628 can't make a3,a4 output

[drolleman]

I can't make the 628 output on a3 and a 4. i created a minimum progran to test for output. but nothing i try works. can anyone help?

#include <16f628.h>
#fuses intrc,WDT,PROTECT,NOBROWNOUT,PUT,NOLVP,NOCPD
#use delay(clock=4000000)
//#use rs232(baud=9600, xmit=PIN_B2, rcv=PIN_B1,enable=pin_a0) // Jumpers: 8
//#use fixed_io(a_outputs=pin_a0, pin_a1, pin_a2, pin_a3, pin_a4)
//#use fixed_io(a_outputs=pin_a0, pin_a1, pin_a2, pin_a3, pin_a4)

/////////////////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////////////
///////////////////// MAIN ///////////////////////////////////////

/////////////////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////////////

main()
{
//set_tris_b(0x00);
set_tris_a(0x00);
//setup_ccp1(ccp_off);
//setup_comparator(a0_a3_a1_a2);

//output_low(PIN_A0);
output_high(PIN_A3);
output_high(PIN_A4);

// for setting the calibration of the rev limiter
//ground the pin on start then within 5 sec then release
// this puts the chip into calibration mode
while(1)

{
output_high(PIN_A0);
output_high(PIN_A1);
output_high(PIN_A2);
output_high(PIN_A3);
output_high(PIN_A4);

delay_ms(500);
output_low(PIN_A0);
output_low(PIN_A1);
output_low(PIN_A2);
output_low(PIN_A3);
output_low(PIN_A4);
delay_ms(500);
}

return 0;
}

[dyeatman]

According to the 16F628 data sheet RA4/AN4 is open collector
so you will need a pullup resistor there.

Try adding the line:

setup_comparator(NC_NC_NC_NC);

To make sure the the comparators are turned off and the pins are in digital mode.

[drolleman]

that fixed a4 but a3 still doesn't work i know the output works because when the device wasn't programed the led that is connected to the pin was on. I added the nc on the comparater that was sugessted. is there somthing else i need to do?

[asjad]

Hi,

I have looked at the datasheet and it seems that when ever your
pic and most pics are powerd up PORTA is not configured as
digital Input/Output

Look at the top right of page 31 of the datasheet.


To cure this you need to look at the A/D convertor commands.

one of the commands will set diffrent pins on port A to digital.
_________________
Best Regards

[drolleman]

the 628 doesn't have a/d convereter.

[Ttelmah]