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

//

// Filename:    helloworld.c

//

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

//

// Purpose:     A very simple program.  This program tests the LEDs, buttons,

//              and UART.  Specifically, if run, this program will cycle through

//      the LEDs at one change per second.  If one button is pressed, it will

//      cycle through turning one LED off once per second while turning the 

//      rest on.  If the other button is pressed, two LED's will never turn on.

//

//      To test the UART, the message "Hello, world!" will be sent to the UART

//      at the top of each second.

//

//      This program is simple.  Although it uses the interrupt controller,

//      interrupts are disabled throughout the program.  The interrupt

//      controller is only used to determine when events have taken place.

//

// 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 "asmstartup.h"

#include "board.h"

const char msg[] = "Hello, world!\r\n";

void entry(void) {

        volatile IOSPACE *const sys = (IOSPACE *)IOADDR;

        int     ledset = 0;

        sys->io_spio = 0x0f0;

        /// Turn off timer B

        sys->io_watchdog = 0;

        while(1) {

                const char      *ptr;

                sys->io_timer = TM_ONE_SECOND; // Ticks per second, 80M

                sys->io_pic  = 0x07fffffff; // Acknowledge and turn off all ints

                ptr = msg;

                while(*ptr) {

                        unsigned iv = *(unsigned char *)ptr++;

                        // Wait while our transmitter is busy

                        while((sys->io_pic & INT_UARTTX)==0)

                                ;

                        sys->io_uart = iv; // Transmit our character

                        sys->io_pic  = INT_UARTTX; // Clear the int flag

                }

                // Now, wait for the top of the second

                while((sys->io_pic & INT_TIMER)==0)

                        ;

                ledset <<= 1;

                ledset &= 15;

                if (ledset == 0)

                        ledset = 1;

                ledset |= 0xf0;

                int     btn = sys->io_spio;

                if (btn&0x10)

                        sys->io_spio = ledset^0x0f;

                else if (btn&0x20)

                        sys->io_spio = ledset&0x0f5;

                else

                        sys->io_spio = ledset;

        }

}