister(uint8(d.Address), REG_TIMEDATE, data)
+	if err != nil {
+		return
+	}
+	second := bcdToInt(data[0] & 0x7F)
+	minute := bcdToInt(data[1])
+	hour := hoursBCDToInt(data[2])
+	day := bcdToInt(data[4])
+	monthRaw := data[5]
+	year := bcdToInt(data[6]) + 2000
+	if monthRaw&(1<<7) != 0x00 {
+		year += 100
+	}
+	month := time.Month(bcdToInt(monthRaw & 0x7F))
+
+	dt = time.Date(year, month, day, hour, minute, second, 0, time.UTC)
+	return
+}
+
+// ReadTemperature returns the temperature in millicelsius (mC)
+func (d *Device) ReadTemperature() (int32, error) {
+	data := make([]uint8, 2)
+	err := d.bus.ReadRegister(uint8(d.Address), REG_TEMP, data)
+	if err != nil {
+		return 0, err
+	}
+	return int32(data[0])*1000 + int32((data[1]>>6)*25)*10, nil
+}
+
+// uint8ToBCD converts a byte to BCD for the DS3231
+func uint8ToBCD(value uint8) uint8 {
+	return value + 6*(value/10)
+}
+
+// bcdToInt converts BCD from the DS3231 to int
+func bcdToInt(value uint8) int {
+	return int(value - 6*(value>>4))
+}
+
+// hoursBCDToInt converts the BCD hours to int
+func hoursBCDToInt(value uint8) (hour int) {
+	if value&0x40 != 0x00 {
+		hour = bcdToInt(value & 0x1F)
+		if (value & 0x20) != 0x00 {
+			hour += 12
+		}
+	} else {
+		hour = bcdToInt(value)
+	}
+	return
+}

ds3231/registers.go

@@ -0,0 +1,48 @@
+package ds3231
+
+// The I2C address which this device listens to.
+const Address = 0x68
+
+// Registers
+const (
+	REG_TIMEDATE = 0x00
+	REG_ALARMONE = 0x07
+	REG_ALARMTWO = 0x0B
+
+	REG_CONTROL = 0x0E
+	REG_STATUS  = 0x0F
+	REG_AGING   = 0x10
+
+	REG_TEMP = 0x11
+
+	REG_ALARMONE_SIZE = 4
+	REG_ALARMTWO_SIZE = 3
+
+	// DS3231 Control Register Bits
+	A1IE  = 0
+	A2IE  = 1
+	INTCN = 2
+	RS1   = 3
+	RS2   = 4
+	CONV  = 5
+	BBSQW = 6
+	EOSC  = 7
+
+	// DS3231 Status Register Bits
+	A1F     = 0
+	A2F     = 1
+	BSY     = 2
+	EN32KHZ = 3
+	OSF     = 7
+
+	AlarmFlag_Alarm1    = 0x01
+	AlarmFlag_Alarm2    = 0x02
+	AlarmFlag_AlarmBoth = 0x03
+
+	None          Mode = 0
+	BatteryBackup Mode = 1
+	Clock         Mode = 2
+	AlarmOne      Mode = 3
+	AlarmTwo      Mode = 4
+	ModeAlarmBoth Mode = 5
+)

examples/ds3231/main.go

@@ -0,0 +1,45 @@
+// Connects to an MAG3110 I2C magnetometer.
+package main
+
+import (
+	"machine"
+	"time"
+
+	"fmt"
+
+	"github.com/tinygo-org/drivers/ds3231"
+)
+
+func main() {
+	machine.I2C0.Configure(machine.I2CConfig{})
+
+	rtc := ds3231.New(machine.I2C0)
+	rtc.Configure()
+
+	valid := rtc.IsTimeValid()
+	if !valid {
+		date := time.Date(2019, 12, 05, 20, 34, 12, 0, time.UTC)
+		rtc.SetTime(date)
+	}
+
+	running := rtc.IsRunning()
+	if !running {
+		err := rtc.SetRunning(true)
+		if err != nil {
+			fmt.Println("Error configuring RTC")
+		}
+	}
+
+	for {
+		dt, err := rtc.ReadTime()
+		if err != nil {
+			fmt.Println("Error reading date:", err)
+		} else {
+			fmt.Printf("Date: %d/%s/%02d %02d:%02d:%02d \r\n", dt.Year(), dt.Month(), dt.Day(), dt.Hour(), dt.Minute(), dt.Second())
+		}
+		temp, _ := rtc.ReadTemperature()
+		fmt.Printf("Temperature: %.2f ºC \r\n", float32(temp)/1000)
+
+		time.Sleep(time.Second * 1)
+	}
+}