Changeset 82d2b68 in avrstuff for chiptest/main.c

Timestamp:

Jul 29, 2014, 9:17:17 PM (10 years ago)

Author:

Adrien Destugues <pulkomandy@…>

Branches:

main

Children:

efe25a8

Parents:

5ef7bfc

Message:

Make baudrate computation aware of F_CPU.

git-svn-id: ​svn://pulkomandy.tk/avrstuff@107 c6672c3c-f6b6-47f9-9001-1fd6b12fecbe

File:

• chiptest/main.c (modified) (2 diffs)

chiptest/main.c

@@ -14 +14 @@
 #define LEDBIT 1 << PB2
 
+#define BAUD 9600 // Safe value even for low clocks. (used by setbaud.h)
+
 int main() {
         wdt_enable(WDTO_2S);
-    // configure timer 0 for a rate of 16M/(256 * 256) = ~244Hz
+    // configure timer 0 for a rate of FCPU/(256 * 256)
     TCCR0A = 0;          // timer 0 prescaler: 256
         TCCR0B = 4;
@@ -25 +27 @@
         PORTLED = 0;
 
-        // Serial PORT
-        UBRRH = 0;
-        UBRRL = 10;
+        // Serial baudrate - use avrlibc magic to compute the baudrate register
+        // values.
+        #include <util/setbaud.h>
+        UBRRH = UBRRH_VALUE;
+        UBRRL = UBRRL_VALUE;
+        #if USE_2X
+                UCSRA |= (1 << U2X);
+        #else
+                UCSRA &= ~(1 << U2X);
+        #endif
 
+        // Enable the serial port.
         UCSRB = (1<<RXEN) |(1<<TXEN);
         UCSRC = (1 << UCSZ1) | (1 << UCSZ0);
 
-        while(1) {
+        // Let's rock!
+        uint8_t counter = 0;
+        for(;;) {
                 wdt_reset();
 
-
-                // check timer if we need periodic reports
+                // Wait for timer overflow...
                 if (TIFR & (1 << TOV0)) {
                         TIFR = (1 << TOV0); // reset flag
-                        PORTLED ^= LEDBIT;
+                        counter++;
+                }
 
-                        UDR = 'H';
+                if (counter == 0)
+                {
+                        PORTLED ^= LEDBIT; // Toggle the LED
+                        UDR = 'H'; // Send a byte to the UART
                 }
         }