C++ “was not declared in this scope” compile error and modification tips


I'm trying to modify this code in an attempt to make it work on an Arduino Mega. I'm pretty much new to C so, I may have made some major mistakes. By the way, this is for a self balancing skateboard. 😛

This code is taken from an ATmega32 (from : [url=http://sites.google.com/site/onewheeledselfbalancing/Home/twin-wheel-self-balancing-skateboard-lightweight-version/code4]http://sites.google.com/site/onewheeledsel…t-version/code4[/url] and I'm trying to make it work on a Arduino Mega.

This code was writen for an ATmega32 developpement board

Thank you!

Here is the first error I encounter :

In function 'void timer_init()':
error: 'TCCR0' was not declared in
this scope In function 'int main()':

Could someone explain me what is wrong?
I'm pretty much a beginner in programming but I've read a lot of books/website and I'm learning fast too! ^^
and here is the complete code (its pretty long):

#include <avr/io.h>
#include <avr/pgmspace.h>
#include <avr/interrupt.h>
#include <math.h>

define CLOCK_SPEED 16000000

define OCR1_MAX 1023

typedef unsigned char u8; void
set_motor_idle(void); void
InitPorts(void); float level=0; float
Throttle_pedal; float aa; float
accelraw; float x_acc; float accsum;
float x_accdeg;

float gyrosum;

float gangleratedeg; float
gangleraterads; float ti = 2.2;

float overallgain; float gaincontrol;
float batteryvolts = 24; float
gyroangledt; float angle; float
anglerads; float balance_torque; float

float cur_speed; float cycle_time =
0.0064; float Balance_point; float a0, a1, a2, a3, a4, a5,
a6;//Savitzky-Golay variables for

int i; int j; int tipstart; void
InitPorts(void) { PORTC=0x00; //Port
C pullups set to low (no output
voltage) to begin with DDRC=0xFF;
//Port C pins all set as output via
the port C direction register //PORTC
|= (1<

DDRA=0x00; //all port A pins set as
input PORTA=0x00; //Port A input
pullups set to low pullups

DDRD=0xFF; //Configure all port D pins
as output as prerequisite for OCR1A
(PinD5) and OCR1B (Pin D4) working

PORTB=0x00; //Port B pullups set to
low (no output voltage) to begin with
DDRB=0xFF; //All port B pins set to

} /* IO: I am using ATMega32 16MHz
with external crystal clock. New
planned pin arrangement to OSMC motor
controller PC4 Onboard LED PD5/OC1A
ALI -> OSMC pin 6 PD4/OC1B BLI ->
OSMC pin 8 PC1 Disable -> OSMC pin 4
PC2 BHI -> OSMC pin 7 PC3 AHI ->
OSMC pin 5 PA6/ADC6 Vbatt/10 ->
OSMC pin 3 PA1/ADC1 pitch rate gyro
PA0/ADC0 accelerometer / void
adc_init(void) { /
turn off
analogue comparator as we don't use it
/ ACSR = (1 << ACD);
select PA0 / ADMUX = 0; ADMUX |=(1< Set ADC
prescaler to 128, enable ADC, and
start conversion / ADCSRA = 0 |
wait until bogus first conversion
finished */ while (ADCSRA & (1 <<
ADSC)) { } }

uint16_t adc_read(uint8_t channel) {
/* select channel / ADMUX =
channel; ADMUX |=(1< start conversion /
ADCSRA |= (1 << ADSC); /
wait until
conversion finished / while (ADCSRA
& (1 << ADSC)) { } /
return the
result */ return ADCW; }

/* 156 cycles per sec, 6.4ms per cycle
the ADC inputs and do some conversion
*/ void sample_inputs(void) {

uint16_t adc0, adc1, adc2, adc3, adc4, adc5;
 gyrosum=0;   adc0 = adc_read(0); /* accelerometer pin PA0 */   accelraw

