Receiving SMS message less that 160 Characters


#1

Hi, I have made an alpha numeric pager I am using the following hardware.

  1. hologram sim card - professional account
  2. sim800l
  3. arduino nano

I am able to send messages to the device but they are either cut off or garbled.
Ex:
Received message: The quick brown fox jmsoertelz dg sanEgihlagae aga
Sent Message: The quick brown fox jumps over the lazy dog

I should add, I am monitoring received sms via the serial monitor.

This happens when I send the message from my phone and from the dash board. I am running the KitchenSink sketch from the hologram github page.

are there settings in the sketch that I need to add in order to increase the buffer so that I can receive the full 160 characters? or is there some other hardware limitation that I am unaware of?


#2

Are you level shifting or otherwise protecting / adjusting the digital voltage between the nano and the sim800l?

The nano Digital IO runs at 3.3V the sim800L runs at 2.8V (Note the sim800L takes ~4V input and internally converts to 2.8V for the serial communication). If you are plugging the two in directly you are operating out of specification and that may be why you are not getting valid data.

Also check your baud rates, also check your grounding between the devices make sure each device is using the same ground and the connections are good. I suspect this is a serial communication issue not a cellular issue.


#3

@AndrewGifft I am connected to the nana directly on the sim800L but via lipo on power. I am not level shifting, could I do this via a diode rather than some specialty circuit? please advise.
Agreed this is definitely a serial communication issue.
Also If I use the v2 5v module does the same level shifting for serial apply?

Regards.


#4

see this thread: Arduino UNO and SIM800L


#5

great info I have that level shifter module as it happens thanks


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