Sim900 ATH and voicemail

[gavagai]

In my application SIM900 wait for incoming call. After RING a relay switchs and ATH is sent to SIM900 to reject the call without cost. The software works fine on TELIT 864 module, but on SIM900 after ATH the voicemail starts.
The problem is similar to this thread: https://www.edaboard.com/threads/222317/
The thread is marked SOLVED, but i don't understand how to realy solve the problem.

Any help appreciated.

Thanks

 

[kgshankar1980]

@gavagai,

Try giving ATH0<enter>...

 

[gavagai]

@kgshankar1980

Thanks for reply.

I tried ATH0. I also tried AT+HVOIC command but unsuccessfully.
The same SIM card on Telit module simply hangs up the call, on SIM900 hangs up and then starts the voicemail.
dgleeson says:"It appears to be related to the time delay before going to voicemail."
I don't find an AT command to disable voicemail after the hang up.

 

[kgshankar1980]

@gavagai,

How you are testing this?

Have you connected SIM900 module to the PC directly or via MCU(microcontroller unit)?

Are you entering initialisation AT commands before testing this?

 

[gavagai]

SIM900 is controlled by a PIC18F25K20.

This is the initialitation
ATE0 //echo off
ATV0 //verbose off
AT+CMEE=0 //Disable +CME ERROR
AT+CLIP=1 //Enable +CLIP notification
AT+CPBS="SM" //Select SIM phonebook
AT+CMGF=1 //SMS Text mode
AT+CSCS="IRA" //Select TE Character Set
AT+CSMP=17,167,0,0 //Set SMS Text Mode Parameters
AT+CNMI=1,1,0,0,0 //New SMS Message Indications
AT+IPR=115200 //Baud rate

After initialization the software waits for unsolicited +CLIP notification due to incoming call. If incoming number is in the phonebook relay is switched and ATH is sent to reject the call.

 

[kgshankar1980]

@gavagai,

Remove ATV0 initialisation as it is not needed.

If incoming number is in the phonebook relay is switched and ATH is sent to reject the call.

For this try the other way...The moment you receive the call, issue ATH<Enter>...And then check the incoming number with the phonebook entry and take necessary action...