Western Jack ground and GPIO ground | Telit Cinterion IoT Developer Community
December 16, 2016 - 11:09pm, 2256 views
Hello,
I would like to confirm if the western jack connector's ground is internally connected to the ground on the GPIO. We are concerned because the GPIO has a limit of 100mA thus if we do not connect the western jack ground could that cause the module to reboot, especially during transmission bursts?
To put the question in an other way is it safe NOT to connect ground on the RJ connector?
We are looking for confirmation because the module can draw more than 100mA via the western jack and we are not sure if this may cause reboots since the ground on GPIO can only draw 100mA.
Thank you.
Hello,
These two grounds are connected so it is possible not to connect one of them.
The 100mA limit is for plus circuit.
Regards,
Bartłomiej
Hello,
We appriciate the answer.
I would like to comment however that the western jack has been causing lots of problems. The old modules we used in the past (TC65) did not have any problems with faulty connections because everything was connected via the GPIO. Even with appropriate tools and cables the western jack seems problematic. We cannot use the standard wall adapter and are forced to crimp our own cables because of the system is powered by solar panels/batteries.
I leave this comment to inform you, I don't know if you have been receiving complaints from other users regarding the western jack. Also, another change from the TC65 that is causing us headaches is the lack of a way to power the internal RTC with an external battery. The old module had a line on the GPIO that we could connect to a battery so in case of power outage the time is maintained. Because of this change we are forced to implement an external RTC which adds complexity to the circut and code because the code now has to synchronize and determine which RTC is most "valid".
Thank you for you help.
Hello,
Thank you for your opinion.
I personally don't remember complains about western jack but I also haven't been searching the databases for that.
You are right that there is no separate pin for powering the RTC (like there was one in TC65 terminal) while the main power is off.
You would need not to cut off the power to have the RTC working but in case of batteries as power source you might not wat to do this.
The alternative would be to synchronize the time on start with NTP for example or just with the network (network dependent - some networks might not support this) which is generally recommended as the accuracy of the module's RTC is not very high.
Regards,
Bartłomiej