Usb_Boot Interface - Quectel EC21 Series Hardware Design

3.19. RI
AT+QCFG="risignaltype","physical" can be used to configure RI behavior. No matter on which port a
URC is presented, the URC will trigger the behaviors of RI pin. See document [3] for details.
NOTE
URC can be outputted from UART port, USB AT port and USB modem port through configuration via
AT+QURCCFG. The default port is USB AT port. See document [2] for details.
In addition, RI behavior can be configured flexibly. The default behaviors of the RI is shown as below.
Table 23: Behaviors of RI
State
Idle
URC
The RI behavior can be changed by AT+QCFG="urc/ri/ring". See document [2] for details.

3.20. USB_BOOT Interface

EC21 series provides a USB_BOOT pin. Customers can pull up USB_BOOT to 1.8 V before VDD_EXT
is powered up, and the module will enter emergency download mode when it is powered on. In this
mode, the module supports firmware upgrade over USB interface.
Table 24: Pin Definition of USB_BOOT Interface
Pin Name Pin No.
USB_BOOT 115
EC21_Series_Hardware_Design
Response
RI keeps at high level
RI outputs 120 ms low pulse when a new URC returns
I/O Description
Force the module to
DI enter emergency
download mode
LTE Standard Module Series
Comment
1.8 V power domain.
Cannot be pulled up before startup.
Active high.
It is recommended to reserve test point.
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