The c example now reads and mirrors UART input.

Author: esden

c-riscv-blink/src/main.c

@@ -1,21 +1,39 @@
 #include <generated/csr.h>
 #include <time.h>
 
+#define UART_EV_TX 0x1
+#define UART_EV_RX 0x2
+
 void isr(void) {
     asm("nop");
 }
 
 
 int main(void) {
     uint32_t x = 0;
+    uint32_t buf = 0;
     while (1) {
-        uart_rxtx_write('a');
-        leds_out_write(x);
-        if (x == 0x02) {
+
+        // Wait for an incoming byte
+        while (uart_rxempty_read()) {
+            // Prevent the while loop from being optimized out
+            asm("nop");
+        }
+
+        // Read an incoming byte
+        buf = uart_rxtx_read();
+        // Tell the UART that we read a byte out of the FIFO
+        // and that it can give us another.
+        uart_ev_pending_write(UART_EV_RX);
+        // Mirror the bytes back
+        uart_rxtx_write(buf);
+
+        // Write new LED output and toggle
+        leds_out_write(x | (buf << 2));
+        if (x == 2) {
             x = 0x00000001;
         } else {
             x = 0x00000002;
         }
-        msleep(80);
     }
 }