Newbie - creating a custom port?

[as702ecs]

forgive me since i'm still trying to get to grips with C and PIC programming. I have a PIC18F452 and am trying to configure a 9-bit output using portB<0:7> and portC<0>. How do i create a single variable to define these 2 ports? what i want to do is loop a variable output of values to this port. e.g.

#define TABLE_SIZE 81 //9-bit ouput

void main() {

int table[TABLE_SIZE] =
{
0, 1, 2, 3,
4, 5, 6, 7,
8, 9, 10,11,
12,13,14,15, ...79, 80
};

int i;

for (i=0; i<TABLE_SIZE; i++) {
CUSTOM_PORT = table[i];
delay_us(20);
}
}


i.e. how do i define portB<0:7> and portC<0> to the variable CUSTOM_PORT? Any help anyone could provide would be appreciated. Thanks

[ckielstra]

You can do this with a struct/union combination, but most flexible is a macro. For examples see: I/O pin management

[as702ecs]

ok, would something like this work?

--------------------------------------------------------
#define TABLE_SIZE 16

int pin;
int16 PORTDATA;
int16 pin_table[] = {PIN_C0, PIN_B7, PIN_B6, PIN_B5, PIN_B4,
PIN_B3, PIN_B2, PIN_B1, PIN_B0 };

PORTDATA = pin_table[pin];

int table[TABLE_SIZE] =
{
0, 1, 2, 3,
4, 5, 6, 7,
8, 9, 54, 11,
12, 13, 14, 511
};

int i;

for (i=0; i<TABLE_SIZE; i++) {
PORTDATA = table[i];
delay_us(20);
}

}

or should i use structs?

[as702ecs]

ckielstra, do you mean something like this?


extern volatile near unsigned char PORTDATA;
extern volatile near union {
struct {
unsigned RB0:1;
unsigned RB1:1;
unsigned RB2:1;
unsigned RB3:1;
unsigned RB4:1;
unsigned RB5:1;
unsigned RB6:1;
unsigned RB7:1;
unsigned RC0:1;
};

[ckielstra]

The keywords 'volatile' and 'near' are not supported in CCS.
For example code check the link I provided above (click the blue colered text).

[Mark]

[as702ecs]

i tried setting it up using macros as suggested in http://www.ccsinfo.com/forum/viewtopic.php?t=18949 by PCW Programmer. Unfortunately the memory addresses associated with each output pin have been excluded from the datasheet for the PIC18F452 (PCW Programmer was using a 16F877). Anyway i can find these?

[Mark]

There are not individual addresses for pins on a pic. Only the ports are addressable. The addresses of the ports are in the datasheet.

[as702ecs]

my mistake. in anycase i still cannot find them on the datasheet:
http://ww1.microchip.com/downloads/en/devicedoc/39564b.pdf

section 9.0, I/O Ports

:(

[Mark]

Table 4-1 on page 47.

[as702ecs]

Thanks, Mark. I've been staring at the computer screen for too long! I'll give it a shot.