Receiving text messages with ZTE MF831 not working

Question

I got myself a ZTE MF831 modem to do some automations over text messages. I changed the mode to factory mode, so I can send instructions over /dev/ttyUSB2 115200 (using screen or node with serialport).

Sending text messages works just fine. I receive the text on my personal phone. But when I send a message back (already sent several) I cannot read them. The folders on my modem are always empty. Even though I receive a notification like +CMTI: ME,0.

These are the commands I send:

ATZ           -> OK
AT+CMGF=1     -> OK
AT+CPMS=?
  -> +CPMS: ("ME","MT","SM","SR"),("ME","MT","SM","SR"),("ME","MT","SM","SR")
  -> OK

AT+CPMS="SM"  -> +CPMS: 0,20,0,100,0,100
              -> OK
AT+CMGL="ALL" -> OK

AT+CPMS="ME"  -> +CPMS: 0,100,0,100,0,100
              -> OK
AT+CMGL="ALL" -> OK

AT+CPMS="MT"  -> +CPMS: 0,100,0,100,0,100
              -> OK
AT+CMGL="ALL" -> OK

AT+CPMS="SR"  -> +CPMS: 0,100,0,100,0,100
              -> OK
AT+CMGL="ALL" -> +CMS ERROR: 500

As you can see, there is always no text available. So I swapped my SIM card to another phone and tried again: I receive messages indeed.

What am I doing wrong?

Answer 1

Ok, I tested a little further and realized that when sending AT+CPMS=? I receive

+CPMS: ("ME","MT","SM","SR"),("ME","MT","SM","SR"),("ME","MT","SM","SR")

That tells me that I can set 3 preferred folders (since there are 3 bracket blocks).

So I thought, I set all to "SM":

AT+CPMS="SM","SM","SM"

I then flush the thing with ATZ and AT (I don't know which one actually does this).

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Now when I receive a text I see +CMTI: SM,<old used space>.