GPS antenna on SIM908 - Not Working

[mihirDG8]

I am using SIM908. I need to get GPS data and send it over GPRS. Since my size is very small, I have to use smallest possible antenna. My GSM and GPRS are working fine, but for GPS I am struggling.

I have on board AH316M157501 from Taiyo Yuden for GPS. Since this is chip antenna, I have kept GPS_VANT_IN and GPS_VANT_OUT floating. I am getting 0,0,0,0 when I try to read GPS co-ordinates. Can you pls. help me know the root cause?

 

[mihirDG8]

Following is the command sequence I followed for testing,.,,,

Code Sequence 1:

1) AT+CGPSPWR=1 (Turned On GPS Power Supply)
OK

2) AT+CGPSRST=1 (Reset GPS in autonomy mode)
OK

3) AT+CGPSINF=0
0,0.000000,0.000000,0.000000,20101010002259.000,0,0,0.000000,0.000000
OK

--------------------------------------------------------------------------------------------------------------------------------
Code Sequence 2:

1) AT+CGPSPWR=1 (Turned On GPS Power Supply)
OK

2) AT+CGPSRST=0 (Reset GPS in cold mode)
OK

3) AT+CGPSINF=0
0,0.000000,0.000000,0.000000,19800105235945.000,0,0,0.000000,0.000000
OK

 

[KaitooKid]

You try a new antenna.
This mudule SIM is unstable. you should test SIM outside greater than inside.
Or you re-test SIM, may be SIM have a problem.

 

[mihirDG8]

I removed my on board antenna connections and plugged Active antenna of 3-5V. I also connected battery supply to GPS_VANT_IN. But still I get "Location Unknown" and 0,0,0,0 as result.

I am stuck with this and do not find resolution. Pls. help.

 

[KaitooKid]

You try supply VBAT power mode.
After that you use command "AT+CGPSOUT=0" and this time,you use 2 pin GPS_TXD & GPS_RXD. Now, SIM wili leakage of the signal will and send to continous. You may be use Terminal and Comport uart to receive on PC to testing

 

[mihirDG8]

I am using Microcontroller UART port with 3.3V operation to communication with SIM908. The VBAT supply is kept standard mobile battery 3.7V. Also the same 3.7V is connected to GPS_VANT_IN. I am not using GPS_TXD/RXD pins. I only have master UART signals connected between SIM908 and Microcontroller. There is no computer com-port connection in complete testing.