interrupt driven sending

src/uartdrv.c

@@ -6,6 +6,10 @@
 
 
 
+#define BUFFER_SIZE 128
+volatile uint8_t buffer[BUFFER_SIZE+5];
+volatile uint8_t bufferReadIdx = 0;
+volatile uint8_t bufferWriteIdx = 0;
 
 void uartdrvInit() {
 
@@ -25,8 +29,16 @@ void uartdrvInit() {
 }
 
 void uartdrvWrite(uint8_t o) {
-  loop_until_bit_is_set(UCSRA, UDRE);
-  UDR = o;
+//  loop_until_bit_is_set(UCSRA, UDRE);
+//  UDR = o;
+  if (bufferWriteIdx == BUFFER_SIZE - 1) {
+    while (bufferReadIdx == BUFFER_SIZE);
+  } else {
+    while (bufferReadIdx == bufferWriteIdx + 1);
+  }
+  buffer[bufferWriteIdx] = o;
+  bufferWriteIdx++;
+  UCSRB |= (1 << UDRIE);
 }
 
 
@@ -38,4 +50,14 @@ int uartdrvPutchar(char c, FILE *stream) {
 }
 
 
-
+ISR(USART_UDRE_vect) {
+  if (bufferReadIdx != bufferWriteIdx) {
+    UDR = buffer[bufferReadIdx];
+    bufferReadIdx++;
+    if (bufferReadIdx > BUFFER_SIZE) {
+      bufferReadIdx = 0;
+    }
+  } else {
+    UCSRB &= ~(1 << UDRIE);
+  }
+}