rtc

Set or get date from realtime clock (Texas Instruments Jacinto 7 J721E (DRA829/TDA4VM) Evaluation Module)

Note:
You must be root or have the correct abilities to run this utility.

Syntax:

Update the current time based on the time from the specified clock: 

rtc [-b [base][,[reg_shift][,[mem_map][,c_offset]]]]
    [-l] [-r rate] [-S seconds] clock_type

Set the time of the specified clock to the current time: 

rtc [-b [base][,[reg_shift][,[mem_map][,c_offset]]]]
    -s [-l] clock_type

Runs on:

QNX OS

Options:

-a enableflag
Enable (set to 1) or disable (set to 0) the RTC alarm based on enableflag value. It is disabled by default (0). All other options are ignored when RTC Alarm-related options, such as the -A option.
-A seconds
Set the RTC alarm to the specified time, in seconds. The RTC Alarm is disabled before setting a new value. All other options are ignored when using other RTC Alarm related options, such as the -a option. are used.
-b [base][,[reg_shift][,[mem_map][,c_offset]]]
The location of the RTC chip:
  • base — the base address of the chip.
  • reg_shift — spacing of the device registers as a power of 2. For example:
    0
    Registers are 1 byte apart.
    1
    Registers are 2 bytes apart.
    2
    Registers are 4 bytes apart.
    n
    Registers are 2n bytes apart.

    The default reg_shift is 0.

  • mem_map — memory or I/O space.
  • c_offset — offset to the century byte in NVRAM.
-l
(el) Set hardware time to local time, not Coordinated Universal Time (UTC). UTC is the standard term for Greenwich Mean Time (GMT). The -l option has no effect if the clock_type is net.
-r rate
The rate at which to adjust the OS time if it's currently within 60 seconds (or the value set by -S) of the time from the source specified by clock_type. The rate is turned into a percentage 1/rate. The default rate is 100 (1%).
-S seconds
Specify the maximum difference, in seconds, between the current time and the new time before jam loading rather than slowly adjusting (see -r for the convergence speed). Default: 60.
-s
Set hardware to current date and time.
clock_type
One of the following:
Clock type Description
hw Hardware clock (automatically selects one based on information provided by the startup)
at (deprecated) IBM PC/AT Compatible hardware clock
ds15x1 Embedded Dallas Semiconductor DS15x1
ds1386 Embedded Dallas Semiconductor DS1386
ds1743 Maxim Integrated real-time clock
ds3232 Maxim Integrated real-time clock
max8925 ATMEL MAX8925 hardware clock
mc146818 IBM PC/AT Compatible hardware clock
mc9s08dz60 NXP (Freescale) MC9S08DZ60 hardware clock
pcf2127a NXP PCF2127A CMOS realtime clock
pmqcom ARM PMQ clock
primecell ARM PrimeCell clock
ps2 (deprecated) IBM PS/2 Compatible hardware clock
rtc72423 Embedded Fox RTC-72423
m41t00 STMicroelectronics real time clock
m41t6x STMicroelectronics TIMEKEEPER Series clock
m48t5x STMicroelectronics TIMEKEEPER Series clock
m48t37 STMicroelectronics TIMEKEEPER Series clock
mcp7941x Microchip real-time clock
mt2712 Mediatek clock
s35390 Ablic real time clock
tps65910 TI real time clock
net [node] Hardware clock on a remote node
ultrazed UltraZed-EG SoC clock

Description:

The rtc command gets or sets the date and time from a battery backed-up hardware clock.

If your machine has a builtin clock/calendar, you should include the following command in your startup script so QNX OS automatically reads the time when the system starts:

rtc hw

If the RTC chip has been set to the UTC timezone, startup sets the correct time of day automatically on booting. If the RTC chip is set to local time, or for some reason startup doesn't know where the RTC chip is, you'll need to include the appropriate rtc command in the startup script specified in your mkifs buildfile.

You can use clock type net [node] to get the date from a specified node, or to set the date on a specified node. If node isn't specified, the default is the local machine. When clock type net [node] is used, the -l option has no effect.

Note:
Be careful if you set the date during the period that a time zone is switching to daylight saving time (DST). When a time zone changes to DST, the local time goes back one hour (for example, 2:00 a.m. becomes 1:00 a.m.). The local time during this hour is ambiguous (e.g. 1:14 a.m. occurs twice in the morning that the time zone switches to DST). To avoid problems, use UTC time to set the date in this period.

Examples:

Update the current date and time from the hardware clock: 

rtc hw

Set hardware clock with current date and time: 

rtc -s hw

Exit status:

0
Successful.
>0
An error occurred.
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