From e4d0dc3cb320e5f0d2e07306bf1462b4fb3284a7 Mon Sep 17 00:00:00 2001
From: "S.J.R. van Schaik" <stephan@whiteboxsystems.nl>
Date: Tue, 18 Jul 2017 12:59:05 +0200
Subject: [PATCH] usart: implement interrupt for USART receive

---
 source/drivers/usart_console.c | 118 +++++++++++++++++++++++++++++++++++------
 1 file changed, 103 insertions(+), 15 deletions(-)

diff --git a/source/drivers/usart_console.c b/source/drivers/usart_console.c
index 92aa4f1..65794aa 100644
--- a/source/drivers/usart_console.c
+++ b/source/drivers/usart_console.c
@@ -2,6 +2,8 @@
 #include <libopencm3/stm32/rcc.h>
 #include <libopencm3/stm32/gpio.h>
 #include <libopencm3/stm32/usart.h>
+#include <libopencm3/cm3/nvic.h>
+#include <libopencm3/cm3/scb.h>
 
 #include <ctype.h>
 #include <stdio.h>
@@ -14,36 +16,115 @@
 
 #include <console.h>
 
-static ssize_t usart_read(void *cookie, char *buf, size_t n)
+#define RECV_BUF_LEN 128
+
+struct usart_console {
+	char recv_buf[RECV_BUF_LEN];
+	volatile size_t cur, next;
+	uint32_t dev;
+};
+
+struct usart_console *usart1 = NULL;
+struct usart_console user_console;
+
+static void usart_isr(struct usart_console *console)
 {
-	uint32_t dev = (uint32_t)cookie;
+	uint32_t reg;
 	size_t i;
 
-	for (i = 0; i < n; ++i) {
-		buf[i] = (char)usart_recv_blocking(dev);
+	if (!console)
+		return;
+
+	do {
+		reg = USART_ISR(console->dev);
+
+		if (!(reg & USART_ISR_RXNE))
+			continue;
+
+		console->recv_buf[console->next] = usart_recv(console->dev);
+
+		if (console->recv_buf[console->next] == '\003')
+			scb_reset_system();
+
+		i = (console->next + 1) % RECV_BUF_LEN;
+
+		if (i != console->cur)
+			console->next = i;
+	} while (usart_get_flag(console->dev, USART_ISR_RXNE));
+}
+
+void usart1_isr(void)
+{
+	usart_isr(usart1);
+}
+
+static char usart_getc(struct usart_console *console, int block)
+{
+	char c = 0;
+
+	while (block && (console->cur == console->next));
+
+	if (console->cur != console->next) {
+		c = console->recv_buf[console->cur];
+		console->cur = (console->cur + 1) % RECV_BUF_LEN;
+	}
+
+	return c;
+}
+
+static ssize_t usart_read(void *cookie, char *buf, size_t n)
+{
+	struct usart_console *console = cookie;
+	char *p = buf;
+	char c;
+
+	*buf = '\0';
+
+	while ((c = usart_getc(console, 1)) != '\r') {
+		switch (c) {
+		case 10:
+		case 127:
+			if (buf < p) {
+				usart_send_blocking(console->dev, '\010');
+				usart_send_blocking(console->dev, ' ');
+				usart_send_blocking(console->dev, '\010');
+				--p;
+			}
 
-		if (buf[i] == '\r') {
-			buf[i++] = '\n';
-			putchar('\n');
 			break;
+		default:
+			*p = c;
+			usart_send_blocking(console->dev, c);
+
+			if (((size_t)p - (size_t)buf) < n) {
+				++p;
+			}
 		}
 
-		putchar(buf[i]);
+		*p = '\0';
 	}
 
-	return i;
+	*p = '\n';
+
+	if (((size_t)p - (size_t)buf) < n) {
+		++p;
+	}
+
+	*p = '\0';
+
+	return p - buf;
 }
 
 static ssize_t usart_write(void *cookie, const char *buf, size_t n)
 {
-	uint32_t dev = (uint32_t)cookie;
+	struct usart_console *console = cookie;
 	size_t i;
 
 	for (i = 0; i < n; ++i) {
 		if (buf[i] == '\n')
-			usart_send_blocking(dev, '\r');
+			usart_send_blocking(console->dev, '\r');
 
-		usart_send_blocking(dev, buf[i]);
+		usart_send_blocking(console->dev, buf[i]);
 	};
 
 	return i;
@@ -67,7 +148,10 @@ static void usart_init(void)
 	usart_set_mode(USART1, USART_MODE_TX_RX);
 	usart_set_flow_control(USART1, USART_FLOWCONTROL_NONE);
 
+	nvic_enable_irq(NVIC_USART1_IRQ);
+
 	usart_enable(USART1);
+	usart_enable_rx_interrupt(USART1);
 }
 
 void console_init(void)
@@ -85,11 +169,15 @@ void console_init(void)
 		.close = NULL,
 	};
 
+	user_console.dev = USART1;
+	user_console.cur = 0;
+	user_console.next = 0;
+	usart1 = &user_console;
 	usart_init();
 
-	stdin = fopencookie((void *)USART1, "r", console_in);
-	stdout = fopencookie((void *)USART1, "w", console_out);
-	stderr = fopencookie((void *)USART1, "w", console_out);
+	stdin = fopencookie(&user_console, "r", console_in);
+	stdout = fopencookie(&user_console, "w", console_out);
+	stderr = fopencookie(&user_console, "w", console_out);
 
 	setbuf(stdout, NULL);
 	//setlinebuf(stdout);