You can maybe try to use debugging command on the router like "debug vpm dsp"
debug vpm dsp
To show messages from the digital signal processor (DSP) on the voice port module VPM) to the router, use the debug vpm dsp command in privileged EXEC mode. To disable debugging output, use the no form of this command.
debug vpm dsp
no debug vpm dsp
Syntax Description
This command has no arguments or keywords.
Command Modes
Privileged EXEC
Usage Guidelines
The debug vpm dsp command shows messages from the DSP on the VPM to the router; this command can be useful if you suspect that the VPM is not functional. It is a simple way to check if the VPM is responding to off-hook indications and to evaluate timing for signaling messages from the interface.
Examples
The following output shows the DSP time stamp and the router time stamp for each event. For SIG_STATUS, the state value shows the state of the ABCD bits in the signaling message. This sample shows a call coming in on an FXO interface.
The router waits for ringing to terminate before accepting the call. State=0x0 indicates ringing; state 0x4 indicates not ringing.
ssm_dsp_message: SEND/RESP_SIG_STATUS: state=0x0 timestamp=58172 systime=40024
ssm_dsp_message: SEND/RESP_SIG_STATUS: state=0x4 timestamp=59472 systime=40154
ssm_dsp_message: SEND/RESP_SIG_STATUS: state=0x4 timestamp=59589 systime=40166
The following output shows the digits collected:
vcsm_dsp_message: MSG_TX_DTMF_DIGIT: digit=4
vcsm_dsp_message: MSG_TX_DTMF_DIGIT: digit=1
vcsm_dsp_message: MSG_TX_DTMF_DIGIT: digit=0
vcsm_dsp_message: MSG_TX_DTMF_DIGIT: digit=0
vcsm_dsp_message: MSG_TX_DTMF_DIGIT: digit=0
