basic uart functionality (not tested)

[cortex-from-scratch] / uart.c

diff --git a/uart.c b/uart.c
index bfef4b4..20a8d5e 100644 (file)
--- a/uart.c
+++ b/uart.c
@@ -6,10 +6,25 @@
 
 void uart_init() {
 
-/* To use the UARTs, the peripheral clock must be enabled by setting the UART0, UART1, or UART2
-bits in the RCGC1 register. (section 12.4: Initialization and Configuration */
+       // enable clock to UART1
+       *RCC_APB2ENR = 0x4005;
+       *GPIOA_CRH = 0x444444D4;
+       *AFIO_EVCR = 0x89;
+       
+       *USART1_CR1 = (0 << 13); // disable control register
+       *USART1_CR3 = 0xC0;
+
+       /* baud rate 9600 
+        * 115200 = 8MHz / (16 * USARTDIV)
+        * USARTDIV = 4.34
+        * FRACTION: 16 x 0.34 = 0d5.44 0d5 -> 0x5
+        * MANTISSA: 0d4.34 0d4 -> 0x4 
+        * USART_BRR = 0x45*/
+
+       *USART1_BRR = 0x00000045;
 
-*SYSCTRL_RCGC1 = *SYSCTRL_RCGC1 | 0x0003;
+       /* parity = 8 bit, UART1 enabled, TX and RX enabled, interrupts enabled */
+       *USART1_CR1 = (volatile uint32_t) 0x000030AC; 
 
 /* 
  * Configure UART0:
@@ -22,7 +37,7 @@ bits in the RCGC1 register. (section 12.4: Initialization and Configuration */
 
 /* TODO: bitrate: How fast is CPU running?*/
 
-*UART0_CTRL = 0;
+/* *UART0_CTRL = 0;
 *UART0_IBRD = 27; 
 *UART0_FBRD = 9;
 *UART0_LCRH = 0x60; 
@@ -33,19 +48,19 @@ bits in the RCGC1 register. (section 12.4: Initialization and Configuration */
 *UART1_FBRD = 9;
 *UART1_LCRH = 0x60; 
 *UART1_CTRL = 0x301;
-
+*/
 
 }
 
 extern void uart_putc(unsigned char ch) {
        
-       if (ch == '\n') {
-               while ((*UART0_FLAG & 0x8)); // busy bit
-               *UART0_DATA = 0x0D; // return line
-       }
-       
-       while ((*UART0_FLAG & 0x8)); // busy bit
-       *UART0_DATA = ch;
+//     if (ch == '\n') {
+//             while ((*UART1_DR & 0x8)); // busy bit
+//             *USART1_DR = 0x0D; // return line
+//     }
+//     
+//     while ((*UART0_FLAG & 0x8)); // busy bit
+       *USART1_DR = ch;
 }
 
 extern void uart_puts(unsigned char *str)