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ble_app_hrs_freertos Increassing MTU Fatal error

Salmat

Hi,

Using SDK 15.3.0 , example "ble_app_hrs_freertos", pca10040 with armgcc.

I want to increase MTU and GAP data length.

I started with MTU to 247, and when I try to connect, on log :

<debug> nrf_sdh_freertos: Creating a SoftDevice task.
<info> app: HRS FreeRTOS example started.
<debug> nrf_sdh_freertos: Enter softdevice_task.
<info> app: Fast advertising.
<error> hardfault: HARD FAULT at 0x0002C004
<error> hardfault:   R0:  0x20008214  R1:  0x002A821C  R2:  0x20008214  R3:  0x20008208
<error> hardfault:   R12: 0x00000000  LR:  0x0002AAF1  PSR: 0x8100020E
<error> hardfault: Cause: Data bus error (PC value stacked for the exception return points to the instruction that caused the fault).
<error> hardfault: Bus Fault Address: 0x002A8228

The modifications I have done to the code are :

diff --git a/config/FreeRTOSConfig.h b/config/FreeRTOSConfig.h
index ae2167d..6dee317 100644
--- a/config/FreeRTOSConfig.h
+++ b/config/FreeRTOSConfig.h
@@ -63,7 +63,7 @@
 #define configTICK_RATE_HZ                                                        1024
 #define configMAX_PRIORITIES                                                      ( 3 )
 #define configMINIMAL_STACK_SIZE                                                  ( 60 )
-#define configTOTAL_HEAP_SIZE                                                     ( 4096 )
+#define configTOTAL_HEAP_SIZE                                                     ( 8192 )
 #define configMAX_TASK_NAME_LEN                                                   ( 4 )
 #define configUSE_16_BIT_TICKS                                                    0
 #define configIDLE_SHOULD_YIELD                                                   1
diff --git a/pca10040/s132/config/sdk_config.h b/pca10040/s132/config/sdk_config.h
index 8edaaed..715d28d 100644
--- a/pca10040/s132/config/sdk_config.h
+++ b/pca10040/s132/config/sdk_config.h
@@ -39,6 +39,9 @@
  */


+#ifndef DEBUG
+#define DEBUG 1
+#endif

 #ifndef SDK_CONFIG_H
 #define SDK_CONFIG_H
@@ -7432,7 +7435,7 @@
 // <e> NRF_LOG_BACKEND_RTT_ENABLED - nrf_log_backend_rtt - Log RTT backend
 //==========================================================
 #ifndef NRF_LOG_BACKEND_RTT_ENABLED
-#define NRF_LOG_BACKEND_RTT_ENABLED 0
+#define NRF_LOG_BACKEND_RTT_ENABLED 1
 #endif
 // <o> NRF_LOG_BACKEND_RTT_TEMP_BUFFER_SIZE - Size of buffer for partially processed strings.
 // <i> Size of the buffer is a trade-off between RAM usage and processing.
@@ -7465,7 +7468,7 @@
 // <e> NRF_LOG_BACKEND_UART_ENABLED - nrf_log_backend_uart - Log UART backend
 //==========================================================
 #ifndef NRF_LOG_BACKEND_UART_ENABLED
-#define NRF_LOG_BACKEND_UART_ENABLED 1
+#define NRF_LOG_BACKEND_UART_ENABLED 0
 #endif
 // <o> NRF_LOG_BACKEND_UART_TX_PIN - UART TX pin
 #ifndef NRF_LOG_BACKEND_UART_TX_PIN
@@ -7582,7 +7585,7 @@
 // <4=> Debug

 #ifndef NRF_LOG_DEFAULT_LEVEL
-#define NRF_LOG_DEFAULT_LEVEL 3
+#define NRF_LOG_DEFAULT_LEVEL 4
 #endif

 // <q> NRF_LOG_DEFERRED  - Enable deffered logger.
@@ -7632,7 +7635,7 @@
 // <e> NRF_LOG_USES_COLORS - If enabled then ANSI escape code for colors is prefixed to every string
 //==========================================================
 #ifndef NRF_LOG_USES_COLORS
-#define NRF_LOG_USES_COLORS 0
+#define NRF_LOG_USES_COLORS 1
 #endif
 // <o> NRF_LOG_COLOR_DEFAULT  - ANSI escape code prefix.

@@ -11069,12 +11072,12 @@

 // <o> NRF_SDH_BLE_GATT_MAX_MTU_SIZE - Static maximum MTU size.
 #ifndef NRF_SDH_BLE_GATT_MAX_MTU_SIZE
-#define NRF_SDH_BLE_GATT_MAX_MTU_SIZE 23
+#define NRF_SDH_BLE_GATT_MAX_MTU_SIZE 247
 #endif

 // <o> NRF_SDH_BLE_GATTS_ATTR_TAB_SIZE - Attribute Table size in bytes. The size must be a multiple of 4.
 #ifndef NRF_SDH_BLE_GATTS_ATTR_TAB_SIZE
-#define NRF_SDH_BLE_GATTS_ATTR_TAB_SIZE 1408
+#define NRF_SDH_BLE_GATTS_ATTR_TAB_SIZE 2000
 #endif

 // <o> NRF_SDH_BLE_VS_UUID_COUNT - The number of vendor-specific UUIDs.

