Add stdio re-targeting to RTT (#84)

Author: VladimirUmek

ARM.CMSIS-Compiler.pdsc

@@ -17,6 +17,8 @@
       Active Development ...
       CLANG:
       - Added standard I/O stream support for LLVM-libc
+      I/O Retarget:
+      - Added reargeting to RTT
     </release>
   </releases>
 
@@ -105,6 +107,11 @@
       <require condition="CORE"/>
       <require condition="CortexDevice_ITM"/>
     </condition>
+    <condition id="CORE RTT">
+      <description>CMSIS-Compiler CORE component and RTT</description>
+      <require condition="CORE"/>
+      <require Cclass="SEGGER" Cgroup="RTT"/>
+    </condition>
     <condition id="CORE UART_CMSIS">
       <description>CMSIS-Compiler CORE component and CMSIS-Driver USART</description>
       <require condition="CORE"/>
@@ -138,6 +145,12 @@
       <require condition="CORE"/>
       <require condition="CortexDevice_ITM"/>
     </condition>
+    <condition id="ARMCC CORE RTT">
+      <description>ARMCC and CORE component and RTT</description>
+      <require Tcompiler="ARMCC"/>
+      <require condition="CORE"/>
+      <require Cclass="SEGGER" Cgroup="RTT"/>
+    </condition>
 
     <condition id="ARMCC CORE CMSIS-RTOS2">
       <description>ARMCC and CORE component and CMSIS-RTOS2</description>
@@ -328,6 +341,16 @@
         <file category="sourceC" name="source/stderr/stderr_itm.c"/>
       </files>
     </component>
+    <component Cclass="CMSIS-Compiler" Cgroup="STDERR" Csub="RTT" Capiversion="1.1.0" Cversion="1.0.0" condition="CORE RTT">
+      <description>Redirect STDERR to RTT (Channel 0)</description>
+      <RTE_Components_h>
+        #define RTE_CMSIS_Compiler_STDERR                /* CMSIS-Compiler STDERR */
+        #define RTE_CMSIS_Compiler_STDERR_RTT            /* CMSIS-Compiler STDERR: RTT */
+      </RTE_Components_h>
+      <files>
+        <file category="sourceC" name="source/stderr/stderr_rtt.c"/>
+      </files>
+    </component>
     <component Cclass="CMSIS-Compiler" Cgroup="STDERR" Csub="UART" Cvariant="CMSIS" Capiversion="1.1.0" Cversion="1.0.0" condition="CORE UART_CMSIS">
       <description>Redirect STDERR to a CMSIS-Driver USART</description>
       <RTE_Components_h>
@@ -370,6 +393,16 @@
         <file category="sourceC" name="source/stdin/stdin_itm.c"/>
       </files>
     </component>
+    <component Cclass="CMSIS-Compiler" Cgroup="STDIN" Csub="RTT" Capiversion="1.1.0" Cversion="1.0.0" condition="CORE RTT">
+      <description>Retrieve STDIN from RTT (Channel 0)</description>
+      <RTE_Components_h>
+        #define RTE_CMSIS_Compiler_STDIN                 /* CMSIS-Compiler STDIN */
+        #define RTE_CMSIS_Compiler_STDIN_RTT             /* CMSIS-Compiler STDIN: RTT */
+      </RTE_Components_h>
+      <files>
+        <file category="sourceC" name="source/stdin/stdin_rtt.c"/>
+      </files>
+    </component>
     <component Cclass="CMSIS-Compiler" Cgroup="STDIN" Csub="UART" Cvariant="CMSIS" Capiversion="1.1.0" Cversion="1.0.0" condition="CORE UART_CMSIS">
       <description>Retrieve STDIN from a CMSIS-Driver USART</description>
       <RTE_Components_h>
@@ -422,6 +455,16 @@
         <file category="sourceC" name="source/stdout/stdout_itm.c"/>
       </files>
     </component>
+    <component Cclass="CMSIS-Compiler" Cgroup="STDOUT" Csub="RTT" Capiversion="1.1.0" Cversion="1.0.0" condition="CORE RTT">
+      <description>Redirect STDOUT to RTT (Channel 0)</description>
+      <RTE_Components_h>
+        #define RTE_CMSIS_Compiler_STDOUT                /* CMSIS-Compiler STDOUT */
+        #define RTE_CMSIS_Compiler_STDOUT_RTT            /* CMSIS-Compiler STDOUT: RTT */
+      </RTE_Components_h>
+      <files>
+        <file category="sourceC" name="source/stdout/stdout_rtt.c"/>
+      </files>
+    </component>
     <component Cclass="CMSIS-Compiler" Cgroup="STDOUT" Csub="UART" Cvariant="CMSIS" Capiversion="1.1.0" Cversion="1.0.0" condition="CORE UART_CMSIS">
       <description>Redirect STDOUT to a CMSIS-Driver USART</description>
       <RTE_Components_h>
@@ -464,6 +507,16 @@
         <file category="sourceC" name="source/tty/tty_itm.c"/>
       </files>
     </component>
+    <component Cclass="CMSIS-Compiler" Cgroup="TTY" Csub="RTT" Capiversion="1.1.0" Cversion="1.0.0" condition="ARMCC CORE RTT">
+      <description>Redirect TTY to RTT (Channel 0)</description>
+      <RTE_Components_h>
+        #define RTE_CMSIS_Compiler_TTY                   /* CMSIS-Compiler TTY */
+        #define RTE_CMSIS_Compiler_TTY_RTT               /* CMSIS-Compiler TTY: RTT */
+      </RTE_Components_h>
+      <files>
+        <file category="sourceC" name="source/tty/tty_rtt.c"/>
+      </files>
+    </component>
 
