SDX55 AT Commands Cheatsheet

Qualcomm SDX55 AT Commands Cheatsheet

A complete reference guide for querying, diagnosing, and configuring Qualcomm Snapdragon X55 (SDX55) 5G modems over the serial diagnostic/AT interface (/dev/smd7 on embedded Linux, or /dev/ttyUSB2 on external hosts).

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1. Device Identification & Diagnostics

Command	Purpose	Example Output
ATI	Module model, manufacturer & revision	Manufacturer: Tri Cascade Inc.\nModel: SG500M2-X
AT+CGMM	Model number	SG500M2-X or RM500Q-GL
AT+CGMR	Baseband firmware revision	RXMG1.20.00.326_0R05
AT+CGSN	Device IMEI	860000000000000
AT+CPIN?	SIM PIN status	+CPIN: READY or +CPIN: SIM PIN
AT+CCID	SIM Card ICCID	+CCID: 8991860000000000000F
AT+CIMI	International Mobile Subscriber Identity (IMSI)	404450000000000

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2. Radio Signal Metrics & Conversion

Command	Purpose	Output Format / Notes
AT+CSQ	Basic signal quality	<rssi>,<ber>. Formula: $\text{dBm} = (\text{rssi} \times 2) - 113$
AT+CESQ	Extended 3GPP signal metrics	Returns 9 fields. Indices 7, 8, 9 contain 5G NR metrics
AT$QCRSRP?	Qualcomm LTE signal & EARFCN	Returns EARFCN, Physical Cell ID (PCI), RSRP per carrier
AT+NRCAINFO	5G NR Carrier Aggregation info	Reports Primary (PCC) and Secondary (SCC) 5G bands

AT+CESQ Index Calculation Reference:

+CESQ: <rxlev>,<ber>,<rscp>,<ecno>,<rsrq>,<rsrp>,<nr_rsrq>,<nr_rsrp>,<nr_sinr>

• LTE RSRP (Field 6): $$\text{RSRP (dBm)} = \text{Index} - 140$$ (Index 45 $\rightarrow -95\text{ dBm}$)
• LTE RSRQ (Field 5): $$\text{RSRQ (dB)} = (\text{Index} \times 0.5) - 19.5$$
• 5G NR RSRP (Field 8): $$\text{NR RSRP (dBm)} = \text{Index} - 156$$ (Index 66 $\rightarrow -90\text{ dBm}$)
• 5G NR SINR (Field 9): $$\text{NR SINR (dB)} = (\text{Index} \times 0.5) - 23$$ (Index 80 $\rightarrow +17\text{ dB}$)

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3. Network Registration & Dual Connectivity

Command	Purpose	Output Interpretation
AT+COPS?	Current operator & access tech	+COPS: 0,0,"Jio",11 (11 = 5G SA)
AT+COPS=?	Scan all available networks	Long timeout (up to 60s). Scans 2G, 4G, 5G
AT+CEREG?	EPS registration status	Status 1 (Home Registered) or 5 (Roaming)
AT+CEREG=2;+CEREG?;+CEREG=0	Full registration with Act	Act 7 = 4G, 11 = 5G SA, 13 = 5G NSA (EN-DC)
AT+CGCONTRDP	Active PDP context details	Current APN, assigned IPv4, IPv6, and carrier DNS

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4. Band Locking & RAT Selection

Network Preferred Mode:

# Set to Auto (5G SA / 5G NSA / 4G LTE)
AT+QNWPREFCFG="mode_pref",AUTO

# Lock to 5G Standalone (SA) only
AT+QNWPREFCFG="mode_pref",NR5G

# Lock to 4G LTE only
AT+QNWPREFCFG="mode_pref",LTE

5G NR Band Masking:

# Query active 5G NR band mask
AT+QNWPREFCFG="nr5g_band"

# Lock to Band n78 (3500 MHz TDD)
AT+QNWPREFCFG="nr5g_band",78

# Lock to Band n28 (700 MHz FDD)
AT+QNWPREFCFG="nr5g_band",28

4G LTE Band Masking:

# Query active LTE band mask
AT+QNWPREFCFG="lte_band"

# Lock to Band 3 (1800 MHz) and Band 40 (2300 MHz)
AT+QNWPREFCFG="lte_band",3:40

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5. SMS & USSD Commands

Command	Purpose	Example / Notes
AT+CMGF=1	Switch SMS to Text Mode	Standard ASCII readability
AT+CPMS="SM","SM","SM"	Select SIM storage memory	Direct SIM memory read/write
AT+CMGL="ALL"	List all stored SMS	Returns index, sender, timestamp, body
AT+CMGD=<index>	Delete SMS message	AT+CMGD=1 (deletes index 1)
AT+CUSD=1,"*121#",15	Send USSD query code	Used for balance and plan queries

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6. Baseband Power & Reset Controls

Warning

Use reset commands judiciously. Resetting restarts the cellular link and causes a temporary loss of internet connectivity.

Command	Purpose	Effect
AT+CFUN=0	Airplane mode	Cuts RF transmit power and disconnects
AT+CFUN=1	Online mode	Powers on RF transceivers and registers on network
AT+CFUN=1,1	Warm baseband reset	Restarts baseband cellular DSP processor
AT+QRST=1	Hardware reset trigger	Reboots whole modem module

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Next Step: Learn how Fresnel scripts automate these commands in Internal Scripts & Architecture.