Issue with Softdevice S140 on Arduino Nano BLE 33 board (nRF52840)

[Sebastien DRI]

Hi Folks,

I am getting in trouble with SoftDevice activation. Indeed, my application did not return from the "nrf_sdh_enable_request()" call, more precisely it hangs into the "sd_softdevice_enable".

I want to mention that I compile the S140 file within my application so I did not flash independently the Softdevice hex previously into my target. Maybe my linker script file is not OK or my sdk_config.h file

My questions are: Is it possible to flash in one shot softdevice + application ?if yes, how must be configured the linker script file?

I have also noticed that the "sd_softdevice_enable" function refers to a sd_softdevice_enable to a SVCALL so I suppose S140 must be flashed first in that configuration so my Arduino board must be in a hard fault reset state. Am I right?

Another file contains a pure C definition , it is located in the named "ser_softdevice_handler.c". Can it serve to implement Softdevice without in a single application file?

I know I ask a lot so I thank u a lot as well.

The best.

Seb

[bjorn-spockeli]

Hi Seb,  

I want to mention that I compile the S140 file within my application so I did not flash independently the Softdevice hex previously into my target. Maybe my linker script file is not OK or my sdk_config.h file

 The SoftDevice is a precompiled binary(hex file) and we provide the header files for the SoftDevice API that you compile into your application. So in order to use the SoftDevice you need to compile the headers into your application and flash the SoftDevice hex file to the nRF52840. 

My questions are: Is it possible to flash in one shot softdevice + application ?if yes, how must be configured the linker script file?

Below is the linker script for the ble_app_blinky application in our nRF5 SDK. You just need to place the application on the first flash page after the SoftDevice and then set the RAM origin according to the minimum RAM requirement stated in the S140 SoftDevice specification

 ble_app_blinky_gcc_nrf52.ld

I have also noticed that the "sd_softdevice_enable" function refers to a sd_softdevice_enable to a SVCALL so I suppose S140 must be flashed first in that configuration so my Arduino board must be in a hard fault reset state. Am I right?

 Correct. The SoftDevice API is implemented as SVCALLs so the S140 must be flashed to the nRF52840, otherwise the the SVCALL will just return and state that it could not find the SVC Handler of the SoftDevice.

Another file contains a pure C definition , it is located in the named "ser_softdevice_handler.c". Can it serve to implement Softdevice without in a single application file?

No, this is the serialization API that allows you to use the nRF52 SoCs as connectivity chips through a serial interface to another MCU. See Running a serialized application and Serialization for further documentation on serialization.

Best regards

Bjørn

[Sebastien DRI]

Thank u a lot.

Very clear explanations!

I have still some issue to run the ble_blinky  example.

I am currently flashing over a SAM -BA Bootloader (the one installed on my Arduino nano board) via USB serial.

I am also running teh blinky example using SDK 15.0.0 with the corresponding Softdevice (6.0.0).

However, it seems that nothing is happening (no Peripheral detected while scanning BLE).

I compile the ble_app_blinky with Keil environment (PCA10056 board) and everything is fine concerning linker script (ROM/RAM offset) and I also set up RC internal clock since the Arduino board does not have XTAL.

So, in a nutshell, I first flash Softdevice with "Bossac" command then perform hex2bin for the blinky app and then flash it again with "Bossac".

Did u suspect something wrong in my procedure? Is Bossac recommended in that case? Or maybe I am missing something 

to make compatible PCA10056 board with the Arduino Nano BLE one (pin configurations or sdk_config.h).

[bjorn-spockeli]

Sebastien DRI said:

No, but I will check if the "sd_ble_enable" return since for instance I have deactivated BLE in the main application.

I hope that RAM_NVIC & RAM_CRASH_DATA sections are detected by Softdevice so that it can shift the application start adress accordingly taking into account them.

What do you suggest in that case? Specify the Softdevice ram section within linker script?

 As long as the ram_start value returned by sd_ble_enable is lower than the origin of the RAM_NVIC region then I think you should be good!

Sebastien DRI said:

Yes, i am talking about the SAM-BA factory bootloader of which I have recently checked the code and I have discovered they do not automate app start adress calculation.

Consequently I'll load a different bootloader (the Adafruit_nRF52_Bootloader compatibles with nano 33 board) as soon as I'll receive the programming board. Hope will be fine once done.

