Which pins to use for LCD

[ZS1BFE]

I have build a development board for PIC16F877 ,which I am very happy with.

I can do Piggie-back Pcb's for ULN driver and many more.

I have done also a 4x20 LCD, BUT never had to use RS232 or any other comms to PIC.

I am using Port E for LCD control and Port C(lower ) for data on LCD.

Now I need some comms (SPI & I2C) but not sure if I want to do another development board and if so, which pins do I use for LCD.

Thx

 

[wp100]

Hi,

Its more typical to used PortD in 4 bit mode for the 6 or 7 pins needed for the lcd as those pins have less alternative functions.

SPI and IC2 are short range comms between devices so you typically do not need anything more than a direct connection.
Usually buying a couple of cheap eerpom chips is the easiest way to test out those protocols.

For RS232 with a PC or other micro over a longer distance then you need a max232 chip to raise the voltage levels.
However if you have a Pickit2 programmer you can use its USART function to connect the pic to the pc without a max232 chip.

 

[mathespbe]

If u want to use PORTE or PORTA pins as digital I/O u need to configure it on ADCONFIG register. Check the datasheet and configure that pins as digital since by default tey 'll be considered as analog pins in PIC16F877... Or else you can use PORTB,C or D if available...

 

[Venkadesh_M]

PORTD is commonly used for LCD....

 

[ZS1BFE]

Thx for all the advice.
I will start to re-do the layout of my board and get the LCD working on Port D, rather..

THX

 

[Jinzpaul4u]

Hi Venkadesh,

PORTD is commonly used for LCD....

Why??

Best regards

 

[mathespbe]

PORTD is commonly used for LCD....

Why do u prefer PORTD?

 

[Venkadesh_M]

Hi Venkadesh,



Why??

Best regards

beause that is the port which doesnt have any famously used special functions, so that can be used integral 8 lines....

 

[mathespbe]

beause that is the port which doesnt have any famously used special functions, so that can be used integral 8 lines....

PORTD also has PSP right? There is a special function available on that port also.. Then how do u say it has no special functions?

 

[Venkadesh_M]

PORTD also has PSP right? There is a special function available on that port also.. Then how do u say it has no special functions?

Read it once aaagain, famously used...

 

[Jinzpaul4u]

Hi guys,

beause that is the port which doesnt have any famously used special functions, so that can be used integral 8 lines....

Read it once aaagain, famously used...

In common PIC MCU, PORTB and PORTD are implemented as a high load drive ports... means LCD can consider as a High load . and one more fact about PORTD, pins will always free for general purpose application if PORTE and PORTF are absent.

Best regards,

 

[Venkadesh_M]

Hi guys,




In common PIC MCU, PORTB and PORTD are implemented as a high load drive ports... means LCD can consider as a High load . and one more fact about PORTD, pins will always free for general purpose application if PORTE and PORTF are absent.

Best regards,

Hi paul,

I cant get high load drive port, what is the output current in each port...

 

[wp100]

Thx for all the advice.
I will start to re-do the layout of my board and get the LCD working on Port D, rather..

THX

Hi,

Have made my own dev boards over the years, probably on version #4 by now.

As you progress you will find you always need to add extra features you never though you would want.

I use some sockets like these Eblocks which means you can retain your core system but easily add on new devices.
Having the micro on a separate plug in board means its easy to switch to a totally different project /micro.
http://www.matrixmultimedia.com/eblocks.php

- - - Updated - - -

I cant get high load drive port, what is the output current in each port...

It depends on the chip you are using, for the 877A all ports/pin can handle 25ma, though there is a restirction on the total current though the whole chip, around 250-300ma.
The datasheet of each chips , electrical specifications, detail the exact current of the port pins and total loads.

 

[Jinzpaul4u]

Hi,

Hi paul,

I cant get high load drive port, what is the output current in each port...

Sorry I/O ports are high current ports capable of directly driving LEDs and LCDs

Best regards,

 

[Venkadesh_M]

Hi,



Sorry I/O ports are high current ports capable of directly driving LEDs and LCDs

Best regards,

yeah i have looked on the port construction, each port having their own construction for the special operation but still their current ratings are same..........

 

[tpetar]

If there is problem with pins, additional solution can be usage of LCD/GLCD over SPI or I2C, this will take only two wires and can drive more displays then one.

Look to make step forward and use faster PIC18 family, PIC16F877 is old.



Best regards,
Peter

 

[Jinzpaul4u]

Hi,

yeah i have looked on the port construction, each port having their own construction for the special operation but still their current ratings are same..........

I/O ports are high current ports capable of directly driving LEDs (up to 25ma output current). Check PIC18 datasheets
Best regards,

 

[Venkadesh_M]

Hi,



I/O ports are high current ports capable of directly driving LEDs (up to 25ma output current). Check PIC18 datasheets
Best regards,

for any pic

 

[tpetar]

PIC16F877 Mature Product
https://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010241

PIC16F877A Mature Product
https://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010242


Page 149:

Maximum output current sunk by any I/O pin.......................................................25 mA
Maximum output current sourced by any I/O pin ....................................... ..........25 mA
Maximum current sunk by PORTA, PORTB, and PORTE (combined) (Note 3) ..............200 mA
Maximum current sourced by PORTA, PORTB, and PORTE (combined) (Note 3) ..........200 mA
Maximum current sunk by PORTC and PORTD (combined) (Note 3) ..........................200 mA
Maximum current sourced by PORTC and PORTD (combined) (Note 3) ......................200 mA


If needed transistor can be used to drive LCD or something else in purpose to lower dissipation on uC.


Best regards,
Peter

 

[Jinzpaul4u]

Hi,

for any pic

View attachment 95776

admitting i was wrong .. but PORTB and PORTD are designed to drive higher loads(MCU dependents).

Best regards.