DS3231(4)              FreeBSD Kernel Interfaces Manual              DS3231(4)

NAME
     ds3231 - Extremely Accurate i2c-integrated RTC/TCXO/Crystal

SYNOPSIS
     device iic
     device iicbus
     device ds3231

DESCRIPTION
     The ds3231 is a low-cost, extremely accurate I2C realtime clock (RTC)
     with an integrated temperature-compensated crystal oscillator (TCXO) and
     crystal.

     The device incorporates a battery input and maintains accurate
     timekeeping when main power to the device is interrupted.

     Access to ds3231 data is made with the sysctl(8) interface:

     dev.ds3231.0.%desc: Maxim DS3231 RTC
     dev.ds3231.0.%driver: ds3231
     dev.ds3231.0.%location: addr=0xd0
     dev.ds3231.0.%pnpinfo: name=rtc compat=maxim,ds3231
     dev.ds3231.0.%parent: iicbus1
     dev.ds3231.0.temperature: 23.2C
     dev.ds3231.0.temp_conv: 0
     dev.ds3231.0.bbsqw: 0
     dev.ds3231.0.sqw_freq: 8192
     dev.ds3231.0.sqw_mode: interrupt
     dev.ds3231.0.32khz_enable: 1

     dev.ds3231.%d.temperature      The read-only value of the current
                                    temperature read by the RTC.

     dev.ds3231.%d.temp_conv        Start a new temperature conversion.  When
                                    read as 1, a temperature conversion is in
                                    progress.  When read as 0 and then set to
                                    1, a temperature conversion is started.
                                    The temperature conversion runs
                                    automatically on power up and once every
                                    64 seconds afterward.

     dev.ds3231.%d.bbsqw            If set to 1 and dev.ds3231.%d.sqw_mode is
                                    set to square-wave, battery-backed square-
                                    wave output is enabled.  If set to 0, the
                                    SQW pin will be set to high impendance
                                    when the RTC is being powered by battery.

     dev.ds3231.%d.sqw_freq         Select the frequency of the SQW pin when
                                    the square-wave output is enabled on
                                    dev.ds3231.%d.sqw_mode.  It can be set to
                                    1, 1024, 4096, and 8192.

     dev.ds3231.%d.sqw_mode         Set the operation mode for the SQW pin.
                                    It can be set to 'interrupt' (default) or
                                    'square-wave'.  In interrupt mode, the SQW
                                    pin is used to generate interrupts for the
                                    RTC alarms.  In square-wave mode, the SQW
                                    pin drives a square-wave of
                                    dev.ds3231.%d.sqw_freq frequency.

     dev.ds3231.%d.32khz_enable     Enable the 32kHz output.

     Please check the ds3231 datasheet for more details.

     On a device.hints(5) based system, such as MIPS, these values are
     configurable for ds3231:

     hint.ds3231.%d.at        The iicbus(4) that the ds3231 is connected to.

     hint.ds3231.%d.addr      The 8-bit i2c address of ds3231.  The default
                              8-bit address for ds3231 is 0xd0.

     On a FDT(4) based system the following properties must be set:

     compatible      Must always be set to "maxim,ds3231".

     reg             The 7-bit i2c address of ds3231.  The default 7-bit
                     address for ds3231 is 0x68.

SEE ALSO
     fdt(4), iic(4), iicbus(4), sysctl(8)

HISTORY
     The ds3231 driver first appeared in FreeBSD 11.0.

AUTHORS
     The ds3231 driver and this manual page were written by Luiz Otavio O
     Souza <loos@FreeBSD.org>.

FreeBSD 13.1-RELEASE-p6        February 12, 2016       FreeBSD 13.1-RELEASE-p6