106 lines
4.7 KiB
C
106 lines
4.7 KiB
C
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/*
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Copyright (C) 2012, Aaron Lindsay <aaron@aclindsay.com>
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This file is part of Aedrix.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along
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with this program; if not, write to the Free Software Foundation, Inc.,
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51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include <types.h>
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#define VC_MMU_IO_OFFSET(addr) (addr - 0x7E000000 + 0x20000000)
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/* Auxiliary IO registers (includes both mini-UART and SPI) */
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#define AUX_IRQ VC_MMU_IO_OFFSET(0x7E215000)
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#define AUX_ENABLES VC_MMU_IO_OFFSET(0x7E215004)
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#define AUX_MU_IO_REG VC_MMU_IO_OFFSET(0x7E215040)
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#define AUX_MU_IER_REG VC_MMU_IO_OFFSET(0x7E215044)
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#define AUX_MU_IIR_REG VC_MMU_IO_OFFSET(0x7E215048)
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#define AUX_MU_LCR_REG VC_MMU_IO_OFFSET(0x7E21504C)
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#define AUX_MU_MCR_REG VC_MMU_IO_OFFSET(0x7E215050)
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#define AUX_MU_LSR_REG VC_MMU_IO_OFFSET(0x7E215054)
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#define AUX_MU_MSR_REG VC_MMU_IO_OFFSET(0x7E215058)
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#define AUX_MU_SCRATCH VC_MMU_IO_OFFSET(0x7E21505C)
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#define AUX_MU_CNTL_REG VC_MMU_IO_OFFSET(0x7E215060)
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#define AUX_MU_STAT_REG VC_MMU_IO_OFFSET(0x7E215064)
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#define AUX_MU_BAUD_REG VC_MMU_IO_OFFSET(0x7E215068)
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#define AUX_SPI0_CNTL0_REG VC_MMU_IO_OFFSET(0x7E215080)
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#define AUX_SPI0_CNTL1_REG VC_MMU_IO_OFFSET(0x7E215084)
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#define AUX_SPI0_STAT_REG VC_MMU_IO_OFFSET(0x7E215088)
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#define AUX_SPI0_IO_REG VC_MMU_IO_OFFSET(0x7E215090)
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#define AUX_SPI0_PEEK_REG VC_MMU_IO_OFFSET(0x7E215094)
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#define AUX_SPI1_CNTL0_REG VC_MMU_IO_OFFSET(0x7E2150C0)
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#define AUX_SPI1_CNTL1_REG VC_MMU_IO_OFFSET(0x7E2150C4)
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#define AUX_SPI1_STAT_REG VC_MMU_IO_OFFSET(0x7E2150C8)
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#define AUX_SPI1_IO_REG VC_MMU_IO_OFFSET(0x7E2150D0)
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#define AUX_SPI1_PEEK_REG VC_MMU_IO_OFFSET(0x7E2150D4)
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/* Constants for mini-UART operation */
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#define MINI_UART_TX_EMPTY 0x20
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/* General GPIO pin registers */
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#define GPFSEL1 VC_MMU_IO_OFFSET(0x7E200004)
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#define GPSET0 VC_MMU_IO_OFFSET(0x7E20001C)
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#define GPCLR0 VC_MMU_IO_OFFSET(0x7E200028)
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#define GPPUD VC_MMU_IO_OFFSET(0x7E200094)
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#define GPPUDCLK0 VC_MMU_IO_OFFSET(0x7E200098)
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void mini_uart_init() {
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uint32 aux_enables;
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uint32 gpfsel1;
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unsigned int i;
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/* Enable the mini-UART */
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aux_enables = (*(uint32 *)AUX_ENABLES) & 0x7;
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*(uint32 *)AUX_ENABLES = aux_enables | 0x1;
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//TODO are these all necessary?
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*(uint32 *)AUX_MU_IER_REG = 0; //disable interrupts
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*(uint32 *)AUX_MU_CNTL_REG = 0; //disable RX and TX
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*(uint32 *)AUX_MU_LCR_REG = 3; //set to 8-bit mode (though this only takes setting bit 0, no clue why bit 1 is set too)
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*(uint32 *)AUX_MU_MCR_REG = 0; //"If clear the UART1_RTS line is high If set the UART1_RTS line is low"
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*(uint32 *)AUX_MU_IER_REG = 0; //disable interrupts again?
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*(uint32 *)AUX_MU_IIR_REG = 0xC6; //why are we setting the interrupt status - this looks like a read-only register?
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//also, the manual says setting bits 2&3 simultaneously shouldn't be possible...
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// baudrate = system_clock_freq / ( 8 * (baudrate_reg + 1))
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// baudrate_reg = system_clock_freq / baudrate / 8 - 1
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// baudrate_reg = 250000000 / 115200 / 8 - 1 = 270
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*(uint32 *)AUX_MU_BAUD_REG = 270;
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//set the GPIO pin to the alternate function for this UART
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gpfsel1 = (*(uint32 *)GPFSEL1) & ~(7<<12); //get the GPIO Function Select 1 register, and keep all the bits except those that are for GPIO pin 14
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gpfsel1 |= 2<<12; // set to 010 (GPIO Pin 14 takes alternate function 5)
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*(uint32 *)GPFSEL1 = gpfsel1;
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//Follow the procedure for change pull-up/pull-down status (see page 101 of the BCM2835 ARM Peripherals datasheet)
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*(uint32 *)GPPUD = 0; //disable pull-up/pull-down for those pins which receive a write to their bit in GPPUDCLK0/1
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for(i = 0; i < 150; i++) asm(""); //wait at least 150 cycles
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*(uint32 *)GPPUDCLK0 = 1<<14; //"Write to GPPUDCLK0/1 to clock the control signal into the GPIO pads you wish to modify" (in our case, this is 14)
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for(i = 0; i < 150; i++) asm(""); //wait at least 150 cycles
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// *(uint32 *)GPPUD = 0; //remove the signal (shouldn't really be necessary since it was 0 anyway in our case)
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*(uint32 *)GPPUDCLK0 = 0; //clear the clock
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*(uint32 *)AUX_MU_CNTL_REG = 2; //enable TX
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}
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void mini_uart_putc(char c) {
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/* Wait until the serial buffer is empty */
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while (!(*(volatile uint32*)AUX_MU_LSR_REG & MINI_UART_TX_EMPTY));
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/* When it's empty, write our character */
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*(volatile uint32*)AUX_MU_IO_REG = c;
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}
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