stm32f469: stdio example update

Added a bit of interactivity on the console (serial port) to
demonstrate how you might use this feature with libopencm3

Author: ChuckM

examples/stm32/f4/stm32f469-discovery/console/main.c

@@ -49,7 +49,8 @@ int main(void)
 	while (1) {
 		console_puts("Enter a string: ");
 		len = console_gets(buf, 128);
-		if (len) {
+		if (len > 1) {
+			buf[len-1] = 0; /* kill trailing newline */
 			console_puts("\nYou entered : '");
 			console_puts(buf);
 			console_puts("'\n");

examples/stm32/f4/stm32f469-discovery/stdio/Makefile

@@ -0,0 +1,25 @@
+#
+# This file is part of the libopencm3 project.
+#
+# This library is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with this library.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+OBJS = ../util/retarget.o ../util/console.o ../util/clock.o
+
+BINARY = main
+
+LDSCRIPT = ../stm32f469-discovery.ld
+
+include ../../Makefile.include
+

examples/stm32/f4/stm32f469-discovery/stdio/README.md

@@ -0,0 +1,22 @@
+Standard I/O Example
+--------------------
+
+This just shows using the native retargeting capability of
+the ARM GCC Embedded compiler. By linking in retarget,
+console, and clock. The startup script will call SystemInit
+in retarget automatically and set things up before main()
+is called, in particular the serial port is set up as the
+standard input, output, and error streams for the program
+and the clock is setup to be 168Mhz (based on the STM32F469-Discovery's
+external (HSE) crystal setup.
+
+Control-C is enabled so when the example is running, if you 
+hold the control key and C the board will reset and restart. 
+
+## Notes ##
+
+Often time people do not use the standard libraries (especially printf!)
+because they include a lot of code that usually is not needed. However
+since the F4 chip on our board has 2 megabytes of flash, there is space
+to have it, and once you pay the price for including it, you can use it
+as often as you like without adding additional space requirements.

examples/stm32/f4/stm32f469-discovery/stdio/main.c

@@ -0,0 +1,69 @@
+/*
+ * This file is part of the libopencm3 project.
+ *
+ * Copyright (C) 2013 Chuck McManis <[email protected]>
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/gpio.h>
+#include "../util/clock.h"
+
+int main(void)
+{
+	double flash_rate = 3.14159;
+	char buf[128];
+	uint32_t done_time;
+
+	/* things printed to standard error stand out */
+	fprintf(stderr, "\nSTM32F469-Discovery");
+	printf(" Retarget demo.\n");
+
+	/* This is the LED on the board */
+	rcc_periph_clock_enable(RCC_GPIOK);
+	gpio_mode_setup(GPIOK, GPIO_MODE_OUTPUT, GPIO_PUPD_NONE, GPIO3);
+
+	/* You can create a running dialog with the console */
+	printf("We're going to start blinking the LED, between 0 and 300 times per\n");
+	printf("second.\n");
+	while (1) {
+		printf("Please enter a flash rate: ");
+		fflush(stdout);
+		fgets(buf, 128, stdin);
+		buf[strlen(buf) - 1] = '\0';
+		flash_rate = atof(buf);
+		if (flash_rate == 0) {
+			printf("Was expecting a number greater than 0 and less than 300.\n");
+			printf("but got '%s' instead\n", buf);
+		} else if (flash_rate > 300.0) {
+			printf("The number should be less than 300.\n");
+		} else {
+			break;
+		}
+	}
+	/* MS per flash */
+	done_time = (int) (500 / flash_rate);
+	printf("The closest we can come will be %f flashes per second\n", 500.0 / done_time);
+	printf("With %d MS between states\n", (int) done_time);
+	printf("Press ^C to restart this demo.\n");
+	while (1) {
+		msleep(done_time);
+		gpio_toggle(GPIOK, GPIO3);
+	}
+}

examples/stm32/f4/stm32f469-discovery/util/README.md

@@ -4,3 +4,13 @@ Utility Functions
 Not part of the library, these utility functions provide some
 helper functions for the examples that simplify things.
 
+**clock.c** - sets up the clock to 168Mhz and and enables the
+	SysTick interrupt with 1khz interrupts.
+
+**console.c** - a set of convienience routines for using the debug
+	serial port (USART3) which is availble as /dev/ttyACM0 on
+	the linux box, as a console port.
+
+**retarget.c** - implements the minimum set of character I/O functions
+	and automatically plumbs them so that you can use standard
+	functions like printf() in your programs.

examples/stm32/f4/stm32f469-discovery/util/console.c

@@ -25,6 +25,7 @@
  */
 
 #include <stdint.h>
+#include <ctype.h>
 #include <libopencm3/stm32/gpio.h>
 #include <libopencm3/stm32/rcc.h>
 #include <libopencm3/stm32/usart.h>
@@ -47,9 +48,9 @@
 /* This is a ring buffer to holding characters as they are typed
  * it maintains both the place to put the next character received
  * from the UART, and the place where the last character was
- * read by the program. See the README file for a discussion of
- * the failure semantics.
+ * read by the program.
  */
+
 #define RECV_BUF_SIZE	128		/* Arbitrary buffer size */
 char recv_buf[RECV_BUF_SIZE];
 volatile int recv_ndx_nxt;		/* Next place to store */
@@ -116,9 +117,6 @@ void console_putc(char c)
  * Check the console for a character. If the wait flag is
  * non-zero. Continue checking until a character is received
  * otherwise return 0 if called and no character was available.
- *
- * The implementation is a bit different however, now it looks
- * in the ring buffer to see if a character has arrived.
  */
 char console_getc(int wait)
 {
@@ -138,6 +136,9 @@ char console_getc(int wait)
  * Send a string to the console, one character at a time, return
  * after the last character, as indicated by a NUL character, is
  * reached.
+ *
+ * Translate '\n' in the string (newline) to \n\r (newline + 
+ * carraige return)
  */
 void console_puts(char *s)
 {
@@ -154,9 +155,11 @@ void console_puts(char *s)
 /*
  * int console_gets(char *s, int len)
  *
- * Wait for a string to be entered on the console, limited
- * support for editing characters (back space and delete)
- * end when a <CR> character is received.
+ * Wait for a string to be entered on the console, with
+ * support for editing characters (delete letter, word,
+ * entire line). It returns when the length is reached
+ * or a carrige return is entered. <CR> is changed to newline
+ * before the buffer is returned.
  */
 int console_gets(char *s, int len)
 {
@@ -165,13 +168,23 @@ int console_gets(char *s, int len)
 
