PORT C problem on PIC18F2550

[Ormiga]

Hi all,

I'm having problem to use the pins C4 and C5 as digital inputs on a PIC18F2550. They always being read as "0". I already look the UCON register and the USBEN (bit 3 of UCON) is set to "0" (USB disable).

What i'm doing wrong? I saw in the datasheet that at the power on, these pins are configured as input.

I'm using the function input(PIN_C4), but i already used the input_C() and C4 and C5 always "0". I checked the hardware too, the pin voltage is 5v...

Please, somebody help me.

Thank's

Ormiga

[sv_shady]

Post your source, otherway we are just having a chat

[Guest]

Shady,

My code is too big to post it all.

The CB's are

///////////////////////////////////////////////////////////////////
#include <18F2550.h>
#device adc=10
#device icd=true
#fuses HS,DEBUG,NOVREGEN
#use delay(clock=20000000)
#use i2c(Master,slow,sda=PIN_C7,scl=PIN_C6)

.
.
.

void main()
{
setup_timer_0(RTCC_INTERNAL);
setup_timer_1(T1_INTERNAL|T1_DIV_BY_1);
setup_timer_2(T2_DIV_BY_16,255,1);
setup_ccp1(CCP_PWM);
setup_ccp2(CCP_PWM);
range_gain();
strat0=input(PIN_C5);
strat1=input(PIN_C4);
strat1=strat1<<1;
strat=strat1+strat0;
.
.
.
/////////////////////////////////////////////

input(PIN_C5) and input(PIN_C4) returns always 0.
I know that these pins are multiplexed with USB drive (D+ D-), but USB disble is default at power on. I can't understand what's wrong...

Are these pins mapped in ccs pcwh?

Thank's

Ormiga

[Ttelmah]

Is this with a simulator, or the real chip?.
Using the MPLAB simulator, it doesn't work....
If you don't get involved with CCS at all, but generate literally a couple of line assembler program, to loop, then use the external stimulus ability, to set C0 high, then C4 high, and C5 high, you will see that the F82 register (which should reflect the input), does not respond to these higher pins, but happily responds to C0. It could be a simulator fault, or it may be that something else is involved in the config. However looking through the data, nothing else should be involved, and the sheet says that the pins should be set as logic inputs on boot....
TRIS is not involved (not implemented for these pins, which are meant to be input only), and the register access done by CCS, is 'correct', to access the pins (wouldn't apply to the assembler test outlined, which shows the same behaviour).
Annoyingly, the data sheet, does not give a logic diagram of the input section of this pin, making any guessing what else may be involved impractical.
If you are using the sim, I'd say this may well be a simulator fault.

Best Wishes

[Guest]

Ttelmah,

I'm not using sim, i'm just debugging the real circuit with ICD-U40. I know that there are no TRIS bit associate to the pins C4 and C5. How you said, they should wake up as digital input.

Watching the register at debugging, i can see the portC register changing in C7 and C6 (my hardware provide external level input), but not in C4 and C5. I also watch the UCON register, and as spec, bit 3 is 0.

Can you think any other problem with my code?

Thank'

Ormiga

[PCM programmer]

[Ttelmah]

That isn't the answer PCM.
I had tried in CCS, with the following code, before posting:

[PCM programmer]

I'm not sure where I said anything wrong. I made this test program
and it works.
Here's the output when I press a switch on pin C4. The 0's represent
the time when the switch is pressed (connected to ground).

[Ttelmah]

Ok. You are fractionally missing the point I was making.
There is a separate fault, in at least one version of MPLAB (I have tested 7.50, and 8.10), which stops the inputs working _in the simulator_, even if everything is setup right. This was why I queried the simulator/chip in the original posting. It is a caveat, for anyone wanting to test a setup using these pins.
Have just tested your code, and it too, does not respond to an external pin stimulus on these pins.

Best Wishes

[taniguti]

REQUIRE: PIN_C4, PIN_C5 use digital input.

DO: UPUEN, UTRDIS bits is 0.
UPUEN is 0 at powerON (not describe).
UTRDIS is 0 by this source.