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By AshanG

I'm using a SARA R4 NB-IOT/CAT M1 shield with an Arduino Uno. I have used TCP_Send_Hologram example to send data to the Hologram dashboard and it works fine. But the problem I'm having is that the module turns itself OFF sometimes and won't turn ON when I try to send a message.

The hookup guide says "The library is designed to toggle the POWER pin if the shield is not communicating, so you may be able to avoid pressing this button at all".

Is there a way to toggle the POWER pin again (without pressing power button) when sending a message or to keep it ON without toggling the POWER pin OFF?
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By TS-Chris
Hello AshanG. Thanks for you post.

I've not seen this behavior before, but an easy way to toggle the power for the SARA module would be to drive Arduino pin D5 low for 3200ms then set D5 as an input. Something like the code below should do the trick.
Code: Select all
    pinMode(5, OUTPUT);      //Make D5 an output pin. (High or Low)
    digitalWrite(5, LOW);    //Drive D5 low.
    delay(3200);             //Wait 3200ms
    pinMode(5, INPUT);       // Return D5 to high-impedance, (rely on SARA module internal pull-up)
User avatar
By AshanG
Hi TS-Chris

I tried doing it but no luck with that. I just realized I may have explained this incorrectly. I'm actually talking about the blue light indicator. I thought the blue light wont stay ON becuause the module won't stay ON. But there could be other reasons for that. I'm not using the on board chip antenna; I'm using a UFL to SMA connector to connect to an external antenna. I observed this behaviour since the day I bought this module. I checked the RF path with the help of a RF engineer, it seems to be fine. It will stay ON for a bit of time, loses connectivity and connects again but won't send any data thereafter. When ever this happens RSSI goes to -1. Is there any reason why RSSI could go to -1? According to the Ublock module datasheet RSSI should stay between 0-31 or if not connected it should be 99. I can upload a video if that helps to understand this behaviour.
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By TS-Chris
Hi again AshanG.

The blue LED indicates a connection to the cellular network and would go out when you lose connection. I'm not sure what a -1 RSSI means, but if you're getting that at the same time you're seeing the blue LED go out, it would seem that your either experiencing some sort of interference or your signal strength is low enough that you're losing connection with the network.

The only thing I can think of would be to try getting closer to the tower you're connecting to to see if that resolves the issue. If it does, a different external antenna with more gain might be needed.
User avatar
By AshanG
Hi TS-Chris,

I found the issue with the module. The power-saving mode has enabled in the module. When I disabled it using AT+CPSMS=0, it started to work normally. But I would like to use power saving mode for future applications. I initially thought the module wakes up whenever there is a message to be send. But it doesn't seem to be doing that.