Problem Recieving SMS from RC7620-1

IoT Modules
1

I am having problems receiving SMS from the RC modems. Sending SMS goes well, data connection is great. I get the unsolicited result code +CMTI with index, but when I try to read from that index I get CMS error 321.

+CMTI: "ME",15
 
AT+CMGR=15

+CMS ERROR: 321

I looked up this error and it means the memory index is invalid.

The !GSTATUS? command shows:

AT!GSTATUS?

!GSTATUS:
Current Time:  18               Temperature: 28
Modem Mitigate Level: 0         ModemProc Mitigate Level: 0    
Reset Counter: 1                Mode:        ONLINE        
System mode:   LTE              PS state:    Attached    
IMS reg state: NOT REGISTERED   IMS mode:    Normal      
IMS Srv State: NO SMS,NO VoIP         
LTE band:      B20              LTE bw:      20 MHz 
LTE Rx chan:   6250             LTE Tx chan: 24250
LTE CA state:  INACTIVE   
EMM state:     Registered       Normal Service
RRC state:     RRC Connected

PCC RxM RSSI:  -47              RSRP (dBm):  -74
PCC RxD RSSI:  -90              RSRP (dBm):  -118
Tx Power:      –               TAC:         1DBC (7612)
RSRQ (dB):     -7               Cell ID:     000D6107 (876807)
SINR (dB):     11.8

I was able to use the same SIM card with the HL7802 modem without any issues to receive SMS.

2

What if you delete all old sms in “ME” by at+cmgd command

4

Seems to work. I will test with a second unit to confirm

AT+CMGF=1

OK

AT+CMGD=1,4

OK

+CMTI: "ME",0
SMS received CMTI_handler: memory index=0 
AT+CMGR=0

+CMGR: "REC UNREAD","+**664******",,"26/04/28,14:38:28+08"
Test message 

OK
5

I still have a problem, but when I try to read SMS after starting and stopping bearer


+CMTI: "ME",2
SMS received CMTI_handler: memory index=2 
...
>
>> Stopping bearer
>
AT

OK
AT+KCNXDOWN=1,1

OK

+KCNX_IND: 1,3

+KCNX_IND: 1,0,0
PDP down in 0 seconds

AT+CMGR=2

+CMS ERROR: 321

What is your advice on when to read the SMS or anything special I need to do, I put a delay of 50ms before reading SMS after PDP is down, still same issue

6

Can the sms be read before starting bearer?

7

This will be a huge firmware re-organization without knowing why. I was hoping for some in depth information on why this would happen for RC modems and not for any other of the HL family.

I have tested with HL7802, HL8548, HL7692 and SL8082TR. They all work fine with this flow. It is important to parse SMS messages after uploading data to the server because it is the expected behavior. If the modem has to be in a specific state, and there is a command to check that, it would be more helpful, then I can implement this at the specific driver level. We have stations with all these different modems and same application firmware.

8

What command have you used for starting bearer?
Which firmware are you using?

9 
Manufacturer of modem:  Sierra Wireless, Incorporated
Type of modem:          RC7620-1
Modem firmware version: SWI9X07H_00.09.10.00 85890e jenkins 2023/09/25 03:16:56

I am not using ppp

AT+CGDCONT=1,"IPV4V6","APN"

OK

+CREG: 0
AT+KCNXCFG=1,"GPRS","APN","user","password"

OK

+CREG: 2

+CGREG: 2

AT+KCNXTIMER=1,30,3

OK
AT+KCNXUP=1

OK
Waiting for PDP up URC for 1 minutes


+KCNX_IND: 1,4,1



+KCNX_IND: 1,1,0
PDP up in 28 seconds

And stopping bearer

AT+KCNXDOWN=1,1

OK


+KCNX_IND: 1,3
PDP down in 0 seconds
10

i don’t see such problem:

ati3
Manufacturer: Sierra Wireless, Incorporated
Model: RC7620-1
Revision: SWI9X07H_01.11.10.00 394448 jenkins 2025/06/06 10:03:06
IMEI: 353635110212345
IMEI SV: 32
FSN: 7T118701512345
+GCAP: +CGSM

OK

+CMTI: "ME",0
AT+KCNXCFG=1,"GPRS","internet"
OK
AT+KCNXTIMER=1,30,3
OK
AT+KCNXUP=1
OK


+KCNX_IND: 1,4,1



+KCNX_IND: 1,1,0

at+cgpaddr=1
+CGPADDR: 1,180.219.182.123

OK
AT+KCNXDOWN=1,1
OK


+KCNX_IND: 1,3



+KCNX_IND: 1,0,0

AT+KCNXCFG=1,"GPRS","smartone"
OK
AT+KCNXTIMER=1,30,3
OK
AT+KCNXUP=1
OK


+KCNX_IND: 1,4,1


+CREG: 0

+CGREG: 0

+CEREG: 0

+CREG: 2

+CGREG: 2

+CEREG: 2

+CREG: 1,"FFFE","16E8A2B",7

+CGREG: 1,"FFFE","16E8A2B",7

+CEREG: 1,"2775","16E8A2B",7


+KCNX_IND: 1,2,1,3,30



+KCNX_IND: 1,4,2



+KCNX_IND: 1,1,0


+CREG: 1,"FFFE","360A2A",7

+CGREG: 1,"FFFE","360A2A",7

+CEREG: 1,"2775","360A2A",7

+CREG: 1,"FFFE","16E8A2B",7

+CGREG: 1,"FFFE","16E8A2B",7

+CEREG: 1,"2775","16E8A2B",7
at+cmgr=0
+CMGR: "REC UNREAD","96682777",,"26/04/29,00:43:39+32"
asdfasdf

OK


AT+KCNXDOWN=1,1
OK


+KCNX_IND: 1,3



+KCNX_IND: 1,0,0

at+cmgr=0
+CMGR: "REC READ","96682777",,"26/04/29,00:43:39+32"
asdfasdf

OK
11

Your modem firmware is newer, you also did not run the command AT+CGDCONT to configure LTE APN.

12

then you can also try the newer firmware and see if it solves the problem

FYI, I already set AT+CGDCONT for the APN before.

13

I updated the firmware, the same error remains.

I will try to soft reset the modem and wait for network connection.

14

It seems the modem or SIM is in a bad state after bearer stop. I did a simple re-configuration of the SMS

AT+CPMS=\"ME\",\"ME\",\"ME\"
AT+CMGF=1
AT+CPIN? -> "+CPIN: READY"

It seems to work OK now, I will test for reproducibility with R10 firmware version.