SimCom SIM800 Hardware Design page 43

Figure 39: Enhance the ESD performance of keypad circuit
Module can detect two buttons pressed synchronously at both the traditional and extended keypad connection,
but customer should notice that, do not assign keys which will be pressed at the same time on same KBC and
KBR when implement the extended keypad design. The following figure is an example to explain this situation,
"CTRL" and "A" can not be recognized if the two buttons were pressed at the same time.
Table 20: Pin definition of the keypad interface
Name Pin
KBC0 51
KBC1 50
KBC2 49
KBC3 48
KBC4 47
KBR0 44
KBR1 43
KBR2 42
KBR3 41
KBR4 40
SIM800_Hardware Design_V1.10
KBCx
<1K
Module
KBRx
KBCx
Module
KBRx
Figure 40: Keypad detected
Function
Keypad matrix column
Keypad matrix row
43
Smart Machine Smart Decision
20K
20K
Default state
Pull up
Pull down
Pull down
Pull down
Pull down
Pull down
Pull down
Pull down
Pull down
Pull down
2018-08-13