MTSMC G-F4 GSM module with AT Command

Halo everyone,

I would like to use MTSMC-G-F4 for basic feature like sending short message service and make missed call..
But until now I cannot register to the network
I have applied AT+CREG?
but there is no data receive on my microcontroller pic.

Is there anyone have experienced with this ?

Any help would be appreciated.

does it reply OK to a simple AT<enter> command?
if so what is the value of signal quality, e.g. at+csq command?

Halo horace,

thanks for your comment,
I cannot receive anything from uart, the interrupt flag never raise.
my pic micro has vcc 3.3v and the module is 5 v.
I use IRF9530 p mosfet in TX so 0-3.3V become 2.5v - 4.3v
for RX, I use voltage divider 3 resistor 10 kohm, so 0-5v become 0-3.3v
it should be okay from datasheet.
I do not really know whether my hardware is incorrect.

I am still new in this.
I have an idea to use MAX3232 which can convert 3.3v and 5v. Is it make sense ?
or maybe I tested it first using Hyperterminal in PC?

Thanks

have you tried looking at the signals with an oscilloscope, e.g. write out to the UART "AT\n\r" in a loop
1. You should see the 3.3V from the UART then 5V into the modem
2. if that works you should the modem reply at 5V then 3.3 V into the UART
this should show where it is failing (could the baudrate be incorrect?)
a MAX3232 sounds a good idea !

if this fails checking with Hyperterminal on a PC is a good idea - you could use a USB to TTL 5V serial cable such as the FTDI TTL-232RG-VSW5V-WE
USB TTL Serial

Hallo horace,

I have checked with multimeter at home because I do not have one. I tested it to put high on the port. It is 4.3V, but it is ok according to datasheet.
Next time I will go to my college and looked on oscilloscope whether the time of switching is fast enough.

Maybe it sounds stupid, but may I ask. If I have already had RS-232 to USB converter, could I just connect the TX, RX, CTS, RTS to the correct pin in the DB9 RS232 ?
It is better for me rather than buy the new one.

wish me luck.
Thanks

If it is a USB to RS232 serial converter such as
USB RS232 Cables

I would not try to connect it. RS232 voltages can be -12 to +12, have a look at
RS-232 - Wikipedia, the free encyclopedia

I see, it seems that I need MAX232 converter and the RS232-USB converter or I can buy the TTL-USB converter. Am I right ?

Anyway, AT command for every GSM modem is all the same, isn't it?
Could I practice the AT command for the module on it SMS Tutorial: How to Send SMS Messages from a Computer/PC Using a Mobile Phone or GSM/GPRS Modem? AT Commands ?

Thanks for your help.

probably simplest to buy a USB-TTL cable about £20 in the UK - saves making up a PCB for the MAX232

basic AT modem commands tend to be similar - firmware commands can vary and operating TCP/IP stack etc

Hi Horace,

I have tried it, but it was very strange.
First I have taken a look with my oscilloscope with my previous circuit. the switching TTL is okay, but there is drop voltage. so I think the modem does not recognize it.

Then I tried to test it with PC using Hyper terminal.
When I send AT, I also receive AT. Whatever I sent was the same with what I received.

Then I think the connection of TXD and RXD is incorrect, but it should be Okay as I checked.
In MTSMC-G-F4 the TXD is used by DTE to send data to the modem
the RXD is used by modem to send data to DTE.

I also try to reverse TXD and RXD connection, However, when I sent AT, there is no respond.

It was really drive me crazy.
Do you have any recommendation to solve it ?
Thank you very much I am really appreciate it.

check your baudrate. default is 9600, no parity 1 stopbit and no flow control

Hallo sei,

I have checked it, the baud rate that I used was 115200bps like on the datasheet.
I also try to change it become 9600 bps, but it did not answer for the moment, and after some AT is sent. It also answer AT, the same like before.
It is so strange how could MTSMC-G-F4 answer the same thing what I transmit ?

Thanks.

what are you transmitting after the AT ? some modems require a linefeed then carriage return combination after an AT command, e.g. "\n\r" in C

Hi Horace,

Thank you very much.
yes, I miss \r or 0D in hex. Now when I sent AT\r, I get OK.

Just now I tried to use AT command to make missed call and send sms, but It was unsuccessful. It seems that there is some wrong comment.

