https://devzone.nordicsemi.com/f/nordic-q-a/98494/monitor-mode-debugging---incorrect-values-in-watchHi, I was trying to add monitor mode debugging to a firmware: nRF5 SDK 15.3.0 running on Acconeer XM122 Radar module, and after I encountered the issue I also tried it on nRF5 SDK 17.0.2 with nRF52840 DK, I got the same result. Basically, I haveen-USTelligent Community 13Wed, 10 May 2023 15:24:34 GMThttps://devzone.nordicsemi.com/thread/424938?ContentTypeID=1Wed, 10 May 2023 15:24:34 GMT137ad170-7792-4731-bb38-c0d22fbe4515:1b054f45-4d1e-47c9-b7dd-9f76bab70691haakonsh<p>I don&#39;t know if it is impossible, but I think the base assumption is that MMD is currently not able to. The easy solution is to use statically allocated variables if you need to debug them with MMD.&nbsp;</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/424857?ContentTypeID=1Wed, 10 May 2023 12:45:23 GMT137ad170-7792-4731-bb38-c0d22fbe4515:bca1838d-6159-4711-9f8b-4a31d564835eenukic<p><a href="https://devzone.nordicsemi.com/members/haakonsh">haakonsh</a>&nbsp;<br />Thank you for the detailed response.<br /><br />And sorry for my very long delay with the followup.</p> <p>To conclude, it&#39;s not possible to watch local variables with MMD?</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/420291?ContentTypeID=1Thu, 13 Apr 2023 14:16:22 GMT137ad170-7792-4731-bb38-c0d22fbe4515:6d0c5b8f-6f32-4edc-8bf4-0f419aeec76fhaakonsh[quote user="enukic"]If I declare it as static or static volatile, I&#39;m getting the correct value in the Watch when the program pauses at a breakpoint.<br />If I only set it to volatile, the value in Watch becomes wrong.[/quote] <p>I think that observation fits well with your disassembly, though my understanding of assembly is limited:&nbsp;</p> <p><pre class="ui-code" data-mode="text">int mainlocal = 0; 2300 movs r3, #0 9301 str r3, [sp, #4] --- main.c -- 321 ------------------------------------------</pre></p> <p>I think the snippet above describes that the compiler/linker have placed the &#39;mainlocal&#39; variable at t<span>he 2nd word of the current stack frame [sp, #4], and</span>&nbsp;how&nbsp;the initial value of &#39;0&#39; is written to it. This means that a new instance of the local varable &#39;mainlocal&#39; is created for each unique invocation of the function &#39;main&#39; and stored&nbsp;in its stack frame.&nbsp;<span style="font-family:inherit;">As far as I know there is no compile-time mechanism that prevents you from calling &#39;main&#39; as many times as you&#39;d like (&nbsp;often leading to stack-overflow).</span></p> <p><span style="font-family:inherit;">When debugging without MMD and the CPU is halted by a breakpoint, the debugger will have easy access to the breakpoint&#39;s&nbsp;stack frame since it is the current/last stack frame in use.&nbsp;That means&nbsp;that the debugger will allways&nbsp;know&nbsp;where&nbsp;the instance of the local variable &#39;mainlocal&#39; is stored. In this case the address of the Stack pointer + 4. No matter how many invocations of &#39;main&#39; you create the address of &#39;mainlocal&#39; is static with respect to&nbsp;its&nbsp;stack frame, and the debugger will always be able to access it.