     <!-- OS Interface -->
     <component Cclass="CMSIS-Compiler" Cgroup="OS Interface" Csub="Custom" Capiversion="1.1.0" Cversion="2.1.0" custom="1" condition="ARMCC CORE">

source/stderr/stderr_rtt.c

@@ -0,0 +1,39 @@
+/*
+ * Copyright (C) 2026 ARM Limited or its affiliates. All rights reserved.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 (the License); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an AS IS BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "retarget_stderr.h"
+
+#include "SEGGER_RTT.h"
+
+/**
+  Put a character to the stderr
+
+  \param[in]   ch  Character to output
+  \return          The character written, or -1 on write error.
+*/
+int stderr_putchar (int ch) {
+  unsigned res;
+
+  res = SEGGER_RTT_PutChar(0U, (char)ch);
+
+  if (res != 1U) {
+    return -1;
+  }
+
+  return (ch);
+}

source/stdin/stdin_rtt.c

@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2026 ARM Limited or its affiliates. All rights reserved.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 (the License); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an AS IS BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "retarget_stdin.h"
+
+#include "SEGGER_RTT.h"
+
+/**
+  Get a character from the stdio
+
+  \return     The next character from the input, or -1 on read error.
+*/
+int stdin_getchar (void) {
+  int ret;
+
+  ret = SEGGER_RTT_WaitKey();
+
+  return ret;
+}

source/stdout/stdout_rtt.c

@@ -0,0 +1,39 @@
+/*
+ * Copyright (C) 2026 ARM Limited or its affiliates. All rights reserved.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 (the License); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an AS IS BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "retarget_stdout.h"
+
+#include "SEGGER_RTT.h"
+
+/**
+  Put a character to the stdout
+
+  \param[in]   ch  Character to output
+  \return          The character written, or -1 on write error.
+*/
+int stdout_putchar (int ch) {
+  unsigned res;
+
+  res = SEGGER_RTT_PutChar(0U, (char)ch);
+
+  if (res != 1U) {
+    return -1;
+  }
+
+  return (ch);
+}

source/tty/tty_rtt.c

@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) 2026 ARM Limited or its affiliates. All rights reserved.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 (the License); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an AS IS BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "retarget_tty.h"
+
+#include "SEGGER_RTT.h"
+
+/**
+  Put a character to the teletypewritter
+
+  \param[in]   ch  Character to output
+*/
+void ttywrch (int ch) {
+  SEGGER_RTT_PutChar(0U, (char)ch);
+}