Sunsea AIoT SIMCom SIM7075G User Manual page 29

SIM7075G User Manual V1.00
Figure 14: Reference circuit with Transistor
NOTE
When it uses the level shifter IC, the pull up resistance on TXD_3.3V, RTS_3.3V, DCD_3.3V and
RI_3.3V should not be less than 47KΩ.
When it uses the transistor, the selection of the transistor must be a high-speed transistor, and the
model MMBT3904 is recommended.
3.3.2 RI and DTR Behavior
The RI pin description:
The RI pin can be used to interrupt output signal to inform the host controller such as application CPU.
Before that, users must use AT command "AT+CFGRI=1" to enable this function.
Normally RI will keep high level until certain conditions such as receiving SMS, or a URC report coming,
then it will output a low level pulse 120ms, in the end, it will become high level.
Figure 15: RI behaviour（SMS and URC report）
The DTR pin description:
After setting the AT command "AT+CSCLK=1", and then pulling up the DTR pin, Module will enter sleep
mode when module is in idle mode. In sleep mode, the UART is unavailable. When SIM7070 enters sleep
mode, pulling down DTR can wake up module.
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