&nbsp;</span></p> <p><span>When debugging with MMD and the CPU is halted by a breakpoint,&nbsp;</span>the debugger jumps into the MMD ISR and it loses access to the stack frame&nbsp;that triggered the breakpoint (loss of context). At this point the debugger knows that &#39;mainlocal&#39; is at address SP + 4, but it does not know what the address of the &#39;breakpoint&#39;s SP is, and is therefore unable to display it, or worse, it displays the value it reads from SP + 4 where SP is the MMD ISR&#39;s Stack Pointer.</p> <p></p> <p>This is where the keyword &#39;static&#39; comes into play. A variable that is statically allocated to memory will be allocated a piece of memory by the linker, the size of its type and&nbsp;placed at an immutable address within&nbsp;a block of memory dedicated to the statically allocated variables.&nbsp;</p> <p>A global variable&#39;s memory is always statically allocated, and a local variable will be statically allocated if it is decleared with the &#39;static&#39; keyword. Only one instance of a statically allocated variable will be created and all stack frames&nbsp;that accesses it will have to share it. This also means that statically allocated variables are not thread-safe btw.</p> <p>The debugger will always know the address of a&nbsp;statically allocated variable(.elf file) regardless of the state of the Stack.&nbsp;</p> <p></p> <p>The &#39;volatile&#39; keyword lets the compiler know that you expect the value of a variable to change at any given point in time outside of the scope of the current stack frame, and that you need the compiler to not to optimize the code by caching the value of the variable for future use and instead make sure that its value is read from memory every time it is to be used in a calculation.&nbsp;</p> <p>The &#39;volatile&#39; and &#39;static&#39; test i asked of you tested whether the debugger&nbsp;was able to resolve &#39;mainlocal&#39;s address, and whether it actually access that address or just cached the variable in a general CPU reg.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/420087?ContentTypeID=1Thu, 13 Apr 2023 06:16:34 GMT137ad170-7792-4731-bb38-c0d22fbe4515:4751413e-ea91-4448-b871-56ad6022b7c7enukic<p>Hi&nbsp;<a href="https://devzone.nordicsemi.com/members/haakonsh">haakonsh</a>&nbsp;</p> <ul> <li>Here is the disassembly</li> </ul> <p><pre class="ui-code" data-mode="text"> 110F asrs r7, r1, #4 9800 ldr r0, [sp] F7F9F9F4 bl 0x00028E18 &lt;app_error_handler&gt; --- main.c -- 269 ------------------------------------------ { ret_code_t err_code = app_timer_init(); APP_ERROR_CHECK(err_code); app_timer_create(&amp;myTim, APP_TIMER_MODE_REPEATED, myTimCb); 4A08 ldr r2, =0x0002F9FD &lt;myTimCb&gt; 2101 movs r1, #1 4808 ldr r0, =0x00032520 &lt;myTim&gt; F7F9FD8B bl 0x00029550 &lt;app_timer_create&gt; --- main.c -- 274 ------------------------------------------ app_timer_start(myTim, APP_TIMER_TICKS(1000), NULL); 4B08 ldr r3, =0x20002230 &lt;myTim_data&gt; 2200 movs r2, #0 F44F4180 mov.w r1, #0x4000 4618 mov r0, r3 F7F9FDB8 bl 0x000295B8 &lt;app_timer_start&gt; --- main.c -- 275 ------------------------------------------ } BF00 nop B003 add sp, sp, #12 F85DFB04 pop.w {pc} 00032524 .word 0x00032524 0002F9FD .word 0x0002F9FD 00032520 .word 0x00032520 20002230 .word 0x20002230 --- main.c -- 277 ------------------------------------------ /**@brief Function for initializing power management. */ static void power_management_init(void) { B500 push {lr} B083 sub sp, sp, #12 --- main.c -- 282 ------------------------------------------ ret_code_t err_code; err_code = nrf_pwr_mgmt_init(); F7FBFB32 bl 0x0002B0CC &lt;nrf_pwr_mgmt_init&gt; 9001 str r0, [sp, #4] --- main.c -- 284 ------------------------------------------ APP_ERROR_CHECK(err_code); 9B01 ldr r3, [sp, #4] 9300 str r3, [sp] 9B00 ldr r3, [sp] 2B00 cmp r3, #0 D005 beq 0x0002FA80 4A04 ldr r2, =0x00032524 F44F718E mov.w r1, #0x011C 9800 ldr r0, [sp] F7F9F9CC bl 0x00028E18 &lt;app_error_handler&gt; --- main.c -- 285 ------------------------------------------ } BF00 nop B003 add sp, sp, #12 F85DFB04 pop.w {pc} 00032524 .word 0x00032524 --- main.c -- 289 ------------------------------------------ * * @details If there is no pending log operation, then sleep until next the next event occurs. */ static void idle_state_handle(void) { B508 push {r3, lr} --- main.c -- 294 ------------------------------------------ if (NRF_LOG_PROCESS() == false) F7F8FA8D bl 0x00027FAC &lt;nrf_log_frontend_dequeue&gt; 4603 mov r3, r0 F0830301 eor r3, r3, #1 B2DB uxtb r3, r3 2B00 cmp r3, #0 D001 beq 0x0002FAA2 --- main.c -- 295 ------------------------------------------ { nrf_pwr_mgmt_run(); F7FBFB2B bl 0x0002B0F8 &lt;nrf_pwr_mgmt_run&gt; --- main.c -- 297 ------------------------------------------ } } BF00 nop BD08 pop {r3, pc} 0000 movs r0, r0 --- main.c -- 299 ------------------------------------------ static void changeCtx(int * p_mainlocal, int * p_varGlobal) { B500 push {lr} B083 sub sp, sp, #12 9001 str r0, [sp, #4] 9100 str r1, [sp] --- main.c -- 302 ------------------------------------------ if(*p_mainlocal &gt; 10) 9B01 ldr r3, [sp, #4] 681B ldr r3, [r3] 2B0A cmp r3, #10 DD27 ble 0x0002FB08 --- main.c -- 303 ------------------------------------------ { *p_mainlocal = 0; 9B01 ldr r3, [sp, #4] 2200 movs r2, #0 601A str r2, [r3] --- main.c -- 305 ------------------------------------------ NRF_LOG_INFO(&quot;reset p_mainlocal&quot;); 4A14 ldr r2, =0x000314C4 &lt;m_nrf_log_app_logs_data_const&gt; 4B14 ldr r3, =0x0003149C &lt;__nrf_balloc_end__&gt; 1AD3 subs r3, r2, r3 08DB lsrs r3, r3, #3 041B lsls r3, r3, #16 F0430303 orr r3, r3, #3 4912 ldr r1, =0x00032564 4618 mov r0, r3 F7F8FA10 bl 0x00027EF4 &lt;nrf_log_frontend_std_0&gt; --- main.c -- 306 ------------------------------------------ NRF_LOG_INFO(&quot;p_varGlobal %d&quot;, *p_varGlobal); 4A0E ldr