reading in a voltage

James

i have a voltage of 700mV outputting from a sensor, i wish to have this value outputted to my LCd display, how do i get the javelin to take that value assumeably from a selected pin say pin 15 and have it ready to be outputted to the LCD?

Ali E.

don't you need an A/D cenverter to convert values from sensor to digital numbers?

Peter Verkaik

You can use the ADC vp.
This gives values 0 (=0V) to 255 (=5V)
so if read value N then
V = (N/255)*5
Calculating a value 0.00 to 5.00 (more decimals is pointless due to adc resolution)
value = (N/255)*500 = (N/51)*100 = 1.9608*N = N + 0.9608*N = N + (62966/65536)*N
Using the UnsignedIntMath class

static ADC myADC = new ADC(inpin,outpin);

int n = myADC.read(); //get value from adc
int value = n + UnsignedIntMath.umulf(n,(short)62966);
now value is in the range 0 to 500
if (value > 500) value = 500; //failsafe for rounding errors

lcd.writebyte((value/100) + '0'); //display integer part
lcd.writebyte('.'); //decimal point
lcd.writebyte((value%100)/10 + '0'); //first decimal
lcd.writebyte((value%10) + '0'); //second decimal

for 700mV N is approx. 36 and value is approx. 70

regards peter

yvesB

Complete Noob to the Javalin but been doing the Basic Stamps for awhile.

I would like to interact with the Jav's ADC as well and as I can understand, it's a sigma-delta type ADC. A bit confused as to what I use for outpin in the example above?? inpin is signal to be measured??

Thanks.

Peter Verkaik

Javelin stamp manual chapter 4, page 55
regards peter

yvesB

Thanks for that· ...I will be reading it again more closely.