EHS8 GPS antenna power always on ? | Telit Cinterion IoT Developer Community
July 1, 2017 - 12:10pm, 2442 views
To my surprise, the active GPS antenna I used for the first experiments with the EHS8 GPS worked right out of the box, even though the necessary settings were not made. That is, SCFG "GPIO/mode/GPSANT" was not set to "std" and SGSPC "Mode/Antenna" was 0 (passive). I even tried changing SGPSC "Power/Antenna" to "off", but whatever I do, there is always 3.3 V on the antenna. Restarting the ME does not change this. The GPS active antenna power seems to be always on.
So I am surprised and slightly confused... What could be the cause of this?
If we leave it at this, conclude that power will always be there and not bother setting it up properly, what will be the risc of future devices not showing this behavior?
Any comments would be welcome!, TIA!
Bart van Hofwegen, Colón Software Development
Hello,
Could you please write more details where you measure the 3.3V or paste some schematic?
ANT_GPS_PWR pin is an input for the antenna power and it should be supplied from the external source if needed. If unused it should be connected to GND. The GPIO12 pin that can be configured as switch for ANT_GPS_PWR with "GPIO/mode/GPSANT" should be connected to the external switch. Please also see the reference example design here https://iot-developer.thalesgroup.com/documentation/example-schematic-eh...
Best regards,
Bartłomiej
Hello Bartłomiej,
Thanks for the reply. I will have to check the design of the device, it is made by an external manufacturer. The function of GPIO12 is clear to me now, and is not the issue in this case. I restored the default settings (not GPSANT) and nothing changed.
Am I right to assume that when we have 3.3V on ANT_GPS_PWR, that ^SGPSC="Power/Antenna","off" should switch power off at the antenna (ANT_GPS)? The point is that it does not... the supply is always on. Neither does "Mode/Antenna" make any difference. And as mentioned, GPIO12 is not configured as GPSANT anymore.
Best regards,
Bart van Hofwegen
Hello,
I think that you should review the HW schematic. As ANT_GPS_PWR line is an input for external power source and not the output maybe your external circuit is supplying this 3.3V or it's from the inside of the module. You should rather measure on the antenna connector if the power is provided or not.
Please remember that changes to "Power/Antenna" parameter will take effect after reboot.
If you have the antenna power circuit connected to ANT_GPS_PWR and to GPIO12 for switching you should rather set the GPIO12 as antenna power switch with "GPIO/mode/GPSANT". If "Mode/Antenna" is set to 1 you should be able to switch the power on and off with "Power/Antenna".
Regards,
Bartłomiej
Hi and thanks,
I understand fully what you mean regarding ANT_GPS_PWR being an input, and we do measure at the GPS antenna connector (ANT_GPS). There is always 3.3V there, whatever setting of ^SGPSC Mode/Antenna or Power/Antenna we use, with ot without restarting. But since you have confirmed that Power/Antenna should work, I will check the manufacturer of the device for the schematic. Maybe 3.3V is supplied directly on the antenna connector and bypassing the EHS8 functionality for this.
Regards, Bart
OK,
Please write if there is anything new.
Regards,
Bartłomiej