GPS Project: PIC18F26K22 or PIC18F46K22

[astanapane]

TRISB = %10000000   'use TRISB to specify which pin is (1 = input) and which (0 = output)  (RB7 PORTB.7 is the RX input pin of the EUART, the rest are output)
TRISC = %10000000   'use TRISC to specify which pin is (1 = input) and which (0 = output)  (RC7 PORTC.7 is the RX input pin of the EUART, the rest are output)
                    'in PORTC the RC3 attached is an LED.

setting the tris incorrectly will stop the eusarts from working


from data sheet

Setting the TXEN bit of the TXSTAx register enables thetransmitter circuitry of the EUSART. Clearing the SYNC
bit of the TXSTAx register configures the EUSART for
asynchronous operation. Setting the SPEN bit of the
RCSTAx register enables the EUSART and
automatically configures the TXx/CKx I/O pin as an
output. If the TXx/CKx pin is shared with an analog
peripheral the analog I/O function must be disabled by
clearing the corresponding ANSEL bit.

To be honest i didnt really understand the statement. I understand that it is not necessary to set a TRIS register at TX bit as automatically the TX configured as an output.....

TRISB = %10000000   'use TRISB to specify which pin is (1 = input) and which (0 = output)  (RB7 PORTB.7 is the RX input pin of the EUART, the rest are output)
TRISC = %10000000   'use TRISC to specify which pin is (1 = input) and which (0 = output)  (RC7 PORTC.7 is the RX input pin of the EUART, the rest are output)
                    'in PORTC the RC3 attached is an LED.

as we have already stated and configured the EUSART with the following:

'*-----------------------------------------------------------------------------|
'*                        |  --------------------- |                           |
'*----------------------- | EUART 1 Configuration  | --------------------------|
'*                        |  --------------------- |                           |
'*-----------------------------------------------------------------------------|

        DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
        DEFINE HSER_TXSTA 24h ' Enable transmit, BRGH = 1
        DEFINE HSER_CLROERR 1 ' Clear overflow automatically
        DEFINE HSER_SPBRG 160 ' 38400 Baud @ 64MHz, -0,08%
        SPBRGH = 1
        BAUDCON.3 = 1         ' Enable 16 bit baudrate generator
        
'*-----------------------------------------------------------------------------|
'*                        |  --------------------- |                           |
'*----------------------- | EUART 2 Configuration  | --------------------------|
'*                        |  --------------------- |                           |
'*-----------------------------------------------------------------------------|

        DEFINE HSER2_RCSTA 90h ' Enable serial port & continuous receive
        DEFINE HSER2_TXSTA 24h ' Enable transmit, BRGH = 1
        DEFINE HSER2_CLROERR 1 ' Clear overflow automatically
        DEFINE HSER2_SPBRG 160 ' 38400 Baud @ 64MHz, -0,08%
        SPBRGH2 = 1
        BAUDCON2.3 = 1         ' Enable 16 bit baudrate generator
        
'*-----------------------------------------------------------------------------|
'*-----------------------------------------------------------------------------|

How Do we configure the rest of the TRIS bits?

TRISB = %1X000000   'use TRISB to specify which pin is (1 = input) and which (0 = output)  (RB7 PORTB.7 is the RX input pin of the EUART, the rest are output)
TRISC = %1X000000   'use TRISC to specify which pin is (1 = input) and which (0 = output)  (RC7 PORTC.7 is the RX input pin of the EUART, the rest are output)
                    'in PORTC the RC3 attached is an LED.

[richard]

How Do we configure the rest of the TRIS bits?

when you read

Setting the SPEN bit of the
RCSTAx register enables the EUSART and
automatically configures the TXx/CKx I/O pin as an
output.

in the eusart section it means its unnecessary to clear the tris bit for the tx pin, keep in mind that on some chips clearing the tx pin tris bit
will stop the eusart from working . I prefer to form good habits ,although the 18f26k22 does not seem to object and functions either way .

[astanapane]

Richard, bardon me. Still im confused from your answer.

