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Jesus Echavarria has tipped us off about his RPi board, which is focused to learn Python with the Raspberry Pi board. The board easily fits on the GPIO headers of Raspberry Pi, and contains basic electronic components like LEDs, tact switches, buzzer, header for 2×16 and LCD display, to get going with basic Python programming.
RPi Board
Most embedded projects require the same common stuff, basically I/O devices such as switches, LEDs, LCD display, buzzer, etc. Connecting these things on a breadboard for prototyping every new project is time consuming and boring. Recently, I have designed a general purpose I/O experimenter board that will not only reduce the prototyping time for a new project but also free up plenty of space on the breadboard.
I/O Experimenter Board
Description
Analog-to-digital conversion (ADC) is necessary because, while embedded systems deal with digital values, their surroundings typically involve many analog signals such as, temperature, speed, pressure, the output of a microphone, etc. They all need to be converted into digital data before being processed by the microcontroller. Today, we will see how to read an external analog signal using a PIC16F688 microcontroller, and display the conversion output (a digital number) on a LCD. The input analog signal will be a varying voltage between 0-5V derived using a potentiometer.
Required Theory
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 10-bit conversion 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. The functionality of the A/D module is controlled by three registers: ANSEL, ADCON0, and ADCON1. The details of these control registers are discussed in ADC channels in PIC16F688.
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