updated uart lib

0x0001_hello-world/include/usart.h

@@ -33,28 +33,55 @@ extern int __io_putchar(int ch) __attribute__((weak));
 static void set_baud_rate(USART_TypeDef *USARTx,  uint32_t periph_clk, uint32_t baud_rate);
 
 /**
- * @brief  Initializes USART2 for transmission on PA2 pin.
+ * @brief  Initializes USART2 for transmission on PA2 pin and receive on PA3 pin.
  *
  *         This function configures the necessary settings for USART2 to enable
- *         transmission on pin PA2. It includes configuring GPIO, setting
- *         alternate function mode, configuring the USART clock, setting the
+ *         transmission on pin PA2 and receive on PA3 pin. It includes configuring 
+ *         GPIO, setting alternate function mode, configuring the USART clock, setting the
  *         baud rate, and enabling the transmitter.
  *
  * @param  None
  * @retval None
  */
-void usart2_tx_init(void);
+void usart2_init(void);
 
 /**
  * @brief  Writes a single byte to USART2 for transmission.
  *
- *         This function writes a single byte to the USART2 transmit data
- *         register for transmission. It ensures that the transmit data register
+ *         This function writes a single byte to the USART2  data
+ *         register for transmission. It ensures that the data register
  *         is empty before writing the byte.
  *
- * @param  ch: The byte to be transmitted.
+ * @param  char_: The byte to be transmitted.
  * @retval None
  */
-void usart2_write(uint8_t ch);
+void usart2_write_char(uint8_t char_);
+
+/**
+ * @brief  Reads a single byte from USART2.
+ *
+ *         This function reads a single byte from the USART2 data
+ *         register. It ensures that the data register is not empty
+ *         before reading the byte.
+ *
+ * @param  None
+ * @retval The byte read from the data register.
+ */
+char usart2_read_char(void);
+
+/**
+ * @brief  Reads a string of characters from input and stores it in the buffer.
+ *
+ *         This function reads characters from input and stores them in the
+ *         provided buffer until either the buffer is full (reaching
+ *         buffer_size - 1 characters) or a newline character is encountered.
+ *         The input is null-terminated, ensuring proper string termination in
+ *         the buffer.
+ *
+ * @param  buffer: Pointer to the buffer where the input characters are stored.
+ * @param  buffer_size: The size of the buffer, including space for the null-terminator.
+ * @retval None
+ */
+void input(char *buffer, size_t buffer_size);
 
 #endif // USART_H

0x0001_hello-world/src/main.c

@@ -13,7 +13,7 @@
 
 int main(void)
 {
-    usart2_tx_init();
+    usart2_init();
 
     while (1)
     {

0x0001_hello-world/src/usart.c

@@ -22,12 +22,12 @@ __attribute__((weak)) int _write(int file, char *ptr, int len)
     return len;
 }
 
-int __io_putchar(int ch)
+int __io_putchar(int char_)
 {
     // write a single char
-    usart2_write(ch);
+    usart2_write_char(char_);
 
-    return ch;
+    return char_;
 }
 
 static void set_baud_rate(USART_TypeDef *USARTx,  uint32_t periph_clk, uint32_t baud_rate)
@@ -36,7 +36,7 @@ static void set_baud_rate(USART_TypeDef *USARTx,  uint32_t periph_clk, uint32_t
     USARTx->BRR = ((periph_clk + (baud_rate / 2)) / baud_rate);
 }
 
-void usart2_tx_init(void)
+void usart2_init(void)
 {
     // enable GPIOA clock
     RCC->AHB1ENR |= RCC_AHB1ENR_GPIOAEN;
@@ -51,6 +51,16 @@ void usart2_tx_init(void)
     GPIOA->AFR[0] |= GPIO_AFRL_AFRL2_1;
     GPIOA->AFR[0] |= GPIO_AFRL_AFRL2_0;
 
+    // set PA3 to output alternate function mode
+    GPIOA->MODER |= GPIO_MODER_MODE3_1;
+    GPIOA->MODER &= ~GPIO_MODER_MODE3_0;
+
+    // set PA3 alternate function type to UART_RX (AF07)
+    GPIOA->AFR[0] &= ~GPIO_AFRL_AFRL3_3;
+    GPIOA->AFR[0] |= GPIO_AFRL_AFRL3_2;
+    GPIOA->AFR[0] |= GPIO_AFRL_AFRL3_1;
+    GPIOA->AFR[0] |= GPIO_AFRL_AFRL3_0;
+
     // enable USART2 clock
     RCC->APB1ENR |= RCC_APB1ENR_USART2EN;
 
@@ -60,15 +70,57 @@ void usart2_tx_init(void)
     // configure TX transmitter enable
     USART2->CR1 |= USART_CR1_TE;
 
+    // configure RX receiver enable
+    USART2->CR1 |= USART_CR1_RE;
+
     // enable UART2
     USART2->CR1 |= USART_CR1_UE;
 }
 
-void usart2_write(uint8_t ch)
+void usart2_write_char(uint8_t char_)
 {
     // verify transmit data register is empty, will return true if the bit is set
     while(!(USART2->SR & USART_SR_TXE)) {};
 
-    // write a single char to the transmit data register
-    USART2->DR = (ch & 0xFF);
+    // write a single char to the data register
+    USART2->DR = (char_ & 0xFF);
+}
+
+char usart2_read_char(void)
+{
+    // verify receive data register is empty, will return true if the bit is set
+    while(!(USART2->SR & USART_SR_RXNE)) {};
+
+    // return a single char from the data register
+    return USART2->DR;
+}
+
+void input(char *buffer, size_t buffer_size)
+{
+    char input;
+    size_t i = 0;
+
+    while (1)
+    {
+        input = usart2_read_char();
+
+        // check for newline or carriage return
+        if (input == '\n' || input == '\r')  
+        {
+            // null-terminate the string
+            buffer[i] = '\0';  
+            break;
+        }
+
+        // append new char from usart into buffer
+        buffer[i++] = input;
+
+        // ensure we don't overflow the buffer
+        if (i >= buffer_size - 1)
+        {
+            // null-terminate the string
+            buffer[i] = '\0';  
+            break;
+        }
+    }
 }