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nuttx-bb/nuttx/arch/arm/src/lpc31xx/lpc31_lowputc.c

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/****************************************************************************
* arch/arm/src/lpc31xx/lpc31_lowputc.c
*
* Copyright (C) 2009-2010, 2012 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/types.h>
#include <stdint.h>
#include <debug.h>
#include <nuttx/arch.h>
#include "up_arch.h"
#include "up_internal.h"
#include "lpc31_cgudrvr.h"
#include "lpc31_uart.h"
/****************************************************************************
* Definitions
****************************************************************************/
/* Configuration ************************************************************/
/* Is the UART enabled? */
#ifdef CONFIG_LPC31_UART
# define HAVE_UART 1
/* Is it a serial console? */
# ifdef CONFIG_UART_SERIAL_CONSOLE
# define HAVE_CONSOLE 1
/* Is initialization performed by up_earlyserialinit()? Or is UART
* initialization suppressed?
*/
# if defined(USE_EARLYSERIALINIT) || defined(CONFIG_SUPPRESS_LPC31_UART_CONFIG)
# undef NEED_LOWSETUP
# else
# define NEED_LOWSETUP 1
# endif
# else
# undef HAVE_CONSOLE
# undef NEED_LOWSETUP
# endif
#else
# undef HAVE_UART
# undef HAVE_CONSOLE
# undef NEED_LOWSETUP
#endif
/****************************************************************************
* Private Types
****************************************************************************/
/****************************************************************************
* Private Variables
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: up_waittxready
****************************************************************************/
#ifdef HAVE_CONSOLE
static inline void up_waittxready(void)
{
int tmp;
/* Limit how long we will wait for the TX available condition */
for (tmp = 1000 ; tmp > 0 ; tmp--)
{
/* Check if the tranmitter holding register (THR) is empty */
if ((getreg32(LPC31_UART_LSR) & UART_LSR_THRE) != 0)
{
/* The THR is empty, return */
break;
}
}
}
#endif
/****************************************************************************
* Name: up_configbaud
****************************************************************************/
#ifdef NEED_LOWSETUP
static inline void up_configbaud(void)
{
/* In a buckled-up, embedded system, there is no reason to constantly
* calculate the following. The calculation can be skipped if the
* MULVAL, DIVADDVAL, and DIVISOR values are provided in the configuration
* file.
*/
#ifndef CONFIG_LPC31_UART_MULVAL
uint32_t qtrclk;
uint32_t regval;
/* Test values calculated for every multiplier/divisor combination */
uint32_t tdiv;
uint32_t terr;
int tmulval;
int tdivaddval;
/* Optimal multiplier/divider values */
uint32_t div = 0;
uint32_t err = 100000;
int mulval = 1;
int divaddval = 0;
/* Baud is generated using FDR and DLL-DLM registers
*
* baud = clock * (mulval/(mulval+divaddval) / (16 * div)
*
* Or
*
* div = (clock/16) * (mulval/(mulval+divaddval) / baud
*
* Where mulval = Fractional divider multiplier
* divaddval = Fractional divider pre-scale div
* div = DLL-DLM divisor
*/
/* Get UART block clock divided by 16 */
qtrclk = lpc31_clkfreq(CLKID_UARTUCLK, DOMAINID_UART) >> 4;
/* Try every valid multiplier, tmulval (or until a perfect
* match is found).
*/
for (tmulval = 1 ; tmulval <= 15 && err > 0; tmulval++)
{
/* Try every valid pre-scale div, tdivaddval (or until a perfect
* match is found).
