serial.c

   1 /*
   2  * (C) Copyright 2014 - 2017 Leo C. <erbl259-lmu@yahoo.de>
   3  *
   4  * SPDX-License-Identifier:     GPL-2.0
   5  */
   6
   7 #include "serial.h"
   8 #include "config.h"
   9 #include <errno.h>
  10 #include <stdio.h>
  11 #include <unistd.h>
  12 #include <libopencm3/stm32/rcc.h>
  13 #include <libopencm3/stm32/gpio.h>
  14 #include <libopencm3/stm32/usart.h>
  15 #include <libopencm3/cm3/nvic.h>
  16
  17 #if (USART_CONSOLE == 1)
  18 #define CON_PORT A
  19 #define CON_GPIO GPIOA
  20 #elif (USART_CONSOLE == 2)
  21 #define CON_PORT A
  22 #define CON_GPIO GPIOA
  23 #elif (USART_CONSOLE == 3)
  24 #define CON_PORT B
  25 #define CON_GPIO GPIOB
  26 #else
  27 #error  USART_CONSOLE undefined or invalid value
  28 #endif
  29
  30 #define CONCAT2(a,b)    a##b
  31 #define CONCAT(a,b)     CONCAT2(a,b)
  32
  33
  34 #define CON_USART       CONCAT(USART,USART_CONSOLE)
  35 #define CON_IRQ         CONCAT(CONCAT(NVIC_USART, USART_CONSOLE), _IRQ)
  36 #define CON_isr         CONCAT(CONCAT(usart, USART_CONSOLE), _isr)
  37 #define CON_GPIO_RX     CONCAT(CONCAT(GPIO_USART, USART_CONSOLE), _RX)
  38 #define CON_GPIO_TX     CONCAT(CONCAT(GPIO_USART, USART_CONSOLE), _TX)
  39 #define RCC_USART_CON   CONCAT(RCC_USART, USART_CONSOLE)
  40 #define RCC_GPIO_CON    CONCAT(RCC_GPIO, CON_PORT)
  41
  42
  43 int _write(int fd, char *ptr, int len)  __attribute__((used));
  44
  45
  46 struct ring {
  47         uint8_t *data;
  48         int size;
  49         volatile int begin;
  50         volatile int end;
  51 };
  52
  53
  54 #define BUFFER_SIZE 256
  55
  56 struct ring rx_ring;
  57 struct ring tx_ring;
  58 uint8_t rx_ring_buffer[BUFFER_SIZE];
  59 uint8_t tx_ring_buffer[BUFFER_SIZE];
  60
  61
  62 static void ring_init(struct ring *ring, uint8_t *buf, int size)
  63 {
  64         ring->data = buf;
  65         ring->size = size;
  66         ring->begin = 0;
  67         ring->end = 0;
  68 }
  69
  70 static int ring_write_ch(struct ring *ring, uint8_t ch)
  71 {
  72         int ep = (ring->end + 1) % ring->size;
  73
  74         if ((ep) != ring->begin) {
  75                 ring->data[ring->end] = ch;
  76                 ring->end = ep;
  77                 return 1;
  78         }
  79
  80         return -1;
  81 }
  82
  83 #if 0 /* unused */
  84 static int ring_write(struct ring *ring, uint8_t *data, int size)
  85 {
  86         int i;
  87
  88         for (i = 0; i < size; i++) {
  89                 if (ring_write_ch(ring, data[i]) < 0)
  90                         return -i;
  91         }
  92
  93         return i;
  94 }
  95 #endif
  96
  97 static int ring_read_ch(struct ring *ring)
  98 {
  99         int ret = -1;
 100
 101         if (ring->begin != ring->end) {
 102                 ret = ring->data[ring->begin];
 103                 ring->begin = (ring->begin +1) % ring->size;
 104         }
 105
 106         return ret;
 107 }
 108
 109 void usart_setup(int baud)
 110 {
 111         /* Initialize output ring buffer. */
 112         ring_init(&rx_ring, rx_ring_buffer, BUFFER_SIZE);
 113         ring_init(&tx_ring, tx_ring_buffer, BUFFER_SIZE);
 114
 115     rcc_periph_clock_enable(RCC_USART_CON);
 116
 117         /* Enable the USART_CONSOLE interrupt. */
 118         nvic_enable_irq(CON_IRQ);
 119     nvic_set_priority(CON_IRQ, 6*16);
 120
 121         /* Setup GPIO pins for CONSOLE TX/RX */
