Concept Board, Send SMS when power shuts down | Telit Cinterion IoT Developer Community
October 17, 2017 - 10:24am, 5027 views
Hello,
I would like to create an application, that sends an SMS to inform the user that the power supply on which the concept board is attached too, has shut down. My initial thought was to connect a condenser that can read the current in the A/D converter, and when that value reaches zero, it starts the "send SMS" application. However, i have not been able to find the pins for the A/D(by this i mean the Vbatt+ and Vbatt-). Have i simply missed them in the schematics or are they not available, and if not, is there another way to construct this application?
Thankfull for any help, Willie
Hello,
You should get undervoltage URC if the average supply voltage falls below below some configured threshold. But in this case that might happen that there is a short voltage drop below the lower limit of 3.3V which should not happen.
To be sure if it does not happen you could connect the oscilloscope directly to the BATT+ pads of the module (there are 2 of them) - they are on the edge of the module and you can access the soldering points on the concept board. There is a drowing and table with pads in the modules hardware description where you can find which pads you need to connect to.
Regards,
Bartłomiej
Hello,
I did a number of tests with the oscillioscope and they each had one of two possible outcomes.
Scenario 1: The voltage on the BATT+ pad (i.e my capacitor) is around 4V when the USB is plugged in. After i remove the main power consumption the board is still online, the oscillioscope shows that the voltage decreases steadily, no drops. At around 3.3V the board dies.
Scenario 2. Everything is the same as in scenario 1 until i remove the main power suply, the board instantaniously dies, the voltage level on the oscillioscope still shows ~4V. When i manually turn the power on again, the voltage is slowly decreasing.
There was never any major voltage drops in any scenario. However, i noticed that the capacitor never discharges entierly, after the module dies the voltage stays around ~3V.
The conclussions i can draw is that there is either something hardcoded or wrong with the board, which shuts down the board once the main power supply is removed. Or that the failure to discharge the capacitor somehow causes this error. I have little faith in both of my conclussions but i am running out of ideas. Does this information say anything to you?
Regards, Willie
Hello,
I think that we cannot exclude that this might have something to do with the developer board design as it was probably not designed for such a scenario.
There is some boder volatge for the module to work (3.3V) and below that it will die - so the capacitor may not discharge completely.
Have you been measuring the BATT+ voltage directly on the module as I suggested and have you checked that there wasn't any drop even very short one?
Regards,
Bartłomiej
Hello,
I am also starting to belive that there is some hidden saftey feature which is causing trouble. My colleague completed a similiar scenario on the TC65i so unless the board itself is hindering it, it should be doable.
I measued the BATT+ lines as instructed and could not detect any drops. I did the test atleast 10 ***** so i belive that is not the issue.
Regards, Willie
Hello,
So it's getting more complicated. Have you managed to connect serial interface to the pins on Concept Board and not via FTDI chip and USB? That would give you an opportynity to see the AT interpreter output at the moment when you disconnect USB cable and maybe you could see some URC. You might also try to check some other lines like VCORE and V180.
If you're stuck we can try to test this scenario on Monday.
Regards,
Bartłomiej
Hello,
connecting a RS232 on the tx/rx did not accomplish anything, the LEDs would light up when the USB cable was removed, but it did not produce any URCs.
Do you mean that i should connect the ADC to VCORE/V180? If you could successfully create this application with a battery/capacitor that would be very be reassuring.
Regards, Willie
Hello,
I've done a similar test with a battery. Unfortunately I've got the same result - when I disconnect the USB cable the module shuts down. Then I can switch it on and it works on the battery. For now I don't know why and I can't see any workaround. This scenario is possible to implement in a real life in a HW project but for some reason on Concept Board it does not work like that. There is already some hardware implemented and you can't change it.
Best regards,
Bartłomiej
That is very unfortunate, anyway, thanks for your help!
Regards, Willie