Link RING0 from EHS5-E modem to GPIO4 pin of an RPi3 | Telit Cinterion IoT Developer Community
May 17, 2016 - 10:00pm, 2720 views
Hi
I am trying to use RING0 in order to get notifications when an SMS arrives. The modem is connnected through USB with an RPi# and I am trying to use a wire between RING0 pin and a GPIO pin of the RPi in order to get notifications from modem (RING0 is put on low). I would like to know if it is enough to use a simple wire between these pins or a pull up resistor should be used.
thanks
Bogdan
Hi Bogdan,
EHS5-E RING0- signal has an internal pullup resistor. You can connect the line directly, assuming that
the signal levels in the RPi are the same.
The RING0 -signal will be active low during startup.
Best Regards,
Antero
Antero Markkula
Communication and Mechatronics
Enkom Active Oy – www.enkom-active.fi
Upseerinkatu 3 A, 02600 Espoo, Finland
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E-mail: antero.markkula@enkom-active.fi
Hello,
There are different voltage levels used by module's RING0 and RPI's GPIO. According to the documentation the high state level is greater than 1.3V on RING0 while on RPI it's around 3.3V. So some level converter would be needed to properly detect the RING0 state on RPI.
Regards,
Bartłomiej
Bartlomiej, Antero, I really appreciate your prompt response for this inquery and a previous one i had a couple of weeks ago.
Bartlomiej, I have persued the documentation and i am unable to find that the output voltage for RING0 is greater then 1.3V. I am not doubting your statement (and it actually makes sense since the interrupt service routine works "some of the *****" only).
I need to find it in the documentation to justify an architecture change for management.
thanks again guys
Hello,
This is described in Hardware Interface Description document for EHS5 module (Table 2: Signal properties).
Do you have this document?
Regards,
Bartłomiej
Hi
I have just noticed that there are actually 2 RING0 pins: one is located on the development board and the other one is on the modem board (the smaller one located on top of the development board). However the voltages that I read on these pins are different: on the modem board I get 1.8V, while on the development board I get 2.5 V. According to the documentation RING0 pin should have 1.8V, so what is the other pin for ?
thanks
Bogdan
Hello,
Could you describe in more details what type of development board and modem board you are using?
The voltages described in the hardware description for the module are valid for the module. So if the module is placed on some developer board the documentation for the board should probably answer this question. Maybe there's some additional circuit connected to the line.
Regards,
Bartłomiej