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ZBasic System Library
106
ZX Microcontroller Family
GetADC (function form)
Type
Function returning Integer
Invocation
GetADC(pin)
Parameter
Method
Type
Description
pin
ByVal
Byte
The pin from which to read an analog voltage.
Discussion
This function performs an analog-to-digital conversion of the voltage present on the specified pin which
must be one of the analog port pins (see the table below). The return value will be a 10-bit digital
approximation of the input voltage with a range from zero to the reference voltage (see below). The
return value represents the measured voltage voltage according to the formula V
ref
* adcVal / FS
where V
ref
is the reference voltage, adcVal is the value returned by GetADC(), and FS is 1024 for mega-
based devices and 4096 for xmega-based devices.
You must make the specified pin an input before calling this routine.
For ATmega-based devices, the conversion is performed using the AVcc reference voltage (connected
internally to Vcc on the ZX-24, ZX-24a, ZX-24p, ZX-24n, ZX-24r, ZX-24s, ZX-24e, ZX-24ae, ZX-24ne, ZX-
24pe, ZX-24nu, ZX-24pu, ZX-24ru, ZX-24su, ZX-328nu, ZX-128e, ZX-128ne, ZX-1281e and ZX-1281ne).
For ATxmega-based devices, the conversion is performed using a reference voltage of Vcc/1.6.
Resource Usage
Only analog port pins may be used to perform an analog-to-digital conversion. The analog port pins vary
depending on the ZX model and some ZX models have more analog input pins available. Also, on some
devices (e.g. ZX-32n, ZX-32l and ZX-328nu) some of the pins are dedicated analog inputs; having no
digital functions.
Analog Ports and Pins
ZX Models
Port
Pins
Port
Pins
ZX-24, ZX-24a, ZX-24p, ZX-24n, ZX-24r, ZX-24s
PortA
13-20
-
-
ZX-40, ZX-40a, ZX-40p, ZX-40n, ZX-40r, ZX-40s
PortA
33-40
-
-
ZX-44, ZX-44a, ZX-44p, ZX-44n, ZX-44r, ZX-44s
PortA
30-37
-
-
ZX-328n, ZX-328l
PortC
23-28
-
-
ZX-32n, ZX-32l
PortC
23-28, 19, 22
-
-
ZX-1281, ZX-1281n
PortF
54-61
-
-
ZX-1280, ZX-1280n
PortF
90-97
PortK
82-89
ZX-24x
PortA
13-20
PortB
7-9
ZX-32a4
PortA
40-44, 1-3
PortB
4-7
ZX-128a1
PortA
95-100, 1, 2
PortB
5-12
ZX-24e, ZX-24ae, ZX-24ne,
ZX-24pe, ZX-24nu, ZX-24pu, ZX-24ru, ZX-24su
PortA
29-36
-
-
ZX-24xu
PortA
29-36
PortB
25-28
ZX-128e, ZX-128ne, ZX-1281e, ZX-1281ne
PortF
29-36
-
-
ZX-328nu
PortC
17-24
-
-
Most ZX processors contain a single analog-to-digital converter thus allowing only one conversion to be
performed at a time. The conversion process takes approximately 220uS during which time the calling
task will be awaiting conversion completion.
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