Thank you again for your support. It helps me to under quickly how it works.

Let's be in touch later if you want to conclude this chapter.

 Yes, let me know once you can program the board directly via SWD.

 

[Sebastien DRI]

Welcome back!!,

I can now boot my application from  the Adafruit_nRF52_Bootloader whatever the application offset is.

First problem solved!

I bought a Segger Jlink mini to perform the flashing operation, perfect.

Now , I have still an issue when initialising softdevice upon mbedos

I have recently posted a detailled explanation on the mbed-os forum:

https://forums.mbed.com/t/svc-exit-when-activating-softdevice/8251

Maybe you have an opinion on how to make work Nordic SDK on mbed OS when you have already flashed a softdevice on target. I seems that mbed OS has its own SVC_Handler and it results in going into application fault since softdevice is not properly initialised.

Thank u again.

Seb

[bjorn-spockeli]

Hi Seb, 

Glad to hear that you can jump to the application to your application the nRF52840 with the Adafruit_nRF52_Bootloader. 

I am afraid that dont have very much experience with Svc handlers, but I guess there may be issues if the mBed OS and SoftDevice API uses the same SVC numbers. In our example projects the SVC Handler is weakly defined in the startup file(.s).  When the SoftDevice is flashed to the nRF52840, then all execptions are processed by the SoftDevice first and then forwarded to either the bootloader or application. THats atleast how it works in our SDK. 

Does sd_softdevice_enable return a non-zero error code ?

Best regards

Bjørn

[Sebastien DRI]

Hi Bjorn,

Thank you again for your quick response.

Yes it is a non-zero error code.

To get deeper in detail, here is the ret_code once the "sd_softdevice_enable" executed:

More precisely, this code come from a SVC_exit call in the irq_cm4f.S (cmis rtos starup code source:) which handles <SVC_Handler>.

Here is the source code for visualization:

https://github.com/maxgerhardt/framework-arduinostm32-modded/blob/master/CMSIS/CMSIS/RTOS2/RTX/Source/GCC/irq_cm4f.S

It seems that it redirect to the <SVC_User> function and try to load address of SVC table at osRtxUserSVC.

At this point it call the exit function since it considers SVC maximum number  out of range.

This is only for examinate this issue, now I will be interested in redirecting the call  to the softdevice SVC_Handler only for SVD call number above 0xF which is my case (0x10 for the softdevice_enable code).

Maybe should I redirect Supervisor calls back to asoftdevice thanks to the sd_softdevice_vector_table_base_set function?

To my mind, this bad call is due to the fact that mbedos has relocated interrupt vector table, maybe this is due to the virtualization of the NVIC (remember the NVIC_RAM) with the CMSIS_NVIC_VIRTUAL define flag on mbedos. However, mbedos can't work if I don't use NVIC_RAM.

I also tried to redefine the <SVC_Handler> compiling nrf_svc_handler.c file but there is a problem of redifinition with the one defined in irq_cm4f.S .

I have also tried to keep default the Mbed configuration to generate an application with mbed + softdevice but it tries to implement a Cordio stack instead when using BLE wrapper functions but I don't want it, I want softdevice

Do you have any suggestions as to how I can get rid of my problem? I know it's mbed-os related, that's why I ask to them first but maybe you have a trick.

Thank you in advance. 

[bjorn-spockeli]

HI Seb, 

I have very limited experience with mbed OS. Am I understanding correctly that the SoftDevice is flashed to the nRF52840 and then the mbed application is placed on the first flashpage after the SoftDevice

If so, then the SVC exeption should be handled by the SoftDevice first. Does the mBed application change the Vector Table Offset Register (VTOR) register so that the SoftDevice is bypassed all together after the initial power up?

Best regards

Bjørn

[Sebastien DRI]

Hi Bjorn,

Thank you for your answer.

I suppose relocation is done into mbedos.

That's why they integrate an old Softdevice version which is unfortunately not maintained and replaced by Cordio stack.

We have decide to migrate to the Adafruit platform so that we can work with your latest softdevice version

Thank you again for your support

[bjorn-spockeli]

Ok, sorry for not being able to provide much help with mbedOS. 

Best regards

Bjørn