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////////////////////////////////////////////////////////////////////////////////

//

// Filename:    display.c

//

// Project:     CMod S6 System on a Chip, ZipCPU demonstration project

//

// Purpose:     A device driver for the SPI controlled display.  The primary

//              purpose of this "device" is to output SPI instructions, though,

//      not to handle screen position or to optimize data set to the display.

//

// Creator:     Dan Gisselquist, Ph.D.

//              Gisselquist Technology, LLC

//

////////////////////////////////////////////////////////////////////////////////

//

// Copyright (C) 2015-2017, Gisselquist Technology, LLC

//

// This program is free software (firmware): you can redistribute it and/or

// modify it under the terms of  the GNU General Public License as published

// by the Free Software Foundation, either version 3 of the License, or (at

// your option) any later version.

//

// This program is distributed in the hope that it will be useful, but WITHOUT

// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or

// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

// for more details.

//

// You should have received a copy of the GNU General Public License along

// with this program.  (It's in the $(ROOT)/doc directory, run make with no

// target there if the PDF file isn't present.)  If not, see

// <http://www.gnu.org/licenses/> for a copy.

//

// License:     GPL, v3, as defined and found on www.gnu.org,

//              http://www.gnu.org/licenses/gpl.html

//

//

////////////////////////////////////////////////////////////////////////////////

//

//

#include "board.h"

#include "display.h"

static void     dispwait(void) {

        // Slow us down to the speed the display can handle

        // We want to delay about 0x800 clocks.

        // Three instructions per loop,

        //      LBL:

        //              NOOP

        //              ADD -1,CTR

        //              BNZ LBL

        //      40 clocks per instruction, as required by the SPI flash memory

        int i = 18;

        do {

                asm("noop");

        } while(i-->0);

}

void    dispchar(char ch) {

        if (!ch) // Don't display null characters

                return;

        int     ich = ch;

        // Send the character

        for(int i=0; i<8; i++) {

                int gpiov = GPOCLRV(GPO_MOSI|GPO_SCK|GPO_SS);

                if (ich&0x80)

                        gpiov |= GPOSETV(GPO_MOSI);

                _sys->io_gpio = gpiov;

                dispwait();

                _sys->io_gpio = GPOSETV(GPO_SCK);

                dispwait();

                ich<<=1;

        }

        // Turn off the clock

        _sys->io_gpio = GPOCLRV(GPO_SCK);

        dispwait();

        // Then the port

        _sys->io_gpio = GPOSETV(GPO_SS);

        dispwait();

}

#ifdef  ZIPOS

#include "../zipos/ktraps.h"

#include "../zipos/kfildes.h"

void    display_task(void) {

        while(1) {

                char    ch;

                read(FILENO_STDIN, &ch, 1);

                dispchar(ch);

        }

}

#endif