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bkamen
Joined: 07 Jan 2004
Posts: 1611
Location: Central Illinois, USA
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| Dumb question on Unions |
 Posted: Sun Feb 06, 2005 7:35 pm |
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This may seem pretty remedial... but I've never used unions before...
| Code: | struct portd_pin_map {
int LED; // LED's 1-8
} portd ;
#byte portd = 8 // Port C
struct portd_pin_map const PORTD_SET = {0};
struct porte_pin_map {
int LED:2; // LED's 9-10
boolean BAT_LED; // Center LED11
} porte ;
#byte porte = 9 // Port C
struct porte_pin_map const PORTE_SET = {0,0};
union led_map {
int portd.led,
int porte.led
} led_display;
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I don't have that right since I get a compile error (expecting a ; or , -- on the first line inside the union)... so I thought I would ask.
Thanks in advance,
-Ben |
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Mark
Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA
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| Posted: Sun Feb 06, 2005 9:16 pm |
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Not sure what you are trying to do
| Code: |
struct portd_pin_map {
int LED; // LED's 1-8
} portd ;
#byte portd = 8 // Port C
struct portd_pin_map const PORTD_SET = {0};
struct porte_pin_map {
int LED:2; // LED's 9-10
boolean BAT_LED; // Center LED11
} porte ;
#byte porte = 9 // Port C
struct porte_pin_map const PORTE_SET = {0,0};
union led_map {
int somevar1;
int somevar2;
} led_display;
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but that's how to declare a union. Do you know what a union is? From your code I think you probably were trying to do this
| Code: |
struct portd_pin_map {
int LED; // LED's 1-8
} portd ;
#byte portd = 8 // Port C
struct portd_pin_map const PORTD_SET = {0};
struct porte_pin_map {
int LED:2; // LED's 9-10
boolean BAT_LED; // Center LED11
} porte ;
#byte porte = 9 // Port C
struct porte_pin_map const PORTE_SET = {0,0};
union led_map {
struct portd_pin_map portd;
struct porte_pin_map porte;
} led_display;
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But that doesn't really make since either since you location where portd and porte are. Basically the above union is an 8 bit variable that can be accessed by different members but won't have anything to do with portd or porte. What exactly are you trying to do? |
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bkamen
Joined: 07 Jan 2004
Posts: 1611
Location: Central Illinois, USA
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| Posted: Sun Feb 06, 2005 9:25 pm |
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I have 10 LED's (8 on port-D and 2 on port-E) of which I want to assign as a single INT16 so when I set them according to their 10bit value, I can just assign...
The 11th LED is for something else - thus I'd like to make it it's own element.
From what I've read online, I think I'm on the wrong track with Union...
MAKE8(); will be fine too. |
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Charlie U
Joined: 09 Sep 2003
Posts: 183
Location: Somewhere under water in the Great Lakes
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| Posted: Sun Feb 06, 2005 10:35 pm |
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Actually, you may be on the right track with the unions. Here's some code that I whipped up and compiled with 3.212 for the 18F452 and it looks like it might do what you want. First the header file:
| Code: |
#include <18F452.h>
#device adc=8
#use delay(clock=20000000)
#fuses NOWDT,WDT128,HS, NOPROTECT, NOOSCSEN, NOBROWNOUT, BORV20, PUT, \
NOSTVREN, NODEBUG, NOLVP, NOWRT, NOWRTD, NOWRTB, NOWRTC, NOCPD, \
NOCPB, NOEBTR, NOEBTRB
#byte port_a = 0x0F80
#byte port_b = 0x0F81
#byte port_c = 0x0F82
#byte port_d = 0x0F83
#byte port_e = 0x0F84
#bit LED8 = port_e.0
#bit LED9 = port_e.1
struct LED_struct
{
int port_d : 8;
int LED8 : 1;
int LED9 : 1;
int filler : 6;
};
union
{
struct LED_struct LEDs;
long int long_led_data;
}LED_union;
#byte LED_union = 0xF83
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Now the main file:
| Code: |
#include "C:\Cfiles\Tests\union1\union1.h"
void main()
{
setup_adc_ports(NO_ANALOGS);
setup_adc(ADC_OFF);
setup_psp(PSP_DISABLED);
setup_spi(FALSE);
setup_wdt(WDT_OFF);
setup_timer_0(RTCC_INTERNAL);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DISABLED,0,1);
setup_timer_3(T3_DISABLED|T3_DIV_BY_1);
LED_union.long_led_data = 0x0555;
LED_union.LEDs = 0x02AA;
LED_union.LEDs.LED8 = 1;
while(1)
{
;
}
}
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Now here's the listing of the important bits where we manipulate the union:
| Code: |
.................... LED_union.long_led_data = 0x0555;
0046: MOVLW 05
0048: MOVWF F84
004A: MOVLW 55
004C: MOVWF F83
.................... LED_union.LEDs = 0x02AA;
004E: MOVLW 02
0050: MOVWF F84
0052: MOVLW AA
0054: MOVWF F83
.................... LED_union.LEDs.LED8 = 1;
0056: BSF F84.0
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It looks like it might be doing what you want. Note the setting of a bit by accessing it with the union.
Let us know if this is what you are looking for.
Charlie |
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bkamen
Joined: 07 Jan 2004
Posts: 1611
Location: Central Illinois, USA
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| Posted: Mon Feb 07, 2005 12:11 am |
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| Charlie U wrote: | Actually, you may be on the right track with the unions. Here's some code that I whipped up and compiled with 3.212 for the 18F452 and it looks like it might do what you want. First the header file:
code removed for redundancy
It looks like it might be doing what you want. Note the setting of a bit by accessing it with the union.
Let us know if this is what you are looking for.
Charlie |
Actually, that is along the lines of what I'm doing... Thanks... the usage is a lot clearer to me now.
I'm using a 16F877. Quite frankly between union{} and make8(), I really don't mind which as long as I can do it quickly.
Thanks for the help everyone,
-Ben |
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