1 files changed, 104 insertions, 0 deletions
diff --git a/src/usart.c b/src/usart.c
new file mode 100644
index 0000000..b0ea2a4
--- /dev/null
+++ b/src/usart.c
@@ -0,0 +1,104 @@
+#include "project.h"
+
+#define BUFFER_SIZE 256
+
+static ring_t output_ring;
+static uint8_t output_ring_buf[BUFFER_SIZE];
+
+void
+usart1_isr (void)
+{
+  uint8_t data;
+
+  /* Check if we were called because of RXNE. */
+  if (((USART_CR1 (USART1) & USART_CR1_RXNEIE) != 0) &&
+      ((USART_SR (USART1) & USART_SR_RXNE) != 0))
+    {
+
+      /* Retrieve the data from the peripheral. */
+      data = usart_recv (USART1);
+
+      kvm_recv (data);
+    }
+
+  /* Check if we were called because of TXE. */
+  if (((USART_CR1 (USART1) & USART_CR1_TXEIE) != 0) &&
+      ((USART_SR (USART1) & USART_SR_TXE) != 0))
+    {
+
+      if (ring_read_byte (&output_ring, &data))
+        {
+          /*No more data, Disable the TXE interrupt, it's no longer needed. */
+          USART_CR1 (USART1) &= ~USART_CR1_TXEIE;
+        }
+      else
+        {
+          usart_send (USART1, data);
+        }
+    }
+
+}
+
+int
+_write (int file, char *ptr, int len)
+{
+  int ret;
+
+  if (file == 1)
+    {
+      ret = ring_write (&output_ring, (uint8_t *) ptr, len);
+
+      if (ret < 0)
+        ret = -ret;
+
+      USART_CR1 (USART1) |= USART_CR1_TXEIE;
+      return ret;
+    }
+
+  errno = EIO;
+  return -1;
+}
+
+void
+usart_queue (uint8_t d)
+{
+  ring_write_byte(&output_ring,d);
+  USART_CR1 (USART1) |= USART_CR1_TXEIE;
+
+#if 0
+  printf ("0x%02x ", d);
+  fflush (stdout);
+#endif
+}
+
+
+void
+usart_init (void)
+{
+  ring_init (&output_ring, output_ring_buf, sizeof (output_ring_buf));
+
+  /* Enable the USART1 interrupt. */
+  nvic_enable_irq (NVIC_USART1_IRQ);
+
+  /* Setup GPIO pin GPIO_USART1_RE_TX on GPIO port B for transmit. */
+  gpio_set_mode (GPIOA, GPIO_MODE_OUTPUT_50_MHZ,
+                 GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, GPIO_USART1_TX);
+
+  /* Setup GPIO pin GPIO_USART1_RE_RX on GPIO port B for receive. */
+  gpio_set_mode (GPIOA, GPIO_MODE_INPUT,
+                 GPIO_CNF_INPUT_FLOAT, GPIO_USART1_RX);
+
+  /* Setup UART parameters. */
+  usart_set_baudrate (USART1, 38400);
+  usart_set_databits (USART1, 8);
+  usart_set_stopbits (USART1, USART_STOPBITS_1);
+  usart_set_parity (USART1, USART_PARITY_NONE);
+  usart_set_flow_control (USART1, USART_FLOWCONTROL_NONE);
+  usart_set_mode (USART1, USART_MODE_TX_RX);
+
+  /* Enable USART1 Receive interrupt. */
+  USART_CR1 (USART1) |= USART_CR1_RXNEIE;
+
+  /* Finally enable the USART. */
+  usart_enable (USART1);
+}