Pcm And I2C Interface - Quectel EC25-V User Manual

MCU/ARM
NOTE
Transistor circuit solution is not suitable for high baud rates exceeding 460Kbps.

3.12. PCM and I2C Interface

EC25 provides one Pulse Code Modulation (PCM) digital interface for audio design, which supports the
following modes:
Primary mode (short sync, works as both master and slave)

Auxiliary mode (long sync, works as master only)

In primary mode, the data is sampled on the falling edge of the PCM_CLK and transmitted on the rising
edge; the PCM_SYNC falling edge represents the MSB. In this mode, PCM_CLK supports 128, 256, 512,
1024 and 2048kHz for different speech codecs.
In auxiliary mode, the data is sampled on the falling edge of the PCM_CLK and transmitted on the rising
edge; while the PCM_SYNC rising edge represents the MSB. In this mode, PCM interface operates with a
128kHz PCM_CLK and an 8kHz, 50% duty cycle PCM_SYNC only.
EC25 supports 8-bit A-law and μ-law, and also 16-bit linear data formats. The following figures show the
primary mode's timing relationship with 8kHz PCM_SYNC and 2048kHz PCM_CLK, as well as auxiliary
mode's timing relationship with 8kHz PCM_SYNC and 128kHz PCM_CLK.
EC25-V_User_Manual
69
VDD_EXT
/TXD
/RXD
10K
VCC_MCU
/RTS
/CTS
GPIO
EINT
GPIO
GND
Figure 21: Reference Circuit with Transistor Circuit
Confidential / Released
4.7K
VDD_EXT
1nF
10K
1nF
VDD_EXT
4.7K
LTE Module Series
EC25-V User Manual
Module
RXD
TXD
RTS
CTS
DTR
RI
DCD
GND
38 /