Cannot make 16F88 work

[komichal]

Hello everybody,
so far I have been messing around with only 16F84 but now I need to switch to 16F88 because of more memory.

My problem is that I cannot make my code work. I believe I am doing some trivial mistake with datasheet readings. Can anyone please help? I have disabled analog inputs, comparators and interrupts - but there must be something more?

Even this easy "hello world" code that should blink the LED does not work:

Code: Select all

program MyProject;

begin
  TRISA := %00000;                  
  ANSEL := 0;                       
  CMCON := 0;                       
  INTCON := 0;
  PORTA := %00000;                   

  while true do
        Begin
             PORTA.0 := 1;
             Delay_ms (1000);
             PORTA.0 := 0;
             Delay_ms (1000);
        End;

end.

The LED just goes ON and never powers off.

[janni]

Try

Code: Select all

CMCON := 0x07;

to disconnect comparator inputs.

[komichal]

Yeah I tried that (actually you are right - this is the correct way according to the datasheet) but no change in behavior.

My schematics (I replaced the LED with a transistor and a relay):
https://screenshot.net/wmk0qu5

I suppose there is no need to wire in a resistor to MCLR as it is defined as IO with config bits, correct?
Whole circuit is currently powered by 3 fresh AA baterries (voltmeter says 4.8V even with the relay engaged)

My config bits look also OK:
https://screenshot.net/w5897i8

I am running out of ideas... I have bought another 16F88 and it behaves the same. I tried every single IO from the circuit and they are all behaving the same. Anything else worth checking please?

[filip.grujcic]

Hello,

Could you please try to load the configuration scheme I attached and see if it will work after you've done that?

Project --> Edit Project --> Load Scheme...

Kind regards,

[komichal]

Hello there,
with this config scheme the relay wildly and irregularly oscillates (oscillation period varies between some 100ms and 5s).

[filip.grujcic]

Hello,

Try adding the line OSCCON := %01110100; at the beginning of main, using your config scheme and set the frequency to 8 MHz in the Project Settings window.

Kind regards,

[komichal]

Hi Filip,
thank you very much, that OSCCON did the trick! I have to check the datasheet what exactly is affected by this and why it started to work.
Thank you and cheers!
Michal

Code: Select all

ANSEL := 0;                       
CMCON := 0x07;                       
INTCON := 0;
OSCCON := %01110100;

[filip.grujcic]

Hi,

It's the oscillator settings register.

You're welcome, glad I could help.

Kind regards,