= (float) adc0;
for (j=0; j<7; j++) {
adc1 = adc_read(1); //gyro pin PA1 gyrosum = (float) gyrosum +
adc1; //using a mean of 7 samples per
loop for the gyro so it gets a
complete update with each loop of the

adc2 = adc_read(2); /* grey wire overallgain (via cutout switch)

position PA2*/ adc3 = adc_read(3);
/* Position lever pulled back position
PA3*/ adc4 = adc_read(4); /*
Throttle_pedal position PA4*/ adc5 =
adc_read(5); /* Position lever pushed
forwards position PA5*/ //adc6 =
adc_read(6); /* Vbatt input from OSMC
(not used at present) position PA6*/
//Sav Golay filter for accel only a0 = a1; a1 = a2; a2 = a3;
a3 = a4; a4 = a5; a5 = a6; a6 =
(float) accelraw; accsum = (float)
((-2*a0) + (3*a1) + (6*a2) + (7*a3) +
(6*a4) + (3*a5) + (-2*a6))/21; //Sav
Golay calculation

    gaincontrol = (float) gaincontrol*0.9 + 0.1*adc2/341;

//smooths any voltage spikes and gives
range 0-3
Throttle_pedal=(float) Throttle_pedal*0.9 + 0.1*adc4/341;
//smooths any voltage spikes and gives
range 0-3

//Cuts the motor if the dead mans
button is let go //(gaincontrol
variable also wired in through this
button to adc2 if (adc2<100) {
overallgain = gaincontrol*softstart;
//what to do if lever pulled back or pushed forwards or not doing
anything: Balance_point = 514;
if (adc3>100) Balance_point=534;

if (adc5>100) Balance_point=494;

 PORTB |= (1<<PB2);//Port B2 turned on/off once per loop so I can

measure loop time with an oscilloscope

/ACCELEROMETER signal processing/
/Subtract offsets/
x_acc=(float) accsum – Balance_point; //accsum is SG value
for accelerometer, not a true "sum" so
no need to divide by 7
if (x_acc<-250) x_acc=-250; //cap accel values to a range of -250 to
+250 (80 degree tilt each way) if (x_acc>250) x_acc=250;
/* Accelerometer angle change is about 3.45 units per degree tilt in
range 0-30 degrees(sin theta) Convert
tilt to degrees of tilt from
accelerometer sensor. Sin angle
roughly = angle for small angles so
no need to do trigonometry. x_acc
below is now in DEGREES*/

x_accdeg= (float) x_acc/-3.45;
//The minus sign corrects for a back
to front accelerometer mounting!

  /*GYRO signal processing*/
 /*Subtract offsets: Sensor reading is 0-1024 so "balance point"

i.e. my required zero point will be
that reading minus 512*/

/Gyro angle change of 20mV per deg
per sec from datasheet gives change of
4.096 units (on the scale of 0 – 1023) per degree per sec angle change This
limits the rate of change of gyro
angle to just less than the maximum
rate it is actually capable of
measuring (100deg/sec). Note all these
fractions are rounded up to an integer
later just before it is sent to the
PWM generator which in turn is
connected to the motor controller
gangleratedeg=(float)((gyrosum/7) – 508)/4.096; //gyrosum is a sum of a group of 7 samples so divide by 7 for
gyro value if (gangleratedeg < -92)
gangleratedeg=-92; if (gangleratedeg

92) gangleratedeg=92 /I turn port B2 on and off once per main program
cycle so I can attach an oscilloscope
to it and work out the program cycle
time I use the cycle time to work out
gyro angle change per cycle where you
have to know the length of this time
/ PORTB &= (0<

/ti represents scaling for the "i"
or integral factor (currently 2.2
here) gyroangledt is anglechange
since last CYCLE in degrees from gyro
sensor, where ti is scaling factor
(should in theory be about 1 but 2.2
makes board feel tighter)
ganglerate is now in units of degrees
per second aa varies the time
constant, i.e smaller aa value makes
accelerometer time constant longer as
it slowly corrects for the gyro

gyroangledt = (float)ticycle_timegangleratedeg;

