Linx Technologies RXM-GPS-FM - Manual (Page 14)

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225 – Receiver Duty Cycle
This command places the module into a duty cycle where it stays on for
a period of time and calculates it position then goes to sleep for a period
of time. This conserves battery power without the need for an external
microcontroller to manage the timing.
This example sets the mode to duty cycle with an on time of 3s, and off
time of 12s, a cold start on time of 18s and a cold start off time of 72s.
$PMTK225,2,3000,12000,18000,72000*15<CR><LF>
The following example sets the mode to normal operation.
$PMTK225,0*2B<CR><LF>
The following example sets the module into AlwaysLocate TM mode.
$PMTK225,8*23<CR><LF>
Receiver Duty Cycle Command and Response
Command
Start Msg ID Mode
On
Time
Standby
Time
Cold On
Cold
Sleep
Checksum End
$PMTK 225 ,Mde ,TO ,TS ,CO ,CS *Cksum <CR><LF>
Response
Start Msg ID CMD Flag Checksum End
$PMTK 001 ,225 ,Flg *Cksum <CR><LF>
Figure 25: Receiver Duty Cycle Command and Response
Receiver Duty Cycle Fields
Field Description
Mde
Operation Mode
0 = Normal Mode
2 = Duty Cycle Mode
8 = AlwaysLocate
TM
TO Receiver on time (ms)
TS Receiver standby time (ms)
CO
Receiver on time in the event of a cold start (ms). Allows more time for
the module to receive ephemeris data in the event of a cold start.
CS
Receiver off time in the event of a cold start (ms). Allows more time for
the module to receive ephemeris data in the event of a cold start.
CR and CS can be null values. In this case the module uses the TO and TS values.
Figure 26: Receiver Duty Cycle Fields
223 – Extended Receive Time
This command extends the amount of time that the receiver is on when in
duty cycle mode. This allows the module to refresh its stored ephemeris
data by staying awake until it received the data from the satellites.
The following example configures an extended on time to trigger if less
than 1 satellite has valid ephemeris data. The satellite must have a signal to
noise ratio higher than 30dB–Hz in order to be used. The module will stay
on for 180,000ms and will have a gap time of 60,000ms.
$PMTK223,1,30,180000,60000*16<CR><LF>
Extended Receive Time Command and Response
Command
Start Msg ID SV
On
Time
Extend
Time
Extend
Gap
Checksum End
$PMTK 223 ,SV ,SNR ,EXT ,EXG *Cksum <CR><LF>
Response
Start Msg ID CMD Flag Checksum End
$PMTK 001 ,223 ,Flg *Cksum <CR><LF>
Figure 23: Extended Receive Time Command and Response
Extended Receive Time Fields
Field Description
SV
The minimum number of satellites required to have valid ephemeris data. The
extend time triggers when the number of satellites with valid ephemeris data
falls below this number. The value is 1 to 4.
SNR
The minimum SNR of the satellites used for a position fix. The module will not
wait for ephemeris data from any satellites whose SNR is below this value.
EXT
The extended time in ms to stay on to receive ephemeris data. This value can
range from 40000 to 180000.
EXG
The minimum time in ms between a subsequent extended receive period. This
value can range from 0 to 3600000.
Figure 24: Extended Receive Time Fields