Post by thread:[PIC]: Noise Filtering on ADC

Here is the code that I have written based on filter feedback. I think the straight average gives a better result. I am using a 877 and seem to get +/- 1.5bits of random noise without filtering (input is pot tied to +5V, also Vref+ tied to +5V). Is there a better way? Are there any good sites covering this subject? ADC_FILT = 0; // Clear out previous count for (i=0; i<64; i++) { ADIE = 0; // Masking the interrupt ADIF = 0; // Resetting the ADC interupt bit ADRESL = 0; // Resetting the ADRES value register ADRESH = 0; ADGO = 1; // Staring the ADC process while(!ADIF) continue; // Wait for conversion complete ADC_VALUE = ADRESL; // ADC registers are split 2 and 8 bit ADC_VALUE += (ADRESH << 8); // Combined into a single integer ADC_FILT += ADC_VALUE; } ADC_FILT = (ADC_FILT/64)+0.5; // Average of 64 readings to reduce noise // ALTERNATIVE FILTER. Change i to <255 in the for statement above // Comment out 3 lines below and replace with 2 lines below. // Adjust delay in analog1.c // // Software low pass filter to attenuate noise by -12dB // ADC_FILT = ADC_FILT + ((ADC_VALUE - ADC_FILT) * 0.0625); // } if (ADC_Channel == 0) ADC_VALUE = ADC_FILT*4.83;// Scaled to read 0 - 5V else ; // All other channels un-scaled ADC_VALUE = bintobcd (ADC_VALUE); // convert to BCD return (ADC_VALUE); // Return the value of the ADC process Ian ------------------------------------------------------ http://mdm1.bravepages.com Technical support for the Multifunction Display Module ------------------------------------------------------ > {Original Message removed}