Digital I/O on AVR in mikroPascal

[mikroSeven]

Programming mikroPascal ( I love it )
for a while but I don't get a clear total overview about digital I/O.

Configuring single bits or complete byte as input or output.


This example confuses me "Button" ( from mikroPascal PRO for AVR Help )

1) DDB0_bit := 0; // set PORTB to be input
2) DDRC := 0xFF; // configure PORTC as output
3) PORTC := 0xAA; // initial PORTC value


Makes sence: DDR makes a complete output on port C ( complete byte, 8bit )


Whole port B is set to be input, but it shows DDB followed by 0_bit...
Why/how?

Tnx in advance.

[mikroSeven]

What I have working since starting mikroPascal-AVR on my 2560:

Digital-out ( by byte and/or single bit )
LCD by 6 wires ( 4-data, 2-signal )
RS232 uart: to from pc (Lazarus)
ADC: 8 channels, still have to find out how to reach all 16 channels

Digital input: I don't get it.

Can't be that hard...

[Aleksandar.Mitrovic]

Hi,

If you take a look at the datashet for the ATmega2560 you will find :

The DDxn bit in the DDRx Register selects the direction of this pin. If DDxn is written logic one,
Pxn is configured as an output pin. If DDxn is written logic zero, Pxn is configured as an input
pin.

So if you want to use pin as a button it should be input, or in this case DDxn = 0.
Number "0" will seet all register to the value 0, no matter how big it is.
If you are setting whole port to "1" we suggest you to use 0xFF.

Can you please explain it which problem exactly do you have with Digital Inputs and ADC?

Kind regards,
Aleksandar

[mikroSeven]

Tnx.

For the moment, I will study the datasheet.

Want to find out how to acces all the 16 ADC inputs ( channel 8 to 15 ) of the 2560
and a ( better ) understanding of declaration/use of digital input


All regards.

[HardWareMan]

Code: Select all

DDRx  := %00110000; <= Input mode where '0', output mode where '1'
PORTx := %01010101; <= In output mode set output level, in input mode '1' enables pullup for input pin
Temp  := PINx;      <= Read pin state, whatever it mode is.

Just like that:

If you want one bit - you should mask it. F.e. PINx and $01.

Some AVRs support the Pin toggling while it in output mode (2560 does). Writing a logic one to PINxn toggles the value of PORTxn, independent on the value of DDRxn. Note that the SBI instruction can be used to toggle one single bit in a port. That's right: PINx can be written.

As for ADC analog inputs, you should set up DIDR0 and DIDR2 registers to switch off digitall part of port. See ADC section in datasheet.

[mikroSeven]

The data sheet makes sence!.

Slowly things are getting clear!

Before I started to use 2560 ( or better said: microcontrollers at all ),
I had only experience with the 82c55a I/O-periphical chip's on my DIY-ISA-slot-pcb's, programmed in TurboPascal 7.
( http://europakade.nl/motion-control-and-robots )
( https://www.youtube.com/playlist?list=P ... uG4mvriLgJ )

Marcel.

[mikroSeven]

See here the ADC's ( channel 0 to 7 ) reading and send by RS232-uart to pc-Lazarus:

( topic: http://forum.mikroe.com/viewtopic.php?f ... 6&start=30 )

screen ADC values.jpg (17.76 KiB) Viewed 7818 times

[mikroSeven]

It's functioning!

Here full byte as input:

Code: Select all

// init

  DDRC:= 0;          
  PORTC:= 255;     


// some code

  for shCntrButton:= 4 to 7 do       // hardware 4..7 connected
    begin
       if ( pinC.shCntrButton )
         then stOut[shPosInStOut]:= '1'
            else stOut[shPosInStOut]:= '0';

       inc(shPosInStOut);
     end;

Don;t mind 'inc[shPosInStOut], it's of the 'upper-loop'.

[mikroSeven]

Ok!

It works in different ways of coding:

Input 'copied' to an LED-output:

Code: Select all

// init
  portH6_bit:= 0;

  DDRC:= %00000000
  portC:= %00000000

One way:

Code: Select all

// some code
  portH6_bit:= pinC3_bit;  

Another way:

Code: Select all

// some code
  portH.6:= pinC.3;

[mikroSeven]

My understanding of the ADC-functioning has been increased a lot also!

for example:
Reading the ADC channel above [0..7] shouldn't be a problem anymore...
Need MUX bit5.

Made an overview:

ADC briefly a.jpg (247.26 KiB) Viewed 7807 times

ADC briefly b.jpg (103.06 KiB) Viewed 7807 times

[mikroSeven]

Thanks to subscriber voodle for the code above.

From that point, I contineu and add more code.