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#include "mcu/task/context.h"
char* stack_init(const char* const mem_low, const char* const mem_high, void (*entry)(char), char args) {
char* sp = (char*) mem_high;
unsigned long address = (unsigned long) entry;
// pattern for debugging purposes
*sp = (char) 0x1;
sp--;
*sp = (char) 0x2;
sp--;
*sp = (char) 0x1;
sp--;
*sp = (char) 0x2;
sp--;
// put return address on stack
*sp = (char) ( address & (unsigned short) 0x00ff );
sp--;
*sp = (char) ( (address >> 8) & ( unsigned short ) 0x00ff );
sp--;
*sp = (char) ( (address >> 16) & ( unsigned short ) 0x00ff );
sp--;
// save registers
*sp = (char) 0x00; //r0
sp--;
*sp = (char) 0x80; //SREG, enable interrupts when task starts
sp--;
*sp = ( char ) 0x00; //r1
sp--;
*sp = ( char ) 0x00; //r2
sp--;
*sp = ( char ) 0x00; //r3
sp--;
*sp = ( char ) 0x00; //r4
sp--;
*sp = ( char ) 0x00; //r5
sp--;
*sp = ( char ) 0x00; //r6
sp--;
*sp = ( char ) 0x00; //r7
sp--;
*sp = ( char ) 0x00; //r8
sp--;
*sp = ( char ) 0x00; //r9
sp--;
*sp = ( char ) 0x00; //r10
sp--;
*sp = ( char ) 0x00; //r11
sp--;
*sp = ( char ) 0x00; //r12
sp--;
*sp = ( char ) 0x00; //r13
sp--;
*sp = ( char ) 0x00; //r14
sp--;
*sp = ( char ) 0x00; //r15
sp--;
*sp = ( char ) 0x00; //r16
sp--;
*sp = ( char ) 0x00; //r17
sp--;
*sp = ( char ) 0x00; //r18
sp--;
*sp = ( char ) 0x00; //r19
sp--;
*sp = ( char ) 0x00; //r20
sp--;
*sp = ( char ) 0x00; //r21
sp--;
*sp = ( char ) 0x00; //r22
sp--;
*sp = ( char ) 0x00; //r23
sp--;
*sp = (char) ( args ); //place first argument in register 24
sp--;
*sp = ( char ) 0x00; //r25
sp--;
*sp = ( char ) 0x00; //r26
sp--;
*sp = ( char ) 0x00; //r27
sp--;
*sp = ( char ) 0x00; //r28
sp--;
*sp = ( char ) 0x00; //r29
sp--;
*sp = ( char ) 0x00; //r30
sp--;
*sp = ( char ) 0x00; //r31
sp--;
return sp;
}
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