pic16f684 portA a0 pin problem

[max]

Hi,

I am using the following simple program to toggle port-A bits, using ccs 5.078 compiler
The port A0 pin is not toggling, permanently high.
The hardware have no problem, i.e no short circuit to supply or other pins.

Regards

[Thiru09]

Code has no problem, simulated with Proteus (CCS 5.078, cof file).
Check your hardware again.
Try to test with another port pin (ex: RC0) to verify whether controller is running or not.

Regards,
Thiru

[h0nk]

Hello max,

check the contents of the ANSEL and CMCON0 Register.
It looks like that the plain IO-function is not enabled.
ANSEL should read all zeros and CMCON0 07h.
(Datasheet pg. 31)


Best Regards

[Thiru09]

This line takes care of that. setup_comparator(NC_NC_NC_NC);
Same for ANSEL

Regards
Thiru

[max]

Hi,

Thanks for reply, the hardware is ok.
The port pin RA1 is toggling, so the controller is running.
I also test the port c pin, working ok.
Only RA0 is permanently High, not toggling.

Regards 

[Thiru09]

Now possibilities narrow down to either specific IC problem or with connected circuit.
Can you post cof or hex file?

Regards,
Thiru

[max]

Hi Thiru

See the attached zip file.
I think the problem is related to compiler.

Regards

[Thiru09]

Hi max,

Your compiled hex/cof is working fine in proteus.
(Since 16F684 is not available with me, I am testing with proteus).

I am attaching sample XC8 (v2.30) project here. Please test with the hex file.
"\dist\default\production\Projects.production.hex" or Projects.production.elf

I have not enabled ADC function on RA2 for testing purpose. Let us check first with basic settings.
Don't bother oscillator configuration. Just test RA0 status

Regards,
Thiru

[max]

Hi Thiru

I tested the hardware with the xc8 hex file, same result as ccs

RA0  High
RA1  Toggling
RC0  Toggling

Regards

[Poty]

Hi, Max.
I had a similar problem with a 18F4620... and it was related to the ANSEL function. You must check that the definition of ADC ports is pretty clear. Check the basic configuration, and, over all that, define EXPLICITELLY which ports are digital and which none. Even if your definition is redundant, it is better an excess...
Just make an intensive lecture of the datasheet. As many times as you need to prerfectly understand which ports are ADC by defect.

Be patient, and good luck.

Regards,

[h0nk]

The PIC 16F684 has no output latches and reads data from the input pins.
I dont know the CCS-implementation of "output_toggle" but i assume that this function reads its data from the input pin also. If there is too much capacitive load on the pin it would not toggle.

Change your code to:

while(TRUE)
  {
   clear_pin(LED1_PIN);
   clear_pin(LED2_PIN);
   delay_ms(500);
   set_pin(LED1_PIN);
   set_pin(LED2_PIN);
   delay_ms(500);
  }

I dont know CCS, so exchange clear_pin and set_pin with the corresponding function of the CCS-library.

Best Regards


P.S.: The 16F684 is not ridiculous overengineered.
Simply write ANSEL=0; and CMCON0=7; in your code,
as even the datasheet suggeste, and you perfectly done.

[max]

Hi,

I manage to toggle the A0 pin.
I use a shadow var to keep the port status, and output this var to port-A
i.e using the function output_a().
This means read-modify-write did not working on A0 pin, while A1 pin
is working properly, both A0 and A1 pins have same type of loading.

Regards

[Poty]

Good evening.

Datasheet explicitly indicates this:

"The ANSEL and CMCON0 registers must
be initialized to configure an analog
channel as a digital input. Pins configured
as analog inputs will read ‘0’."

 I´m not familiar with mcc, but as I understand from datasheet, you have to configure ANSEL and CMCON0 to define A0 and A1 as digital ports, and then configure TRISA to define this ones as input/ouput pins. As default (POR, BOR or any  other reset), ANSEL has "1" in all its bits, so, all of them are defined as analog ports.
I guess you have to check mcc instructions, and verify that ANSEL definitions are explicitly followed.

Anyway, if you got it through that shadow var, and don´t mess with memory capacity, well, fine! 

Happy new year!!!!

Regards,