PiDP-8/I Software

/*
 * gpio-common.c: functions common to both gpio.c and gpio-nls.c
 *
 * Copyright © 2015, 2019 Oscar Vermeulen, © 2016-2019 by Warren Young
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:

    }
    for (size_t row = 0; row < NLEDROWS; ++row) {
        INP_GPIO (ledrows[row]);
    }
}


//// init_bcm2711_gpio /////////////////////////////////////////////////
// Called from init_pidp8i_gpio() when it sees that it's running on a Pi
// 4 which uses the BCM 2711 GPIO peripheral, which behaves differently
// than GPIO was done in all prior Pi models.  This code is based on
// https://github.com/RPi-Distro/raspi-gpio/blob/master/raspi-gpio.c
//
// Note that there is no "serial mod" handling here: no one has come up
// with such a hardware hack for the Pi 4 yet, and no one has verified
// that you can do one of the existing ones atop the Pi 4.

static void init_bcm2711_gpio (void)
{
    int gpiox, pullreg, pullshift;
    unsigned int pullbits, pull;

    // Configure "columns" GPIO pins
    for (size_t i = 0; i < 12; ++i) {
        gpiox = cols[i];
        pullreg = GPPUPPDN0 + (gpiox>>4);
        pullshift = (gpiox & 0xf) << 1;
        pull = 1;

        pullbits = *(gpio.addr + pullreg);
        pullbits &= ~(3 << pullshift);
        pullbits |= (pull << pullshift);
        *(gpio.addr + pullreg) = pullbits;
    }

    // Configure "rows" GPIO pins
    for (size_t i = 0; i < 3; ++i) {
        gpiox = rows[i];
        pullreg = GPPUPPDN0 + (gpiox>>4);
        pullshift = (gpiox & 0xf) << 1;
        pull = 0;

        pullbits = *(gpio.addr + pullreg);
        pullbits &= ~(3 << pullshift);
        pullbits |= (pull << pullshift);
        *(gpio.addr + pullreg) = pullbits;
    }

    // Configure "ledrows" GPIO pins
    for (size_t i = 0; i < 6; ++i) {
        gpiox = ledrows[i];
        pullreg = GPPUPPDN0 + (gpiox>>4);
        pullshift = (gpiox & 0xf) << 1;
        pull = 0;

        pullbits = *(gpio.addr + pullreg);
        pullbits &= ~(3 << pullshift);
        pullbits |= (pull << pullshift);
        *(gpio.addr + pullreg) = pullbits;
    }
}


//// init_bcm2835_gpio /////////////////////////////////////////////////
// Called from init_pidp8i_gpio() when it sees that it's running on a Pi
// 3 or older.  This is the "classic" Pi GPIO mode.  See page 101 in the
// peripheral's datasheet and // http://elinux.org/RPi_Low-level_peripherals#Internal_Pull-Ups_.26_Pull-Downs

static void init_bcm2835_gpio (void)
{
    // Configure "columns" GPIO pins
    GPIO_PULL = 2;  // pull-up
    usleep(1);  // must wait 150 cycles
#if defined(PCB_SERIAL_MOD_OV) || defined(PCB_SERIAL_MOD_JLW)
    // The Oscar Vermeulen and James L-W serial mods rearrange the PiDP-8/I
    // GPIO matrix to use Pi GPIO pins 2..13, freeing up the hardware
    // serial port on GPIO pins 14 & 15.
    GPIO_PULLCLK0 = 0x03ffc;
#else
    // The standard PiDP-8/I board drive scheme uses Pi GPIO pins 4..15.
    GPIO_PULLCLK0 = 0x0fff0;
#endif
    usleep(1);
    GPIO_PULL = 0; // reset GPPUD register
    usleep(1);
    GPIO_PULLCLK0 = 0; // remove clock
    usleep(1); // probably unnecessary










    // Configure "rows" GPIO pins

    GPIO_PULL = 0;  // no pull-up no pull down just float
    usleep(1);  // must wait 150 cycles
    GPIO_PULLCLK0 = 0x070000; // selects GPIO pins 16..18
    usleep(1);
    GPIO_PULL = 0; // reset GPPUD register
    usleep(1);
    GPIO_PULLCLK0 = 0; // remove clock
    usleep(1); // probably unnecessary

    // Configure "ledrows" GPIO pins
    GPIO_PULL = 1;  // pull-down to avoid ghosting
    usleep(1);  // must wait 150 cycles
    GPIO_PULLCLK0 = 0x0ff00000; // selects GPIO pins 20..27
    usleep(1);
    GPIO_PULL = 0; // reset GPPUD register
    usleep(1);
    GPIO_PULLCLK0 = 0; // remove clock
    usleep(1); // probably unnecessary
}


//// init_pidp8i_gpio //////////////////////////////////////////////////
// Initialize the GPIO pins to the initial states required by
// gpio_thread().   It's a separate exported function so that scanswitch
// can also use it.

void init_pidp8i_gpio (void)
{
    // Set GPIO pins to their starting state
    turn_on_pidp8i_leds ();
    for (size_t i = 0; i < NROWS; i++) {       // Define rows as input
        INP_GPIO (rows[i]);
    }

    // Configure GPIO pin pull-ups
    if (gpio.addr_p == 0xfe200000) {
        init_bcm2711_gpio();
    }
    else {
        init_bcm2835_gpio();
    }
}


//// gpio_thread ///////////////////////////////////////////////////////
// The GPIO thread entry point: initializes GPIO and then calls
// the gpio_core () implementation linked to this program.

/*
 * gpio-common.h: public interface for the PiDP-8/I's GPIO module
 *
 * Copyright © 2015, 2019 by Oscar Vermeulen, © 2016-2019 by Warren Young
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:

#define GPIO_CLR  *(pgpio->addr + 10) // clears bits which are 1 ignores bits which are 0

#define GPIO_READ(g)  *(pgpio->addr + 13) &= (1<<(g))

#define GPIO_PULL *(pgpio->addr + 37) // pull up/pull down
#define GPIO_PULLCLK0 *(pgpio->addr + 38) // pull up/pull down clock

// Pi 4 GPIO pull up/down peripheral I/O offsets.  Based on
// https://github.com/RPi-Distro/raspi-gpio/blob/master/raspi-gpio.c
#define GPPUPPDN0 57        // pins 15:0
#define GPPUPPDN1 58        // pins 31:16
#define GPPUPPDN2 59        // pins 47:32
#define GPPUPPDN3 60        // pins 57:48

// Switch masks, SSn, used against switchstatus[n]
#define SS0_SR_B11 04000
#define SS0_SR_B10 02000
#define SS0_SR_B09 01000
#define SS0_SR_B08 00400
#define SS0_SR_B07 00200