ETRA SBC/Interfaces and Connectors/RTC

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Issue Date Notes
2021/01/14 First Release

RTC device[edit | edit source]

Description[edit | edit source]

There are two RTC devices on the Evaluation Kit, one is provided by the STM32MP1 SoC, the other is a Maxim DS3232M I2C device.

Both RTC can retain time and custom data over blackouts using a backup power source as:

  • the lithium rechargeable battery (BT1) optionally mounted on the carrier board
  • an external battery connected to J3 (alternate mounting option to the battery)
BT1 or connector battery options

Signals[edit | edit source]

The following table describes the interface signals for J3:

Pin# SOM Pin# Pin name Pin function Pin Notes
1 J18.14 VBAT can be configured for battery connection
2 - DGND Ground

Device mapping[edit | edit source]

RTC is mapped to /dev/rtc0 device in Linux.

Device usage[edit | edit source]

The peripheral can be accessed through the date and hwclock linux commands.