rpi4-osdev/part7-bluetooth/bt.c

#include "io.h"
#include "fb.h"

// UART0

enum {
    ARM_UART0_BASE	= PERIPHERAL_BASE + 0x201000,
    ARM_UART0_DR	= ARM_UART0_BASE + 0x00,
    ARM_UART0_FR     	= ARM_UART0_BASE + 0x18,
    ARM_UART0_IBRD   	= ARM_UART0_BASE + 0x24,
    ARM_UART0_FBRD   	= ARM_UART0_BASE + 0x28,
    ARM_UART0_LCRH   	= ARM_UART0_BASE + 0x2C,
    ARM_UART0_CR     	= ARM_UART0_BASE + 0x30,
    ARM_UART0_IFLS   	= ARM_UART0_BASE + 0x34,
    ARM_UART0_IMSC   	= ARM_UART0_BASE + 0x38,
    ARM_UART0_RIS    	= ARM_UART0_BASE + 0x3C,
    ARM_UART0_MIS    	= ARM_UART0_BASE + 0x40,
    ARM_UART0_ICR    	= ARM_UART0_BASE + 0x44
};

unsigned int bt_isReadByteReady() { return (!(mmio_read(ARM_UART0_FR) & 0x10)); }

unsigned char bt_readByte()
{
    unsigned char ch = mmio_read(ARM_UART0_DR) & 0xff;
    return ch;
}

unsigned char bt_waitReadByte()
{
    while (!bt_isReadByteReady());
    return bt_readByte();
}

void bt_writeByte(char byte)
{
    while ((mmio_read(ARM_UART0_FR) & 0x20) != 0);
    mmio_write(ARM_UART0_DR, (unsigned int)byte);
}

void bt_flushrx()
{
    while (bt_isReadByteReady()) bt_readByte();
}

void bt_init()
{
    gpio_useAsAlt3(30);
    gpio_useAsAlt3(31);
    gpio_useAsAlt3(32);
    gpio_useAsAlt3(33);

    bt_flushrx();

    mmio_write(ARM_UART0_IMSC, 0x00);
    mmio_write(ARM_UART0_ICR,  0x7ff);
    mmio_write(ARM_UART0_IBRD, 0x1a);
    mmio_write(ARM_UART0_FBRD, 0x03);
    mmio_write(ARM_UART0_IFLS, 0x08);
    mmio_write(ARM_UART0_LCRH, 0x70);
    mmio_write(ARM_UART0_CR,   0xB01);
    mmio_write(ARM_UART0_IMSC, 0x430);

    wait_msec(0x100000);
}