Technical information

Chapter 2: Hardware Interface Description
November 15, 2008 G24-L Module Hardware Description 39
A/D Interface
The G24-L includes 4 Analog to Digital Converter (ADC) signals with 8-bit resolution, for
environmental and electrical measurements. The ADC signals measure an analog DC voltage
level on their inputs which is converted to a 8-bit digital value for further processing by G24-L or
the user application.
The A/D signals operation and reporting mechanism is defined by the AT+MMAD command.
Each A/D can be defined to provide several reports:
• A single measurement.
A single A/D measurement will take place and will be reported upon activation of the AT
command.
• An automatic periodical measurement.
The A/D measures its input signal at a rate that is defined by the user application. Every
measurement will generate an unsolicited message over the serial interface.
• An automatic periodical measurement with predefined limits.
The A/D measures its input signal at a rate that is defined by the user. The user also defines
upper and/or lower limits for the A/D measurements. Each measurement is compared to
these limits, and an unsolicited message is generated only if these limits are exceeded.
Important: In case the defined periodical measurement rate is equal to, or shorter than, the
defined sleep mode delay settings (ATS24), G24-L will not enter low power mode.
Table 2-16 below, lists the internal and external A/D signals provided by G24-L.
General Purpose A/D
The G24-L provides 3 general purpose A/D (GPAD) signals for customer application use. Each
A/D signal can monitor a separate external voltage and report its measured level independently to
the application, through the AT command interface.
The GPAD signals measure a DC voltage level of 0 - 2.66 V, which is converted internally to a
8-bit digital value. The user application can monitor the A/D voltage level through the
AT+MMAD command, which returns the measured DC level in Volts times 100.
For example, a measured analog DC level of 1.75 Volts will be presented as 175 by the MMAD
command.
Table 2-16:
A/D Signals
ADC Name Description Pin #
ADC
#
Min Max Unit
VCC Power Supply A/D - 5 3.0 4.5 V
ADC3 GPAD 3 47 3 0 2.66 V
ADC2 GPAD 2 43 2 0 2.66 V
ADC1 GPAD 1 37 1 0 2.66 V