User guide

M33 EVB User Guide
Table 6: Pins of Serial Port 1
Pin Signal I/O Description
1_1 RS232_DCD1 O Data carrier detection
1_2 RS232_TXD1 O Transmit data
1_3 RS232_RXD1 I Receive data
1_4 RS232_DTR1 I Data terminal ready
1_5 GND GND
1_7 RS232_RTS1 I Request to send
1_8 RS232_CTS1 O Clear to send
1_9 RS232_RI1 O Ring indicator
Note: The voltage level of the module’s Serial Ports signals has been shifted to RS-232 level, so
it can be directly connect to PC by USB to UART converter cable.
Serial Port 1 is used for AT command, GPRS data, CSD FAX, multiplexing function and
firmware upgrade.
Table 7: Pins of Serial Port 2
Pin Signal I/O Description
2_2 RS232_TXD2 O Transmit data
2_3 RS232_RXD2 I Receive data
2_5 GND GND
Note: Customer can debug software through Serial Port 2, which is not for AT command,
GPRS service, CSD call or FAX call.
Table 8: Pins of Serial Port 3
Pin Signal I/O Description
3_2 RS232_TXD3 O Transmit data
3_3 RS232_RXD3 I Receive data
3_5 GND GND
Note: This port is designed for AT command only.
M33_EVB_UGD_V1.0 - 16 -
Quectel
Confidential