r2, =0x000314C4 &lt;m_nrf_log_app_logs_data_const&gt; 4B0F ldr r3, =0x0003149C &lt;__nrf_balloc_end__&gt; 1AD3 subs r3, r2, r3 08DB lsrs r3, r3, #3 041B lsls r3, r3, #16 F0430003 orr r0, r3, #3 9B00 ldr r3, [sp] 681B ldr r3, [r3] 461A mov r2, r3 490C ldr r1, =0x00032578 F7F8FA11 bl 0x00027F10 &lt;nrf_log_frontend_std_1&gt; --- main.c -- 307 ------------------------------------------ NRF_LOG_INFO(&quot;varStaticGlobal %d&quot;, varStaticGlobal); 4A08 ldr r2, =0x000314C4 &lt;m_nrf_log_app_logs_data_const&gt; 4B08 ldr r3, =0x0003149C &lt;__nrf_balloc_end__&gt; 1AD3 subs r3, r2, r3 08DB lsrs r3, r3, #3 041B lsls r3, r3, #16 F0430303 orr r3, r3, #3 4A08 ldr r2, =0x20002288 &lt;varStaticGlobal&gt; 6812 ldr r2, [r2] 4908 ldr r1, =0x00032588 4618 mov r0, r3 F7F8FA04 bl 0x00027F10 &lt;nrf_log_frontend_std_1&gt; --- main.c -- 308 ------------------------------------------ } } BF00 nop B003 add sp, sp, #12 F85DFB04 pop.w {pc} 000314C4 .word 0x000314C4 0003149C .word 0x0003149C 00032564 .word 0x00032564 00032578 .word 0x00032578 20002288 .word 0x20002288 00032588 .word 0x00032588 --- main.c -- 311 ------------------------------------------ /** * @brief Function for application main entry. */ int main(void) { B500 push {lr} B083 sub sp, sp, #12 --- main.c -- 316 ------------------------------------------ #if CONFIG_JLINK_MONITOR_ENABLED NVIC_SetPriority(DebugMonitor_IRQn, _PRIO_APP_HIGH); 2102 movs r1, #2 F06F0003 mvn r0, #3 F7FFFE2B bl 0x0002F78C &lt;__NVIC_SetPriority&gt; --- main.c -- 318 ------------------------------------------ #endif int mainlocal = 0; 2300 movs r3, #0 9301 str r3, [sp, #4] --- main.c -- 321 ------------------------------------------ // Initialize. log_init(); F7FFFF2D bl 0x0002F998 &lt;log_init&gt; --- main.c -- 324 ------------------------------------------ timers_init(); F7FFFF67 bl 0x0002FA10 &lt;timers_init&gt; --- main.c -- 325 ------------------------------------------ leds_init(); F7FFFF43 bl 0x0002F9CC &lt;leds_init&gt; --- main.c -- 326 ------------------------------------------ power_management_init(); F7FFFF8B bl 0x0002FA60 &lt;power_management_init&gt; --- main.c -- 327 ------------------------------------------ ble_stack_init(); F7FFFEEF bl 0x0002F92C &lt;ble_stack_init&gt; --- main.c -- 328 ------------------------------------------ advertising_init(); F7FFFE61 bl 0x0002F814 &lt;advertising_init&gt; --- main.c -- 329 ------------------------------------------ // Start execution. NRF_LOG_INFO(&quot;Beacon example started.&quot;); 4A1D ldr r2, =0x000314C4 &lt;m_nrf_log_app_logs_data_const&gt; 4B1D ldr r3, =0x0003149C &lt;__nrf_balloc_end__&gt; 1AD3 subs r3, r2, r3 08DB lsrs r3, r3, #3 041B lsls r3, r3, #16 F0430303 orr r3, r3, #3 491B ldr r1, =0x0003259C 4618 mov r0, r3 F7F8F9C6 bl 0x00027EF4 &lt;nrf_log_frontend_std_0&gt; --- main.c -- 332 ------------------------------------------ advertising_start(); F7FFFEB6 bl 0x0002F8D8 &lt;advertising_start&gt; --- main.c -- 333 ------------------------------------------ // Enter main loop. for (;; ) { idle_state_handle(); F7FFFF8E bl 0x0002FA8C &lt;idle_state_handle&gt; --- main.c -- 338 ------------------------------------------ if(mySem) 4B18 ldr r3, =0x20002287 781B ldrb r3, [r3] 2B00 cmp r3, #0 D0F9 beq 0x0002FB6C --- main.c -- 340 ------------------------------------------ { mySem = false; 4B16 ldr r3, =0x20002287 2200 movs r2, #0 701A strb r2, [r3] --- main.c -- 342 ------------------------------------------ NRF_LOG_INFO(&quot;main local %d&quot;, mainlocal++); 4A12 ldr r2, =0x000314C4 &lt;m_nrf_log_app_logs_data_const&gt; 4B12 ldr r3, =0x0003149C &lt;__nrf_balloc_end__&gt; 1AD3 subs r3, r2, r3 08DB lsrs r3, r3, #3 041B lsls r3, r3, #16 F0430003 orr r0, r3, #3 9B01 ldr r3, [sp, #4] 1C5A adds r2, r3, #1 9201 str r2, [sp, #4] 461A mov r2, r3 4910 ldr r1, =0x000325B4 F7F8F9BB bl 0x00027F10 &lt;nrf_log_frontend_std_1&gt; --- main.c -- 343 ------------------------------------------ NRF_LOG_INFO(&quot;static global %d&quot;, varStaticGlobal++); 4A0B ldr r2, =0x000314C4 &lt;m_nrf_log_app_logs_data_const&gt; 4B0B ldr r3, =0x0003149C &lt;__nrf_balloc_end__&gt; 1AD3 subs r3, r2, r3 08DB lsrs r3, r3, #3 041B lsls r3, r3, #16 F0430003 orr r0, r3, #3 4B0C ldr r3, =0x20002288 &lt;varStaticGlobal&gt; 681B ldr r3, [r3] 1C5A adds r2, r3, #1 490B ldr r1, =0x20002288 &lt;varStaticGlobal&gt; 600A str r2, [r1] 461A mov r2, r3 490A ldr r1, =0x000325C4 F7F8F9AB bl 0x00027F10 &lt;nrf_log_frontend_std_1&gt; --- main.c -- 344 ------------------------------------------ changeCtx(&amp;mainlocal, &amp;varStaticGlobal); AB01 add r3, sp, #4 4907 ldr r1, =0x20002288 &lt;varStaticGlobal&gt; 4618 mov r0, r3 F7FFFF72 bl 0x0002FAA8 &lt;changeCtx&gt; --- main.c -- 337 ------------------------------------------ idle_state_handle(); E7D2 b 0x0002FB6C BF00 nop 000314C4 .word 0x000314C4 0003149C .word 0x0003149C 0003259C .word 0x0003259C 20002287 .word 0x20002287 000325B4 .word 0x000325B4 20002288 .word 0x20002288 000325C4 .word 0x000325C4 --- SEGGER_RTT.c -- 276 ------------------------------------ */ #define INIT() do { \ if (_SEGGER_RTT.acID[0] == &#39;\0&#39;) { _DoInit(); } \ } while (0) static void _DoInit(void) { B500 push {lr} B083 sub sp, sp, #12 --- SEGGER_RTT.c -- 281 ------------------------------------ SEGGER_RTT_CB* p; // // Initialize control block // p = &amp;_SEGGER_RTT; 4B1F ldr r3, =0x2000228C &lt;_SEGGER_RTT&gt; 9301 str r3, [sp, #4] --- SEGGER_RTT.c -- 286 ------------------------------------ p-&gt;MaxNumUpBuffers = SEGGER_RTT_MAX_NUM_UP_BUFFERS; 9B01 ldr r3, [sp, #4] 2202 movs r2, #2 611A str r2, [r3, #16] --- SEGGER_RTT.c -- 287 ------------------------------------ p-&gt;MaxNumDownBuffers = SEGGER_RTT_MAX_NUM_DOWN_BUFFERS; 9B01 ldr r3, [sp, #4] 2202 movs r2, #2 615A str r2, [r3, #20] --- SEGGER_RTT.c -- 288 ------------------------------------ // // Initialize up buffer 0 // p-&gt;aUp[0].sName = &quot;Terminal&quot;; 9B01 ldr r3, [sp, #4] 4A1C ldr r2, =0x000325D8 619A str r2, [r3, #24] --- SEGGER_RTT.c -- 292 ------------------------------------ p-&gt;aUp[0].pBuffer = _acUpBuffer; 9B01 