SEGGER SystemView + FreeRTOS: Install, Integrate, Record (the clean way)

SystemView lets you see your RTOS: who ran, when, how long, and why. You’ll install the host app, drop target sources into your project, enable timestamping, and then record—either real-time (via RTT/J-Link) or single-shot (dump a RAM buffer).

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✅ Minimal wiring (headers + start)

// main.c
#include "SEGGER_SYSVIEW.h"
#include "SEGGER_SYSVIEW_Conf.h"   // from target sources

int main(void) {
  // ... HAL/init ...
  SEGGER_SYSVIEW_Conf();           // configure app/device names, RTT, etc.
  SEGGER_SYSVIEW_Start();          // begin recording (single-shot or live)
  // create tasks...
  vTaskStartScheduler();
}

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⏱ Enable precise timestamps (Cortex-M3/M4/M7)

// Enable DWT cycle counter (timestamps)
#define DEMCR      (*(volatile uint32_t*)0xE000EDFC)
#define DWT_CTRL   (*(volatile uint32_t*)0xE0001000)
#define DWT_CYCCNT (*(volatile uint32_t*)0xE0001004)

static inline void dwt_time_start(void){
  DEMCR |= (1u<<24);        // TRCENA
  DWT_CYCCNT = 0;           // reset
  DWT_CTRL  |= 1u;          // CYCCNTENA
}

Call dwt_time_start() early in main() before starting the scheduler.

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⚙️ FreeRTOS config touch-ups

// FreeRTOSConfig.h
#define configUSE_TRACE_FACILITY   1
#define configTICK_RATE_HZ         1000   // 1 ms ticks (typical)

(If you don’t use software timers, you can set configUSE_TIMERS to 0 to skip the timer task.)

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🔁 Real-time vs. 🖼 Single-shot

• Real-time (continuous): J-Link + RTT streams events to the PC as they happen.

• Single-shot: Fill the RTT buffer in RAM, pause, dump it to a .SVDat file, then File → Load Data in SystemView.

Tip (single-shot): In your IDE, locate the RTT control symbol (e.g., _SEGGER_RTT), open Memory Browser at its address, and Export RAW for the configured buffer size (e.g., 4096 bytes).

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🗣 Sending messages to the timeline (cleanly)

#include <stdio.h>
static char msg[100];

snprintf(msg, sizeof(msg), "Hello from %s", "Task-1");
SEGGER_SYSVIEW_PrintfTarget("%s", msg);   // appears in Terminal & Timeline

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🧹 Avoid garbled prints under pre-emption

Shared sinks (ITM/UART) need a mutex or switch to co-operative segments using taskYIELD() after complete messages.

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⚡ Pro Tips

• Increase SEGGER_SYSVIEW_RTT_BUFFER_SIZE (e.g., 4096) if you drop events.

• Define the right core in SystemView config (e.g., Cortex-M3/M4/M7).

• Keep include paths for SEGGER/Config, SEGGER/OS, and SEGGER target folders.

• In Cube projects, put changes inside USER CODE BEGIN/END blocks.

🎯 Conclusion

Wire up SystemView once, and you’ll never guess again—timestamps, context switches, ISR time, CPU load are all on one timeline.

Written By: Musaab Taha

This article was improved with the assistance of AI.