source: rtems/c/src/lib/libbsp/arm/stm32f4/console/usart.c @ 78c9fe8

5
Last change on this file since 78c9fe8 was c499856, checked in by Chris Johns <chrisj@…>, on Mar 20, 2014 at 9:10:47 PM

Change all references of rtems.com to rtems.org.

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File size: 5.0 KB
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1/*
2 * Copyright (c) 2012 Sebastian Huber.  All rights reserved.
3 *
4 *  embedded brains GmbH
5 *  Obere Lagerstr. 30
6 *  82178 Puchheim
7 *  Germany
8 *  <rtems@embedded-brains.de>
9 *
10 * The license and distribution terms for this file may be
11 * found in the file LICENSE in this distribution or at
12 * http://www.rtems.org/license/LICENSE.
13 */
14
15#include <libchip/sersupp.h>
16
17#include <bsp.h>
18#include <bsp/io.h>
19#include <bsp/rcc.h>
20#include <bsp/irq.h>
21#include <bsp/usart.h>
22#include <bsp/stm32f4.h>
23
24static volatile stm32f4_usart *usart_get_regs(const console_tbl *ct)
25{
26  return (stm32f4_usart *) ct->ulCtrlPort1;
27}
28
29#if 0
30static rtems_vector_number usart_get_irq_number(const console_tbl *ct)
31{
32  return ct->ulIntVector;
33}
34#endif
35
36static const stm32f4_rcc_index usart_rcc_index [] = {
37  STM32F4_RCC_USART1,
38  STM32F4_RCC_USART2,
39  STM32F4_RCC_USART3,
40  STM32F4_RCC_UART4,
41  STM32F4_RCC_UART5,
42#ifdef STM32F4_FAMILY_F4XXXX
43  STM32F4_RCC_USART6
44#endif /* STM32F4_FAMILY_F4XXXX */
45};
46
47static stm32f4_rcc_index usart_get_rcc_index(const console_tbl *ct)
48{
49  return usart_rcc_index [ct->ulCtrlPort2];
50}
51
52static const uint8_t usart_pclk_index [] = { 1, 0, 0, 0, 0, 1 };
53
54static const uint32_t usart_pclk_by_index [] = {
55  STM32F4_PCLK1,
56  STM32F4_PCLK2
57};
58
59static uint32_t usart_get_pclk(const console_tbl *ct)
60{
61  return usart_pclk_by_index [usart_pclk_index [ct->ulCtrlPort2]];
62}
63
64static uint32_t usart_get_baud(const console_tbl *ct)
65{
66  return ct->ulClock;
67}
68
69/*
70 * a = 8 * (2 - CR1[OVER8])
71 *
72 * usartdiv = div_mantissa + div_fraction / a
73 *
74 * baud = pclk / (a * usartdiv)
75 *
76 * usartdiv = pclk / (a * baud)
77 *
78 * Calculation in integer arithmetic:
79 *
80 * 1. div_mantissa = pclk / (a * baud)
81 *
82 * 2. div_fraction = pclk / (baud - a * div_mantissa)
83 */
84static uint32_t usart_get_bbr(
85  volatile stm32f4_usart *usart,
86  uint32_t pclk,
87  uint32_t baud
88)
89{
90  uint32_t a = 8 * (2 - ((usart->cr1 & STM32F4_USART_CR1_OVER8) != 0));
91  uint32_t div_mantissa_low = pclk / (a * baud);
92  uint32_t div_fraction_low = pclk / (baud - a * div_mantissa_low);
93  uint32_t div_mantissa_high;
94  uint32_t div_fraction_high;
95  uint32_t high_err;
96  uint32_t low_err;
97  uint32_t div_mantissa;
98  uint32_t div_fraction;
99
100  if (div_fraction_low < a - 1) {
101    div_mantissa_high = div_fraction_low;
102    div_fraction_high = div_fraction_low + 1;
103  } else {
104    div_mantissa_high = div_fraction_low + 1;
105    div_fraction_high = 0;
106  }
107
108  high_err = pclk - baud * (a * div_mantissa_high + div_fraction_high);
