VIC™ - A compiler for Microchip’s PIC® Microcontrollers


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Examples

This chapter lists a variety of examples demonstrating how to use VIC™. Most of these examples can be found in the share/examples folder in the source code and in your installation.

Wherever necessary the code is explained. Most of the code is quite obvious and very readable.

Hello World!

This example lights up an LED and can be found in the file share/examples/helloworld.vic. We also demonstrate how to verify everything with a simulator sim_assert statement and other statements to visually display the lighting up of the LED in the simulator interface.

PIC P16F690;

# enable gpsim as a simulator
pragma simulator gpsim;

Main {
    digital_output RC0; # mark pin RC0 as output
    write RC0, 0x1; # write the value 1 to RC0
    sim_assert RC0 == 0x1, "Pin RC0 should be 1";
}

Simulator {
    attach_led RC0;
    stop_after 1s;
    logfile "helloworld.lxt";
    log RC0;
    scope RC0;
}

Synchronous Time Delays

This is a generic piece of code that can be used to test whether the delay functions work as expected and can create the exact delay needed. That’s where the simulators stopwatch function come in handy. The code is available in the file share/examples/delay.vic.

PIC P16F690;

Main {
    delay 1ms;
    sim_assert "*** EARLY STOP ***";
}

Simulator {
    stopwatch 1ms;
}

Blinking an LED

This example blinks an LED and can be found in the file share/examples/blinker.vic.

PIC P16F690;

# enable gpsim as a simulator
pragma simulator gpsim;

Main {
     digital_output RC0;
     Loop {
         write RC0, 1;
         delay 1s;
         write RC0, 0;
         delay 1s;
     }
}

Simulator {
    attach_led RC0, 1, 'green';
    stop_after 30s;
    logfile;
    log RC0;
}

Rotating over LEDs

This example rotates the lighting up of an LED in a loop with a port connected to 4 LEDs. It can be found in the file share/examples/rotater.vic.

PIC P16F690;

# enable gpsim as a simulator
pragma simulator gpsim;

Main {
    digital_output PORTC;
    $display = 0x08; # create a 8-bit register by checking size
    sim_assert $display == 0x08, "$display should be 0x08";
    Loop {
        write PORTC, $display;
        delay 100ms;
        # improve this depiction
        # circular rotate right by 1 bit
        ror $display, 1;
    }
}

Simulator {
    attach_led PORTC, 4; # attach 4 LEDs to PORTC on RC0-RC7;
    stop_after 60s;
    logfile "rotater.lxt";
    log PORTC;
    scope PORTC;
}

Using a 7-segment LED

This example demonstrates how to use a simulator 7-segment LED, a look up table and array indexing to periodically change digits in the LED. Note that the LED look up table is specific to gpsim, and to use a real 7-segment LED these values may have to be changed as per the chosen 7-segment LED. This is also found in the source code as the file share/examples/led7seg.vic.

PIC p16f690;

pragma variable export;
# enable gpsim as a simulator
pragma simulator gpsim;

Main {
    $led7 = table [ 0x3F, 0x06, 0x5B, 0x4F, 0x66, 0x6D,
              0x7D, 0x07, 0x7F, 0x67, 0x77, 0x7C, # this is gpsim specific
              0x58, 0x5E, 0x79, 0x71 ];
    $digit = 0;
    digital_output PORTA;
    digital_output PORTC;
    write PORTA, 0;
    Loop {
        write PORTC, $led7[$digit];
        $digit++;
        $digit &= 0x0F; # bounds check
    }
}

Simulator {
    attach_led7seg RA0, PORTC;
    stop_after 5s;
}

Conditional Loops

This example demonstrates how to use loops and conditional blocks in VIC™. It is available in the source code as the file share/examples/conditional.vic. The simulator code is left as an exercise for the reader.

