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199 lines
6.0 KiB
HTML
199 lines
6.0 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Debugging (Embed with GNU)</title>
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<meta name="description" content="Debugging (Embed with GNU)">
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<meta name="keywords" content="Debugging (Embed with GNU)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="leds_002ec.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Libc.html#Libc" rel="up" title="Libc">
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<link href="GDB.html#GDB" rel="next" title="GDB">
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<link href="Misc-Support.html#Misc-Support" rel="prev" title="Misc Support">
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<style type="text/css">
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<!--
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a.summary-letter {text-decoration: none}
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blockquote.indentedblock {margin-right: 0em}
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blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
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blockquote.smallquotation {font-size: smaller}
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-->
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</style>
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</head>
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<body lang="en">
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<a name="Debugging"></a>
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<div class="header">
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<p>
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Previous: <a href="Misc-Support.html#Misc-Support" accesskey="p" rel="prev">Misc Support</a>, Up: <a href="Libc.html#Libc" accesskey="u" rel="up">Libc</a> [<a href="leds_002ec.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p>
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</div>
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<hr>
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<a name="Useful-debugging-functions"></a>
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<h4 class="subsection">3.4.4 Useful debugging functions</h4>
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<p>There are always a few useful functions for debugging your project in
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progress. I typically implement a simple <code>print()</code> routine that
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runs standalone in liblgoss, with no <code>newlib</code> support. The I/O
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function <code>outbyte()</code> can also be used for low level debugging. Many
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times print will work when there are problems that cause <code>printf()</code> to
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cause an exception. <code>putnum()</code> is just to print out values in hex
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so they are easier to read.
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</p>
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<div class="smallexample">
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<pre class="smallexample">/*
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* print -- do a raw print of a string
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*/
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int
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print(ptr)
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char *ptr;
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{
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while (*ptr) {
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outbyte (*ptr++);
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}
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}
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/*
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* putnum -- print a 32 bit number in hex
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*/
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int
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putnum (num)
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unsigned int num;
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{
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char buffer[9];
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int count;
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char *bufptr = buffer;
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int digit;
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for (count = 7 ; count >= 0 ; count--) {
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digit = (num >> (count * 4)) & 0xf;
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if (digit <= 9)
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*bufptr++ = (char) ('0' + digit);
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else
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*bufptr++ = (char) ('a' - 10 + digit);
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}
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*bufptr = (char) 0;
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print (buffer);
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return;
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}
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</pre></div>
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<p>If there are LEDs on the board, they can also be put to use for
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debugging when the serial I/O code is being written. I usually implement
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a <code>zylons()</code> function, which strobes the LEDS (if there is more
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than one) in sequence, creating a rotating effect. This is convenient
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between I/O to see if the target is still alive. Another useful LED
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function is <code>led_putnum()</code>, which takes a digit and displays it as
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a bit pattern or number. These usually have to be written in assembler
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for each target board. Here are a number of C based routines that may be
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useful.
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</p>
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<p><code>led_putnum()</code> puts a number on a single digit segmented
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LED display. This LED is set by setting a bit mask to an address, where
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1 turns the segment off, and 0 turns it on. There is also a little
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decimal point on the LED display, so it gets the leftmost bit. The other
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bits specify the segment location. The bits look like:
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</p>
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<div class="smallexample">
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<pre class="smallexample"> [d.p | g | f | e | d | c | b | a ] is the byte.
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</pre></div>
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<p>The locations are set up as:
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</p>
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<div class="smallexample">
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<pre class="smallexample"> a
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-----
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f | | b
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| g |
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-----
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| |
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e | | c
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-----
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d
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</pre></div>
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<p>This takes a number that’s already been converted to a string, and
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prints it.
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</p>
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<div class="smallexample">
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<pre class="smallexample">#define LED_ADDR 0xd00003
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void
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led_putnum ( num )
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char num;
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{
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static unsigned char *leds = (unsigned char *)LED_ADDR;
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static unsigned char num_bits [18] = {
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0xff, /* clear all */
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0xc0, 0xf9, 0xa4, 0xb0, 0x99, 0x92, 0x82, 0xf8, 0x80, 0x98, /* numbers 0-9 */
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0x98, 0x20, 0x3, 0x27, 0x21, 0x4, 0xe /* letters a-f */
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};
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if (num >= '0' && num <= '9')
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num = (num - '0') + 1;
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if (num >= 'a' && num <= 'f')
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num = (num - 'a') + 12;
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if (num == ' ')
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num = 0;
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*leds = num_bits[num];
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}
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/*
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* zylons -- draw a rotating pattern. NOTE: this function never returns.
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*/
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void
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zylons()
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{
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unsigned char *leds = (unsigned char *)LED_ADDR;
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unsigned char curled = 0xfe;
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while (1)
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{
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*leds = curled;
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curled = (curled >> 1) | (curled << 7);
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delay ( 200 );
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}
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}
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</pre></div>
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<hr>
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<div class="header">
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<p>
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Previous: <a href="Misc-Support.html#Misc-Support" accesskey="p" rel="prev">Misc Support</a>, Up: <a href="Libc.html#Libc" accesskey="u" rel="up">Libc</a> [<a href="leds_002ec.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p>
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</div>
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</body>
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</html>
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