ldr r3, [sp, #4] 4A1B ldr r2, =0x20002304 &lt;_acUpBuffer&gt; 61DA str r2, [r3, #28] --- SEGGER_RTT.c -- 293 ------------------------------------ p-&gt;aUp[0].SizeOfBuffer = sizeof(_acUpBuffer); 9B01 ldr r3, [sp, #4] F44F7200 mov.w r2, #0x0200 621A str r2, [r3, #32] --- SEGGER_RTT.c -- 294 ------------------------------------ p-&gt;aUp[0].RdOff = 0u; 9B01 ldr r3, [sp, #4] 2200 movs r2, #0 629A str r2, [r3, #0x28] --- SEGGER_RTT.c -- 295 ------------------------------------ p-&gt;aUp[0].WrOff = 0u; 9B01 ldr r3, [sp, #4] 2200 movs r2, #0 625A str r2, [r3, #0x24] --- SEGGER_RTT.c -- 296 ------------------------------------ p-&gt;aUp[0].Flags = SEGGER_RTT_MODE_DEFAULT; 9B01 ldr r3, [sp, #4] 2200 movs r2, #0 62DA str r2, [r3, #0x2C] --- SEGGER_RTT.c -- 297 ------------------------------------ // // Initialize down buffer 0 // p-&gt;aDown[0].sName = &quot;Terminal&quot;; 9B01 ldr r3, [sp, #4] 4A12 ldr r2, =0x000325D8 649A str r2, [r3, #0x48] --- SEGGER_RTT.c -- 301 ------------------------------------ p-&gt;aDown[0].pBuffer = _acDownBuffer; 9B01 ldr r3, [sp, #4] 4A13 ldr r2, =0x20002504 &lt;_acDownBuffer&gt; 64DA str r2, [r3, #0x4C] --- SEGGER_RTT.c -- 302 ------------------------------------ p-&gt;aDown[0].SizeOfBuffer = sizeof(_acDownBuffer); 9B01 ldr r3, [sp, #4] 2210 movs r2, #16 651A str r2, [r3, #0x50] --- SEGGER_RTT.c -- 303 ------------------------------------ p-&gt;aDown[0].RdOff = 0u; 9B01 ldr r3, [sp, #4] 2200 movs r2, #0 659A str r2, [r3, #0x58] --- SEGGER_RTT.c -- 304 ------------------------------------ p-&gt;aDown[0].WrOff = 0u; 9B01 ldr r3, [sp, #4] 2200 movs r2, #0 655A str r2, [r3, #0x54] --- SEGGER_RTT.c -- 305 ------------------------------------ p-&gt;aDown[0].Flags = SEGGER_RTT_MODE_DEFAULT; 9B01 ldr r3, [sp, #4] 2200 movs r2, #0 65DA str r2, [r3, #0x5C] --- SEGGER_RTT.c -- 307 ------------------------------------ // Finish initialization of the control block. // Copy Id string in three steps to make sure &quot;SEGGER RTT&quot; is not found // in initializer memory (usually flash) by J-Link // strcpy(&amp;p-&gt;acID[7], &quot;RTT&quot;); 9B01 ldr r3, [sp, #4] 3307 adds r3, #7 490C ldr r1, =0x000325E4 4618 mov r0, r3 F001FBBA bl 0x000313C2 &lt;strcpy&gt; --- SEGGER_RTT.c -- 312 ------------------------------------ strcpy(&amp;p-&gt;acID[0], &quot;SEGGER&quot;); 9B01 ldr r3, [sp, #4] 490A ldr r1, =0x000325E8 4618 mov r0, r3 F001FBB5 bl 0x000313C2 &lt;strcpy&gt; --- SEGGER_RTT.c -- 313 ------------------------------------ p-&gt;acID[6] = &#39; &#39;; 9B01 ldr r3, [sp, #4] 2220 movs r2, #32 719A strb r2, [r3, #6] --- SEGGER_RTT.c -- 314 ------------------------------------ } BF00 nop B003 add sp, sp, #12 F85DFB04 pop.w {pc} BF00 nop 2000228C .word 0x2000228C 000325D8 .word 0x000325D8 20002304 .word 0x20002304 20002504 .word 0x20002504 000325E4 .word 0x000325E4 000325E8 .word 0x000325E8 --- SEGGER_RTT.c -- 331 ------------------------------------ * * Return value * &gt;= 0 - Number of bytes written into buffer. */ static unsigned _WriteBlocking(SEGGER_RTT_BUFFER_UP* pRing, const char* pBuffer, unsigned NumBytes) { B500 push {lr} B089 sub sp, sp, #0x24 9003 str r0, [sp, #12] 9102 str r1, [sp, #8] 9201 str r2, [sp, #4] --- SEGGER_RTT.c -- 342 ------------------------------------ #endif // // Write data to buffer and handle wrap-around if necessary // NumBytesWritten = 0u; 2300 movs r3, #0 9306 str r3, [sp, #24] --- SEGGER_RTT.c -- 347 ------------------------------------ WrOff = pRing-&gt;WrOff; 9B03 ldr r3, [sp, #12] 68DB ldr r3, [r3, #12] 9305 str r3, [sp, #20] --- SEGGER_RTT.c -- 348 ------------------------------------ do { RdOff = pRing-&gt;RdOff; // May be changed by host (debug probe) in the meantime 9B03 ldr r3, [sp, #12] 691B ldr r3, [r3, #16] 9304 str r3, [sp, #16] --- SEGGER_RTT.c -- 350 ------------------------------------ if (RdOff &gt; WrOff) { 9A04 ldr r2, [sp, #16] 9B05 ldr r3, [sp, #20] 429A cmp r2, r3 D905 bls 0x0002FCAE --- SEGGER_RTT.c -- 351 ------------------------------------ NumBytesToWrite = RdOff - WrOff - 1u; 9A04 ldr r2, [sp, #16] 9B05 ldr r3, [sp, #20] 1AD3 subs r3, r2, r3 3B01 subs r3, #1 9307 str r3, [sp, #28] E007 b 0x0002FCBE --- SEGGER_RTT.c -- 352 ------------------------------------ } else { NumBytesToWrite = pRing-&gt;SizeOfBuffer - (WrOff - RdOff + 1u); 9B03 ldr r3, [sp, #12] 689A ldr r2, [r3, #8] 9904 ldr r1, [sp, #16] 9B05 ldr r3, [sp, #20] 1ACB subs r3, r1, r3 4413 add r3, r2 3B01 subs r3, #1 9307 str r3, [sp, #28] --- SEGGER_RTT.c -- 354 ------------------------------------ } NumBytesToWrite = MIN(NumBytesToWrite, (pRing-&gt;SizeOfBuffer - WrOff)); // Number of bytes that can be written until buffer wrap-around 9B03 ldr r3, [sp, #12] 689A ldr r2, [r3, #8] 9B05 ldr r3, [sp, #20] 1AD3 subs r3, r2, r3 9A07 ldr r2, [sp, #28] 4293 cmp r3, r2 BF28 it cs 4613 movcs r3, r2 9307 str r3, [sp, #28] --- SEGGER_RTT.c -- 356 ------------------------------------ NumBytesToWrite = MIN(NumBytesToWrite, NumBytes); 9A07 ldr r2, [sp, #28] 9B01 ldr r3, [sp, #4] 4293 cmp r3, r2 BF28 it cs 4613 movcs r3, r2 9307 str r3, [sp, #28] --- SEGGER_RTT.c -- 362 ------------------------------------ while (NumBytesToWrite--) { *pDst++ = *pBuffer++; }; #else SEGGER_RTT_MEMCPY(pRing-&gt;pBuffer + WrOff, pBuffer, NumBytesToWrite); 9B03 ldr r3, [sp, #12] 685A ldr r2, [r3, #4] 9B05 ldr r3, [sp, #20] 4413 add r3, r2 9A07 ldr r2, [sp, #28] 9902 ldr r1, [sp, #8] 4618 mov r0, r3 F001FB0E bl 0x0003130A &lt;__aeabi_memcpy&gt; --- SEGGER_RTT.c -- 367 ------------------------------------ NumBytesWritten += NumBytesToWrite; 9A06 ldr r2, [sp, #24] 9B07 ldr r3, [sp, #28] 4413 add r3, r2 9306 str r3, [sp, #24] --- SEGGER_RTT.c -- 368 ------------------------------------ pBuffer += NumBytesToWrite; 9A02 ldr r2, [sp, #8] 9B07 ldr r3, [sp, #28] 4413 add r3, r2 9302 str r3, [sp, #8] --- SEGGER_RTT.c -- 369 ------------------------------------ NumBytes -= NumBytesToWrite; 9A01 ldr r2, [sp, #4] 9B07 ldr r3, [sp, #28] 1AD3 subs r3, r2, r3 9301 str r3, [sp, #4] --- SEGGER_RTT.c -- 370 ------------------------------------ WrOff += NumBytesToWrite; 9A05 ldr r2, [sp, #20] 9B07 ldr r3, [sp, #28] 4413 add r3, r2 9305 str r3, [sp, #20] --- SEGGER_RTT.c -- 371 ------------------------------------ #endif if (WrOff == pRing-&gt;SizeOfBuffer) { 9B03 ldr r3, [sp, #12] 689B ldr r3, [r3, #8] 9A05 ldr r2, [sp, #20] 429A cmp r2, r3 D101 bne 0x0002FD1C --- SEGGER_RTT.c -- 373 ------------------------------------ WrOff = 0u; 2300 movs r3, #0 9305 str r3, [sp, #20] --- SEGGER_RTT.c -- 374 ------------------------------------ } pRing-&gt;WrOff = WrOff; 9B03 ldr r3, [sp, #12] 9A05 ldr r2, [sp, #20] 60DA str r2, [r3, #12] --- SEGGER_RTT.c -- 376 ------------------------------------ } while (NumBytes); 9B01 ldr r3, [sp, #4] 2B00 cmp r3, #0 D1B5 bne 0x0002FC94 --- SEGGER_RTT.c -- 377 ------------------------------------ // return NumBytesWritten;</pre></p> <p></p> <ul> <li>Interrupt priorities</li> </ul> <p>I&#39;m not sure how I can set the main() priority. Could you guide me on where to read/set this?</p> <p>Timer ISR priority is set to 6:</p> <p><code>#define APP_TIMER_CONFIG_IRQ_PRIORITY 6</code></p> <p>I tried with different MMD priorities, none of them worked. I hope that this is is what you are referring to:</p> <p><code>NVIC_SetPriority(DebugMonitor_IRQn, _PRIO_APP_HIGH);</code></p> <p></p> <ul> <li>As for the mainlocal as static/volatile:</li> </ul> <p>If I declare it as static or static volatile, I&#39;m getting the correct value in the Watch when the program pauses at a breakpoint.<br />If I only set it to volatile, the value in Watch becomes wrong.</p> <p>Please let me know if you need any additional info.<br />Thanks</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/419815?ContentTypeID=1Tue, 11 Apr 2023 18:51:58 GMT137ad170-7792-4731-bb38-c0d22fbe4515:da790398-461b-4d7f-8309-c823c3deaf8fhaakonsh<p>Can you share a dissasembly of your program?&nbsp;</p> <p>Can you share your interrupt priorities? We need to know at what priority main(), timer ISR, and MMD ISR runs at.&nbsp;&nbsp;</p> <p>What happens if you declare &#39;mainlocal&#39; as &#39;volatile&#39;&nbsp;or &#39;static&#39;, or both?</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/419480?ContentTypeID=1Mon, 10 Apr 2023 11:44:21 GMT137ad170-7792-4731-bb38-c0d22fbe4515:7462993f-24d2-40de-9f5d-d5feba9c8169enukic<p>HI Martin <span class="emoticon" data-url="https://devzone.nordicsemi.com/cfs-file/__key/system/emoji/1f60a.svg" title="Blush">&#x1f60a;</span><br />Thanks for the reply. <br /><br />Compiler optimization was off during initial testing.<br />I tested again, using various optimization levels, but it made no difference.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/419422?ContentTypeID=1Fri, 07 Apr 2023 04:36:08 GMT137ad170-7792-4731-bb38-c0d22fbe4515:a7858d1e-059f-49bf-ba98-cf8ffa2bdcf8mtsunstrum<p>Do you have compiler optimizations on or off ?</p> <p>For `mainlocal` it seems like it may have been optimized to be a register variable. The debugger may then have problem inspecting such variables.</p><div style="clear:both;"></div>