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U10 Quectel Cellular Engine
U10 PCM
User Guide U10_PCM_User_Guide_V1.0
U10 PCM User Guide
U10_PCM_User_Guide_V1.0 - 5 -
0. Revision history
Revision Date Author Description of change
1.0 2012-03-27 Alan ZHU Initial
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U10 PCM User Guide
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1. Introduction
This document specifies U10 PCM working mode and PCM interface assignment. This document
is only available for Quectel U10 series modules.
1.1. Reference
Table 1: Reference
SN Document name Remark
[1] U10_HD U10 hardware design
1.2. Terms and abbreviations
Table 2: Terms and abbreviations
Terms Description
PCM Pulse Coding Modulation
DSP Digital Signal Processor
WCDMA Wideband Code Division Multiple Access
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2. U10 PCM overview
U10 provides hardware PCM interface for external codec. PCM interface pins are multiplexed
with AUX_RXD , AUX_TXD and RTS.
The PCM interface is a 4 pin, digital interface that enables PCM to communicate between the
module and an external codec. U10 only supports 16 bits (linear) PCM format. The table
below shows the hardware PCM interface of Quectel U10 module. For more detailed
information about U10 PCM pin assignment, please refer to the document [1].
Table 3: U10 PCM interface
Module AT Command PIN Name Note
U10 AT+QPCMEN=1/0 PCM_OUT
AUX_TXD/PCM_SYNC
RTS/PCM_CLK
AUX_RXD/PCM_IN
The PCM_OUT pin is not
multiplexed with other pin.
Table 4: PCM pins assignment
PIN
No.
PIN Name PCM
Functionality
I/O Note
86 RTS PCM_CLK O (Master) VILmin=-0.3V
VILmax=0.25*VDD_EXT
VIHmin=0.75*VDD_EXT
VIHmax= VDD_EXT +0.3V
VOLmin=GND
VOLmax=0.15*VDD_EXT
VOHmin= 0.85*VDD_EXT
VOHmax= VDD_EXT
79 AUX_TXD PCM_SYNC O (Master)
81 AUX_RXD PCM_IN I (Master)
74 PCM_OUT PCM_OUT O (Master)
Notes:
1. Module’s internal reference power supply:VDD_EXT=2.8V.
2. PCM interface’s electric level must match with your codec
or MCU.
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3. Hardware PCM interface
3.1. PCM mode
Master mode and slave mode are the working modes of PCM. In Master mode, the module drives
the clock and sync signals that are sent out to the external codec via the PCM Interface. When in
Slave mode, the external codec drives the clock and sync signals that are sent out to the module.
U10 can only work in Master mode which can supply the clock and sync signals for the external
codec via the PCM Interface.
When the PCM interface is configured, PCM Tx data will be transmitted from the external
microphone through the DSP encode path to the module. PCM Rx data will be transmitted through
the DSP decode path to the external speaker. Under PCM, the data is output on the rising edge of
PCM_CLK and sampled at the falling edge of PCM_CLK.
3.2. U10 PCM interface and mode
U10 PCM interface supplies base clock and sync clock for external codec, shown as Figure 1.
Customer Device
(slave)Module
(master)
PCM_CLK
PCM_SYNC
PCM_DOUT
PCM_DIN
PCM_CLK
PCM_SYNC
PCM_IN
PCM_OUT
Figure 1: U10 PCM interface to external device
U10 uses linear format, so per frame can transmit data up to 16 bits. And the sync clock is short
frame clock of which high level length is only a base clock. The Sign-extended mode is being
used when data transmission. In standard 13-bit mode, the first bit is the sign bit. In this mode, the
device transmits and receives 16-bit data where the sign bit is extended to the first four data bits.
The PCM timing is illustrated below.
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PCM_CLK
PCM_SYNC
PCM_DIN
PCM_DOUT
Figure 2: U10 PCM data transmitting timing
All data is 8 kHz sampling and 16 bits with the following PCM bit format:
Tx (External codec →U10) –DDDD DDDD DDDD DVVV
Rx (U10 → external codec) –DDDD DDDD DDDD DVVV
Note:
D means Data, V means Zero Pending.
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4. AT Command
Customers can use AT command AT+QPCMEN to enable or disable PCM function.
4.1. Detailed description of AT+QPCMEN
AT+QPCMEN Enable or diasble PCM function
Test Command
AT+QPCMEN=?
+ QPCMEN: (list of supported <n>)
OK
Write Command
AT+QPCMEN
=<n>
Response
OK
Parameter
<n> 0 Disable PCM, switch to AUX_TXD, RTS
(Main UART), AUX_RXD
1 Enable PCM function
Example:
AT+QPCMEN=1
OK
AT+QPCMEN =?
+QPCMEN: 0 = PCM OFF, 1 = PCM ON
OK
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Shanghai Quectel Wireless Solutions Co., Ltd.
Room 501, Building 13，No.99 Tianzhou Road, Shanghai, China 200233
Tel: +86 21 5108 6236
Mail: [email protected]
