DS3231(4)

📦 version 12.2, in debian bookworm, debian trixie, ubuntu jammy, ubuntu noble, ubuntu questing, ubuntu resolute, ubuntu stonking

💖 DS3231(4) 💖

ok so this is a page from the Kernel Interfaces Manual, and it's all about ds3231 — the Extremely Accurate i2c-integrated RTC/TCXO/Crystal. yes bestie, that's the full government name. 🕐✨

🌸 NAME 🌸

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

✨ SYNOPSIS ✨

device iic
device iicbus
device ds3231

🎀 DESCRIPTION 🎀

ok so the ds3231 is a low-cost, extremely accurate I2C realtime clock (RTC) with an integrated temperature-compensated crystal oscillator (TCXO) and crystal. it's giving "tiny chip, huge responsibility." 👑

the device has a battery input and it keeps accurate timekeeping even when main power to the device is interrupted. it literally does not care about your power outage. main character energy fr. 💅

you get at the ds3231 data through the sysctl(8) interface, and it looks like this:

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. you can look, you cannot touch. 🙈
  • dev.ds3231.%d.temp_conv — start a new temperature conversion. when you read it as 1, a temperature conversion is in progress. when you read it as 0 and then set it to 1, a temperature conversion is started. the temperature conversion runs automatically on power up and once every 64 seconds afterward. it's on its own lil schedule, no notes. ⏱️
  • dev.ds3231.%d.bbsqw — if you set it to 1 and dev.ds3231.%d.sqw_mode is set to square-wave, battery-backed square-wave output is enabled. if you set it 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. (yes bestie, the datasheet. it's the lore. 📖)

🦋 device.hints(5) systems 🦋

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.

🌈 FDT(4) systems 🌈

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

  • compatible — must always be set to "maxim,ds3231". no negotiating. 🚫
  • reg — the 7-bit i2c address of ds3231. the default 7-bit address for ds3231 is 0x68.
⚠️ heads up bestie: device.hints(5) systems want the 8-bit address (0xd0 default), FDT systems want the 7-bit address (0x68 default). two different numbers, same chip. don't mix them up, it's not the vibe. 😭

⭐ SEE ALSO ⭐

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

👑 HISTORY 👑

the ds3231 driver first appeared in FreeBSD 11.0. a legend from day one, honestly. 🔥

💜 AUTHORS 💜

the ds3231 driver and this manual page were written by Luiz Otavio O Souza <loos@FreeBSD.org>. we stan. 🫶

ok that's the whole page bestie, you're officially a ds3231 girlie now 💅✨

this was DS3231(4) from the Debian build, dated February 12, 2016 — yeah it's an old baddie but she still slays. bye ily, go read your datasheet 🎀🦋💖

📦 where this page comes from