PIC P16F690;

Main {
    digital_output PORTC;
    $var1 = TRUE;
    $var2 = FALSE;
    Loop {
        if ($var1 != FALSE && $var2 != FALSE) {
            $var1 = !$var2;
            sim_assert $var1 == FALSE, "$var1 == FALSE. block 1";
            write PORTC, 1;
            sim_assert "pause. block 1";
        } else if $var1 || $var2 {
            $var2 = $var1;
            write PORTC, 2;
            sim_assert "pause. block 2";
        } else if !$var1 {
            $var2 = !$var1;
            write PORTC, 4;
            sim_assert "pause. block 3";
        } else if $var2 {
            $var2 = !$var1;
            write PORTC, 4;
            sim_assert "pause. block 4";
        } else {
            write PORTC, 8;
            $var1 = !$var2;
            sim_assert "pause. block 5";
            break;
        };
        $var3 = 0xFF;
        while $var3 != 0 {
            $var3 >>= 1;
        }
    }
    sim_assert "pause. end of main";
}

Simulator {
    attach_led PORTC, 8;
    stop_after 5s;
}

Breaking Out of Nested Loops

This example demonstrates how to use nested loops and the break and continue statements to change the execution logic. The simulator code is left as an exercise to the reader. The code is available in the file share/examples/loopbreak.vic.

PIC P16F690;

Main {
    digital_output PORTC;
    Loop {
        $dummy = 0xFF;
        while $dummy != 0 {
            $dummy >>= 1;
            write PORTC, 1;
            sim_assert $dummy > 0x0F, "dummy is > 0x0F";
            if $dummy <= 0x0F {
                break;
            }
        }
        sim_assert $dummy == 0x0F, "dummy is 0x0F";
        while $dummy > 1 {
            $dummy >>= 1;
            write PORTC, 3;
            continue;
        }
        sim_assert $dummy == 1, "dummy is 1";
        if $dummy == TRUE {
            write PORTC, 2;
            break;
        } else {
            write PORTC, 4;
            continue;
        }
    }
    sim_assert "we have exited the infinite loop 1";
    # we have broken from the loop
    while TRUE {
        write PORTC, 0xFF;
    }
}

Simulator {
    attach_led PORTC, 8;
    stop_after 3s;
}

Mathematical Operations

This code demonstrates the various mathematical operations supported by VIC™ along with verifying them using the simulator’s sim_assert function. All the mathematics is done in 8-bit mode and the code is available in the file share/examples/math8bit.vic.

PIC P16F690;

pragma variable bits = 8;
pragma variable export;

Main {
    $var1 = 12345;
    sim_assert $var1 == 57, "12345 was placed as 57 due to 8-bit mode";
    $var2 = 113;
    $var3 = $var2 + $var1;
    sim_assert $var3 == 170, "57 + 113 = 170";
    $var3 = $var2 - $var1;
    sim_assert $var3 == 56, "113 - 57 = 56";
    $var3 = $var2 * $var1;
    sim_assert $var3 == 41, "113 * 57 = 41";
    $var2 = $var2 * 5;
    sim_assert $var2 == 53, "113 * 5 = 565 => 53 in 8-bit mode";
    $var3 = $var2 / $var1;
    sim_assert $var3 == 0, "53 / 57 = 0 in integer mathematics";
    $var3 = $var2 % $var1;
    sim_assert $var3 == 53, "53 % 57 = 53";
    --$var3;
    sim_assert $var3 == 52, "--53 = 52";
    ++$var3;
    sim_assert $var3 == 53, "++52 = 53";
    $var4 = 64;
    $var4 -= $var1;
    sim_assert $var4 == 7, "64 - 57 = 7";
    $var3 *= 3;
    sim_assert $var3 == 159, "53 * 3 = 159";
    $var2 /= 5;
    sim_assert $var2 == 10, "53 / 5 = 10";
    $var4 %= $var2;
    sim_assert $var4 == 7, "7 % 10 = 7";
    $var4 = 64;
    $var4 ^= 0xFF;
    sim_assert $var4 == 0xBF, "64 ^ 0xFF = 0xBF";
    $var4 |= 0x80;
    sim_assert $var4 == 0xBF, "0xBF | 0x80 = 0xBF";
    $var4 &= 0xAA;
    sim_assert $var4 == 0xAA, "0xBF & 0xAA = 0xAA";
    $var4 = $var4 << 1;
    sim_assert $var4 == 84, "0xAA << 1 = 340 which is 84 in 8-bit mode";
    $var4 = $var4 >> 1;
    sim_assert $var4 == 42, "84 >> 1 = 42";
    $var4 <<= 1;
    sim_assert $var4 == 84, "42 << 1 = 84";
    $var4 >>= 1;
    sim_assert $var4 == 42, "84 >> 1 = 42";
    $var5 = $var1 - $var2 + $var3 * ($var4 + 8) / $var1;
    sim_assert $var5 == 47, "57 - 10 + ((159 * (42 + 8)) & 0xFF) / 57";
    $var7 = 13;
    $var5 = ($var1 + (($var3 * ($var4 + $var7) + 5) + $var2));
    sim_assert $var5 == 113,
        "57 + (((159 * (42 + 13)) & 0xFF + 5) + 10) = 113";
    $var6 = 19;
    $var8 = ($var1 + $var2) - ($var3 * $var4) / ($var5 % $var6);
    sim_assert $var8 == 66, "(57 + 10) - ((159 * 42) & 0xFF) / (113 % 19)";
    # sqrt is a modifier
    $var3 = sqrt $var4;
    sim_assert $var3 == 6,
        "sqrt(42) = 6.4807 which is 6 in integer mathematics";
    sim_assert "*** Completed the simulation ***";
}

