From eaf5d4799cc52e9dd1ebcaeafbf8f670658fea98 Mon Sep 17 00:00:00 2001
From: root <root@no.no.james.local>
Date: Tue, 13 Jun 2017 21:10:37 +0100
Subject: inital commit

---
 app/usart.c | 90 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 90 insertions(+)
 create mode 100644 app/usart.c

(limited to 'app/usart.c')

diff --git a/app/usart.c b/app/usart.c
new file mode 100644
index 0000000..ecd8e56
--- /dev/null
+++ b/app/usart.c
@@ -0,0 +1,90 @@
+#include "project.h"
+
+#define BUFFER_SIZE 512
+
+ring_t usart_rx_ring;
+static uint8_t usart_rx_ring_buf[BUFFER_SIZE];
+
+ring_t usart_tx_ring;
+static uint8_t usart_tx_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);
+    ring_write_byte (&usart_rx_ring, 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 (&usart_tx_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);
+    }
+  }
+}
+
+void usart_kick (void)
+{
+  if (!ring_empty (&usart_tx_ring)) {
+    USART_CR1 (USART1) |= USART_CR1_TXEIE;
+  }
+}
+
+
+int
+_write (int file, char *ptr, int len)
+{
+  int ret;
+
+  if (file == 1) {
+    ret = ring_write (&usart_tx_ring, (uint8_t *) ptr, len);
+    usart_kick();
+
+    if (ret < 0) {
+      ret = -ret;
+    }
+
+    return ret;
+  }
+
+  errno = EIO;
+  return -1;
+}
+
+
+
+
+void
+usart_init (void)
+{
+  ring_init (&usart_rx_ring, usart_rx_ring_buf, sizeof (usart_rx_ring_buf));
+  ring_init (&usart_tx_ring, usart_tx_ring_buf, sizeof (usart_tx_ring_buf));
+  /* Enable the USART1 interrupt. */
+  nvic_enable_irq (NVIC_USART1_IRQ);
+  /* Map pins */
+  gpio_set_mode (GPIOA, GPIO_MODE_OUTPUT_50_MHZ,
+                 GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, GPIO_USART1_TX);
+  gpio_set_mode (GPIOA, GPIO_MODE_INPUT, GPIO_CNF_INPUT_FLOAT,
+                 GPIO_USART1_RX);
+  /* Setup UART1 parameters. */
+  usart_set_baudrate (USART1, 115200);
+  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 USART1. */
+  usart_enable (USART1);
+}
-- 
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