/new angle in DEGREES is old angle
plus change in angle from gyro since
last cycle with little bit of new
accel reading factored in
/ angle =
(float)((1-aa) * (angle+gyroangledt))
+ (aa * x_accdeg); //the main angle calculating function*/ //Convert
angle from degrees to radians


+ (0.5*gangleraterads);

cur_speed = (float)(cur_speed +
(Throttle_pedal * balance_torque *
cycle_time)) * 0.999;

/*The level value is from -1 to +1 and
represents the duty cycle to be sent
to the motor. Converting to radians
helps us stay within these limits
level = (balance_torque + cur_speed) * overallgain;


void timer_init() { TCCR0 = 0 |

// PWM mode is "PWM, Phase Correct,
10-bit" TCCR1A = 0 | (1<


void set_motor()

/* The leveli terms is the level term
rescaled from -1023 to +1023 as an
integer ready to send to the PWM motor
control ports that are in turn
connected to the OSMC*/ {

//if (level<-0.9) level=
-0.9;//checks we are within sensible limits //if (level>0.9) level=0.9;

int16_t leveli =
(int16_t)(level*1023); //NOTE here we
take the floating point value we have
ended up with for "level", we multiply
it by 1023 and then make it into an
integer before feeding the value into
the PWM generator as "leveli"

if (leveli<-1020)
leveli=-1020;//double-checks we are
within sensible PWM limits as do not
want to suddenly be thrown off the
board if (leveli>1020) leveli=1020;

/Set up LED or buzzer on Port B1 to
warn me to slow down if torque to be
delivered is more than 50% of max
possible The reason for this is that
you always need some reserve motor
power in case you start tipping
forward at speed If motor already
running flat-out you would be about to
fall over at high speed! Some use an
auto-tip back routine to automatically
limit top speed. For now I will do it
this way as easier

if (level<-0.7 || level>0.7) {
PORTB |= (1<
PORTB &= (0<

softstart = (float) softstart+0.001;
if (softstart>1.0) softstart=1.0;

//PORTC |= (0<<PC1);   // AHI=1  PinC3, BHI=1 PinC2 set both to ON for

OSMC to work and both to OFF to shut
motor down /*NOTE: Not sure why but to
stop motor cutting out on direction
changes I had in the end to hard wire
AHI and BHI to +12V / /
OSMC by setting PinC1 output to zero,
a 1 would disable the OSMC*/ PORTC
|= 0x0c; //make C1 pulled down so
un-disables the OSMC i.e. enables it.
PORTC &= ~0x02; //disable is off if
(leveli<0) {
OCR1A = -leveli; // ALI is PWM going backwards as leveli variable is
a negative signed value, keep the
minus sign in here! OCR1B = 0; //
BLI = 0 } else { OCR1A = 0; //
ALI = 0 going forwards as leveli
variable is a positive signed value
OCR1B = leveli; // BLI is PWM } }

int main(void) {



/* Initial tilt-start code Turn on
micro while board tipped to one side,
rider about to step onto it, if tilt
angle crosses zero (mid) point balance
algorithm becomes operational
otherwise locked in this loop forever
until it is tipped to level position
as rider gets onto board*/
tipstart=0; accelraw = 0;

while (tipstart<1){

// you need this to allow the SG
filter to wind up to the proper stable
value when you first turn machine on,
before looking at the value of accsum

for (i=0; i<20; i++) {

if (accsum<504 || accsum>524) { //
if (x_accdeg>0) { tipstart=0; }
else { tipstart=1;
softstart=0.4; } }

angle=0; cur_speed=0; /* end of tilt
start code. If go beyond this point
then machine has become level and is


while (1) { sample_inputs();


} }

Best Solution

You most likely have the wrong MCU specified for your build. While DDRA exists on the ATmega1280 on an Arduino Mega, DDRA does not exist on the ATmega328 of a regular Arduino.

If you're using the Arduino UI, go to Tools | Board and choose Arduino Mega.

If you're using your own build system, you'll need to update the value that you specify for -mmcu= on the gcc command line.

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