DS3231(4FREEBSD) - Linux man page online | Special files

Extremely Accurate i2c-integrated RTC/TCXO/Crystal.

February 12, 2016
DS3231(4) BSD Kernel Interfaces Manual DS3231(4)


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


device iic device iicbus device ds3231


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 tempera‐ ture conversion is in progress. When read as 0 and then set to 1, a temperature conversion is started. The temperature conver‐ sion 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 pow‐ ered 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 'inter‐ rupt' (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: 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.


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


The ds3231 driver first appeared in FreeBSD 11.0.


The ds3231 driver and this manual page were written by Luiz Otavio O Souza <>.
BSD February 12, 2016 BSD
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