Debouncing a Switch

This example shows how to debounce a pin input RA3 connected to a switch and simulate the pressing of the switch using the stimulate statement. The example can be found in share/examples/debouncer.vic.

PIC P16F690;

pragma debounce count = 5;
pragma debounce delay = 1ms;

Main {
    digital_output PORTC;
    digital_input RA3;
    $display = 0;
    Loop {
        debounce RA3,
        Action {
            ++$display;
            write PORTC, $display;
        };
    }
}

Simulator {
    attach_led PORTC, 4, 'red';
    logfile "debouncer.lxt";
    log RA3;
    scope RA3;
    # stimulus should reflect the debounce delay to be viable
    stimulate RA3, every 5s, wave [
        300, 1, 1300, 0,
        1400, 1, 2400, 0,
        2500, 1, 3500, 0,
        3600, 1, 4600, 0,
        4700, 1, 5700, 0,
        5800, 1, 6800, 0,
        6900, 1, 8000, 0
    ];
    stop_after 30s;
    autorun;
}

Analog-to-Digital Converter (ADC) Test

This example demonstrates how to use the ADC of the MCU to read analog information into a digital variable. We also use that variable to adjust the delays to modify the speed of the blinking of an LED connected to the pin RC0. In our case, we tested this on physical hardware where the pin AN0 was connected to a potentiometer switch (variable rotation) and the pin RC0 was connected to an LED. The code can be found in share/examples/adctest.vic.

The difference in use of the stimulate statement is that it accepts floating point values. When the values are floating point then the stimulus is assumed to be analog.

PIC P16F690;

pragma adc right_justify = 0;
Main {
    digital_output RC0;
    analog_input AN0;
    adc_enable 500kHz, AN0;
    Loop {
        adc_read $display;
        delay_ms $display;
        write RC0, 1;
        delay_ms $display;
        write RC0, 0;
        delay 100us;
    }
}

Simulator {
    attach_led RC0;
    stop_after 10s;
    log RC0;
    scope RC0;
    #adc stimulus
    stimulate AN0, every 3s, wave [
        500000, 2.85, 1000000, 3.6,
        1500000, 4.5, 2000000, 3.2,
        2500000, 1.8
    ];
}

Variable Rotation of LEDs

In this example we use the ADC to change the speed of rotation of 4 LEDs connected to the PORTC (pins RC0-RC7) of the MCU. The value is read from the ADC on the AN0 analog pin connected to a variable potentiometer which changes the speed of the lights blinking between the 4 LEDs following the right rotation pattern of bits. It is an enhanced version of the rotating over LEDs example. This example can be found in share/examples/varrotate.vic.

