uart.c

/*
 * Copyright (C) 2022 (Unix69@github)
 *
 * 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:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 *
 */




#include "gpio.h"
#include "mbox.h"
#include "delays.h"
#include "uart.h"
#include "types.h"




/**
 * Set baud rate and characteristics (115200 8N1) and map to GPIO
 */

void uart_init()
{
    	register unsigned int r;

    	/* initialize UART */
    	*UART0_CR = 0;         // turn off UART0

    	/* set up clock for consistent divisor values */
    	mbox[0] = 9*4;
    	mbox[1] = MBOX_REQUEST;
    	mbox[2] = MBOX_TAG_SETCLKRATE; // set clock rate
    	mbox[3] = 12;
    	mbox[4] = 8;
    	mbox[5] = 2;           // UART clock
    	mbox[6] = 4000000;     // 4Mhz
    	mbox[7] = 0;           // clear turbo
    	mbox[8] = MBOX_TAG_LAST;
    	mbox_call(MBOX_CH_PROP);

    	/* map UART0 to GPIO pins */
    	r=*GPFSEL1;
    	r&=~((7<<12)|(7<<15)); // gpio14, gpio15
    	r|=(4<<12)|(4<<15);    // alt0
    	*GPFSEL1 = r;
    	*GPPUD = 0;            // enable pins 14 and 15
    	wait_cycles(150);
    	*GPPUDCLK0 = (1<<14)|(1<<15);
    	wait_cycles(150);
    	*GPPUDCLK0 = 0;        // flush GPIO setup

    	*UART0_ICR = 0x7FF;    // clear interrupts
    	*UART0_IBRD = 2;       // 115200 baud
    	*UART0_FBRD = 0xB;
    	*UART0_LCRH = 0b11<<5; // 8n1
    	*UART0_CR = 0x301;     // enable Tx, Rx, FIFO
}

/**
 * Send a character
 */
void uart_send(uint8_t c) {
    /* wait until we can send */
    do{asm volatile("nop");}while(*UART0_FR&0x20);
    /* write the character to the buffer */
    *UART0_DR=c;
}

/**
 * Receive a character
 */
char uart_getc() {
    char r;
    /* wait until something is in the buffer */
    do{asm volatile("nop");}while(*UART0_FR&0x10);
    /* read it and return */
    r=(char)(*UART0_DR);
    /* convert carrige return to newline */
    return r=='\r'?'\n':r;
}

/**
 * Display a string
 */
void uart_puts(char *s) {
    	while(*s) {
		/* convert newline to carrige return + newline */
       	 	if(*s=='\n')
			uart_send('\r');
        	uart_send(*s++);
    	}
	return;
}

/**
 * Display a binary value in hexadecimal
 */
void uart_hex_uint32(uint32_t d) {
	uint8_t n;
    	int c;
    	for(c=28;c>=0;c-=4) {
        	// get highest tetrad
        	n=(d>>c)&0xF;
        	// 0-9 => '0'-'9', 10-15 => 'A'-'F'
        	n+=n>9?0x37:0x30;
        	uart_send(n);
    	}
    	return;
}


void uart_hex_uint64(uint64_t d) {
    	unsigned int n;
    	int c;
    	for(c=60;c>=0;c-=4) {
        	// get highest tetrad
        	n=(d>>c)&0xF;
        	// 0-9 => '0'-'9', 10-15 => 'A'-'F'
        	n+=n>9?0x37:0x30;
        	uart_send(n);
    	}
    	return;
}