Real Time Terminal

SEGGER's Real Time Terminal (RTT) is the new technology for interactive user I/O in embedded applications.
With RTT it is possible to output information from the target microcontroller as well as sending input to the application at a very high speed without affecting the target's real time behaviour.

RTT supports multiple up (to the host) and down (to the target) channels to write and read data of different kinds. The default implementation uses one channel per direction:

Channel	Typical Purpose
Up-channel 0	Terminal output
Down-Channel 0	Keyboard input

SEGGER RTT can be used with any J-Link model and any supported target processor which allows background memory access, which are Cortex-M and RX targets.

Data from Up-channel 0 can be read via a Telnet connection to localhost:19021, which is opened by the J-Link software locally on the computer, when the J-Link is active. The Telnet connection also receives keyboard input for Down-channel 0.

The J-Link RTT Client, which automatically connects and re-connects to an open J-Link connection is part of the J-Link Software and Documentation Pack and can be used instead of a simple Telnet client.

With J-Link RTT Logger, data from Up-Channel 1 can be read and logged to a file. This channel can for example be used to send performance analysis data to the host.

J-Link RTT Logger opens a dedicated connection to J-Link and can be used stand-alone, without running a debugger.

The application is part of the J-Link Software and Documentation Pack.

//
// Allocate buffers for channel 0
//
static char _acUpBuffer  [BUFFER_SIZE_UP];
static char _acDownBuffer[BUFFER_SIZE_DOWN];
//
// Initialize SEGGER Real-time-Terminal control block (CB)
//
static SEGGER_RTT_CB _SEGGER_RTT = {
  "SEGGER RTT",
  SEGGER_RTT_MAX_NUM_UP_BUFFERS,
  SEGGER_RTT_MAX_NUM_DOWN_BUFFERS,
  {{ "Terminal", &_acUpBuffer[0], sizeof(_acUpBuffer), 0, 0, SEGGER_RTT_MODE_NO_BLOCK_SKIP }},
  {{ "Terminal", &_acDownBuffer[0], sizeof(_acDownBuffer), 0, 0, SEGGER_RTT_MODE_NO_BLOCK_SKIP }},
};

_SEGGER_RTT 会有两个副本, 第一个副本用来初始化第二个副本
当在FLASH中运行, 第一个副本位于FLASH, 第二个副本位于SRAM, 程序启动时, 从第一个副本复制到第二个副本.
这样在SRAM中只有一个字符串 "SEGGER RTT" RTT 可以正确定位 _SEGGER_RTT 在 SRAM 中的地址 ( 搜索整个SRAM区域 )

当在SRAM中运行, 两个副本均在 SRAM, 这样 RTT 可能错误定位 _SEGGER_RTT 于用来初始化第二个副本的第一个副本
用来初始化第二个副本的第一个副本的 RING_BUFFER 的 WrOff 和 RdOff 一直是 0, 所以没有数据可读取.

修改 static SEGGER_RTT_CB _SEGGER_RTT = {  "SEGGER RTT", ...
成为 static SEGGER_RTT_CB _SEGGER_RTT = {  "SEGGER_RTT", ...

然后添加函数

void SEGGER_RTT_Init( void )
{
  _SEGGER_RTT.acID[6] = ' '; // SEGGER RTT
}

然后

  SEGGER_RTT_Init(); // 初始化之后, RTT 可以正确定位 _SEGGER_RTT 在 SRAM 中的地址 ( 搜索整个SRAM区域 )

  SEGGER_RTT_ConfigUpBuffer( 0, NULL, NULL, 0, SEGGER_RTT_MODE_BLOCK_IF_FIFO_FULL );
  SEGGER_RTT_WriteString( 0, "SEGGER Real-Time-Terminal Sample " );

在SRAM调试解决方法

修改 static SEGGER_RTT_CB _SEGGER_RTT = {  "SEGGER RTT", ...
成为 static SEGGER_RTT_CB _SEGGER_RTT = {  "SEGGER_RTT", ...

然后添加函数

void SEGGER_RTT_Init( int UpFlags, int DownFlags )
{
  _SEGGER_RTT.acID[6] = ' '; // SEGGER RTT  _SEGGER_RTT.aUp[ 0 ].Flags = UpFlags;
  _SEGGER_RTT.aDown[ 0 ].Flags = DownFlags;
}

  // 初始化之后, RTT 可以正确定位 _SEGGER_RTT 在 SRAM 中的地址 ( 搜索整个SRAM区域 )
  SEGGER_RTT_Init( SEGGER_RTT_MODE_NO_BLOCK_SKIP, SEGGER_RTT_MODE_NO_BLOCK_SKIP );
  SEGGER_RTT_WriteString( 0, "SEGGER Real-Time-Terminal Sample " );

JLINK RTT 新版本 SRAM 调试解决方案

新版本 SRAM 调试解决方案  : RTT_Implementation_140925.zip

// ******************************* SEGGER_RTT_Conf.h ************************************
//
// Define SEGGER_RTT_IN_RAM as 1
// when using RTT in RAM targets (init and data section both in RAM).
// This prevents the host to falsly identify the RTT Callback Structure
// in the init segment as the used Callback Structure.
//
// When defined as 1,
// the first call to an RTT function will modify the ID of the RTT Callback Structure.
// To speed up identifying on the host,
// especially when RTT functions are not called at the beginning of execution,
// SEGGER_RTT_Init() should be called at the start of the application.
//
#define SEGGER_RTT_IN_RAM                      (1)

// ******************************* SEGGER_RTT.c ************************************
//
// Initialize SEGGER Real-time-Terminal control block (CB)
//
static SEGGER_RTT_CB _SEGGER_RTT = {
#if SEGGER_RTT_IN_RAM
  "SEGGER RTTI",
#else
  "SEGGER RTT",
#endif
  SEGGER_RTT_MAX_NUM_UP_BUFFERS,
  SEGGER_RTT_MAX_NUM_DOWN_BUFFERS,
  {{ "Terminal", &_acUpBuffer[0], sizeof(_acUpBuffer), 0, 0, SEGGER_RTT_MODE_NO_BLOCK_SKIP }},
  {{ "Terminal", &_acDownBuffer[0], sizeof(_acDownBuffer), 0, 0, SEGGER_RTT_MODE_NO_BLOCK_SKIP }},
};

/*********************************************************************
*
*    _Init
*
*  Function description
* In case SEGGER_RTT_IN_RAM is defined,
* _Init() modifies the ID of the RTT CB to allow identifying the
* RTT Control Block Structure in the data segment.
*/
static void _Init(void) {
#if SEGGER_RTT_IN_RAM
  if (_SEGGER_RTT.acID[10] == 'I') {
_SEGGER_RTT.acID[10] = '';
  }
#endif
}