 	*t = '\000';
 	/* read until a <CR> is received */
-	while ((c = console_getc(1)) != '\r') {
+	while (((c = console_getc(1)) != '\r') && ((t - s) < len) ) {
 		if ((c == '\010') || (c == '\127')) {
 			if (t > s) {
 				/* send ^H ^H to erase previous character */
 				console_puts("\010 \010");
 				t--;
 			}
+		} else if (c == 0x17) {	// ^W erase a word
+			while ((t > s) &&  (!(isspace((int) (*t))))) {
+				t--;
+				console_puts("\010 \010");
+			}
+		} else if (c == 0x15) { // ^U erase the line
+			while (t > s) {
+				t--;
+				console_puts("\010 \010");
+			}
 		} else {
 			*t = c;
 			console_putc(c);
@@ -182,6 +195,10 @@ int console_gets(char *s, int len)
 		/* update end of string with NUL */
 		*t = '\000';
 	}
+	if ((t < s) < len) {
+		*t++ = '\n';
+		*t = 0;
+	}
 	return t - s;
 }
 
@@ -226,3 +243,11 @@ void console_setup(int baud)
 	/* Specifically enable recieve interrupts */
 	usart_enable_rx_interrupt(CONSOLE_UART);
 }
+
+/*
+ * Set a different baud rate for the console.
+ */
+void console_baud(int baud_rate)
+{
+	usart_set_baudrate(CONSOLE_UART, baud_rate);
+}

examples/stm32/f4/stm32f469-discovery/util/console.h

@@ -7,6 +7,7 @@ char console_getc(int wait);
 void console_puts(char *s);
 int console_gets(char *s, int len);
 void console_setup(int baud);
+void console_baud(int baudrate);
 
 /* this is for fun, if you type ^C to this example it will reset */
 #define RESET_ON_CTRLC

examples/stm32/f4/stm32f469-discovery/util/retarget.c

@@ -0,0 +1,131 @@
+/*
+ * This file is part of the libopencm3 project.
+ *
+ * Copyright (C) 2015 Chuck McManis <[email protected]>
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/* retarget.c
+ *
+ * Stub routines to connect the board's USART3 which is wired into the
+ * STLink port, into the C library functions for standard I/O.
+ */
+#include <stdio.h>
+#include <stdint.h>
+#include <ctype.h>
+#include "../util/clock.h"
+#include "../util/console.h"
+
+#ifndef NULL
+#define NULL	0	
+#endif
+
+#define BUFLEN 127
+
+static void SystemInit(void);
+
+/*
+ * These are the functions to define to enable the
+ * newlib hooks to implement basic character I/O
+ */
+int _write (int fd, char *ptr, int len);
+int _read (int fd, char *ptr, int len);
+
+/*
+ * A 128 byte buffer for getting a string from the
+ * console.
+ */
+static char buf[BUFLEN+1] = {0};
+static char *next_char;
+
+/* 
+ * Called by libc stdio functions
+ */
+int 
+_write (int fd, char *ptr, int len)
+{
+	int i = 0;
+
+	/* 
+	 * Write "len" of char from "ptr" to file id "fd"
+	 * Return number of char written.
+	 */
+	if (fd > 2) {
+		return -1;  // STDOUT, STDIN, STDERR
+	}
+	if (fd == 2) {
+		/* set the text output YELLOW when sending to stderr */
+		console_puts("\033[33;40;1m");
+	}
+	while (*ptr && (i < len)) {
+		console_putc(*ptr);
+		if (*ptr == '\n') {
+			console_putc('\r');
+		}
+		i++;
+		ptr++;
+	}
+	if (fd == 2) {
+		/* return text out to its default state */
+		console_puts("\033[0m");
+	}
+  return i;
+}
+
+
+/*
+ * Depending on the implementation, this function can call
+ * with a buffer length of 1 to 1024. However it does no
+ * editing on console reading. So, the console_gets code 
+ * implements a simple line editing input style.
+ */
+int
+_read (int fd, char *ptr, int len)
+{
+	int	my_len;
+
+	if (fd > 2) {
+		return -1;
+	}
+
+	/* If not null we've got more characters to return */
+	if (next_char == NULL) {
+		console_gets(buf, BUFLEN);
+		next_char = &buf[0];
+	}
+
+	my_len = 0;
+	while ((*next_char != 0) && (len > 0)) {
+		*ptr++ = *next_char++;
+		my_len++;
+		len--;
+	}
+	if (*next_char == 0) {
+		next_char = NULL;
+	}
+	return my_len; // return the length we got
+}
+
+/* SystemInit will be called before main 
+ * This works because we tell GCC that it is a constructor
+ * which means "run this before main is invoked".
+ */
+__attribute__((constructor))
+static void SystemInit()
+{
+	clock_setup();
+	console_setup(115200);
+	next_char = NULL;
+}