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weg22
Joined: 08 Jul 2005
Posts: 91
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| not enough RAM for all variables?? |
 Posted: Mon Aug 01, 2005 5:49 am |
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Does anyone know what the limit is on the amount of variables you can define? I listed my variables below (which I didn't think was a lot) which have prompted the "not enough RAM for all variables" error. I'd like to know just how many variables I have to eliminate? I know the "data" array is taking up a lot, but I'm using it to receive 9 BYTES of data over RS232. Also, maybe there is a better way of doing this?
Oh yeah, I am using a PIC16F84
| Code: |
int i;
int rud_pwm, elev_pwm, ail_pwm;
int data[9];
int ref;
double r, p, y;
double Kp, error;
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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| Posted: Mon Aug 01, 2005 6:42 am |
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From the CCS manual: | Quote: | | double Is a reserved word but is not a supported data type. |
Tricky, I've no clue as to what the compiler will do with this. Fix this first.
Let's assume a double has the same size as a float, then you are allocating a total of 34 bytes. The PIC16F84A has 68 bytes of RAM so this shouldn't be a problem.
In many PIC16 parts the 'out of RAM' problem is caused by the RAM being spread over multiple banks, for the compiler to effectively address these banks you have to add the '#device *=16' directive to tell the compiler to use 16 bit addressing. Your processor has all RAM in a single bank so I don't think this is the cause of your error. You might try to add '#device *=8' at the top of your program, it won't hurt. |
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Mark
Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA
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| Posted: Mon Aug 01, 2005 6:44 am |
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| I can't believe that you are out of RAM with just those. The 16F84 has 128 bytes. double is not a valid datatype for CCS. Maybe that is causing the problem. Try changing the data type. What range do those values need to be? Refer to the CCS manual or help file to see the valid types and their ranges. |
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weg22
Joined: 08 Jul 2005
Posts: 91
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| Posted: Mon Aug 01, 2005 6:54 am |
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Yeah, I thought it had 64 bytes of memory. I tried your suggestions (i.e. changing double to float and the #device), but still no luck. One thing I didn't mention is that I am using interrupts - I am not sure how this effects the memory? Also, I am declaring 4 of those variables globally. I included the entire first part of my code to get a better idea of what I am doing...
Thanks in advance,
weg
| Code: |
#include <16F84.H>
#include <stdlib.h>
#include <math.h>
#define A0 PIN_A0
#define A1 PIN_A1
#define B0 PIN_B0
#define B1 PIN_B1
/*-----------------------------------------------------*/
/* No Watch Dog Timer (NOWDT)
/* No Protect
/* Power Up Timer (PUT)
/* 10 MHz Clock
/* RS232 define for PIC-IMU communication (IMU)
/* RS232 define for PIC-PC communication (PC)
/*-----------------------------------------------------*/
#fuses HS,NOWDT,NOPROTECT, PUT
#use delay(clock=10000000)
#use rs232(baud=38400, xmit=A1, rcv=A0)
int i;
int rud_pwm, elev_pwm, ail_pwm;
//Timer interrupt to generate PWM signals
#INT_TIMER0
void pwm_signal()
{
//One of the parameters used to cause the interrupt to occur every 22.5 msec
set_timer0(37); // 61 for 20 msec
/*--------RUDDER 0 (right), 255 (left) --------*/
output_high(B0); // generates initial high time ie 1 msec
delay_us(1000);
i=0;
for(i=0;i<rud_pwm;i++) // generates remaining high time, varied by variable "pwm"
{
//use this to tune duty cycle
delay_us(1);
}
output_low(B0);
/*--------ELEVATOR 0 (up), 255 (down) --------*/
output_high(B1); // generates initial high time ie 1 msec
delay_us(1000);
i=0;
for(i=0;i<elev_pwm;i++) // generates remaining high time, varied by variable "pwm"
{
//use this to tune duty cycle
delay_us(1);
}
output_low(B1);
}
main()
{
int data[9];
int ref;
float r, p, y;
float Kp, error;
// enable timer interrupts
enable_interrupts(INT_TIMER0);
enable_interrupts(GLOBAL);
//the other parameter used to cause interrupt to occur every 20 msec
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_256);
while(1)
{
// main code is here
}
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weg22
Joined: 08 Jul 2005
Posts: 91
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| Posted: Mon Aug 01, 2005 7:07 am |
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In addition to the last post, I found something else I thought was strange and thought this might help you help me :-) Executing the following:
r=1/2;
p=1/4;
y=1/3;
and compiling it, everything works nicely. However, if I do something a little more complicated:
r = 2*asin((data[3]*256 + data[4])/8192)*180/3.14; // roll angle
p = 2*asin((data[5]*256 + data[6])/8192)*180/3.14; // pitch angle
y = 2*asin((data[7]*256 + data[8])/8192)*180/3.14; // yaw angle
I get the "not enough RAM" error? |
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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| Posted: Mon Aug 01, 2005 7:56 am |
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In general: Calculations with float variables require a lot of ROM and RAM, in processors with limited memory you should try to avoid using float at all.
I compiled your program and added some simple calculations using float additions, this resulted in a 64 to 81 bytes RAM usage. Adding a call to sin() increased the RAM usage to 134 bytes.
There is no way you will be able to optimize your current code so it will fit in a PIC16F84. Either use a chip with triple the amount of RAM, or change your code so it doesn't use floats. |
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