SimCom SIM900B Hardware Design page 13

DISP _CS 22
DISP_RST 26
Keypad interface / GPIOs
GPIO1/KBC4 35
GPIO2/KBC3 33
GPIO3/KBC2 31
GPIO4/KBC1 29
GPIO6/KBR3 45
GPIO7/KBR4 43
GPIO8/KBR2 41
GPIO9/KBR1 39
GPIO5/KBC0 27
GPIO10/KBR0 37
Serial port
RXD 40
TXD 42
RTS 44
CTS 46
RI 48
DCD 28
DTR 38
Debug interface
DBG_TXD 49
DBG_RXD 47
SIM interface
SIM_VDD 19
SIM_DATA 21
SIM_CLK 23
SIM_RST 25
SIM_PRESEN 16
CE
ADC
ADC0 52
Pulse Width Modulation
BUZZER 36
SIM900B_Hardware Design_V2.01
O
O
I/O
I/O
I/O
Defaults are as GPIO, they can be
I/O
multiplexed as keypad
I/O
I/O
I/O
I/O
I/O
GPIO
I Receive data
O Transmit data
I Request to send
O Clear to send
O Ring indicator
O Data carry detect
I Data terminal Ready
O Serial interface for debugging and
firmware upgrade
I
O Voltage supply for SIM card. Support
1.8V or 3V SIM card
I/O SIM data input/output
O SIM clock
O SIM reset
I SIM card detection
I General purpose analog to digital
converter. Input voltage range: 0V ~
2.8V
O PWM Output
13
Smart Machine Smart Decision
If these pins are
unused ,keep open
Just can be used as
GPIO, if these pins are
unused, keep open
This pin should be
pulled up to 3V
externally.
If these pins are unused,
keep open.
If these pins are unused,
keep open.
All signals of SIM
interface should be
protected against ESD
with a TVS diode array.
If SIM_PRESENCE is
unused, just keep open
If it is unused ,keep open
If it is unused, keep open
2012-05-07