*/
for (tdivaddval = 0 ; tdivaddval <= 15 && err > 0; tdivaddval++)
{
/* Calculate the divisor with these fractional divider settings */
uint32_t tmp = (tmulval * qtrclk) / ((tmulval + tdivaddval));
tdiv = (tmp + (CONFIG_UART_BAUD>>1)) / CONFIG_UART_BAUD;
/* Check if this candidate divisor is within a valid range */
if (tdiv > 2 && tdiv < 0x10000)
{
/* Calculate the actual baud and the error */
uint32_t actualbaud = tmp / tdiv;
if (actualbaud <= CONFIG_UART_BAUD)
{
terr = CONFIG_UART_BAUD - actualbaud;
}
else
{
terr = actualbaud - CONFIG_UART_BAUD;
}
/* Is this the smallest error we have encountered? */
if (terr < err)
{
/* Yes, save these settings as the new, candidate optimal settings */
mulval = tmulval ;
divaddval = tdivaddval;
div = tdiv;
err = terr;
}
}
}
}
/* Set the Divisor Latch Access Bit (DLAB) to enable DLL/DLM access */
regval = getreg32(LPC31_UART_LCR);
regval |= UART_LCR_DLAB;
putreg32(regval, LPC31_UART_LCR);
/* Configure the MS and LS DLAB registers */
putreg32(div & UART_DLL_MASK, LPC31_UART_DLL);
putreg32((div >> 8) & UART_DLL_MASK, LPC31_UART_DLM);
regval &= ~UART_LCR_DLAB;
putreg32(regval, LPC31_UART_LCR);
/* Configure the Fractional Divider Register (FDR) */
putreg32((mulval << UART_FDR_MULVAL_SHIFT) |
(divaddval << UART_FDR_DIVADDVAL_SHIFT),
LPC31_UART_FDR);
#else
/* Set the Divisor Latch Access Bit (DLAB) to enable DLL/DLM access */
regval = getreg32(LPC31_UART_LCR);
regval |= UART_LCR_DLAB;
putreg32(regval, LPC31_UART_LCR);
/* Configure the MS and LS DLAB registers */
putreg32(CONFIG_LPC31_UART_DIVISOR & UART_DLL_MASK, LPC31_UART_DLL);
putreg32((CONFIG_LPC31_UART_DIVISOR >> 8) & UART_DLL_MASK, LPC31_UART_DLM);
regval &= ~UART_LCR_DLAB;
putreg32(regval, LPC31_UART_LCR);
/* Configure the Fractional Divider Register (FDR) */
putreg32((CONFIG_LPC31_UART_MULVAL << UART_FDR_MULVAL_SHIFT) |
(CONFIG_LPC31_UART_DIVADDVAL << UART_FDR_DIVADDVAL_SHIFT),
LPC31_UART_FDR);
#endif
}
#endif
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: lpc31_lowsetup
*
* Description:
* Called early in up_boot. Performs chip-common low level initialization.
*
****************************************************************************/
void lpc31_lowsetup(void)
{
#ifdef NEED_LOWSETUP
uint32_t regval;
/* Enable UART system clock */
lpc31_enableclock(CLKID_UARTAPBCLK);
lpc31_enableclock(CLKID_UARTUCLK);
/* Clear fifos */
putreg32((UART_FCR_RXFIFORST|UART_FCR_TXFIFORST), LPC31_UART_FCR);
/* Set trigger */
putreg32((UART_FCR_FIFOENABLE|UART_FCR_RXTRIGLEVEL_16), LPC31_UART_FCR);
/* Set up the LCR */
regval = 0;
#if CONFIG_UART_BITS == 5
regval |= UART_LCR_WDLENSEL_5BITS;
#elif CONFIG_UART_BITS == 6
regval |= UART_LCR_WDLENSEL_6BITS;
#elif CONFIG_UART_BITS == 7
regval |= UART_LCR_WDLENSEL_7BITS;
#else
regval |= UART_LCR_WDLENSEL_8BITS;
#endif
#if CONFIG_UART_2STOP > 0
regval |= UART_LCR_NSTOPBITS;
#endif
#if CONFIG_UART_PARITY == 1
regval |= UART_LCR_PAREN;
#elif CONFIG_UART_PARITY == 2
regval |= (UART_LCR_PAREVEN|UART_LCR_PAREN);
#endif
putreg32(regval, LPC31_UART_LCR);
/* Set the BAUD divisor */
up_configbaud();
/* Configure the FIFOs */
putreg32((UART_FCR_RXTRIGLEVEL_16|UART_FCR_TXFIFORST|
UART_FCR_RXFIFORST|UART_FCR_FIFOENABLE),
LPC31_UART_FCR);
/* The NuttX serial driver waits for the first THRE interrrupt before
* sending serial data... However, it appears that the lpc313x hardware
* does not generate that interrupt until a transition from not-empty
* to empty. So, the current kludge here is to send one NULL at
* startup to kick things off.
*/
putreg32('\0', LPC31_UART_THR);
#endif
}
/****************************************************************************
* Name: up_lowputc
*
* Description:
* Provide priority, low-level access to support OS debug writes
*
****************************************************************************/
void up_lowputc(char ch)
{
#ifdef HAVE_CONSOLE
up_waittxready();
putreg32((uint32_t)ch, LPC31_UART_THR);
#endif
}
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