[avr-gcc-list] if statement problem

[Paulo Abreu]

I am doing this peace of code:

 

(my problem is expressed in the end)

*****************************************************************************

#include <io8535.h>
#include <io.h>
#include <interrupt.h>
#include <sig-avr.h>

 

///////////////////////////////////////////////////////////////////////////////////////////////////
// uart
//#define UART_9BIT          0x00
//#define UART_8BIT          0x01
//
#define F_CPU         6144000     /* 6,144Mhz */
#define UART_BAUD_RATE       9600     /* 9600 baud */
#define UART_BAUD_SELECT (F_CPU/(UART_BAUD_RATE*16l)-1)
#define UART_INSTRUCTION_SIZE     4

 

#define NONE   0
#define RECEIVING  1
#define RESPONDING  2
#define SHARPS_NUMBER 5
#define COMMAND_SIZE 1
#define MY_ID   0x10

 

uint8_t g_orderStatus;

 

uint8_t g_sharps[SHARPS_NUMBER]= {'A', 'B', 'C', 'D', 'E'};
uint8_t g_lastCommand[COMMAND_SIZE]= {0}; // stores last uart command
  
static uint8_t g_index;     // indice do array a usar

 

// ----------------------------------------------------------------------------
//  Recepção de caracter
SIGNAL(SIG_UART_RECV)
{
 register uint8_t sreg_temp= inp(SREG);   
 register uint8_t temp= inp(UDR);    
 
 switch (g_orderStatus)
 {
  case NONE:
   if ((temp & 0xf0) == MY_ID)
   {
    g_orderStatus= RECEIVING;
    g_index= 0;
    g_lastCommand[g_index++]= temp;
   }
   break;
  case RECEIVING:
   if (g_index <COMMAND_SIZE)
   {
    g_lastCommand[g_index++]= temp;
   }
   else
   {
    cbi(UCR, RXCIE); 
    g_index=0;
    g_orderStatus= RESPONDING;
   }
 }
 outp(sreg_temp, SREG);           
 sei();
}

 

int main(void)
{ 
 g_orderStatus= NONE;
 
 // Inicializações */

 

 outp( BV(RXCIE) | BV(RXEN) | BV(TXEN), UCR ); // Permite o envio e a recepção e activa a interrupção de recepção
 outp((unsigned char)UART_BAUD_SELECT, UBRR); // set baud rate
 sei();

 

 // inicialmente a uart espera por uma intrução. Após receber uma instrução só volta a receber outra quando a instrução for avaliada
 while(1)
 {
  if (g_orderStatus == RESPONDING)
  {
   register uint8_t *p;

 

   // verifica o comando
   switch(g_lastCommand[0] & 0x0f)
   {
    case 0x01:
     // enviar os charps todos
     p=  g_sharps;
     g_index= SHARPS_NUMBER;
     break;
   } 
   
   for(; g_index > 0; --g_index)
   {
    outp(*p++, UDR);
    loop_until_bit_is_set(USR, TXC);
    g_orderStatus= NONE;
   }

 

   sbi(UCR, RXCIE);   // activa a interrupção de recepção
  }

 

 }
}

 

 

**************************************************************************

 

In debug mode, sending 0x11, g_orderStatus is set with 0x2 ... gowever when I get to if (g_orderStatus == RESPONDING), the _expression_ is evaluated as false;

 

register uint8_t temp= inp(UDR);  

+00000039: B12C      IN      R18,0xC

 

After R18 get RESPONDING something is wrong, when I rich: if (g_orderStatus == RESPONDING)

debugger points to +0000006F, and LDS     R18,0x0067 never runs ... (+00000069).

 

Since in interrup routine maques a pop to R18 at the end, and R18 is never restored,  if (g_orderStatus == RESPONDING) is always false ...

 

I don't get ..... I also tried a break point at +00000069 and never stops ....

 

 +00000069: 91200067  LDS     R18,0x0067
   +0000006B: 91300065  LDS     R19,0x0065
   +0000006D: 91900066  LDS     R25,0x0066
   +0000006F: 3022      CPI     R18,0x02          ; 0x02 = 0b00000010 = 2
   +00000070: F7F1      BRNE    -0x02             ; Destination: 0x00006F
   +00000071: 2F83      MOV     R24,R19
   +00000072: 708F      ANDI    R24,0x0F          ; 0x0F = 0b00001111 = 15
   +00000073: 3081      CPI     R24,0x01          ; 0x01 = 0b00000001 = 1
   +00000074: F059      BREQ    +0x0B             ; Destination: 0x000080

Thanks for your attention,

 

Paulo Abreu