Diff: morsemsg.cpp

Revision:

0:023075f6fafd

diff -r 000000000000 -r 023075f6fafd morsemsg.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/morsemsg.cpp	Tue Oct 26 23:13:58 2010 +0000
@@ -0,0 +1,108 @@
+#include "mbed.h"
+
+DigitalOut myled(LED1);
+
+/// Send the string message in morse code on 'myled
+void morse_string(char *msg);
+
+// Timing constants for morse code generation
+#define TDOT   0.2
+#define TDASH  (3*TDOT)
+#define TSPLIT (1*TDOT)
+#define TSPACE (3*TDASH)
+
+int main() {
+    while (1) {
+        morse_string("hello world");
+        wait(2*TSPACE);
+    }
+}
+
+/// Table with morse code bit-patterns.
+/// Each symbols dot/dash sequence is stored starting at bit 0 where
+/// a set bit encodes a dash and cleared bit a dot. The sequence is terminated by a set trailing bit-
+unsigned char alphabet[] = {
+    0x06, // .-     a
+    0x11, // -...     b
+    0x15, // -.-.     c
+    0x09, // -..     d
+    0x02, // .     e
+    0x14, // ..-.     f
+    0x0b, // --.     g
+    0x10, // ....     h
+    0x08, // ..     i
+    0x1e, // .---     j
+    0x0d, // -.-     k
+    0x12, // .-..     l
+    0x07, // --     m
+    0x05, // -.     n
+    0x0F, // ---     o
+    0x16, // .--.     p
+    0x1b, // --.-     q
+    0x0a, // .-.     r
+    0x08, // ...     s
+    0x03, // -     t
+    0x0c, // ..-     u
+    0x18, // ...-     v
+    0x0e, // .--     w
+    0x19, // -..-     x
+    0x1d, // -.--     y
+    0x13, // --..     z
+    0x3f, // ----- 0
+    0x3e, // .---- 1
+    0x3c, // ..--- 2
+    0x38, // ...-- 3
+    0x30, // ....- 4
+    0x20, // ..... 5
+    0x21, // -.... 6
+    0x23, // --... 7
+    0x27, // ---.. 8
+    0x2f, // ----. 9
+    0x73, // --..-- ,
+    0x6a, // .-.-.- .
+    0x00
+};
+
+/// Convert a character to a morse-code bit pattern.
+unsigned char getCode(char symbol) {
+    if      (symbol >= 'a' && symbol <= 'z')    return alphabet[symbol-'a'];
+    else if (symbol >= '0' && symbol <= '9')    return alphabet[symbol-'0'+26];
+    else if (symbol == '.')            return alphabet[37];
+    else if (symbol == ',')            return alphabet[36];
+    else return 0;
+}
+
+/// Pattern of current symbol being send.
+unsigned char morse_pattern = 0;
+
+/// Set the symbol to be morsed.
+/// Returns bit pattern of morse code or zero if symbol not found (e.g. for a space)
+int morse_setsymbol(char symbol) {
+    return morse_pattern = getCode(symbol);
+}
+
+/// Generate next dot/dash to transmit
+/// Returns 0 for dot, 1 for dash and -1 for finished
+int morse_next() {
+    int retval = (morse_pattern & 1) ? 1 : 0;
+    morse_pattern >>= 1;
+    if (! morse_pattern) retval = -1;
+    return retval;
+}
+
+void morse_string(char *msg) {
+    int x;
+    for (; *msg; msg++) {
+        if (!morse_setsymbol(*msg)) {
+            wait(TSPACE);
+            continue;
+        }
+        for (x=morse_next(); x != -1; x=morse_next()) {
+            myled = 1;
+            wait(x ? TDASH : TDOT);
+            myled = 0;
+            wait(TSPLIT);
+        }
+        wait(TDASH);
+    }
+}