Quectel EG21-G User Manual

LTE Module Series
EG21-G Hardware Design
EG21-G_Hardware_Design 44 / 100
MCU/ARM
TXD
RXD
VDD_EXT
10K
VCC_MCU
4.7K
10K
VDD_EXT
TXD
RXD
RTS
CTS
DTR
RI
RTS
CTS
GND
GPIO DCD
Module
GPIO
EINT
VDD_EXT
4.7K
GND
1nF
1nF
Figure 21: Reference Circuit with Transistor Circuit
Transistor circuit solution is not suitable for applications with high baud rates exceeding 460Kbps.
3.12. PCM and I2C Interfaces
EG21-G provides one Pulse Code Modulation (PCM) digital interface for audio design, which supports the
following modes and one I2C interface:
 Primary mode (short frame synchronization, works as both master and slave)
 Auxiliary mode (long frame synchronization, 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, the PCM interface supports
256kHz, 512kHz, 1024kHz or 2048kHz PCM_CLK at 8kHz PCM_SYNC, and also supports 4096kHz
PCM_CLK at 16kHz PCM_SYNC.
In auxiliary mode, the data is sampled on the falling edge of the PCM_CLK and transmitted on the rising
edge. The PCM_SYNC rising edge represents the MSB. In this mode, the PCM interface operates with a
256kHz, 512kHz, 1024kHz or 2048kHz PCM_CLK and an 8kHz, 50% duty cycle PCM_SYNC.
EG21-G supports 16-bit linear data format. The following figures show the primary mode’s timing
relationship with 8KHz PCM_SYNC and 2048KHz PCM_CLK, as well as the auxiliary mode’s timing
relationship with 8KHz PCM_SYNC and 256KHz PCM_CLK.
NOTE

Quectel EG21-G Specifications

General

Brand	Quectel
Model	EG21-G
Category	Wireless modules
Language	English