Page 141 of 346 Start Back Next End ZBasic System Library 129 ZBasic Microcontrollers 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 ATtiny and ATmega target 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 target 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 number and location of analog port pins vary depending on the ZBasic target device. See the section Analog-to-Digital Converters for more information. Most ZBasic target devices contain a single analog-to-digital converter thus allowing only one conversion to be performed at a time (some have none at all). The conversion process takes approximately 220uS during which time the calling task will be awaiting conversion completion. Compatibility Although the BasicX manual indicates that that it is not necessary to configure the pin to be an input before calling, tests indicate that it is, in fact, necessary to do so. Consequently, the behavior of this implementation matches the actual behavior of the BasicX platform.