First I sent AT\r, then modem answer OK\r\n
Next I sent AT+CREG?\r , then modem +CREG: 0,2\r\n\r\nOK\r\n
I try to make missed call and sent ATD( +country code and my phone number);\r , then modem -> NO CARRIER\r\n
I do not understand what is NO CARRIER means..

then I try to send sms
I sent AT+CMGS="+country code and my phone number"\r , then modem answer with \n\r>
then I sent my message >halo \r , then modem answer \n\r> again.
I was stuck here. I have read the datasheet for MTCBA-G-U-F4 because I cannot get for MTSMC-G-F4. I hope that they are the same
They said that I have to hit CTRL+Z to send message, but It was not worked.
I will attach the datasheet (page 27).

Then I try to follow from SMS Tutorial: How to Send SMS Messages from a Computer/PC Using a Mobile Phone or GSM/GPRS Modem? AT Commands
AT\r
OK\n\r
AT+CMGF=1\r
OK\n\r
AT+CMGW="+country code and my phone number"\n\r
\n\r>
> A simple demo of SMS text messaging.\r
\n\r>
> A simple demo of SMS text messaging.\r
\n\r>
AT\r
\n\r>

I was stuck on here again, the modem always answer \n\r>

Please help me to solve it.
I will really appreciate.
Thanks

good to hear you are making progress!
the "no carrier" sounds like you are not connecting to the network and/or signal strength is low
have you tried signal quality "at+csq" , checking the SIM is OK and what service center you are connected to (if any) ?

looking t the manual FAQ it says
I can’t make outgoing calls. I just receive a NO CARRIER response.
• Make sure the antenna is connected and SIM is inserted correctly.
• Check signal and registration: ‘AT+CSQ’ (10-31 is good), ‘AT+CREG?’ (0,1 is registered & 0,5 is roaming).
• Check NO CARRIER reason with ‘AT+CEER’. Look up error code in Reference Guide.

Hi horace,

Thank you very much, it is also because of you.

I have tried AT+CSQ, the answer is +CSQ : 99,99
AT+CREG?
CREG= 0,2
(Searching for network. This response tells you that the Sagem radio is
currently looking for a GSM network on which to attach.)

AT+CEER
+CEER = Error 226
(Unsuccessful attach cause NO SERVICE)

I used SIM from asia country. we do not have such T-mobile, AT&T.
but I have tried the SIM with my handphone, and there is no problem.

Is that means, I need GSM antenna ?
my connection is MMCX female so I need antenna with MMCX male.
Do you have any suggestion?

Thanks.

looking at a manual the signal quality +CSQ : 99,99 means "not known or not detectable" indicates you have no signal so you need a GSM antenna. Getting a new antenna can sometimes be difficult and costs nearly as much a new modem!
cannot you get an electronics engineer to put something together?

Hi

I got Quad-band Cellular Duck Antenna SMA - SparkFun Electronics or Quad-band Wired Cellular Antenna SMA - SparkFun Electronics
then use this connector Interface Cable MMCX to SMA - SparkFun Electronics
What do you think about them ?

I will also ask my lecture, I hope they can give me some suggestions for cheap soultion.

Thanks

looks as though it could work - ask your lecturer or one of the electronics technicians. We often end up cutting cables and solding combinations of plugs and sockets to get an antenna to fit a modem where the original antenna has been lost or broken.

Hi horace,

I might be that there is misunderstanding or I do not really understand
My modem does not have original antenna.
MTSMC-G-F4 does not come with GSM antenna. It is only socket modem.
As you can see on my attachment file. There is MMCX female that should be attached with antenna.

Before, I think that it can catch signal and have internal antenna, but after this I change my mind.

My lecture does not really master on this, they suggest me to check again the software and find gsm antenna.
I try
AT+COGS?
+COGS = 0
(I read from other article that this is used to check the provider of SIM)
0 means that it is automatic, but modem does not specify the name of provider, it might be because it have not connected yet.

What do you think ?
Hope we can solve this soon.

Thanks

certainly looks like you need an antenna to get any signal
if you look at the Universal Socket Developers kit
https://www.multitech.com/pdfs/devkit.go

it comes with cables to connect to modems and antennas