From a93e506b78b7379e14c23ae80a5281485897faee Mon Sep 17 00:00:00 2001
From: Clyne Sullivan <tullivan99@gmail.com>
Date: Sat, 6 Jan 2018 19:47:40 -0500
Subject: serial support

---
 src/main.c   | 25 ++++++++++++++++++-------
 src/serial.c | 27 +++++++++++++++++++++++++++
 2 files changed, 45 insertions(+), 7 deletions(-)
 create mode 100644 src/serial.c

(limited to 'src')

diff --git a/src/main.c b/src/main.c
index d974ebc..30bb183 100644
--- a/src/main.c
+++ b/src/main.c
@@ -5,6 +5,7 @@
 #include <gpio.h>
 #include <lcd.h>
 #include <initrd.h>
+#include <serial.h>
 
 /**
  * Accomplishments:
@@ -15,7 +16,8 @@
  *   - gpio lib
  *   - lcd support
  *   - initrd support
- *   - lua?
+ *   - lua? - no, something better, smaller
+ *   - serial IO
  */
 
 void pulse(uint8_t byte);
@@ -35,12 +37,14 @@ int main(void)
 
 	gpio_mode(GPIOA, 5, OUTPUT);
 
+	serial_init();
+
 	task_init(kmain);
 
 	while (1);
 }
 
-void task(void);
+void serial_getter(void);
 void kmain(void)
 {
 	asm("cpsie i");
@@ -48,12 +52,11 @@ void kmain(void)
 	task_start(lcd_handler, 128);
 	delay(200);
 
-	char *s = initrd_getfile("test.txt");
-	const char *t = "Yoyoyo";
-
-	asm("mov r0, %0; svc 2" :: "r" (s));
-	asm("mov r0, %0; svc 2" :: "r" (t));
+	//char *s = initrd_getfile("test.txt");
+	// svc puts
+	//asm("mov r0, %0; svc 2" :: "r" (s));
 
+	task_start(serial_getter, 128);
 	while (1) {
 		gpio_dout(GPIOA, 5, 1);
 		delay(500);
@@ -62,3 +65,11 @@ void kmain(void)
 	}
 }
 
+void serial_getter(void)
+{
+	char buf[2] = { 0, 0 };
+	while (1) {
+		buf[0] = serial_get();
+		asm("mov r0, %0; svc 2" :: "r" (buf));
+	}
+}
diff --git a/src/serial.c b/src/serial.c
new file mode 100644
index 0000000..692faf0
--- /dev/null
+++ b/src/serial.c
@@ -0,0 +1,27 @@
+#include <stm32l476xx.h>
+#include <gpio.h>
+
+void serial_init(void)
+{
+	gpio_mode(GPIOA, 2, ALTERNATE);
+	gpio_mode(GPIOA, 3, ALTERNATE);
+	GPIOA->AFR[0] &= ~(0x0000FF00);
+	GPIOA->AFR[0] |= 0x00007700;
+	RCC->APB1ENR1 |= RCC_APB1ENR1_USART2EN;
+
+	// start usart device
+	USART2->BRR = 80000000L / 115200L;
+	USART2->CR1 |= USART_CR1_TE | USART_CR1_RE | USART_CR1_UE;
+}
+
+void serial_put(int c)
+{
+	while (!(USART2->ISR & USART_ISR_TXE));
+	USART2->TDR = c & 0xFF;
+}
+
+char serial_get(void)
+{
+	while (!(USART2->ISR & USART_ISR_RXNE));
+	return USART2->RDR & 0xFF;
+}
-- 
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