GPIODCF(4)

GPIODCF(4) — Kernel Interfaces Manual ✨

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🎀 NAME 🎀

okay so bestie, welcome to the main character page for gpiodcf — DCF77 timedelta sensor through GPIO pin. That's the name, that's the vibe, periodt. 👑

✨ SYNOPSIS ✨

here's the copy-paste synopsis, no cap:

gpiodcf* at gpio? offset 0 mask 0x1
gpiodcf* at gpio?

🦋 DESCRIPTION 🦋

okay so the gpiodcf driver decodes the DCF77 time signal code using one GPIO pin. That pin is literally used as a data signal, and the GPIO pin must be able to read an input. 🎀

Pin number tea: you can specify the pin number in the kernel configuration with the offset locator. In that case, the mask locator should always be 0x1 — periodt. You can also specify the offset and mask when gpiodcf is attached at runtime using the GPIOATTACH ioctl(2) on the gpio(4) device. ✨

gpiodcf implements a timedelta sensor, and the delta — in nanoseconds — between the received time information and the local time can be accessed through the sysctl(8) interface. The clock type is indicated in the sensor description:

• DCF77 — German DCF77 time signal station (77.5 kHz longwave transmitter located in Mainflingen near Frankfurt). 🌈

the quality of the timedelta is reported as the sensor status, and this is the vibe check you actually need:

• UNKNOWN — No valid time information has been received yet. 🙈
• OK — The time information is valid and the timedelta is safe to use for applications like ntpd(8). slay. 💖
• WARN — The time information is still valid, but no new time information has been decoded for at least 5 minutes due to a reception or parity error. The timedelta should be used with care. lowkey important, bestie. ⭐
• CRITICAL — No valid time information has been received for more than 15 minutes since the sensor state degraded from OK to WARN. This is an indication that hardware should be checked to see if it is still functional. The timedelta will eventually degrade to a lie as all computer internal clocks have a drift. 😭

okay but fr fr, CRITICAL is your cue to check the hardware — no cap, not me ignoring that. 💀

💜 SEE ALSO 💜

the see-also crew, go read these too:

• gpio(4)
• intro(4)
• ntpd(8)
• sysctl(8)

👑 HISTORY 👑

the gpiodcf driver first appeared in OpenBSD 4.5. iconic. 🎀

🫶 AUTHORS 🫶

the gpiodcf driver was written by Marc Balmer <mbalmer@openbsd.org>. 💅

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xoxo, this page is from Debian, dated June 7, 2015 — GPIODCF(4) 💖