Read Date and Time from DS3234 Real Time Clock

This application reads the date and time values from the Sparkfun DeadOn RTC Breakout Board. This board contains the DS3234 Real Time Clock module.

Code

using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;
using SecretLabs.NETMF.Hardware.NetduinoPlus;
using System.Threading;

namespace ReadDS3234
{
    public class Program
    {
        /// <summary>
        /// Position of the time elements in the array of bytes read from the DS3234.
        /// </summary>
        public const int REG_SECONDS = 0;
        public const int REG_MINUTE = REG_SECONDS + 1;
        public const int REG_HOUR = REG_MINUTE + 1;
        public const int REG_WEEKDAY = REG_HOUR + 1;
        public const int REG_DAY = REG_WEEKDAY + 1;
        public const int REG_DATE = REG_DAY + 1;
        public const int REG_MONTH = REG_DATE + 1;
        public const int REG_YEAR = REG_MONTH + 1;
        public const int REG_SIZE = REG_YEAR + 1;

        /// <summary>
        /// Convert the BCD byte into a a byte.
        /// </summary>
        /// <param name="value">Value to convert</param>
        /// <returns>Decimal representation of the BCD number.</returns>
        public static byte ConvertBCDToByte(byte value)
        {
            byte result;

            result = (byte) ((value & 0xf0) >> 4);
            result *= 10;
            result += (byte) (value & 0x0f);
            return (result);
        }

        /// <summary>
        /// Convert a byte value into a BCD encoded version of the data.
        /// </summary>
        /// <param name="value">Byte value to convert.</param>
        /// <returns>Byte containing the BCD representation of value.</returns>
        public static byte ConvertByteToBCD(byte value)
        {
            byte result = (byte) (value % 10);
            result |= (byte) ((value / 10) << 4);
            return (result);
        }

        /// <summary>
        /// Decode the data from the DS3234 and return a string representation of the date / time.
        /// </summary>
        /// <param name="dataFromChip">Byte array containing the date / time registers from the DS3234.</param>
        /// <returns>String representation of the date and time.</returns>
        public static string DecodeTime(byte[] dataFromChip)
        {
            byte hour, minutes, seconds, day, month;
            int year;

            seconds = ConvertBCDToByte(dataFromChip[REG_SECONDS]);
            minutes = ConvertBCDToByte(dataFromChip[REG_MINUTE]);
            if ((dataFromChip[REG_HOUR] & 0x40) > 0)
            {
                hour = ConvertBCDToByte((byte) (dataFromChip[REG_HOUR] & 0x1f));
                if ((dataFromChip[REG_HOUR] & 0x20) > 0)
                {
                    hour += 12;
                }
            }
            else
            {
                hour = ConvertBCDToByte((byte) (dataFromChip[REG_HOUR] & 0x3f));
            }
            day = ConvertBCDToByte(dataFromChip[REG_DAY]);
            month = ConvertBCDToByte((byte) (dataFromChip[REG_MONTH] & 0x7f));
            year = 1900 + ConvertBCDToByte(dataFromChip[REG_YEAR]);
            if ((dataFromChip[REG_MONTH] & 0x80) > 0)
            {
                year += 100;
            }
            return ("Current time: " + hour.ToString() + ":" + minutes.ToString() + ":" + seconds.ToString() + " Date: " + day.ToString() + "-" + month.ToString() + "-" + year.ToString());
        }

        /// <summary>
        /// Convert the data byte into a hexadecimal string representation of the number.
        /// </summary>
        /// <param name="data">Value to convert.</param>
        /// <returns>String containing the hexadecimal representation of the number.</returns>
        public static string Hexadecimal(byte data)
        {
            const string characters = "0123456789abcdef";
            string result = "0x";

            result += characters[data >> 4];
            result += characters[data & 0x0f];
            return (result);
        }

        /// <summary>
        /// Main program loop.
        /// </summary>
        public static void Main()
        {
            SPI.Configuration spiConfig = new SPI.Configuration(
                            ChipSelect_Port: Pins.GPIO_PIN_D7,      // Chip select is digital IO 7.
                            ChipSelect_ActiveState: false,          // Chip select is active low.
                            ChipSelect_SetupTime: 0,                // Amount of time between selection and the clock starting
                            ChipSelect_HoldTime: 0,                 // Amount of time the device must be active after the data has been read.
                            Clock_Edge: false,                      // Sample on the falling edge.
                            Clock_IdleState: false,                 // Clock is idle when low.
                            Clock_RateKHz: 10,                      // 10KHz clock speed.
                            SPI_mod: SPI_Devices.SPI1               // Use SPI1
                        );

            SPI spi = new SPI(spiConfig);
            int count = 0;
            while (true)
            {
                byte[] dataOut = new byte[] { 0 };
                byte[] dataIn = new byte[REG_SIZE];
                spi.WriteRead(dataOut, dataIn, 1);
                count++;
                string message = "Read " + count.ToString() + ":";
                for (int index = 0; index < dataIn.Length; index++)
                {
                    message += " " + Hexadecimal(dataIn[index]);
                }
                Debug.Print(message);
                Debug.Print(DecodeTime(dataIn));
                Thread.Sleep(2000);
            }
        }
    }
}

Hardware

The DS3234 should be connected to the Netduino as follows:

Netduino Samples Github Repository

Full source code for all of the samples can be found in the Netduino Samples repository on Github.