Basic UART/console functionality

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@1697 42af7a65-404d-4744-a932-0658087f49c3

1 files changed, 128 insertions, 0 deletions

diff --git a/nuttx/arch/arm/src/imx/imx_lowputc.S b/nuttx/arch/arm/src/imx/imx_lowputc.S
new file mode 100644
index 000000000..e146c5bec
--- /dev/null
+++ b/nuttx/arch/arm/src/imx/imx_lowputc.S
@@ -0,0 +1,128 @@
+/**************************************************************************
+ * arch/arm/src/imx/imx_lowputc.S
+ * arch/arm/src/chip/imx_lowputc.S
+ *
+ *   Copyright (C) 2009 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ **************************************************************************/
+
+/**************************************************************************
+ * Included Files
+ **************************************************************************/
+
+#include <nuttx/config.h>
+#include "up_internal.h"
+#include "up_arch.h"
+
+/**************************************************************************
+ * Private Definitions
+ **************************************************************************/
+
+/**************************************************************************
+ * Private Types
+ **************************************************************************/
+
+/**************************************************************************
+ * Private Function Prototypes
+ **************************************************************************/
+
+/**************************************************************************
+ * Global Variables
+ **************************************************************************/
+
+/**************************************************************************
+ * Private Variables
+ **************************************************************************/
+
+/**************************************************************************
+ * Private Functions
+ **************************************************************************/
+
+/**************************************************************************
+ * Public Functions
+ **************************************************************************/
+
+/**************************************************************************
+ * Name: up_lowputc
+ **************************************************************************/
+
+/* This assembly language version has the advantage that it can does not
+ * require a C stack and uses only r0-r1.  Hence it can be used during
+ * early boot phases.
+ */
+
+	.text
+	.global	up_lowputc
+	.type	up_lowputc, function
+up_lowputc:
+	/* On entry, r0 holds the character to be printed */
+
+#ifdef CONFIG_UART1_SERIAL_CONSOLE
+	ldr	r2, =IMX_UART1_VBASE	/* r2=UART1 base */
+#else
+	ldr	r2, =IMX_UART2_VBASE	/* r2=UART0 base */
+#endif
+
+	/* Poll the TX fifo trigger level bit of the UART status register #2 . 
+	 * When the bit is non-zero, the TX Buffer FIFO is empty.
+	 */
+
+1:	ldr	r1, [r2, #UART_USR2]
+	tst	r1, #UART_USR2_TXFE
+	beq	1b
+
+	/* Send the character by writing it into the UART_DTRR
+	 * register.
+	 */
+
+	str	r0, [r2, #UART_TXD0]
+
+	/* If the character that we just sent was a linefeed,
+	 * then send a carriage return as well.
+	 */
+
+	teq     r0, #'\n'
+	moveq   r0, #'\r'
+	beq     1b
+
+	/* Wait for the tranmsit regiser to be emptied. When the bit is
+	 * non-zero, the TX Buffer FIFO is empty.
+	 */
+
+2:	ldrh	r1, [r2, #UART_USR2]
+	tst	r1, #UART_USR2_TXFE
+	beq	2b
+
+	/* Then return */
+
+	mov     pc, lr
+	.end
+