Experiment No. 4: External Interrupt

PIC12F683 has got one external interrupt pin (GP2, pin 5) which is edge-triggered:

• rising edge if INTEDG bit in OPTION register is SET,or 
• falling edge if INTEDG bit in OPTION register is CLEAR

In this experiment we are going to simulate an external interrupt event by a tact switch which when pressed gives a falling edge (5->0V) to external interrupt pin. When a valid edge appears on GP2/INT pin, the INTF bit (INTCON<1>) is set. This interrupt can be disabled by clearing INTE control bit (INTCON<4>). While exiting from the Interrupt Service Routine, INTF flag must be cleared to re-enable the interrupt again. ANSEL and CMCON0 must be initialized to configure GPIO as digital I/Os.

On the arrival of an interrupt, the new value of counter will increase by 1 and is displayed as no. of interrupts serviced. 

Experimental Setup:
External interrupt will be simulated by a tact switch on the board. So connect SW1 to GP2 with a jumper wire. For display purpose we will again use a hyperterminal window on a PC.

Experiment No. 3: Analog to Digital Converter with PIC12F683

As mentioned before, 4 out of 6 GPIOs in a PIC12F683 also provide analog-to-digital converter inputs with 10-bit resolution. They are GP0-GP2, and GP4. In this experiment we will feed an analog voltage to one of the ADC inputs (say AN0, which is GP0) and display the output digital value on a hyper-terminal window on PC. The analog voltage will be simulated with the potentiometer on our board.

Experimental Setup:
Connect the output of potentiometer (POT2) to AN0 (pin 7). GP5 (pin 2) will serve as TX pin for Software UART so connect it to input Tx of TTL to RS232 Level Shifter circuit. Also connect Rx (2) and Gnd (5) of a RS232 port to the board. This is similar to what we did in Experiment No. 2.

Experiment No. 2: User Inputs from Tact Switches and Software UART

In this experiment, we will demonstrate how to read inputs from tact switches, and then will also show how to send character data from PIC12F683 to a desktop PC Hyper-Terminal program through UART communication. Remember that PIC12F683 doesn't have hardware UART module, so we are going to use the Soft_UART library routines from mikroC for this purpose. Regarding the Hyper-Terminal setup on PC, read this. Besides, to read the user inputs from tact switches, Button Library routines in mikroC will be used.

Snapshots of the required Library Routines from mikroC User's Manual

Setup:
The two switch inputs in our board will be connected to GP0 and GP1 port (Pins 7 and 6 respectively). GP5 (Pin 2) will be used for Software UART Tx. So here is what you need to do:

• Connect SW1 and SW2 (tact switches) to GP0 and GP1 using jumper wires,
• Connect GP5 to input Tx of TTL to RS232 Level Shifter circuit,
• Connect Rx(2) and Gnd(5) pins of a RS232 port to the board.

Make Your Own PIC12F683 Microcontroller Development Board

Our purpose here is to explore the potential of PIC12F683 microcontroller for which we need a development board. The good thing is we are going to make our own board. The schematic and the actual board that I have built are shown below. I soldered all the components on a 12 x 8 cm general purpose prototyping board. 

 

Completed Board

It has following features in it:

1. A Regulated +5V power supply.

2. 3 Output LEDs that can be connected to any GPIO pins using jumper wires.

3. ON/OFF power supply switch.

4. A Green LED as a power ON indicator.

5. An 8-pin IC socket for PIC12F683 microcontroller.

6. Two potentiometers: one for providing Vref, and other for simulating analog input to ADC.

7. An ICSP header connector.

8. Two tactile switches for input operation.

9. A TTL to RS232 level shifter using a transistor circuit.

10. A piezo buzzer.

11. A DC motor with driving circuit.