IO error when configuring modem

Question

Hi, 
 I have a project where my nrf9160 is able to enable and get a fix with GPS and turn in on and off. I am trying to enable LTE when the GPS is off. Here is my procedure: 
 Enable GPS as is in the GPS sample. 
 Get GPS fix 
 Close GPS socket 
 Send AT command AT%XSYSTEMMODE=0,0,0,0 
 Send AT command AT%XSYSTEMMODE=1,0,0,0 
 call lte_lc_init_and_connect(); 
 
 Upon the last call, I get error code -5, and occasionally +CEREG: 5,"D113","03318501",7 as output. 
 What more must I do to deactivate GPS and activate LTE effectively? 
 
 Thanks.

jlienau03 · Accepted Answer

I think I solved it. By calling lte_lc_offline() (effectively AT+CFUN=4) before modem_configure, I was able to connect to LTE without error. I guess lte_lc_init_and_connect() expects the modem to be in this state before issuing its commands. Comments about this and other quirks in the lte_lc.c file would be nice. 
 
 For others experiencing this, this is now effectively my procedure: 
 1. Start Device 
 2. AT+CFUN=4, AT%XSYSTEMMODE=1,0,0,0, AT+CFUN=1 
 3. lte_lc_offline() (AT+CFUN=4) 
 4. modem_configure() 
 5. Do LTE stuff 
 6. AT+CFUN=4 
 7. init_app() as shown in the GPS sample (basically sets up the gps socket and sends "AT+CFUN=4", "AT%XSYSTEMMODE=0,0,1,0", "AT%XMAGPIO=1,0,0,1,1,1574,1577", "AT+CFUN=1") 
 8. Do GPS stuff 
 9. Disable GPS the way MJD093 does it 
 10. Continue

IO error when configuring modem

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