SIM340 Hardware Design
about the keypad is as shown in the following figure. The GND column is added for the additional
5 keys.
Figure 31: Reference circuit of the keypad interface
Note: This function is not supported in the default firmware. There must be special firmware if
you want. Please contact SIMCom for more details
3.14 ADC
SIM340 provides one auxiliary ADC (General purpose analog to digital converter.) as voltage
input pin, which can be used to detect the values of some external items such as voltage,
temperature etc. We can use AT command “AT+CADC” to read the voltage value added on
ADC0. For detail of this AT command, please refer to
document [1]
.
Table
20
: ADC specification
Min
Typ
Max
Units
Voltage range
0
2.4
V
ADC Resolution
16
16
bits
ADC accuracy*
0.59
mV
Sampling rate
5
Sec
SIM340_HD_V3.09
18.03.2009
49
