Sharp GP2D12 Range Finder???

[Gixxer]

hmm.. .

Doing some more testing with a2d I've noticed that in order to get an accurate voltage reading for example on porta.0, the input must come from some form of voltage divider with both 0 and +5v as ref.(a pot for example with a2d on wiper)
Is this due to an adcon setting or something like that. My point is does the sharp sensor need a voltage divider at input??? Getting more confused.....

john

[BrianT]

The Sharp distance sensor is powered from 5 volts, the same as your PIC. I just take the Sharp output direct to the PIC with a 1 uF smoothing capacitor from the sensor output to ground. The Sharp updates every 40 mSecs or so and the smoothing capacitor is probably unnecessary but I usually smooth all inputs to the ADC out of habit.

After setting up ADCON0 and ADCON1 I leave at least 50 uSecs for the ADC to settle before I set the Go/Done bit to start the conversion.

Code snips for a PIC 16F877A

ReadSharpSensor: ' channel 5
ADCON0 = %11101001
ADCON1 = %10000000
gosub getadcval
Height = adcval

This is the GetADC subroutine

GetADCVal: ' the calling point needs to set ADCON0 & ADCON1 first
pauseus 50
clearwdt
ADCON0.2 = 1 ' starts conversion
WaitConversion: ' get ADC result
IF ADCON0.2 = 1 then waitconversion ' loop until conversion ends
adcval.highbyte = ADRESH ' upper two bits of result
adcval.lowbyte = ADRESL ' lower eight bits of result
return

HTH
Brian