109  low_err = baud * (a * div_mantissa_low + div_fraction_low) - pclk;
110
111  if (low_err < high_err) {
112    div_mantissa = div_mantissa_low;
113    div_fraction = div_fraction_low;
114  } else {
115    div_mantissa = div_mantissa_high;
116    div_fraction = div_fraction_high;
117  }
118
119  return STM32F4_USART_BBR_DIV_MANTISSA(div_mantissa)
120    | STM32F4_USART_BBR_DIV_FRACTION(div_fraction);
121}
122
123static void usart_initialize(int minor)
124{
125  const console_tbl *ct = Console_Port_Tbl [minor];
126  volatile stm32f4_usart *usart = usart_get_regs(ct);
127  uint32_t pclk = usart_get_pclk(ct);
128  uint32_t baud = usart_get_baud(ct);
129  stm32f4_rcc_index rcc_index = usart_get_rcc_index(ct);
130
131  stm32f4_rcc_set_clock(rcc_index, true);
132
133  usart->cr1 = 0;
134  usart->cr2 = 0;
135  usart->cr3 = 0;
136  usart->bbr = usart_get_bbr(usart, pclk, baud);
137  usart->cr1 = STM32F4_USART_CR1_UE
138    | STM32F4_USART_CR1_TE
139    | STM32F4_USART_CR1_RE;
140}
141
142static int usart_first_open(int major, int minor, void *arg)
143{
144  rtems_libio_open_close_args_t *oc = (rtems_libio_open_close_args_t *) arg;
145  struct rtems_termios_tty *tty = (struct rtems_termios_tty *) oc->iop->data1;
146  const console_tbl *ct = Console_Port_Tbl [minor];
147  console_data *cd = &Console_Port_Data [minor];
148
149  cd->termios_data = tty;
150  rtems_termios_set_initial_baud(tty, ct->ulClock);
151
152  return 0;
153}
154
155static int usart_last_close(int major, int minor, void *arg)
156{
157  return 0;
158}
159
160static int usart_read_polled(int minor)
161{
162  const console_tbl *ct = Console_Port_Tbl [minor];
163  volatile stm32f4_usart *usart = usart_get_regs(ct);
164
165  if ((usart->sr & STM32F4_USART_SR_RXNE) != 0) {
166    return STM32F4_USART_DR_GET(usart->dr);
167  } else {
168    return -1;
169  }
170}
171
172static void usart_write_polled(int minor, char c)
173{
174  const console_tbl *ct = Console_Port_Tbl [minor];
175  volatile stm32f4_usart *usart = usart_get_regs(ct);
176
177  while ((usart->sr & STM32F4_USART_SR_TXE) == 0) {
178    /* Wait */
179  }
180
181  usart->dr = STM32F4_USART_DR(c);
182}
183
184static ssize_t usart_write_support_polled(
185  int minor,
186  const char *s,
187  size_t n
188)
189{
190  ssize_t i = 0;
191
192  for (i = 0; i < n; ++i) {
193    usart_write_polled(minor, s [i]);
194  }
195
196  return n;
197}
198
199static int usart_set_attributes(int minor, const struct termios *term)
200{
201  return -1;
202}
203
204const console_fns stm32f4_usart_fns = {
205  .deviceProbe = libchip_serial_default_probe,
206  .deviceFirstOpen = usart_first_open,
207  .deviceLastClose = usart_last_close,
208  .deviceRead = usart_read_polled,
209  .deviceWrite = usart_write_support_polled,
210  .deviceInitialize = usart_initialize,
211  .deviceWritePolled = usart_write_polled,
212  .deviceSetAttributes = usart_set_attributes,
213  .deviceOutputUsesInterrupts = false
214};
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