April 24, 2014 - 8:08pm, 3422 views
The EHS5-US has an RTC that is active even in the lowest power mode. I can't find much information about this RTC functionality. Is it possible to set an alarm with this RTC and have either wake up the module or throw a GPIO high/low?
you can set alarms triggered by RTC with AT+CALA command. There is no build-in option to toggle GPIO on alarm, the expiration is announced by dispatching an URC. You can set an alarm and disable the module with AT^SMSO - the module will enable itself and an URC will be displayed when the module will be back on.
This functionality works also in airplane mode and with power saving enabled on UART interface.
Hope my guidance will help you.
Thank you Jedrzej.
My application involves using a RTC for waking up our microcontroller at specific times (by using an alarm on the RTC that throws an interrupt pin on the microcontoller). I'm trying to determine if I can reduce my BOM cost by using the EHS5's internal RTC to perform this function.
I cannot find any information about AT+CALA in the datasheets. Where can I find information on this AT command?
please check updated documentation page.
Familiarize with following solutions for your application:
1. Connect your external microcontroller's ignition/wake-up pin to module's power indication circuit (check example circuit in Hardware Description documentation) so start of the module triggers microcontroller to wake up. Now you can setup an alarm and power down the module - indication goes down. It will go back up on alarm expiration and your microcontroller will be woken up.
2. Configure RING0 line to blink on URC appearance with AT^SCFG and connect it to uC's ignition pin. Alarm expiration triggers +CALA URC, which triggers RING0 indication of URCs, which wakes your microcontroller up. This solution is superior to above as changes on ringline may be observed without powering down EHS5, so you can exclusively power down only your uC without powering down the module.
Remember that in such setup all URCs will cause ringline to blink, which in dependence on your setup may be wanted or unwanted behavior.
3. Implement Java MIDlet that switches gpio according to your needs and put it in EHS5 autostart. Set alarm within the MIDlet using ATCommand class and put the module into power down state. When the module powers up on alarm expiration, your MIDlet will start.
Hope you'll find my advices helpful.
Does the above also apply to the EHS6?
Yes, it does.
© 2013-2014 Gemalto M2M GmbH