Configurable UART

sw/c/common/demo_system.c

@@ -138,4 +138,3 @@ void simple_exc_handler(void) {
 
   while(1);
 }
-

sw/c/common/demo_system.h

@@ -112,4 +112,4 @@ uint32_t get_mcycle(void);
 void reset_mcycle(void);
 
 
-#endif
+#endif

sw/c/common/link.ld

@@ -0,0 +1,76 @@
+/* Copyright lowRISC contributors.
+   Licensed under the Apache License, Version 2.0, see LICENSE for details.
+   SPDX-License-Identifier: Apache-2.0 */
+
+OUTPUT_ARCH(riscv)
+
+MEMORY
+{
+    /* 60 KiB should be enough for anybody... */
+    ram         : ORIGIN = 0x00100000, LENGTH = 0xE000 /* 56 KiB */
+    stack       : ORIGIN = 0x0010E000, LENGTH = 0x2000  /* 4 KiB */
+}
+
+/* Stack information variables */
+_min_stack      = 0x1000;   /* 4K - minimum stack space to reserve */
+_stack_len     = LENGTH(stack);
+_stack_start   = ORIGIN(stack) + LENGTH(stack);
+
+_entry_point = _vectors_start + 0x80;
+ENTRY(_entry_point)
+
+SECTIONS
+{
+    .text : {
+        . = ALIGN(4);
+		_vectors_start = .;
+        KEEP(*(.vectors))
+		_vectors_end = .;
+        *(.text)
+        *(.text.*)
+        . = ALIGN(4);
+    }  > ram
+
+    .rodata : {
+        . = ALIGN(4);
+        /* Small RO data before large RO data */
+        *(.srodata)
+        *(.srodata.*)
+        *(.rodata);
+        *(.rodata.*)
+        . = ALIGN(4);
+    } > ram
+
+    .data : {
+        . = ALIGN(4);
+        /* Small data before large data */
+        *(.sdata)
+        *(.sdata.*)
+        *(.data);
+        *(.data.*)
+        . = ALIGN(4);
+    } > ram
+
+    .bss :
+    {
+        . = ALIGN(4);
+        _bss_start = .;
+        /* Small BSS before large BSS */
+        *(.sbss)
+        *(.sbss.*)
+        *(.bss)
+        *(.bss.*)
+        *(COMMON)
+        _bss_end = .;
+        . = ALIGN(4);
+    } > ram
+
+    /* ensure there is enough room for stack */
+    .stack (NOLOAD): {
+        . = ALIGN(4);
+        . = . + _min_stack ;
+        . = ALIGN(4);
+        stack = . ;
+        _stack = . ;
+    } > stack
+}

sw/c/common/uart.c

@@ -1,7 +1,3 @@
-// Copyright lowRISC contributors.
-// Licensed under the Apache License, Version 2.0, see LICENSE for details.
-// SPDX-License-Identifier: Apache-2.0
-
 #include "uart.h"
 #include "dev_access.h"
 #include "demo_system.h"
@@ -26,3 +22,18 @@ void uart_out(uart_t uart, char c) {
 
   DEV_WRITE(uart + UART_TX_REG, c);
 }
+
+void uart_enable(uart_t uart, char en) {
+
+  DEV_WRITE(uart + UART_ENABLE_REG, en);
+}
+
+void uart_disable(uart_t uart) {
+
+  DEV_WRITE(uart + UART_ENABLE_REG, 0x00);
+}
+
+void uart_setup(uart_t uart, char parameters) {
+
+  DEV_WRITE(uart + UART_PARAMETERS_REG, parameters);
+}

sw/c/common/uart.h

@@ -1,13 +1,13 @@
-// Copyright lowRISC contributors.
-// Licensed under the Apache License, Version 2.0, see LICENSE for details.
-// SPDX-License-Identifier: Apache-2.0
-
 #ifndef UART_H__
 #define UART_H__
 
-#define UART_RX_REG 0
-#define UART_TX_REG 4
-#define UART_STATUS_REG 8
+#include <stdint.h>
+
+#define UART_RX_REG         0x00
+#define UART_TX_REG         0x04
+#define UART_STATUS_REG     0x08
+#define UART_ENABLE_REG     0x0C
+#define UART_PARAMETERS_REG 0x10
 
 #define UART_STATUS_RX_EMPTY 1
 #define UART_STATUS_TX_FULL 2
@@ -18,9 +18,32 @@ typedef void* uart_t;
 
