Hi Maynard,
I seem to have made some progress. It looks like a problem with the initialization of the modem.
>>[214] AT READY
<<ATE0
>>[160] ATE0
>>[160] OK
<<AT+CGMI
>>[161] MeiG
>>[161] OK
<<AT+CGMM
>>[162] SLM320PE_TK
>>[162] OK
<<AT+CGMR
>>[163] SLM320PE_TK_V51_U03
>>[163] OK
<<AT+IPR=921600
>>[159] OK
<<AT+CMEE=2
>>[117] OK
<<AT+CGMR
>>[164] SLM320PE_TK_V51_U03
>>[164] OK
<<AT+CGSN
>>[104] 866907058069310
>>[104] OK
<<AT+CSQ
>>[129] +CSQ: 99,0
>>[129] OK
<<AT+QCCID
>>[110] +QCCID: 8942102480007879766F
>>[110] OK
<<AT^CPINC
>>[105] ^CPINC:3,10,3,10
>>[105] OK
<<AT+CLCK="SC",2
>>[119] +CLCK: 1
>>[119] OK
<<AT+CPIN?
>>[106] +CPIN: SIM PIN
>>[106] OK
<<****
>>[144] OK
<<AT+CREG=2
>>[111] OK
<<AT+CREG?
>>[137] +CREG: 2,3,"001a","8d2f",0
>>[137] OK
<<AT+SIM=0
>>[122] +SIM: ABSENT
>>[214] OK
<<AT+CSTT?
>>[184] +CSTT: "","",""
>>[184] OK
<<AT+CSTT="internet","",""
>>[184] OK
>>[214] +SIM Ready
>>[214] +CREG: 2,1,"001a","00013201",7
<<ATE0
>>[160] OK
<<AT+CGMI
>>[161] MeiG
>>[161] OK
<<AT+CGMM
>>[162] SLM320PE_TK
>>[162] OK
<<AT+CGMR
>>[163] SLM320PE_TK_V51_U03
>>[163] OK
<<AT+IPR=921600
>>[159] OK
<<AT+CMEE=2
>>[117] OK
<<AT+CGMR
>>[164] SLM320PE_TK_V51_U03
>>[164] OK
<<AT+CGSN
>>[104] 866907058069310
>>[104] OK
<<AT+CSQ
>>[129] +CSQ: 30,99
>>[129] OK
<<AT+QCCID
>>[110] +QCCID: 8942102480007879766F
>>[110] OK
<<AT^CPINC
>>[105] ^CPINC:3,10,3,10
>>[105] OK
<<AT+CLCK="SC",2
>>[119] +CLCK: 1
>>[119] OK
<<AT+CPIN?
>>[106] +CPIN: READY
>>[106] OK
<<AT+CREG=2
>>[111] OK
<<AT+CREG?
>>[137] +CREG: 2,1,"001a","00013201",7
>>[137] OK
<<AT+SIM=0
>>[122] +USIM: NORMAL
>>[122] OK
<<AT+CTZU=1
>>[176] OK
<<AT+CTZR=2
>>[177] OK
<<AT+COPS=3,2
>>[121] OK
<<AT+COPS?
>>[112] +COPS: 0,2,"23102",7
>>[112] OK
<<AT+QLTS=1
>>[183] +QLTS: "2022/07/23,19:34:01+08,1"
>>[183] OK
<<AT+CIMI
>>[168] 231020108909508
>>[168] OK
<<AT+CGEREP=1,1
>>[169] OK
<<AT+CLIP=1
>>[113] OK
<<AT+IFC=2,2
>>[172] OK
<<ATS0=0
>>[173] OK
<<AT+CIPSRIP=1
>>[203] OK
<<AT+CIPMUX=1
>>[204] +CME ERROR: parameters are invalid
<<AT+CIPMUX=1
>>[214] +CME ERROR: parameters are invalid
<<AT+CIPMUX=1
>>[214] +CME ERROR: parameters are invalid
<<AT+QNWINFO
>>[131] +QNWINFO: "FDD LTE","23102","LTE BAND 3",1650
>>[131] OK
<<ATE0
>>[160] OK
<<AT+CGMI
>>[161] MeiG
>>[161] OK
<<AT+CGMM
>>[162] SLM320PE_TK
>>[162] OK
<<AT+CGMR
>>[163] SLM320PE_TK_V51_U03
>>[163] OK
<<AT+IPR=921600
>>[159] OK
<<AT+CMEE=2
>>[117] OK
<<AT+CGMR
>>[164] SLM320PE_TK_V51_U03
>>[164] OK
<<AT+CGSN
>>[104] 866907058069310
>>[104] OK
<<AT+CSQ
>>[129] +CSQ: 30,99
>>[129] OK
<<AT+QCCID
>>[110] +QCCID: 8942102480007879766F
>>[110] OK
<<AT^CPINC
>>[105] ^CPINC:3,10,3,10
>>[105] OK
<<AT+CLCK="SC",2
>>[119] +CLCK: 1
>>[119] OK
<<AT+CPIN?
>>[106] +CPIN: READY
>>[106] OK
<<AT+CREG=2
>>[111] OK
<<AT+CREG?
>>[137] +CREG: 2,1,"001a","00013201",7
>>[137] OK
<<AT+SIM=0
>>[122] +USIM: NORMAL
>>[122] OK
<<AT+CTZU=1
>>[176] OK
<<AT+CTZR=2
>>[177] OK
<<AT+COPS=3,2
>>[121] OK
<<AT+COPS?
>>[112] +COPS: 0,2,"23102",7
>>[112] OK
<<AT+QLTS=1
>>[183] +QLTS: "2022/07/23,19:34:06+08,1"
>>[183] OK
<<AT+CIMI
>>[168] 231020108909508
>>[168] OK
<<AT+CGEREP=1,1
>>[169] OK
<<AT+CLIP=1
>>[113] OK
<<AT+IFC=2,2
>>[172] OK
<<ATS0=0
>>[173] OK
<<AT+CIPSRIP=1
>>[203] OK
<<AT+CIPMUX=1
>>[204] +CME ERROR: parameters are invalid
<<AT+CIPMUX=1
>>[214] +CME ERROR: parameters are invalid
<<AT+CIPMUX=1
>>[214] +CME ERROR: parameters are invalid
>>[214] +CREG: 2,1,"001a","00013203",7
<<AT+QNWINFO
>>[131] +QNWINFO: "FDD LTE","23102","LTE BAND 3",1650
>>[131] OK
<<ATE0
>>[160] OK
<<AT+CGMI
>>[161] MeiG
>>[161] OK
...
When I removed the PIN from the sim card, the problem did not recur. I will continue to monitor the situation.
regards
Miro