Moxa W406-T-LX [62/74] Rtc real time clock

W315A/325A Linux User's Manual Programmer's Guide

6-3

RTC (Real Time Clock)

The RTC device node is located at /dev/rtc. The W315A/325A supports Linux standard simple RTC control.

You must

include <linux/rtc.h

1. Function: RTC_RD_TIME

int ioctl(fd, RTC_RD_TIME, struct rtc_time *time);

Description: read time information from RTC. It will return the value on argument 3.

2. Function: RTC_SET_TIME

int ioctl(fd, RTC_SET_TIME, struct rtc_time *time);

Description: set RTC time. Argument 3 will be passed to RTC.

Buzzer

The buzzer device node is located at /dev/console. The W315A/325A supports Linux standard buzzer control,

with the W315A/325A’s buzzer running at a fixed frequency of 100 Hz. You must

include <sys/kd.h

Function: KDMKTONE

ioctl(fd, KDMKTONE, unsigned int arg);

Description: The buzzer’s behavior is determined by the argument arg. The “high word” part of arg gives the

length of time the buzzer will sound, and the “low word” part gives the frequency.

The buzzer’s on/off behavior is controlled by software. If you call the “ioctl” function, you MUST set the

frequency at 100 Hz. If you use a different frequency, the system could crash.

WDT (Watch Dog Timer)

Introduction

The WDT works like a watchdog function. You can enable it or disable it. When the user enables WDT but the

application does not acknowledge it, the system will reboot. You can set the acknowledgement time from a

minimum of 50 msec up to a maximum of 60 seconds.

How to Enable the WDT

You will need to write your own application to enable the WDT function for the computer. Refer to the

following APIs to write the application.

The user API

The user application must include <moxadevic.h

, and link moxalib.a. A makefile example is shown

below:

all:

arm-linux-gcc –o xxxx xxxx.c -lmoxalib

int swtd_open(void)

Description: Opens the file handle to control the WDT. If you want to control the WDT, you must first call

this function and then use the file handle for other tasks.

Arguments: None

Return Value: The file handle; a negative number indicates that an error occurred.