 #define UART_FROM_BASE_ADDR(addr)((uart_t)(addr))
 
+#define DATA_SIZE_6     0x00
+#define DATA_SIZE_7     0x01
+#define DATA_SIZE_8     0x02
+#define DATA_SIZE_9     0x03
+
+#define PARITY_NONE     0x00
+#define PARITY_EVEN     0x04
+#define PARITY_ODD      0x0C
+
+#define STOP_BITS_ONE    0x00
+#define STOP_BITS_TWO    0x10
+
+#define BAUD_RATE_4800      0x00
+#define BAUD_RATE_9600      0x20
+#define BAUD_RATE_57600     0x40
+#define BAUD_RATE_115200    0x60
+
+#define UART_RX_EN 0x01
+#define UART_TX_EN 0x02
+
 void uart_enable_rx_int(void);
 int uart_in(uart_t uart);
 void uart_out(uart_t uart, char c);
 
-#endif // UART_H__
+void uart_enable(uart_t uart, char en);
+void uart_disable(uart_t uart);
+void uart_setup(uart_t uart, char parameters);
 
+#endif

sw/c/demo/hello_world/main.c

@@ -1,30 +1,30 @@
 // Copyright lowRISC contributors.
 // Licensed under the Apache License, Version 2.0, see LICENSE for details.
 // SPDX-License-Identifier: Apache-2.0
-
+#include "uart.h"
 #include "demo_system.h"
 #include "timer.h"
 #include "gpio.h"
 #include "pwm.h"
 #include <stdbool.h>
+#include <stdint.h>
 
 #define USE_GPIO_SHIFT_REG 0
 
 void test_uart_irq_handler(void) __attribute__((interrupt));
 
 void test_uart_irq_handler(void) {
-  int uart_in_char;
-
-  while ((uart_in_char = uart_in(DEFAULT_UART)) != -1) {
-    uart_out(DEFAULT_UART, uart_in_char);
-    uart_out(DEFAULT_UART, '\r');
-    uart_out(DEFAULT_UART, '\n');
-  }
+    unsigned char u;
+    u = getchar();
+    putchar(u);
 }
 
 int main(void) {
   install_exception_handler(UART_IRQ_NUM, &test_uart_irq_handler);
   uart_enable_rx_int();
+
+  uart_enable(DEFAULT_UART, UART_RX_EN | UART_TX_EN);
+  uart_setup(DEFAULT_UART, DATA_SIZE_8 | PARITY_NONE | STOP_BITS_ONE | BAUD_RATE_115200);
 
   // This indicates how often the timer gets updated.
   timer_init();
@@ -41,37 +41,21 @@ int main(void) {
   bool ascending = true;
   // The three least significant bits correspond to RGB, where B is the leas significant.
   uint8_t color = 7;
-
+
+  const char str[] = " Hello World ";
+  uint32_t c = 0;
   while(1) {
     uint64_t cur_time = get_elapsed_time();
 
     if (cur_time != last_elapsed_time) {
       last_elapsed_time = cur_time;
-
-      // Disable interrupts whilst outputting to prevent output for RX IRQ
-      // happening in the middle
+
       set_global_interrupt_enable(0);
-
-      // Print this to UART (use the screen command to see it).
-      puts("Hello World! ");
-      puthex(last_elapsed_time);
-      puts("   Input Value: ");
-      uint32_t in_val = read_gpio(GPIO_IN_DBNC);
-      puthex(in_val);
-      putchar('\n');
-
-      // Re-enable interrupts with output complete
+      puts(str);
+      puthex(c++);
+      puts("\r\n");
       set_global_interrupt_enable(1);
-
-      // Cycling through green LEDs when BTN0 is pressed
-      if (USE_GPIO_SHIFT_REG) {
-        set_outputs(GPIO_OUT_SHIFT, in_val);
-      } else {
-        uint32_t out_val = read_gpio(GPIO_OUT);
-        out_val = ((out_val << 1) & GPIO_OUT_MASK) | (in_val & 0x1);
-        set_outputs(GPIO_OUT, out_val);
-      }
-
+
       // Going from bright to dim on PWM
       for(int i = 0; i < NUM_PWM_MODULES; i++) {
         set_pwm(PWM_FROM_ADDR_AND_INDEX(PWM_BASE, i),
@@ -94,8 +78,8 @@ int main(void) {
           }
         }
       }
+
     }
-
     asm volatile ("wfi");
   }
 }