User's Manual

M10 Hardware Design
M10_HD_V3.0 - 47 -
Table 11: Pin definition of Audio interface
 AIN1 and AIN2, which may be used for both microphone and line inputs. An electret
microphone is usually used. AIN1 and AIN2 are both differential input channels.
 AOUT1 and AOUT2, which may be used for both receiver and speaker outputs. AOUT1
channel is typically used for a receiver built into a handset, while AOUT2 channel is typically
used with headset or hands-free speaker. AOUT1 channel is a differential channel and
AOUT2 is a single-ended channel. SPK2P and AGND can establish a pseudo differential
mode. If customer needs to play Melody or Midi ringtone for incoming call, AOUT2 Channel
should always be used.
 These two audio channels can be swapped by “AT+QAUDCH” command. For more details,
please refer to
document [1].
Use AT command “AT+QAUDCH” to select audio channel:
0--AIN1/AOUT1 (normal audio channel), the default value is 0.
1--AIN2/AOUT2 (aux audio channel).
For each channel, customer can use AT+QMIC to adjust the input gain level of microphone.
Customer can also use “AT+CLVL” to adjust the output gain level of receiver and speaker.
“AT+QECHO” is to set the parameters for echo cancellation control. “AT+QSIDET” is to set the
side-tone gain level. For more details, please refer to
document [1].
3.9.1. Decrease TDD noise and other noise
The 33pF capacitor is applied for filtering out 850MHz/900MHz RF interference when the
module is transmitting at GSM900MHz. Without placing this capacitor, TDD noise could be
heard. Moreover, the 10pF capacitor here is for filtering out 1800MHz/1900MHz RF interference.
However, the resonant frequency point of a capacitor largely depends on the material and
production technique. Therefore, customer would have to discuss with its capacitor vendor to
choose the most suitable capacitor for filtering out GSM850MHz, GSM900MHz, DCS1800MHz
and PCS1900MHz separately.
Interface Name Pin Function
(AIN1/AOUT1)
MIC1P 23 Microphone1 input +
MIC1N 24 Microphone1 input -
SPK1P 22 Audio1 output+
SPK1N 21 Audio1 output-
(AIN2/AOUT2)
MIC2P 25 Microphone2 input +
MIC2N 26 Microphone2 input -
SPK2P 20 Audio2 output+
AGND 19 Suggested to be used in audio circuit. Do not
connect to digital GND in host PCB as it could
produce TDD noise.