Specifications

SIM900 AT Command Manual
SIM900_AT Command Manual_V1.03 152 12/24/2010
the output frequency equals to (26MHz/8)/(period+1).
<level> 0-100: tone level, which can be converted to duty ratio.
Reference Note
z We have a 26MHz crystal oscillator. The MAX frequency of PWM is
26/8=3.25Mhz.
z The equation of final frequency and <period> is this: frequency
=3.25/(period+1), for example, if <period> is set to 100, we get a
frequency: 3.25/101 = 32.178Khz.
z The equation of <level> and duty factor is: duty factor = (level+1).
6.2.48 AT+ECHO Echo Cancellation Control
AT+ECHO Echo Cancellation Control
Response
+ECHO: MIC:(list of supported <mic>s), ES:( list of supported <es>s),
SES:(list of supported <ses>s), MODE:(list of supported <mode>s)
OK
Test Command
AT+ECHO=?
Parameters
See Write Command
Response
+ECHO: (0, <es>, <ses>, <mode>),(1, <es>, <ses>, <mode>),(2, <es>,
<ses>, <mode>),(3, <es>, <ses>, <mode>)
OK
Read Command
AT+ECHO?
Parameters
See Write Command
Response
OK
If error is related to ME functionality:
+CME ERROR: <err>
Write Command
AT+ECHO=
<mic>,<es>[,<ses
>[,<mode>]]
Parameters
<mic> audio channel
0 main audio handset channel
1 aux audio headset channel
2 main audio handfree channel
3 aux audio handfree channel
<es> echo suppression
0-8 (when mic=0or1 default value is 0; when mic=2 or 3 default
value is 7 ) the bigger the value, the stronger the restraint.
<ses> selective echo suppression