I understand the part of setting up the EUSART, automatically we make the TX port as an output.

My question is, what do we do with the rest of the TRISB and TRISC bits apart from the RX/TX.

TRISA = %00000000   'use TRISA to specify which pin is (1 = input) and which (0 = output)  (ALL pins are output)
TRISB = %10000000   'use TRISB to specify which pin is (1 = input) and which (0 = output)  (RB7 PORTB.7 is the RX input pin of the EUART, the rest are output)
TRISC = %10000000   'use TRISC to specify which pin is (1 = input) and which (0 = output)  (RC7 PORTC.7 is the RX input pin of the EUART, the rest are output)
                    'in PORTC the RC3 attached is an LED. 

'           --------------- TRIS A-B-C ---------------
'------------------------------------------------------------------------|
' PORTA.7  PORTA.6  PORTA.5  PORTA.4  PORTA.3  PORTA.2  PORTA.1  PORTA.0 |
'  bit7     bit6     bit5     bit4     bit3     bit2     bit1     bit0   |
'   0        0        0        0        0        0        0        0     |
'------------------------------------------------------------------------|
'------------------------------------------------------------------------|
' PORTB.7  PORTB.6  PORTB.5  PORTB.4  PORTB.3  PORTB.2  PORTB.1  PORTB.0 |
'  bit7     bit6     bit5     bit4     bit3     bit2     bit1     bit0   |
'   1        0        0        0        0        0        0        0     |
'------------------------------------------------------------------------|
'------------------------------------------------------------------------|
' PORTC.7  PORTC.6  PORTC.5  PORTC.4  PORTC.3  PORTC.2  PORTC.1  PORTC.0 |
'  bit7     bit6     bit5     bit4     bit3     bit2     bit1     bit0   |
'   1        0        0        0        0        0        0        0     |
'------------------------------------------------------------------------|

I feel like i'm missing something. Sorry for my questions, but i would like to be sure i understand every part of the code. And when i configure the ports as an input or outputs, or Digital/Analogue, i need to know exactly what am i doing.

In our case as we want to configure the EUSART, as you stated from the manual -datasheet, we have automatically the TX pin as an output. But dont we continue to specify the other pins with the TRIS command?

[richard]

My question is, what do we do with the rest of the TRISB and TRISC bits apart from the RX/TX

.
that would depend entirely on what you want do with each pin , if and only if you need it to be an output clear the corresponding tris bit

[astanapane]

.
that would depend entirely on what you want do with each pin , if and only if you need it to be an output clear the corresponding tris bit

Thanks a lot for your answer. I guess we cant leave unassigned the bits. Normally as far as i have learned from what i have read in this forum, it is better to configure the bits of each port and give an Input or Output direction in addition to high or low stage.

[richard]

I guess we cant leave unassigned the bits

there is no such state , pins are either inputs or outputs or analog inputs , outputs can only be high or low
if you have no reason to use a pin as an output then leave as an input , if you have no reason to use a pin as a digital input you can leave it analog
the pic chip won't care. the pic chip does not care if outputs are high or low its only what they connect to that cares , it up to you to initialise the pins
in use to the correct type/state and direction to match the requirement of what they connect to and then make sure they stay that way.

[astanapane]

there is no such state , pins are either inputs or outputs or analog inputs , outputs can only be high or low
if you have no reason to use a pin as an output then leave as an input , if you have no reason to use a pin as a digital input you can leave it analog
the pic chip won't care. the pic chip does not care if outputs are high or low its only what they connect to that cares , it up to you to initialise the pins
in use to the correct type/state and direction to match the requirement of what they connect to and then make sure they stay that way.

now it is clear. Really appreciate your help.

Thanks a lot Richard.

[Ioannis]

I have my doubts on leaving inputs floating.

Usually if I have any unused ports, I turn them as outputs and clear them.

If they are inputs, maybe enable the pull ups if any or tie them to ground.

A floating pin can cause troubles in certain cases.

Ioannis