AtoD - first attempts

malc-c · - 29th December 2006, 13:05

Guys, I'm getting a little out of my depth and would like some feedback here.

From my previous posts some of you (two Steves !) will remember that I'm playing with a 16F873 to come up with a better version of some disco lights based on an 16F628a. I'm now looking at hooking up the audio output from a CD player but I've never played with A - D conversion and not sure what I need to do. I've used the example varibles in the manual so I have

Code:

B0 VAR BYTE
ADCIN 0, B0		' Read channel 0 to B0

I want to use RA0/AN0 (pin 2) for the input, and I've used a win-scope to obtain the voltage levels that the CD player is kicking out (see attached). How do I go about calibrating the A-D so that I can display the values of B0 on port B relative to the music level ?

EDIT:

I tried the obvious:

Code:

ADCIN 0, B0		' Read channel 0 to B0
Portb=B0
RETURN

However even with no music present the first 5 bits of Port B seem to display a random pattern, rather than just PB0 being lit. There is however a noticable change of state when a music signla present, I get more LEDs light up and it extends over the full port.. but it's not seqentially lighting them up like a VU meter.

EDIT:
Sorry should of added that I copied the settings form the manual too

Code:

DEFINE ADC_BITS 8	' Set number of bits in result
DEFINE ADC_CLOCK 3	' Set clock source (rc = 3)
DEFINE ADC_SAMPLEUS 50	' Set sampling time in microseconds

And have the following config:

Code:

ADCON1=$07
CMCON = 7                               ' Digital inputs
CCP1CON = 0                             ' PWM off
TRISA=%11111111                         'set PORTA as all input