Hardware Interface Description - KORE Telematics

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XT55/56 Hardware Interface Description Confidential / Released s 4.3 GPS operating modes Mode Normal operation Trickle Power mode Push-to-Fix mode Function The receiver is continuously running in Normal mode, as long as the operating voltage Vcc is supplied. Position fixes are generated at the maximum update rate. This enables the receiver a warm- and hotstart. However, the cold- and warmstart times of the receiver do not differ significantly under good visibility conditions. Vcc is continuously supplied to the receiver in Trickle Power mode. By using a especially configurable software, the user can force the receiver to acquire a position fix periodically. Between two fixes, the receiver will be in a low power mode. The power-on scenario in Trickle Power mode on the XT55/56 GPS part differs from one in continuous mode. If the receiver fails to acquire satellites within a given period of time (approx. 150 sec), the receiver enters an extended sleep phase. The duration of this sleep phase is approx. 30 sec. After that, the receiver wakes up, starts a reset and tries to acquire satellites. This procedure will be repeated until the GPS receiver can detect satellites. For further details refer to [1]. In this mode the receiver will turn on every 30 minutes to perform a system update consisting of a GPS RTC calibration and satellite ephemeris data collection if required (i.e. a new satellite has become visible) as well as all software tasks to support SnapSart in the event of an NMI. Ephemeris collection time in general takes 18 to 30 seconds. If ephemeris data is not required the system will recalibrate and shut down. In either case, the amount of time the receiver remains off will be in proportion to how long it stayed on: Off period = On Period*(1-Duty Cycle) Duty Cycle The off period has a possible range between 10 and 7200 seconds. The default is 1800 seconds. XT55/56_hd_v02.06a Page 72 of 125 17.12.2004
XT55/56 Hardware Interface Description Confidential / Released s 4.3.1 Trickle Power mode The default mode of XT55/56 GPS part is continuous mode, but the user can set the XT55/56 GPS part into the Trickle Power mode using the input command message. The XT55/56 GPS part enters the Trickle Power mode corresponding to Figure 27 (800ms OFF time and 200ms ON time) as soon as valid GPS data are available. As a result the average power consumption is reduced by approximately 80 % (approximately 150mW). The settings for the Trickle Power mode can be modified by using the SiRFstar demo software. For example if the XT55/56 GPS part is configured to enter the OnTime mode each 10s for a duration of 200ms the average power consumption can be reduced up to approx. 95% (approx. 15mW, ca. 4.8mA at Vcc=3.3V). For more details refer to [1]. Figure 27: Example for current in Trickle Power mode XT55/56_hd_v02.06a Page 73 of 125 17.12.2004
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Hardware Interface Description - KORE Telematics

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