From 21d4c65d789e3b60b063e48e71bdc2912aa7dc2b Mon Sep 17 00:00:00 2001
From: Alexander Haarer <alex@haarer.com>
Date: Tue, 21 May 2024 14:26:27 +0200
Subject: [PATCH] uart

---
 examples/arm-none-eabi-example-cpp/main.cpp | 21 ++++-------
 examples/arm-none-eabi-example-cpp/uart.c   | 28 ++++++++++++---
 examples/arm-none-eabi-example-cpp/uart.h   | 39 +++++++++++++++++++--
 3 files changed, 66 insertions(+), 22 deletions(-)

diff --git a/examples/arm-none-eabi-example-cpp/main.cpp b/examples/arm-none-eabi-example-cpp/main.cpp
index 5f498a8..d3b0351 100644
--- a/examples/arm-none-eabi-example-cpp/main.cpp
+++ b/examples/arm-none-eabi-example-cpp/main.cpp
@@ -1,10 +1,11 @@
 
-/* a simple blink example */
+/* a simple blink example and serial out */
 #include <stdint.h>
 extern "C"
 {
 #include "stm32f10x.h"
 #include "system.h"
+#include "uart.h"
 }
 #include <stdio.h>
 //#include <iostream>
@@ -94,7 +95,7 @@ int main(void)
 {
 
 	static std::vector<int> vec;
-
+    uartInit(115200);
 
 	RCC->APB2ENR |= RCC_APB2ENR_IOPCEN; // enable port c
 
@@ -102,36 +103,26 @@ int main(void)
 	pinConfg(GPIOC,13,OUTPUT_PUSH_PULL);
 
 
-
-
 	SysTick_Config(SystemCoreClock/1000);
 
-	
-
 	while (1)
 	{
 
-
 		highPin(GPIOC,13);
-
 		myDelay(100);
 
-
-		printf("enough is enough\n ");
-
-
 		lowPin(GPIOC,13);
 		myDelay(100);
 
 
-
+        //does not fit into flash
 		//std::cout << "hello" << std::endl;
 		vec.push_back(0);
 		printf("hello vector contains %d elements \n",vec.size());
-		if (vec.size() > 1000)
+		if (vec.size() > 100)
 		{
 			vec.clear();
-			
+            printf("enough is enough, resetting\n ");
 		}
 
 	}
diff --git a/examples/arm-none-eabi-example-cpp/uart.c b/examples/arm-none-eabi-example-cpp/uart.c
index 363784f..8978299 100644
--- a/examples/arm-none-eabi-example-cpp/uart.c
+++ b/examples/arm-none-eabi-example-cpp/uart.c
@@ -1,18 +1,36 @@
 
+#include "stm32f10x.h"
 
 #include <uart.h>
 
-static void __attribute__((constructor)) uartInit(void)
+char uartGetch(void)
 {
-
+  return 0;
 }
 
-int uartGetch(void)
+void uartPutch(char c)
 {
-  return 0;
+    // wait for tx data register to be empty
+    while (!(USART1->SR & USART_SR_TXE))
+        ;
+    USART1->DR = 0x000000ff & c;
 }
 
-void uartPutch(unsigned int ch)
+void uartPuts(const char *ch)
 {
+    while (*ch)
+    {
+        uartPutch(*ch);
+        ch++;
+    }
+}
+
 
+void USART1_IRQHandler(void)
+{
+    if (USART1->SR & USART_SR_RXNE)
+    {
+        // this clears RXNE flag
+        uartPutch(USART1->DR & 0xff);
+    }
 }
diff --git a/examples/arm-none-eabi-example-cpp/uart.h b/examples/arm-none-eabi-example-cpp/uart.h
index 42e9255..124528d 100644
--- a/examples/arm-none-eabi-example-cpp/uart.h
+++ b/examples/arm-none-eabi-example-cpp/uart.h
@@ -4,8 +4,43 @@
 #define UART_H
 
 
-extern int uartGetch(void);
-extern void uartPutch(unsigned int ch);
+#include "stm32f10x.h"
+#include "system.h"
+extern char uartGetch(void);
+extern void uartPutch(char ch);
+extern void USART1_IRQHandler(void);
+
+
+
+/**
+ * @brief Initialize USART1 peripheral
+ * 
+ * @param baudrate baudrate to be configurate
+ */
+static inline void uartInit(uint32_t baudrate)
+{
+    // enable clock for GPIOA and USART1
+    RCC->APB2ENR |= RCC_APB2ENR_USART1EN | RCC_APB2ENR_IOPAEN;
+
+    // reset pin configurations for PA9 and PA10
+    GPIOA->CRH &= ~(GPIO_CRH_MODE10 | GPIO_CRH_MODE9 | GPIO_CRH_CNF10 | GPIO_CRH_CNF9);
+
+    // PA9 as Output@50Hz Alternate function
+    GPIOA->CRH |= GPIO_CRH_MODE9_0 | GPIO_CRH_MODE9_1 | GPIO_CRH_CNF9_1;
+
+    // PA10 as floating input
+    GPIOA->CRH |= GPIO_CRH_CNF10_0;
+
+    uint32_t baud = (uint32_t)(SystemCoreClock / baudrate);
+
+    USART1->BRR = baud;
+
+    // transmitter enable, receiver enable, receiver interrupt enable and USART enable
+    USART1->CR1 = USART_CR1_TE | USART_CR1_RE | USART_CR1_RXNEIE | USART_CR1_UE;
+
+    // enable USART1 interrupt
+    NVIC_EnableIRQ(USART1_IRQn);
+}
 
 
 #endif