Documentation Index
Fetch the complete documentation index at: https://docs.hologram.io/llms.txt
Use this file to discover all available pages before exploring further.
Overview
AT commands help you diagnose connectivity, SIM, registration, signal, and SMS issues. This reference includes standard 3GPP commands and vendor variations with example outputs and actions.
Note: Responses vary by vendor and firmware. Use vendor AT manuals in parallel.
1. AT - Basic connectivity check
| Response | Meaning | Next steps |
|---|
| OK | Modem responsive | — |
| ERROR | Not responding to basic cmd | Check serial, baud, power |
| No response | Host not connected | Verify hardware |
2. Identify device: ATI / +CGMI / +CGMM / +CGMR / +CGSN / +GSN
ATI
AT+CGMI
AT+CGMM
AT+CGMR
AT+CGSN
AT+GSN
ATI
Quectel
BG96
Revision: BG96MAR02A07M1G
OK
3. +CPIN? - SIM status
| Response | Meaning | Next steps |
|---|
| +CPIN: READY | SIM detected and unlocked | — |
| +CPIN: SIM PIN | PIN required | Enter with AT+CPIN=“xxxx” |
| +CPIN: SIM PUK | SIM blocked | Contact SIM provider |
| +CPIN: NOT INSERTED | SIM not detected | Check tray/orientation |
| +CPIN: SIM FAILURE | SIM unreadable | Try another SIM |
| +CPIN: PH-SIM PIN | SIM network lock | Unlock with carrier code |
4. +CCID - ICCID retrieval
+CCID: 894450XXXXXXXXXXXXXX
OK
5. +CREG? / +CGREG? / +CEREG? - Registration status
AT+CREG?
AT+CGREG?
AT+CEREG?
| Stat | Meaning | Common causes | Next steps |
|---|
| 0 | Not registered | Modem off, antenna issue | AT+CFUN=1, check +CPIN? |
| 1 | Registered (home) | Normal | — |
| 2 | Searching | Scanning | Wait / relocate |
| 3 | Registration denied | SIM blocked or wrong RAT | Check SIM/APN |
| 4 | Unknown | Transient | Retry |
| 5 | Registered (roaming) | Normal for global SIMs | — |
| 8 | Emergency only | Weak coverage | Move |
6. +COPS - Operator selection
AT+COPS?
AT+COPS=?
AT+COPS=mode,format,oper,AcT
- Modes: 0 Auto, 1 Manual, 2 Deregister, 4 Manual/auto fallback
- Formats: 0 Long name, 1 Short name, 2 Numeric MCCMNC
- AcT: 0 GSM, 2 UTRAN, 7 LTE, 8 LTE-M, 9 NB-IoT
+COPS: 0,0,"T-Mobile",8
+COPS: 1,2,"310260",7
7. +CSQ - Signal strength
| RSSI | dBm | Meaning | Action |
|---|
| 0 | ≤ -113 | No signal | Check antenna |
| 1-9 | -111 to -93 | Very weak | Relocate |
| 10-14 | -91 to -81 | Weak | Expect drops |
| 15-19 | -79 to -69 | Fair | May drop |
| 20-24 | -67 to -57 | Good | — |
| 25-30 | -55 to -45 | Strong | — |
| 31 | ≥ -51 | Excellent | — |
| 99 | Unknown | Not camped | Check registration |
8. +CESQ - Extended signal quality
- RSRP (dBm) = -140 + rsrp
- RSRQ (dB) = -19.5 + (rsrq × 0.5)
9. +CGATT / +CGACT - Attach and activate PDP
AT+CGATT?
AT+CGATT=1
AT+CGACT?
AT+CGACT=1,1
| Response | Meaning | Next steps |
|---|
| +CGATT: 1 | Attached | — |
| +CGATT: 0 | Not attached | Check SIM, signal, registration |
10. +CGDCONT - Define PDP context
AT+CGDCONT=<cid>,"<PDP_type>","<APN>"
AT+CGDCONT=1,"IP","hologram"
11. +CNMI - New SMS indication
AT+CNMI=<mode>,<mt>,<bm>,<ds>,<bfr>
| Mode | Meaning |
|---|
| 0 | PDU (raw hex) |
| 1 | Text (human-readable) |
13. +CSCA - SMSC address
AT+CSCA?
AT+CSCA="<SMSC_number>",<type>
14. +CMGS - Send SMS
AT+CMGF=1
AT+CMGS="+1234567890"
>Hello World<CTRL+Z>
+CMGS: 45
OK
15. +CME ERROR - Equipment errors
+CME ERROR: 10 // SIM not inserted
+CME ERROR: 30 // No network service
16. +CMS ERROR - SMS errors
+CMS ERROR: 1 // Unassigned number
+CMS ERROR: 27 // Invalid SMSC
17. +CFUN - Functionality level
AT+CFUN?
AT+CFUN=<fun>[,<rst>]
18. +CGEREP - Packet domain event reporting
19. +CGPADDR - Show PDP address
20. +CGCONTRDP - Read PDP context parameters
21. +COPS=? - Network scan
+COPS: (1,"T-Mobile","TMO","310260",8),
(1,"AT&T","ATT","310410",7)
22. +CSCON - RRC connection status
23. +CEDRXS / +CPSMS - Power saving modes
AT+CEDRXS=<mode>,<AcT_type>,<eDRX_value>
AT+CPSMS=<mode>[,<Requested_PeriodicTAU>,<Requested_Active_Time>]
24. 3GPP reject cause codes
| Code | Meaning | Action |
|---|
| 2 | IMSI unknown | SIM not active |
| 3 | Illegal MS | Contact provider |
| 7 | GPRS not allowed | SIM plan issue |
| 15 | No suitable cells | Move/check bands |
| 33 | Service option unsupported | APN issue |
| 40 | No EPS bearer | LTE network problem |
Appendix - Vendor-specific commands
Quectel
- AT+QNWINFO - Network & RAT info
- AT+QENG=“servingcell” - Serving cell
- AT+QCSQ - Extended signal
- AT+QCFG - RAT/band selection
SIMCom
- AT+CSERVINFO - Service info
- AT+CNETSCAN - Scan with metrics
- AT+CSQEXT - Extended CSQ
u-blox
- AT+URAT - RAT selection
- AT+UBANDMASK - Band mask
- AT+UCGED - Cell info