PIC P16F690;

pragma adc right_justify = 0;

Main {
    digital_output PORTC; # all pins
    analog_input RA3;
    adc_enable 500kHz, AN0;
    $display = 0x08; # create a 8-bit register
    Loop {
        write PORTC, $display;
        adc_read $userval;
        $userval += 100;
        delay_ms $userval;
        ror $display, 1;
    }
}

Simulator {
    attach_led PORTC, 4, 'red';
    #adc stimulus
    stimulate AN0, every 3s, wave [
        500000, 2.85, 1000000, 3.6,
        1500000, 4.5, 2000000, 3.2,
        2500000, 1.8
    ];
    scope AN0;
    log AN0;
    stop_after 10s;
}

Reversing LEDs on Switch Press

This is a combination of the debouncing a switch example and the variable rotation example. In this we assume that a push button switch has been connected to the RA3 pin, 4 LEDs have been connected to each pin on PORTC (pins RC0-RC7) and that the analog channel/pin AN0 is connected to a variable potentiometer.

When the user presses a switch the direction of lighting up the 4 LEDs changes from left to right and back. When the user rotates the potentiometer, the speed of blinking of the 4 LEDs changes accordingly. This example can be found in share/examples/reversible.vic. Here we see both the digital and analog stimulus being applied in the Simulator block.

PIC P16F690;

pragma debounce count = 2;
pragma debounce delay = 1ms;
pragma adc right_justify = 0;

Main {
    digital_output PORTC;
    digital_input RA3;
    analog_input AN0;
    adc_enable 500kHz, AN0;
    $display = 0x08; # create a 8-bit register
    $dirxn = FALSE;
    Loop {
        write PORTC, $display;
        adc_read $userval;
        $userval += 100;
        delay_ms $userval;
        debounce RA3, Action {
            $dirxn = !$dirxn;
        };
        if $dirxn == TRUE {
            rol $display, 1;
        } else {
            ror $display, 1;
        };
    }
}

Simulator {
    attach_led PORTC, 4, 'red';
    logfile "reversible.lxt";
    log RA3, AN0;
    scope RA3, AN0;
    # stimulus should reflect the debounce delay to be viable
    stimulate RA3, every 5s, wave [
        300, 1, 1300, 0,
        1400, 1, 2400, 0,
        2500, 1, 3500, 0,
        3600, 1, 4600, 0,
        4700, 1, 5700, 0,
        5800, 1, 6800, 0,
        6900, 1, 8000, 0
    ];
    #adc stimulus
    stimulate AN0, every 3s, wave [
        500000, 2.85, 1000000, 3.6,
        1500000, 4.5, 2000000, 3.2,
        2500000, 1.8
    ];
    stop_after 30s;
    autorun;
}

Timer Usage

This example demonstrates how to use the synchronous timer functions to perform the same task as the delay functions. This is very similar to the Rotating over LEDs example, except that instead of rotating the blinking of the LEDs, it displays the binary values ranging from 0-15 on the LEDs connected to PORTC (pins RC0-RC7). This can be found in the share/examples/timer.vic file.

The timer features, if used, are automatically simulated by the simulator and the user does not have to create any fake stimuli for it.

PIC P16F690;

Main {
    digital_output PORTC;
    $display = 0;
    timer_enable TMR0, 4kHz;
    Loop {
        timer Action {
            ++$display;
            write PORTC, $display;
        };
    }
}

Simulator {
    attach_led PORTC, 8, 'red';
    stop_after 1s;
    autorun;
}

Interrupt Service Routine Usage

This example demonstrates how to use the interrupt service routines to accomplish the same task as in the Reversing LEDs on Switch Press example. This is available in the share/examples/interrupt.vic file. As you can see, the ADC is beign read using the interrupt. This is more efficiently implemented as checking the ADC is now done on an event-based timer instead of using a synchronous MCU loop.

The interrupt handling is automatically simulated by the simulator, but the external stimuli like debouncing the switch and analog stimulus have to still be added by the user.