 122     rcc_periph_clock_enable(RCC_GPIO_CON);
 123         gpio_set_mode(CON_GPIO, GPIO_MODE_OUTPUT_2_MHZ,
 124                 GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, CON_GPIO_TX);
 125         gpio_set_mode(CON_GPIO, GPIO_MODE_INPUT,
 126                 GPIO_CNF_INPUT_FLOAT, CON_GPIO_RX);
 127
 128         /* Setup UART parameters. */
 129         usart_set_baudrate(CON_USART, baud);
 130         usart_set_databits(CON_USART, 8);
 131         usart_set_stopbits(CON_USART, USART_STOPBITS_1);
 132         usart_set_parity(CON_USART, USART_PARITY_NONE);
 133         usart_set_flow_control(CON_USART, USART_FLOWCONTROL_NONE);
 134         usart_set_mode(CON_USART, USART_MODE_TX_RX);
 135
 136         /* Enable CONSOLE Receive interrupt. */
 137         USART_CR1(CON_USART) |= USART_CR1_RXNEIE;
 138
 139         /* Finally enable the USART. */
 140         usart_enable(CON_USART);
 141 }
 142
 143
 144 void CON_isr(void)
 145 {
 146         /* Check if we were called because of RXNE. */
 147         if (((USART_CR1(CON_USART) & USART_CR1_RXNEIE) != 0) &&
 148             ((USART_SR(CON_USART) & USART_SR_RXNE) != 0)) {
 149
 150                 /* Retrieve the data from the peripheral. */
 151                 ring_write_ch(&rx_ring, USART_DR(CON_USART) & USART_DR_MASK);
 152
 153         }
 154
 155         /* Check if we were called because of TXE. */
 156         if (((USART_CR1(CON_USART) & USART_CR1_TXEIE) != 0) &&
 157             ((USART_SR(CON_USART) & USART_SR_TXE) != 0)) {
 158
 159                 int data;
 160
 161                 data = ring_read_ch(&tx_ring);
 162
 163                 if (data == -1) {
 164                         /* Disable the TXE interrupt, it's no longer needed. */
 165                         USART_CR1(CON_USART) &= ~USART_CR1_TXEIE;
 166                 } else {
 167                         /* Put data into the transmit register. */
 168                         usart_send(CON_USART, data);
 169                 }
 170         }
 171 }
 172
 173 /*--------------------------------------------------------------------------*/
 174
 175 void serial_setup(int baud)
 176 {
 177         usart_setup(baud);
 178 }
 179
 180 void serial_setbaudrate(int baud)
 181 {
 182         usart_set_baudrate(CON_USART, baud);
 183 }
 184
 185 /*--------------------------------------------------------------------------*/
 186
 187 /**
 188  * Use USART_CONSOLE as a console.
 189  * This is a syscall for newlib
 190  * @param fd
 191  * @param ptr
 192  * @param len
 193  * @return
 194  */
 195 int _write(int fd, char *ptr, int len)
 196 {
 197         int i;
 198
 199         if (fd == STDOUT_FILENO || fd == STDERR_FILENO) {
 200                 for (i = 0; i < len; i++) {
 201                         if (ptr[i] == '\n') {
 202                                 serial_putc('\r');
 203                         }
 204                         serial_putc(ptr[i]);
 205                 }
 206                 return i;
 207         }
 208         errno = EIO;
 209         return -1;
 210 }
 211
 212 int serial_getc(void)
 213 {
 214         return ring_read_ch(&rx_ring);
 215 }
 216
 217 void serial_putc(int data)
 218 {
 219         while (ring_write_ch(&tx_ring, data) < 0)
 220                 ;
 221
 222         /* Enable the TXE interrupt. */
 223         USART_CR1(CON_USART) |= USART_CR1_TXEIE;
 224 }