PIC16F688 Microcontroller

Description

The PIC16F688 microcontroller has a built-in 10-bit ADC with eight input channels. The eight channels are available at RA0, RA1, RA2, RA4, RC0, RC1, RC2, and RC3. They have alternate labels, AN0-AN7, for this function, and are multiplexed into a single sample and Hold circuit. The?output of the sample and hold is?connected to the input of the A/D converter. The A/D conversion is successive approximation based and the 10-bit result is stored??into the ADC result registers ADRESH (A/D Result Higher byte) and ADRESL (A/D Result Lower byte). Each of these registers is 8-bit. Pin diagram of the PIC16F688 microcontroller Functional block diagram of ADC The functionality of the A/D module is controlled by three registers: ANSEL, ADCON0, and ADCON1. The ANSEL register is used to configure the input mode of an I/O pin to analog. Setting the appropriate ANSEL bit High will cause all digital reads on the pin to be read as 0, and allow analog function on the pin to operate correctly. The state of ANSEL bits has no effect on digital O/P function. A pin with TRIS bit clear and ANSEL bit set will operate as digital O/P but the input mode will be analog. ANSEL register bits The ADCON0 register selects which analog input is to be measured. This is required, since there are several channels for?analog input but only one A/D converter circuitry.?The channel select bits CHS0-CHS2 of ADCON0 register controls which analog channel is connected to the internal Sample and Hold circuit. For example, i