I also modified "nrf_sdh_freertos.c" :

#define NRF_BLE_FREERTOS_SDH_TASK_STACK 256 to 512

(not sur it is useful ?)

I also have seen normal ble_app_hrs is with 247 MTU and 251 GAP data lenth, and it works !

Regards,

  • 0 in reply to Susheel Nuguru

    Hi,

    As said I already tried to increase : #define NRF_BLE_FREERTOS_SDH_TASK_STACK 256 to 512
    And it is the only task !
    I just tried with 2096, and it is not better ... :

    <debug> nrf_sdh_ble: RAM starts at 0x20002B88
<debug> nrf_sdh_freertos: Creating a SoftDevice task.
<info> app: HRS FreeRTOS example started.
<debug> nrf_sdh_freertos: Enter softdevice_task.
<info> app: Fast advertising.
<debug> nrf_sdh_ble: BLE event: 0x10.
<debug> nrf_ble_gatt: Requesting to update ATT MTU to 247 bytes on connection 0x0.
<debug> nrf_ble_gatt: Updating data length to 251 on connection 0x0.
<info> app: Connected
<debug> nrf_sdh_ble: BLE event: 0x24.
<debug> nrf_ble_gatt: Data length updated to 27 on connection 0x0.
<debug> nrf_ble_gatt: max_rx_octets: 27
<debug> nrf_ble_gatt: max_tx_octets: 27
<debug> nrf_ble_gatt: max_rx_time: 328
<debug> nrf_ble_gatt: max_tx_time: 328
<debug> nrf_sdh_ble: BLE event: 0x3A.
<debug> nrf_ble_gatt: ATT MTU updated to 247 bytes on connection 0x0 (response).
<error> hardfault: HARD FAULT at 0x0002C194
<error> hardfault:   R0:  0x200075E4  R1:  0x002B75EC  R2:  0x200075E4  R3:  0x200075D8
<error> hardfault:   R12: 0x00000000  LR:  0x0002AC81  PSR: 0x8100020E
<error> hardfault: Cause: Data bus error (PC value stacked for the exception return points to the instruction that caused the fault).
<error> hardfault: Bus Fault Address: 0x002B75F8

    It should be very easy to change only the few parameters from the SDK example to make it work !
    And as I said, it works with all other profile I have tried ...

  • 0 in reply to Salmat

    I reproduced it, At first i thought nRF52832 has little heap memory is spare to be able to support 247 MTU size, so I tested this on nRF52840 with huge heap space in reserve. But I still managed to replicate it, I will take a look into this tomorrow to see where the stack corruption is happening.

  • 0

    This one took time for me since I had to use SystemView to understand the flow of the data.

    I also enabled stack overflow triggers by enabling 

    #define configCHECK_FOR_STACK_OVERFLOW                                            2

    and adding to main.c

    I can see that there is stack overflow happening in Tmr thread.

    It was actually Timer which needed to have more stack space when ou increase the MTU size. At certain point, the context data within the Tmr thread is increasing in size with increased MTU size. I do not still have the full picture as to why this is happening, but in your case you can increase the timer thread stack space to about 400 bytes and then you won't see this

    #define configTIMER_TASK_STACK_DEPTH                                              ( 400 )

  • 0 in reply to Susheel Nuguru

    Thanks !

    It works increasing configTIMER_TASK_STACK_DEPTH to just 120
    But I do not understand neither ...

    It is the only thing to modify with MTU, on the SDK example !

  • 0 in reply to Susheel Nuguru

    Any updates on this? What is the root cause of the hardfault that happens when increasing the MTU size?

    I just ran into this same issue myself. I am using the FreeRTOS HRS example as basis for my project. I increased the MAX MTU setting in sdk_config.h from 23 to 512 (maximum allowed). Then I get the hard fault immediately startup (before any connections are made). The debug print in RTT is:

    <00> info> app: Fast advertising.
<00> error> hardfault: HARD FAULT at 0x20006A0A
<00> error> hardfault:   R0:  0x200069C8  R1:  0x20006904  R2:  0x00000004  R3:  0x20006A0A
<00> error> hardfault:   R12: 0x20008050  LR:  0x0002C577  PSR: 0x80000000
<00> error> hardfault: Cause: The processor has attempted to execute an instruction that makes illegal use of the EPSR.

    I tried to get around the issue by increasing the timer thread stack size from default 80 to 800 but it does not help at all.

    EDIT: by using MTU size 247 (instead of the 512 that was my first edit) the hard fault goes away. It is enough to allow me to continue working on my project, but I think it seems kind of weird that changing MTU max value causes a stack overflow. I would need to understand what is happening under the hood so that I can set the stack sizes corretly (not based on guessing or trial/error but on some facts)

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