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rikotech8
Joined: 10 Dec 2011
Posts: 376
Location: Sofiq,Bulgariq
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| SFRs access |
 Posted: Sat Aug 09, 2014 4:09 am |
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Why we cant access SFRs by using pointers?
MB its safety precaution?!?
_________________
A person who never made a mistake never tried anything new. |
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temtronic
Joined: 01 Jul 2010
Posts: 9162
Location: Greensville,Ontario
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| Posted: Sat Aug 09, 2014 5:28 am |
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You need to show us your code as there is no technical reason why you can't.
jay |
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rikotech8
Joined: 10 Dec 2011
Posts: 376
Location: Sofiq,Bulgariq
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| Posted: Sat Aug 09, 2014 7:10 am |
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| Code: |
#include <18F4620.h>
#DEVICE *=16
#use delay(clock=40000000)
#fuses H4, NOWDT, NOLVP, NODEBUG
#use rs232(BAUD=9600, UART1, errors)
#define BUTT PIN_A4
#define BUTT_PRESSED (!INPUT(BUTT))
#define G_LED PIN_A5
#define R_LED PIN_B5
#define Y_LED PIN_B4
#DEFINE LED_OFF(X) OUTPUT_HIGH(X)
#DEFINE LED_ON(X) OUTPUT_LOW(X)
#define LCD_ENABLE_PIN PIN_E2
#define LCD_RS_PIN PIN_E0
#define LCD_RW_PIN PIN_E1
#define LCD_DATA4 PIN_D4
#define LCD_DATA5 PIN_D5
#define LCD_DATA6 PIN_D6
#define LCD_DATA7 PIN_D7
#include <lcd.c>
void *port_b_ponter;
void chip_init(void)
{
led_off(r_led);
led_off(y_led);
led_off(g_led);
port_b_ponter = getenv ("SFR:PORTB");
set_tris_b(0xFF);
lcd_init();
}
void main()
{
chip_init();
while (true)
{
*port_b_ponter = 0xFF;
printf(lcd_putc,"\fAddress = 0x%lX \nValue of reg = 0x%X", port_b_ponter, *port_b_ponter);
delay_ms(500);
*port_b_ponter = 0x00;
printf(lcd_putc,"\fAddress = 0x%lX \nValue of reg = 0x%X", port_b_ponter, *port_b_ponter);
delay_ms(500);
}
} |
_________________
A person who never made a mistake never tried anything new. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19329
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| Posted: Sat Aug 09, 2014 8:57 am |
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| You need to cast the pointer to a type, or actually make the pointer be to a type. A void pointer, does not know how large the object it points to is, until it is told how large this object is. Some languages _assume_ a size, but this is not correct. |
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rikotech8
Joined: 10 Dec 2011
Posts: 376
Location: Sofiq,Bulgariq
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| Posted: Sat Aug 09, 2014 9:42 am |
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OMG I just noticed that I have adjusted the TRIS as inputs.
It works now.
Nevertheless the pointer doesn't have a type, it works.
I might be a problem if increment the pointer (since it doesn't know the memory block length(I dont know what the default for void is. . .)) but it works with void type, structured this way.
I cant believe I didn't notice this (TRIS as inputs).
Excuse me I lost your time.
This way it works, despite of void type of pointer.
As long as I don't increment/ decrement the pointer here is no problem with the void type (my opinion and test approved).
| Code: |
#include <18F4620.h>
#DEVICE *=16
#use delay(clock=40000000)
#fuses H4, NOWDT, NOLVP, NODEBUG
#use rs232(BAUD=9600, UART1, errors)
#define BUTT PIN_A4
#define BUTT_PRESSED (!INPUT(BUTT))
#define G_LED PIN_A5
#define R_LED PIN_B5
#define Y_LED PIN_B4
#DEFINE LED_OFF(X) OUTPUT_HIGH(X)
#DEFINE LED_ON(X) OUTPUT_LOW(X)
#define LCD_ENABLE_PIN PIN_E2
#define LCD_RS_PIN PIN_E0
#define LCD_RW_PIN PIN_E1
#define LCD_DATA4 PIN_D4
#define LCD_DATA5 PIN_D5
#define LCD_DATA6 PIN_D6
#define LCD_DATA7 PIN_D7
#include <lcd.c>
void *port_b_ponter;
void chip_init(void)
{
led_off(r_led);
led_off(y_led);
led_off(g_led);
port_b_ponter = getenv ("SFR:PORTB");
set_tris_b(0x00); //Problem was actualu here
lcd_init();
}
void main()
{
chip_init();
while (true)
{
*port_b_ponter = 0xFF;
printf(lcd_putc,"\fAddress = 0x%lX \nValue of reg = 0x%X", port_b_ponter, *port_b_ponter);
delay_ms(500);
*port_b_ponter = 0x00;
printf(lcd_putc,"\fAddress = 0x%lX \nValue of reg = 0x%X", port_b_ponter, *port_b_ponter);
delay_ms(500);
}
} |
_________________
A person who never made a mistake never tried anything new. |
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rikotech8
Joined: 10 Dec 2011
Posts: 376
Location: Sofiq,Bulgariq
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| Posted: Sat Aug 09, 2014 9:44 am |
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OMG I just noticed that I have adjusted the TRIS as inputs.
It works now.
Nevertheless the pointer doesn't have a type, it works.
I might be a problem if increment the pointer (since it doesn't know the memory block length(I dont know what the default for void is. . .)) but it works with void type, structured this way.
I cant believe I didn't notice this (TRIS as inputs).
Excuse me I lost your time.
This way it works, despite of void type of pointer.
As long as I don't increment/ decrement the pointer here is no problem with the void type (my opinion and test approved).
| Code: |
#include <18F4620.h>
#DEVICE *=16
#use delay(clock=40000000)
#fuses H4, NOWDT, NOLVP, NODEBUG
#use rs232(BAUD=9600, UART1, errors)
#define BUTT PIN_A4
#define BUTT_PRESSED (!INPUT(BUTT))
#define G_LED PIN_A5
#define R_LED PIN_B5
#define Y_LED PIN_B4
#DEFINE LED_OFF(X) OUTPUT_HIGH(X)
#DEFINE LED_ON(X) OUTPUT_LOW(X)
#define LCD_ENABLE_PIN PIN_E2
#define LCD_RS_PIN PIN_E0
#define LCD_RW_PIN PIN_E1
#define LCD_DATA4 PIN_D4
#define LCD_DATA5 PIN_D5
#define LCD_DATA6 PIN_D6
#define LCD_DATA7 PIN_D7
#include <lcd.c>
void *port_b_ponter;
void chip_init(void)
{
led_off(r_led);
led_off(y_led);
led_off(g_led);
port_b_ponter = getenv ("SFR:PORTB");
set_tris_b(0x00); //Problem was actualu here
lcd_init();
}
void main()
{
chip_init();
while (true)
{
*port_b_ponter = 0xFF;
printf(lcd_putc,"\fAddress = 0x%lX \nValue of reg = 0x%X", port_b_ponter, *port_b_ponter);
delay_ms(500);
*port_b_ponter = 0x00;
printf(lcd_putc,"\fAddress = 0x%lX \nValue of reg = 0x%X", port_b_ponter, *port_b_ponter);
delay_ms(500);
}
} |
_________________
A person who never made a mistake never tried anything new. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19329
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| Posted: Sat Aug 09, 2014 1:52 pm |
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| You are implicitly casting, when you read the object inside printf (you read an int). However it will fail if you add an offset, or do any actual pointer operation. Since there is no 'point' in using pointers except to perform a pointer operation, it is important to use a type. |
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