Interrupt Service Routine

• In websrv65_v310/src/mxwebsrvr.c
• Change:
• /////////////////////////////////////////////////
• //High Interrupt ISR
• TickUpdate();
• To:
• /////////////////////////////////////////////////
• //High Interrupt ISR
• //------------------------------------------------
• // Preset TMR0 for next interrupt
• // in 1/1200th of a second
• //------------------------------------------------
• TMR0H = TICK_COUNTER_HIGH;
• TMR0L = TICK_COUNTER_LOW;
• //------------------------------------------------
• // read the 10bit Analog to Digital Converter
• // output initiated during the prior ISR
• //------------------------------------------------
• Adc_sample = ((WORD)ADRESH << 8) | (WORD)ADRESL;
• Input = Adc_sample;
• metric += Input;
• //------------------------------------------------
• // Digital IIR Filter "Temp" scaled by 2^8 coef's
• //------------------------------------------------
• Temp = 185*Intermediate2 - 425*Intermediate1;

• The ISR routine begins with presetting for the next timer to trigger the next interrupt.

• The A/D output is read from ADRESH & ADRESL, transferred to “Input”, and an input summation “metric” is accumulated. The metric is to later judge whether signal is present on an input.

• “Temp” is the IIR Filter multiplication of prior intermediate values times filter coefficients inflated by 256