hwa/atmel/avr/examples/04-1-fade-adc/main.c

Fade a LED according to ADC conversion.

This can also be used to drive a servo (brown->ground, red->+6V, yellow->pwm). In that case, it is recommended to use a separated power supply for the servo as an USB RS232 module may not provide enough current.

 
/*  This file is part of the HWA project.
 *  Copyright (c) 2012,2015 Christophe Duparquet.
 *  All rights reserved. Read LICENSE.TXT for details.
 */
 
/*  Include the target board definitions (includes hwa.h)
 */
#include BOARD_H
 
 
/*  The counter used for PWM
 */
#define COUNTER                 counter1
#define COUNTER_CLK_DIV         8
 
 
/*  PWM timings
 */
#if HW_BITS(COUNTER)==16
#  define PWM_PERIOD            0.02            /* 50 Hz */
#  define PWM_TMIN              0               /* set to 0.000300 for servo */
#  define PWM_TMAX              PWM_PERIOD      /* set to 0.003000 for servo */
#else
#  define PWM_PERIOD            0.0002          /* 5 kHz */
#  define PWM_TMIN              0
#  define PWM_TMAX              PWM_PERIOD
#endif
 
 
/*  Clock divider for the ADC
 */
#define ADC_CLK_DIV             128             /* T=~13*128/8=208 µs @8MHz */
 
 
/*  Top value and range of duty value according to PWM timings
 */
#define count_t                 hw_uint_t(HW_BITS(COUNTER))
#define COUNT_TOP               (uint32_t)(HW_SYSHZ*PWM_PERIOD/COUNTER_CLK_DIV)
#define COMPARE_MIN             (count_t)(PWM_TMIN*HW_SYSHZ/COUNTER_CLK_DIV)
#define COMPARE_MAX             (count_t)(PWM_TMAX*HW_SYSHZ/COUNTER_CLK_DIV)
 
 
/*  ATtinyX5s use compare2 as top value, others use compare0
 */
#if defined HW_DEVICE_ATTINYX5
#  define TOP_OBJ               compare2
#else
#  define TOP_OBJ               compare0
#endif
 
 
/*  Use pin AVCC as Vref when possible
 */
#if HW_ADDRESS((pin,avcc)) == -1
#  define VREF                  vcc
#else
#  define VREF                  (pin,avcc)
#endif
 
 
/*  Value to store in the compare unit (must be the same size as the count
 *  register)
 */
static volatile count_t         duty ;
 
 
/*  Service ADC "conversion completed" IRQ: compute duty
 *  Make the ISR interruptible so that counter IRQs are serviced promptly.
 */
HW_ISR( (adc0,irq), interruptible )
{
  /*  Get the new value
   */
  uint16_t adc = hw( read, adc0 );
 
  /*  Low-pass filter
   */
  const uint8_t                 ns = 32 ;       /* # of samples   */
  static uint16_t               lpfsum ;        /* sum of samples */
 
  lpfsum = lpfsum - (lpfsum + ns/2)/ns + adc ;
 
  /*  Compute duty in the range [COMPARE_MIN .. COMPARE_MAX] from lpfsum in the
   *  range [0..ns*1023]
   */
  uint32_t tmp32 = lpfsum ;
  tmp32 = (tmp32 * (COMPARE_MAX-COMPARE_MIN) + ns*1023/2) / (ns*1023) + COMPARE_MIN ;
 
  count_t tmp = tmp32 ;
  if ( sizeof(count_t) > 1 ) {
    hw( disable, interrupts );
    duty = tmp ;
    hw( enable, interrupts );
    /* HW_ATOMIC( */
    /*        duty = tmp ; */
    /*        ); */
  }
  else
    duty = tmp ;
 
  /*  Start a new conversion
   */
  hw( trigger, adc0 );
}
 
 
/*  Service counter-overflow IRQ: turn the LED on and enable the compare IRQ
 *  that turns it off
 */
HW_ISR( (COUNTER,irq,overflow), non_interruptible )
{
  /*  No need to protect access to duty since interrupts are not allowed */
 
  if ( duty ) {
    hw( write, PIN_LED, 1 );
    if ( duty < COUNT_TOP ) {
      hw( write, (COUNTER,compare1), duty );
      hw( enable, (COUNTER,compare1,irq) );
    }
    else
      hw( disable, (COUNTER,compare1,irq) );
  }
  else {
    hw( write, PIN_LED, 0 );
    hw( disable, (COUNTER,compare1,irq) );
  }
}
 
 
/*  Service compare-match IRQ: turn the LED off
 *
 *  Note: if the address of the port register is < 0x40 (assembler 0x20) we can
 *  spare a few bytes and have a faster code using a naked ISR.
 */
#if HW_ADDRESS((PIN_LED,port,port)) < 0x40
HW_ISR( (COUNTER,compare1,irq), naked )
{
  hw( write, PIN_LED, 0 );
  hw_asm("reti");
}
#else
HW_ISR( COUNTER, compare1 )
{
  hw( write, PIN_LED, 0 );
}
#endif
 
 
int main ( )
{
  /*  Create a HWA context to collect the hardware configuration
   *  Preload this context with RESET values
   */
  hwa( begin, reset );
 
  /*  Have the CPU enter idle mode when the 'sleep' instruction is executed.
   */
  hwa( configure,  core0,
       sleep,      enabled,
       sleep_mode, idle      );
 
  /*  Configure LED pin
   */
  hwa( configure, PIN_LED,
       mode,     digital_output   );
 
  /*  Configure analog input pin in analog mode (disable digital input buffer)
   *  and enable the internal pull-up resistor
   */
  hwa( configure, PIN_ANALOG_INPUT,
       mode,      analog_input_pullup );
 
  /*  Check that the counter can handle the top value. This must be done
   *  here since the C preprocessor does not allow floats in expressions.
   */
  if ( COUNT_TOP > ((1UL<<HW_BITS(COUNTER))-1) )
    HWA_E("PWM_COUNTER can not afford PWM_PERIOD.") ;
 
  /*  Configure the counter prescaler
   */
  hwa( configure, (COUNTER,prescaler),
       clock,     ioclk );
 
  /*  Configure the counter to overflow periodically and trigger an interrupt
   *  The counter overflow ISR manages the compare IRQ
   */
  hwa( configure, COUNTER,
       clock,     ioclk / COUNTER_CLK_DIV,
       direction, up_loop,
       bottom,    0,
       top,       TOP_OBJ );
 
  hwa( write, (COUNTER,TOP_OBJ), COUNT_TOP );
  hwa( enable, (COUNTER,irq,overflow) );
 
  /*  Configure the ADC to make a single conversion and trigger an
   *  IRQ. The ISR will start a new conversion after its hard job is done.
   */
  hwa( configure, adc0,
       clock,     ioclk / ADC_CLK_DIV,
       trigger,   manual,
       vref,      VREF,
       align,     right,
       input,     PIN_ANALOG_INPUT );
 
  hwa( enable, (adc0,irq) );
  hwa( trigger, adc0 );
 
  /*  Write this configuration into the hardware
   */
  hwa( commit );
 
  hw( enable, interrupts );
 
  for(;;)
    hw( wait, irq );
 
  return 0 ;
}