PIC P16F690;

pragma debounce count = 2;
pragma debounce delay = 1ms;
pragma adc right_justify = 0;

Main {
    digital_output PORTC;
    analog_input AN0;
    digital_input RA3;
    adc_enable 500kHz, AN0;
    $display = 0x08; # create a 8-bit register
    $dirxn = FALSE;
    timer_enable TMR0, 4kHz, ISR { #set the interrupt service routine
        adc_read $userval;
        $userval += 100;
    };
    Loop {
        write PORTC, $display;
        delay_ms $userval;
        debounce RA3, Action {
            $dirxn = !$dirxn;
        };
        if ($dirxn == TRUE) {
            rol $display, 1;
        } else {
            ror $display, 1;
        };
    }
}

Simulator {
    attach_led PORTC, 4, 'red';
    log RA3, AN0;
    scope RA3, AN0;
    # stimulus should reflect the debounce delay to be viable
    stimulate RA3, every 5s, wave [
        300, 1, 1300, 0,
        1400, 1, 2400, 0,
        2500, 1, 3500, 0,
        3600, 1, 4600, 0,
        4700, 1, 5700, 0,
        5800, 1, 6800, 0,
        6900, 1, 8000, 0
    ];
    #adc stimulus
    stimulate AN0, every 3s, wave [
        500000, 2.85, 1000000, 3.6,
        1500000, 4.5, 2000000, 3.2,
        2500000, 1.8
    ];
    stop_after 30s;
    autorun;
}

Reading From Pins

The reading from pins examples are in the files share/examples/reader.vic, share/examples/reader_pin.vic and share/examples/reader_port.vic.

Reading is also supported in the simulator by simulating an input read. Each of these examples demonstrate the various ways of reading from a pin or a port using direct read, Action block read or ISR read.

Direct Read

This example reads from pin RC0 and writes to pin RC1 the value it has read. The wave stimulus can be seen in the simulator’s scope as well.

PIC P16F690;

Main {
    digital_input RC0;
    digital_output RC1;
    read RC0, $value;
    read RC0, Action {
        $value = shift;
        write RC1, $value;
    };
    sim_assert $value == 1;
}

Simulator {
    attach_led RC1;
    log RC1, RC0;
    scope RC1, RC0;
    # a simple 100us high
    stimulate RC0, wave [
        1, 1, 101, 0
    ];
    stop_after 100ms;
    autorun;
}

Interrupt-on-Change Read

This example demonstrates using the interrupt-on-change feature of MCU P16F690’s pin RA0. We simulate a wave after a few microseconds that lasts about 2000 microseconds and then see on the scope if the wave has been replicated on pin RC0 with a delay. This example is in share/examples/reader_pin.vic. A similar example is in share/examples/reader_port.vic.

PIC P16F690;

Main {
    digital_output RC0;
    digital_input RA0;
    read RA0, ISR {
        $value = shift;
        write RC0, $value;
    };
}

Simulator {
    attach_led RC0;
    log RA0, RC0;
    scope RA0, RC0;
    # a simple 100us high
    stimulate RA0, wave [
        100, 1, 2000, 0
    ];
    stop_after 10ms;
    autorun;
}

Pulse Width Modulation (PWM)

Single PWM

The single PWM example can be found in share/examples/pwm2.vic. This example starts a PWM duty cycle at 20% and then updates it to 30%.

The PWM is automatically simulated by the simulator and the user just has to attach an LED and/or a scope to view the output.

PIC P16F690;

Main {
    pwm_single 1220Hz, 20%, CCP1;
    delay 5s;
    pwm_update 1220Hz, 30%; # update duty cycle
    delay 5s;
}
Simulator {
    attach_led CCP1;
    log CCP1;
    scope CCP1;
    autorun;
}

Half-bridge and Full-bridge Modes

This example can be modified to run all the different PWM modes by uncommenting the appropriate line with the required pwm_*bridge function call. It can be found in share/examples/pwm.vic. Here we see the half bridge mode being used and uncommenting the other lines will turn on the forward or reverse full bridge modes.

PIC P16F690;

Main {
    pwm_halfbridge 1220Hz, 20%, 4us;
    #pwm_fullbridge 'forward', 1220Hz, 20%;
    #pwm_fullbridge 'reverse', 1220Hz, 20%;
}

Simulator {
    attach_led CCP1;
    stop_after 100ms;
    log CCP1;
    scope CCP1;
    autorun;
}

This brings us to the end of the list of examples.


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Vikas N Kumar (@vikasnkumar) is the author of VIC™. All copyrights belong to the author and Selective Intellect LLC.

VIC™ is licensed under the license terms of Perl.
The development of VIC™ is sponsored by Selective Intellect LLC.

This page was last updated on 2015-04-02 16:10:35 -0400.