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>.